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Olje, ki se absorbira v človeško kožo – kam gre?

Olje, ki se absorbira v človeško kožo – kam gre?



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Na primer, dvakrat na dan nanesem petrolatum na suhe roke, saj sem pozimi običajno v 20-30% RH okolju. V eni uri se zdi, da se petrolatum popolnoma absorbira.

Po [1] petrolatum in druga tam testirana olja "ne dosežejo sposobnih celic povrhnjice, saj nasitijo le najvišje poroženele plasti kože."

Moje vprašanje je torej: Kam gre olje? Ne verjamem, da dovolj hitro odstranjujem nevidne plasti kože in ne prenašam olja na druge predmete dovolj hitro, da bi lahko ponovila in nanašala dvakrat na dan, ne da bi olje zašlo globlje od "najvišjih poroženelih plasti" in se izločilo navznoter. (Prek limfe? krvi?) Prav tako si redko umivam roke z milom.

[1] Konfokalna Ramanova mikroskopija za raziskovanje prodiranja različnih olj v človeško kožo in vivo. Choe C, Lademann J, Darvin ME. J Dermatol Sci. avgust 2015 https://atlasofscience.org/oil-penetration-into-the-human-skin/ Dostop 8. 2. 2019


Ali se minerali/kemikalije med kopanjem absorbirajo skozi kožo?

Moj prijatelj je v komentarju na spletu pred kratkim dejal:

Vaše telo med petminutnim tuširanjem skozi kožo absorbira več mineralov kot če v enem tednu popijete 64 oz (približno 1,9 litra) vode.

To se mi sliši kot norost, toda ali so bile opravljene kakšne študije o absorpciji mineralov ali kemikalij (šamponi, mila itd.) skozi vašo kožo ali z vdihavanjem med tuširanjem?

Nekateri viri trditev, da človeško telo med prhanjem absorbira kemikalije skozi kožo:


Kaj je kokosovo olje?

Preden se potopimo v nego kože kokosovega olja, poglejmo, od kod prihaja in kako deluje. Kokosovo olje je pridobljeno iz kokosove palme in ga tradicionalne kulture tako zelo cenijo kot vir hrane in zdravila, da ga imenujejo “Drevo življenja.”

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Kokosovo olje je po naravi rafiniran izdelek, saj olje ne raste na drevesu. Olje se pridobiva iz jedrca ali mesa nabranih kokosovih oreščkov. Tehnično gledano je edino resnično »nerafinirano« kokosovo olje, ki ga lahko zaužijete, olje, ki je še vedno v mesu iz svežega kokosa, ki ste ga pravkar pobrali z drevesa. Najmanj rafinirana vrsta je deviško kokosovo olje.

Sadno olje je pretežno sestavljeno iz nasičenih maščob z veliko količino srednjeverižnih maščobnih kislin, pri čemer je dober odstotek maščobne kisline lavrinska kislina. (1) Vsebuje vitamin E, za katerega je znano, da ščiti kožo pred poškodbami prostih radikalov. (2)


3. Ali vam otroško olje pomaga pri porjavenju?

Otroško olje deluje kot reflektor UV žarkov, ki lahko pritegnejo več sonca. Pomaga tudi, da se žarki globlje vpijejo v kožo, kar povzroči, da porjavite do temnejšega odtenka.

Kljub temu ne bo zaščitil vaše kože pred škodljivimi učinki sonca – zlasti pred sončnimi opeklinami –, zato ga nikoli ne smete uporabljati samega med sončenjem. Nikoli ne ležite neposredno na soncu brez kreme za sončenje.

Johnson & Johnson Baby Oil

Ali kozmetične sestavine res prodrejo v kožo? Epizoda 92

Začnimo našo razpravo o resnici prodiranja v kožo z omembo nekaj priljubljenih napačnih predstav o tej temi.

Napačne predstave

Eden od razlogov, zakaj smo se želeli lotiti te teme, je, da je tam veliko napačnih informacij. Mislim, da je večina potrošnikov lepotnih izdelkov videla naslove, ki povzročajo strah, kot so naslednji:

  • Naša koža vsako leto absorbira __X__ število kilogramov kozmetike.
  • “Visok odstotek” vsega, kar vsak dan nanesemo na kožo, prodre.
  • VSE, kar nanesemo na kožo, prodre v krvni obtok.
  • Če v človeškem urinu najdemo kemikalijo, to pomeni, da je kozmetika, iz katere izvira, nevarna.
  • Če koža ni absorbirala vsega, kar nanjo nanesemo, zakaj potem obliž z zdravili deluje tako dobro?

Če bi bili ti naslovi resnični, nam ne bi bilo treba jesti, ker bi lahko absorbirali hranila samo z drgnjenjem hrane na kožo. To očitno ni tako, čeprav je res, da lahko NEKATERE kemikalije prodrejo v kožo.

Zdaj se v eni sami 30-minutni oddaji ne moremo poglobiti v podatke za vsako kozmetično sestavino, uporabljeno v vsakem izdelku, vendar lahko razložimo ...

  • Kako deluje penetracija v kožo
  • 4 glavni dejavniki, ki nadzorujejo prodiranje v kožo
  • In morda je najbolj relevantno vprašanje – penetracija nujno slaba stvar.

Kako deluje penetracija v kožo

Naredimo zelo hiter pregled biologije kože. Koža se je razvila v zaščitni mehanizem. To je dobesedno ovira, ki nas loči od zunanjega sveta. Sestavljen je iz 3 glavnih plasti…

Povrhnjica
"Epi" je grški izraz, ki se uporablja kot predpona, ki pomeni na ali nad dermisom, tako da je epidermis plast, ki je na ali nad dermisom. To je del kože, s katerim neposredno komunicirate. Pomembno je razumeti, da je zunanja plast, imenovana stratum corneum, mrtva. Debelina te plasti se razlikuje glede na lokacijo. Na vaših vekah je na primer zelo tanek, na spodnjih delih stopal pa veliko debelejši. Nižje ravni povrhnjice so tam, kjer nastajajo nove kožne celice. Je tudi plast, ki je odgovorna za tvorbo melanina, ki koži daje barvo. In kot smo že rekli, je odgovoren za zaščito vašega telesa.

Dermis
Naslednja plast, dermis, je od koder prihajajo dlake, znoj in olje. Prav tako je dom živčnih končičev, ki so odgovorni za vaš občutek za dotik. V dermisu so tudi krvne žile.

Hipodermis
Spodnja plast kože je podkožna maščobna plast, ki se imenuje tudi hipodermis. Ta plast v bistvu pritrdi zgornje plasti kože na kosti in mišice spodaj. Maščoba vas izolira pred temperaturnimi nihanji in fizičnimi šoki, vsebuje pa še več, večjih krvnih žil.

Torej, kot lahko vidite, ima sestavina precej poti, da potuje, preden lahko popolnoma prodre skozi vašo kožo. Nato se pogovorimo o tem, kaj natančno določa, kako dobro bo ta prodor deloval.

O tej ravni kože govorimo z uporabo analogije “opeke in malte”, ker si lahko kožne celice predstavljamo kot drobne opeke, naložene ena na drugo z nekakšno malto ali cementom med njimi. Tu torej začnemo našo razpravo o prodiranju v kožo, saj je prva stvar, ki jo mora sestavina narediti, najti pot med temi plastmi opeke in malte, da pride v kožo.

Zdaj pa se pogovorimo, kateri mehanizmi so odgovorni za to penetracijo in kateri pogoji nadzorujejo stopnjo penetracije.

4 Dejavniki, ki nadzorujejo prodiranje v kožo

1. Velikost/molekulska masa
Pomemben dejavnik je velikost molekule, ki je vezana na njeno molekulsko maso. Večina molekul je preprosto prevelika, da bi zdrsnila med tistimi razpokami med "opekami" odmrlih kožnih celic.

Obstaja nekaj presenetljivih izjem, na primer v epizodi 75 smo govorili o odkritju, da se hialuronska kislina lahko prebije skozi kožo. Toda na splošno bodo manjše molekule bolje prodrle. Velja pravilo, da lahko vse, kar je manjše od 500 daltonov, prodre v kožo, medtem ko vse, kar je večje od 500 daltonov, ne more. Dalton, mimogrede, je standardna enota, ki se uporablja za označevanje mase na atomskem ali molekularnem merilu. Pogosti alergeni so tudi manjši od 500 daltonov.

2. Topen v olju proti vodotopen
Na splošno v olju topne sestavine prodirajo veliko bolje kot vodotopne sestavine, ker je koža sama vodoodporna. Tehnično to opisujemo kot hidrofilno ali lipofilno ravnovesje sestavine.

Klasičen primer je vodotopna alfahidroksi kislina, kot je mlečna kislina, ki deluje na površini kože. Primerjajte to z bolj v olju topno beta hidroksi kislino, kot je salicilna kislina, ki lahko prodre v pore za boj proti aknam.
To je smiselno, ker je velik del medceličnega prostora zapolnjen z lipidi, kot so ceramidi.

3. Polarnost/naboj
Nazadnje je pomembna tudi polarnost ali naboj molekule. Na primer, sladkor in sol sta topna v vodi, vendar je ena polarna, druga pa ne, tako da bi pričakovali, da bosta prodrla drugače.

Te lastnosti skupaj pomagajo določiti, kako verjetno je, da sestavina prodre v kožo. Drugi dejavnik, ki ga je treba upoštevati, je stanje kože.

4. Stanje kože
Kot smo pojasnili pred minuto, je koža na nekaterih delih telesa tanjša od drugih. Koža pod očmi je na primer zelo tanka, kar je eden od razlogov, da se temni kolobarji pojavljajo tako veliko. Tanka koža je bolj nagnjena k penetraciji kot debela koža. Če upoštevamo kinetiko, je smiselno, da je smiselno, da bi lahko prešla več razdalje, če je manjša razdalja.

Prav tako je odrgnjena koža bolj dovzetna za penetracijo kot nepoškodovana koža. To pomeni, da če si brijete obraz ali pazduhe, obstaja večja verjetnost, da bodo sestavine na teh območjih prodrle globlje v kožo. Smiselno je tudi, da bi to veljalo za kožo, ki je močno luščena.

Razmislite o dostavnem vozilu

Pomembno je upoštevati formulo, iz katere se sestavina dobavlja iz dveh razlogov. Prvič, če je izdelek za izpiranje, je malo verjetno, da bo povzročil veliko prodiranja. To je zato, ker se penetracija meri v miligramih na kvadratni centimeter na enoto časa. Ta časovna enota je pogosto ure, ne minute in zagotovo ne sekunde. Zato je zelo malo verjetno, da bi karkoli, kar se spere s kože, imelo čas, da prodre. Izdelek, ki ostane na izdelku, kot vlažilni losjon, daje sestavinam veliko več časa, da prodrejo. (Opomba: izjema so lahko sestavine, ki so zelo pomembne za kožo.)

Drugič, v formuli so lahko druge sestavine, ki povečajo penetracijo. Ti »pospeševalci penetracije« so običajno bodisi oljni materiali ali sestavine s poliolnimi (OH) skupinami. Lahko so kemikalije, ki so sintetičnega ali naravnega izvora in naj bi delovale tako, da spremenijo način pakiranja lipidov med kožnimi celicami. (Tako kot model »opeke in malte«, o katerem smo govorili.) Nekateri dobro znani primeri vključujejo etanol, nekaj PEG, metil pirolidon, jojobino olje in olje poprove mete. Našli smo nekaj zanimivih člankov o ojačevalcih penetracije in povezave do teh bomo dali v zapiske oddaje.

Je penetracija vedno slaba stvar?

Če za trenutek pustimo ob strani vprašanje, ali sestavina prodre v kožo ali ne, si je treba zastaviti še eno pomembno vprašanje. Če prodre v kožo, je to vedno slabo?

Če le prodre skozi zgornje plasti kože in se ne absorbira v krvni obtok, se bo sčasoma samo odstranil kot del odmrlih kožnih celic. Da bi predstavljal sistemsko nevarnost, mora ne le prodreti v kožo, ampak se mora iz kože absorbirati v krvni obtok.

Ko so v krvnem obtoku, imajo naša telesa zelo učinkovit mehanizem filtriranja za odstranjevanje toksinov. To je še en razlog, zakaj je koncept odmerka strup tako pomemben. Nizke ravni kontaminantov bodo izločile ledvice in izstopili boste v P ali blatu.

Seveda lahko nekateri onesnaževalci preplavijo naravni sistem filtriranja telesa in so nevarni za vaše zdravje. Svinec je dober primer – zelo majhne količine svinca se izločijo iz vašega telesa (to je eden od razlogov, da je svinec v šminki v redu), vendar se večji odmerki svinca kopičijo v vašem telesu in povzročajo zdravje težave.

Moje mnenje je, da je razlika med prodiranjem v kožo in vpijanjem v kožo pomembna razlika.
Pomembno je tudi vedeti, da je tveganje, da sestavina prodre v kožo, vključena v oceno varnosti kozmetičnih sestavin.

Končni rezultat Beauty Brains

Sestavine ne morejo zlahka prodreti skozi kožo zaradi njene strukture iz opeke in malte.

Sestavina mora imeti pravo velikost in ustrezno združljivost s kožnimi lipidi, da "zdrsne skozi".

Obstajajo tudi druge sestavine, imenovane ojačevalci penetracije, ki povečajo penetracijo (zlasti v transdermalnih obližih z zdravili).

Miti NISO resnični o tem, da vaše telo absorbira velike količine kemikalij skozi vašo kožo.

Regulativni organi, ki določajo varnost kozmetičnih sestavin, v svojo oceno zagotovo upoštevajo prodiranje in vpijanje v kožo.

Reference
http://personalcaretruth.com/2011/03/skin-penetration-enhancers-friend-or-foe/
http://personalcaretruth.com/2011/01/the-impermeable-facts-of-skin-penetration-and-absorption/

Neverjetni izdelki

Ta teden smo igrali posebno “wake up and dišej slanino” izdajo naše igre. Kateri od teh izdelkov za osebno nego s temo slanine je ponaredek? (Poslušajte oddajo za odgovor.)


Uvod

Eterična olja se pogosto uporabljajo v kozmetični, farmacevtski, medicinski in prehrambeni industriji kot protibakterijska, protiglivična in protivirusna sredstva. 1 Imajo antioksidativno in protivnetno delovanje, 2 delujejo proti raku, 3 spodbujajo celjenje ran, 4 lahko nadomestijo konvencionalno uporabljene konzervanse, 5 pesticide 6 in igrajo številne druge biološke vloge. 7 Številne biološke aktivnosti eteričnih olj in njihovih sestavin se široko uporabljajo za preprečevanje in zdravljenje številnih človeških bolezni. 8 Zato imajo lahko ta naravna sredstva prednost pred tradicionalno uporabljenimi sintetičnimi materiali kot varni in primerni ojačevalci prepustnosti za spodbujanje perkutane absorpcije številnih zdravil iz lokalne formulacije v spodnje plasti kože.

Ta pregled zajema vlogo eteričnih olj in njihovih sestavin v transdermalnem sistemu dajanja zdravil kot ojačevalca prepustnosti kože. Opisani so tudi možni mehanizem njihovega prodiranja skozi kožo in njihova toksičnost.

Prodor eteričnih olj in njihovih spojin skozi kožo

Na dermalno absorpcijo vplivajo številni dejavniki, vključno z izvorom (človeški, živalski) in tipom kože, fizikalno-kemijskimi lastnostmi testirane spojine in sistemi za dovajanje, pa tudi možna predhodna obdelava kože in okoljski dejavniki. V ta namen se uporabljajo številni modeli in vitro in in vivo za preučevanje prodiranja aktivnih spojin skozi kožo. 9 Med njimi je človeška koža najbolj zanesljiv model za oceno perkutane penetracije aktivnih spojin. Vendar je njegova razpoložljivost omejena. Zato se živalska koža običajno uporablja za izvajanje testov penetracije. Kot primeren nadomestek za človeško kožo je bila predlagana široka paleta živalskih modelov (primati, prašič, miš, podgana, morski prašiček, kača). Na žalost se anatomska struktura kože (debelina, sestava lipidov medcelične rožene plasti (SC), število kožnih žil, gostota lasnih mešičkov, anatomija žil in razporeditev kolagenskih vlaken) med človeško in živalsko vrsto razlikuje. 9 Te razlike v strukturi kože vplivajo na količino, trak in enostavnost prodiranja pregledanih snovi skozi kožo. Razen kože prašičev in podgan koža glodalcev na splošno kaže višje stopnje prepustnosti kot človeška koža. 9-12 Zato je iskanje korelacije med živalskimi in človeškimi modeli za napovedovanje perkutane absorpcije pri ljudeh še vedno izziv za raziskovalce.

Drugi parameter, ki vpliva na transepidermalno penetracijo, je struktura kože. Glavna omejitev za prodiranje aktivnih spojin skozi kožo je premagovanje najbolj zunanje plasti nesposobne povrhnjice – SC. SC služi kot lipofilna ovira, ki omejuje hitrost proti privzemu kemičnih in bioloških toksinov ter transepidermalni izgubi vode. 13 Obstaja le nekaj možnih poti za epidermalno penetracijo aktivnih spojin, ki vključujejo čezcelično (intracelularno) permeacijo preko korneocitov SC, penetracijo skozi medcelične prostore SC in penetracijo priveska skozi lasni mešiček, lojnice in/ali znojne žleze (slika 1). Hidrofilne spojine se prednostno razdelijo na znotrajcelične domene, lipofilni permeanti prečkajo SC po medcelični poti, vendar večina molekul preide skozi SC po obeh poteh. 14 Vendar pa se medcelična pot na splošno šteje za glavno pot in glavno oviro za permeacijo večine zdravil. Polarnost, molekulska masa (<500 Da), koncentracija aktivnih spojin v formulaciji, topnost molekul v olju in vodi ter sestava pripravka pomembno vplivajo na njihovo prodiranje skozi kožo. 15 Zato lahko le manjšina molekul s specifičnimi fizikalno-kemijskimi lastnostmi zadostno preide skozi kožo in v primeru zdravil s krvnim obtokom cilja podkožno tkivo. Med njimi so eterična olja in njihove aktivne sestavine. 13, 15-17

Poti prodiranja zdravil skozi kožo.

Mehanizem prodiranja eteričnih olj in njihovih aktivnih spojin

Ojačevalci penetracije so sredstva, ki lahko povečajo difuzivnost zdravila skozi kožo z zmanjšanjem pregradne odpornosti SC, ne da bi poškodovali sposobne celice. V idealnem primeru mora imeti ojačevalec naslednje lastnosti: farmakološko inerten, ne draži, nestrupen, nealergen, združljiv z zdravili, ima dobre lastnosti topila, brez vonja, okusa, brezbarven, poceni, ne kaže izgube telesnih tekočin. , elektrolitov in drugih endogenih materialov, enostavno odstranjevanje s kože in hitro ponovno vzpostavitev naravne pregrade. 16, 18 Z leti so obsežni pregledi in testiranja odkrili različne razrede kemikalij kot potencialne ojačevalce prodiranja v kožo. Najbolj raziskani ojačevalci penetracije so: sulfoksidi (dimetil sulfoksid, dimetilacetamid), azon (1-dodecilazacikloheptan-2-on, laurokapran), pirolidoni (2-pirolidon, N-metil-2-pirolidon), sečnina in derivati ​​maščobnih kislin ( lavrinska kislina, miristinska kislina, kaprilna kislina, oleinska kislina), alkoholi (etanol, 2-propanol, kaprilni alkohol), polioli (propilen glikol, glicerol), površinsko aktivne snovi (ionske: SLS in neionske: polisorbati), kelatna sredstva (EDTA , citronska kislina), kot tudi eterična olja in njihove sestavine (terpeni, terpenoidi). 15, 18 Ta naravna sredstva lahko prenašajo zdravila po koži z različnimi mehanizmi delovanja: (1) motnja visoko urejene medcelične lipidne strukture med korneociti v SC, zaradi česar je ta plast prepustna za zdravila, (2) interakcija z medcelično domeno protein, ki inducira njihovo konformacijsko modifikacijo in naredi SC bolj prepusten, (3) pospeševanje delitve – številna topila spremenijo lastnosti SC in tako povečajo porazdelitev zdravila in (4) ojačevalec, ki deluje na desmosomske povezave med korneociti ali spreminja presnovno aktivnost znotraj koža. 18, 19 Splošni ojačevalec, ki spreminja polarne poti, povzroči spremembo konformacije beljakovin ali otekanje topila, medtem ko ojačevalci maščobnih kislin povečajo pretočnost lipidnega dela SC. Nekateri ojačevalci delujejo tako na polarno kot nepolarno pot s spreminjanjem večlaminatne poti za penetracijo. 15

Eterična olja in njihove sestavine so bila široko raziskana kot varni in primerni ojačevalci prodiranja v kožo za hidrofilna in hidrofobna zdravila, vendar mehanizem njihovega delovanja ni popolnoma razumljen. Nielson 20 je pokazal, da lokalno uporabljeno olje evkaliptusa, čajevca in poprove mete zmanjšajo celovitost kože na način, ki je odvisen od odmerka. Nizke koncentracije olja poprove mete so zmanjšale perkutano prodiranje benzojske kisline in delovale zaščitno pred perkutano penetracijo, medtem ko so njegove višje koncentracije zmanjšale celovitost dermalne pregrade. Eterična olja iz sladke bazilike (Ocimum basilicum), saj so ojačevalci prepustnosti kože spodbujali perkutano absorpcijo indometacina s povečanjem porazdelitve zdravila v SC in z motenjem morfologije kože. 21 Olja terpentina, evkaliptusa in poprove mete so izboljšala permeacijo ketokonazola s spremembo kožne pregrade, vendar brez spremembe njihove strukture. 22 Alpinia oxyphylla olje je pokazalo večjo afiniteto za lipofilni SC in verjetno zmanjšalo polarnost SC in s tem povečalo permeacijo lipofilnega indometacina v hrbtno kožo podgan. 23 Poleg tega so študije in vivo pokazale, da so bile spremembe transepidermalne izgube vode zanemarljive, kar kaže na omejeno prekinitev medceličnih poti, kot tudi ni prišlo do draženja in/ali toksičnosti teh ojačevalcev permeacije zdravil. Na koncu so avtorji ugotovili, da je glavni mehanizem učinka povečanja penetracije v kožo A. oxyphylla eteričnih olj je posledica povečane pregrade med kožo in vozilom. Charoo et al. 24 je pokazalo, da je terpentinsko olje v koncentraciji 5 % (v/v) učinkovito sredstvo za izboljšanje permeacije flurbiprofena, verjetno zaradi vse večje motnje SC in povzročanja manjšega draženja kože. Pokazalo se je, da eterično olje črne kumine pri koncentraciji 5 % (v/v) v izopropil alkoholu ekstrahira lipide iz SC in povzroči denaturacijo α-keratina, ki je spremenila sestavo kožnih beljakovin z izgubo vodikovih vezi med ceramidi, kar je povzročilo fluidizacijo lipidov. dvosloj, kar je posledično ustvarilo prehod za lipofilno zdravilo – karvedilol, da prečka dermis. 25

Mehanizmi delovanja aktivnih spojin, pridobljenih iz eteričnih olj, temeljijo predvsem na spreminjanju strukture SC pregrade in interakciji z medceličnimi SC lipidi za povečanje difuzivnosti zdravil. Kot možen mehanizem za krepitev delovanja d-limonen in etanol skozi kožo podgan, je veljalo, da d-limonen je v sožitju z etanolom prodrl v kožo in bi lahko spremenil difuzivnost indometacina s spreminjanjem strukture SC plasti. 26 Williams in Barry 27 sta pokazala, da glavni način delovanja testiranih cikličnih terpenov (α-pinen, α-terpineol, karvon, 1,8-cineol, askaridol) temelji na njihovi interakciji z medceličnimi SC lipidi za povečanje difuzivnosti za hidrofilno permeant 5 -fluorouracil (5-FU) skozi človeške epidermalne membrane. Po drugi strani pa po zdravljenju s terpeni niso opazili pomembne interakcije z beljakovinami ali večjih sprememb porazdelitve. Mehanizem delovanja L-mentola, ki se uporablja kot ojačevalec penetracije pri transdermalnem dajanju propranolol hidroklorida skozi izrezano kožo brez dlake miši, vključuje njegovo porazdelitev prednostno v medcelične prostore SC in možno reverzibilno motnjo medcelične lipidne domene. 28 Mentol je povečal perkutani tok nikardipin hidroklorida iz 2 % m/m hidroksipropilceluloznega gelnega sistema skozi izrezano povrhnjico podgane z delno ekstrakcijo lipidov v SC. 29 Mehanizem delovanja timola in mentola je povečal porazdelitev tamoksifena v SC, medtem ko karvon in 1–8-cineol delujeta z motnjo lipidov SC. 30

Tudi kemična struktura sestavin eteričnih olj kot ojačevalcev vpliva na proces prodiranja zdravila skozi kožo. Običajno transdermalno absorpcijo hidrofilnih zdravil bolje izboljšajo terpeni s polarnimi funkcionalnimi skupinami, medtem ko absorpcijo lipofilnih zdravil bolj izboljšajo ogljikovodiki terpeni. 31 Vendar je bilo ugotovljeno, da je ogljikovodik terpen učinkovitejši od ketonov in oksid terpena, kar je mogoče pripisati nižji termodinamični aktivnosti ketonov v gelih. Prisotnost dokončnih ogljikovodikovih repnih skupin poleg polarne skupine glave naredi strukture geraniola in nerolidola primerne za motnje lipidne pakiranja SC, kar omogoča prodiranje natrijevega diklofenaka skozi celotno debelo kožo trebuha samca podgane. 31 Terpeni, ki se pojavljajo v bazilikem olju, predstavljajo alkoholno skupino, ki jim omogoča bolj konkurenčno interakcijo z amidnimi skupinami kožnih ceramidov kot terpeni s karbonilno skupino. 32 Vodikova vez med terpeni in kožnimi ceramidi zrahlja tesne stike lipidnih plasti in ustvari nove poti za molekularno permeacijo. V nasprotju s temi ugotovitvami je bilo ugotovljeno, da so geraniol, timol in olje nageljnovih žbic pokazali nižje razmerje izboljšanja kot kafra, kljub temu, da ta olja vsebujejo več alkoholnih kisikovih atomov. 32 Mehanizem za povečanje permeacije imipramin hidroklorida po hrbtni koži podgan s terpeni (mentol, terpineol) je bil predlagan kot prekinitev mreže vodikovih vezi na glavah ceramidov. 33 V primeru mentona, pulegona, karvona in cineola pa so prisotni le deli, ki sprejemajo vodikove vezi (karbonilne ali etrske skupine), kar vodi do manjšega prekinitve mreže vodikovih vezi med ceramidnimi glavami. 33 Študije o mehanizmu delovanja eteričnih olj in njihovih aktivnih spojin za povečanje penetracije so pokazale, da fizikalno-kemijske lastnosti permeantnih molekul poleg lastnosti ojačevalcev bistveno spremenijo prepustnost molekule po koži in ustvarjajo različne mehanizme delovanja. .

Eterična olja kot pospeševalci prodiranja v kožo

Izkazalo se je, da so eterična olja uspešna pri zagotavljanju vrste različnih zdravil po koži, vključno z: 5-FU, ibuprofenom, aminofilinom, p-aminobenzojsko kislino, labetolol hidrokloridom, flurbiprofenom, piroksikamom, trazodon hidrokloridom, estradiolom, ketokonazolom, klorheksidin kloridom. nitrendipin, natrijev diklofenak, indometacin, benzojska kislina in karvedilol (tabela 1).

Niaouli olje (10 % w/w) je bilo najboljši promotor permeacije za estradiol med vsemi testiranimi eteričnimi olji

Med glavnimi terpenskimi komponentami niaoulija (1,8 cineol, α-pinen, α-terpineol, d-limonen) je bil 1,8-cineol najboljši spodbujevalec prepustnosti kože za estradiol

Mešanice terpenov (1 – je vseboval 62 % 1,8-cineola, 20 % α-pinena, 10 % α-terpineola, 7,4 % d-limonen in 2 – je vseboval 69,2 % 1,8-cineola, 22,5 % α-pinena, 8,3 % d-limonen) je pokazal podoben čas zamika kot pri eteričnem olju niaouli in znatno nižjo permeacijo

A. oxyphylla eterično olje je znatno povečalo vnos indometacina v kožo pri koncentracijah 3 in 5 %

Visokopolarna frakcija (soksigenirani seskviterpeni) A. oxyphylla eterično olje je pokazalo večjo izboljšanje in sposobnost povečanja vnosa v kožo kot frakcija nižje polarnosti (ogljikovodiki seskviterpeni)

Frakcija z nizko polarnostjo (estragol, skvalen, α-bergamoten, θ-muurolen) in visokopolarna frakcija (fitol, d-linalool, butilirani hidroksitoluen, (+)-epi-bicyclosesquiphellandrene) je povečala prepustnost indometacina v kožo

Frakcija z nizko polarnostjo se je izkazala za učinkovitejšo in učinkovitejšo krepitev

Izboljšanje učinka kardamonovega olja je bilo odvisno od njegove koncentracije, 1% (v/v) koncentracija je bila učinkovitejša od 0,5% (v/v) eteričnega olja

Kardamomovo olje ima okrepilni učinek, ki je odvisen od pH topila, indeks penetracije pri pH 5,8 in pH 7,4 z 1 % kardamomovega olja je bil najvišji za piroksikam, sledita mu indometacin in nato diklofenak

Malo je študij, ki bi primerjale delovanje eteričnih olj s kemičnimi ojačevalci penetracije za pronicanje zdravil skozi kožo. Krepitev učinka Rhizoma Et Radix Notopterygii eterično olje (5 %) pri permeaciji palmatinijevega klorida je bilo večje kot pri azonu. 46 Ločeno uporabljeno delovanje eteričnega olja fructus cnidii in azona je dalo enako intenzivnost absorpcije metronidazola, medtem ko je njuna kombinacija povzročila večji prodor metronidazola skozi kožo. 47 Ugotovljeno je bilo, da je okrepilni učinek olja evkaliptusa, poprove mete in terpentina manjši kot pri azonu, vendar so vsa testirana olja povečala permeacijo 5-FU skozi izrezano kožo podgan. 48 Razmerje povečanja je bilo naslednje: azon – 89,45, olje evkaliptusa – 59,63, olje poprove mete – 45,2 in terpentinsko olje – 27,16.

Spojine eteričnih olj kot ojačevalci prodiranja v kožo

Naravne spojine iz eteričnih olj, kot so terpeni (monoterpeni, seskviterpeni, diterpeni, triterpeni), so bile predlagane kot obetavni netoksični, nedražeči ojačevalci transdermalne penetracije za lipofilna in hidrofilna zdravila. 13, 49 Izkazalo se je, da so terpeni iz eteričnih olj uspešni pri dajanju različnih zdravil po koži, vključno z: nikardipin hidrokloridom, 5-FU, kofeinom, hidrokortizonom, triamcinolon acetonidom, natrijevim diklofenakom, propranolol hidrokloridom, srebrovim sulfadiazinom, kurkumininom, haloperidol, dihidrotestosteron, sumatriptan sukcinat, azidotimidin, imipramin hidroklorid in tamoksifen (tabela 2).

Vrstni red učinka povečanja nikardipinijevega klorida je bil limonen & gt nerolidol & gt fenchone & gt timol

Vsebnost karbamazepina v koži so znatno povečali nerolidol, limonen, timol in fenhon

Pri nobenem od terpenov kot ojačevalcev niso ugotovili pomembnega povečanja vsebnosti hidrokortizona in tamoksifena v koži

Kombinacija terpenov v propilen glikolu je znatno izboljšala prepustnost kofeina in hidrokortizona skozi mišjo kožo

(+)-neomentol in geraniol sta povečala permeacijo med 13-krat in 16-krat in se izkazala za najučinkovitejša sredstva za povečanje penetracije kofeina med vsemi drugimi terpeni

(+)-terpinen-4-ol in α-terpineol sta bila učinkovita ojačevalca za perkutano penetracijo hidrokortizona in povečano permeacijo med 3,9- in 5-kratno

Preiskane spojine niso bistveno povečale oddajanja triamcinolon acetonida, najbolj aktivna spojina alfa-terpineol je povečala oddajanje le 2,5-krat, medtem ko je naslednja najbolj aktivna spojina (+)-karvon povečala oddajanje le 1,7-krat

Razvrstitev učinka povečanja za natrijev diklofenak za 2,5 % (v/v) terpene je bila nerolidol & gt farnezola & gt karvona & gt metona & gt limonena, medtem ko je bil pri nizki koncentraciji 0,25 % terpenov vrstni red farnesol & gt karvona & gt nerolimodola

Najbolj izjemen ojačevalec penetracije je bil nerolidol, ki je zagotovil skoraj 198-kratno povečanje koeficienta prepustnosti natrijevega diklofenaka, sledil mu je farnesol z 78-kratnim povečanjem

Propranolol hidroklorid je pokazal primerljive čase zamika z mentolom pri 1%, 5% in 10% w/v koncentracijah

Propranolol hidroklorid je pokazal 2,4 in 2,2-kratno povečanje časa zamika v primerjavi s 5 % oziroma 10 % ravnmi karvakrola

Propranolol hidroklorid je pokazal največji čas zamika (med 3,0 in 3,3 h) pri 1%, 5% in 10% w/v koncentracijah limonena

Časi zamika za PL s 5 % in 10 % koncentracijami linalola so bili 7,0- in 5,2-krat krajši v primerjavi z 1 % koncentracijo tega ojačevalca

Limonen je bil učinkovitejši od linalola in cineola (v kombinaciji s propilen glikolom) za izboljšanje prepustnosti haloperidola čez žensko človeško trebušno kožo

Linalool in cineol sta pokazala le zmerno izboljšanje in podaljšan zamik, medtem ko je limonen izboljšal prepustnost haloperidola za 26,5-krat in zmanjšal čas zamika transporta haloperidola po koži trebuha pri ženskah.

R-(+)-limonene showed a high ability to enhance in-vitro percutaneous transport of sumatriptan succinate across porcine skin

α-bisabolol shows the same enhancer effect than ethanol

Span 20, oleic acid and polyethylene glycol 600 have shown moderate enhancing activity on transdermal flux of sumatriptan succinate

5% thymol, carvacrol, trans-anethole, L-menthol and linalool were found to enhance the transdermal transport of azidothymidine

There was no correlation between the amount of azidothymidine (30 mg/ml) in isopropyl : water (60 : 40 v/v) retained in the skin and the enhancers levels (0–10% w/w)

Also novel vesicles, invasomes prepared by phospholipids, small amounts of ethanol and terpenes/terpene mixture as enhancer have been described for transdermal drug delivery. 63 Invasomes have higher penetration rate through the skin as compared with liposomes and ethosomes. These vesicles have shown to possess the combined advantages of liposomes, which are potential carriers and penetration enhancement of the terpenes, which are having the ability to modify the order of SC packing thus promoting skin delivery. 64 Invasomes with 1% terpenes (limonene, carvone, nerolidol) showed two-fold higher deposition of finasteride in the SC when compared with the ethanolic solution and 3.5-fold higher deposition when compared with conventional liposomes. 65 Moreover, formulation containing limonene (0.5%) enhanced permeation by 21.17 fold when compared with control (aqueous solution). In-vitro skin penetration study revealed that invasome composed of non-hydrogenated soybean lecithin, ethanol and 1% mixture of terpenes (cineole, citral and d-limonene) significantly enhanced deposition of the temoporfin in the SC compared with liposomes without terpenes. 66 Dragicevic-Curic et al. 67 reported invasomes with 1% terpenes (cineole, citral, d-limonene) delivered temoporfin 2.7-fold higher than liposomes containing 3.3% ethanol. Ultradeformable liposomes with monoterpenes (d-limonene, 1,8-cineole, geraniol) significantly improved fluorescein sodium penetration through the skin. 68 Invasomes could be use to increase the permeation of the active substances encapsulated in these vesicles. The effectiveness of invasomes as drug carriers was reported for ferulic acid loaded into invasomes composed of phosphatidylcholine from soybean lecithin, ethanol and terpenes (limonene, citral, cineole), 69 meloxicam encapsulated into menthosomes consisting of phospholipids, cholesterol, cetylpyridinium chloride, L-menthol 70 and temoporfin loaded into invasomes comprising of phosphatidylcholine from soybean lecithin, ethanol and terpenes (D-limonene, citral, 1,8-cineole). 71

There are few studies comparing the activity of essential oils constituents with chemical penetration enhancers for drug permeation through the skin. The study comparing the activity of essential oils constituents with chemical penetration enhancers showed that 2% menthol and 5% eucalyptus oil was effective as a natural penetration enhancer when used alone, but their average penetration rate reached only half of that of 8% azone. The penetration potency of either menthol oil or menthol combined with azone was more effective than that of azone alone. 72 Menthol and azone used separately can remarkably enhance the percutaneous absorption of indomethacin and the enhancing effect is stronger when they are used in combination. 73 In the other hand, 2% azone and 5% propylene glycol are better penetration enhancer for ibuprofen than menthol and borneol. 74

Skin irritancy and toxicity due to permeation enhancers: essential oils and their compounds

Many potent skin penetration enhancers due to their ability to disruption the corneocytes or highly ordered lipid bilayers of the SC are associated with cytotoxicity, skin irritation, allergic reaction which limiting their clinical application. In general, the potency of penetration enhancers in causing skin irritation scales increases proportionally with their ability to cause skin disruption. 75 Therefore, it is important to find an optimum balance between the safety and potency of chemical enhancers. Some essential oils can cause skin irritation and allergy which is closely associated with their increasing concentration. Adverse reactions may be minimized by topically applying only diluted essential oil in lowest possible concentration and their safety / toxicity should be confirmed by research. 76

Formulation Backhousia citriodora (lemon myrtle) essential oil in 1% concentration was found to be low in toxicity against primary cell cultures of human skin fibroblasts and human fibroblast cell line derived from normal skin (F1-73) as well as their application to human full-thickness abdominal skin discs (4.9 cm 2 ) at 8 h exposure indicated limited damage of epidermal cells. 77, 78 The in-vivo skin tolerance study determined by transepidermal water loss and colorimetry confirmed that no irritation of the skin was detected when using Magnolia fargesii essential oil as enhancer for transdermal absorption of theophylline and cianidanol. 79 Also theophylline and cianidanol components of M. fargesii essential oil showed low or negligible cytotoxicity. Carvacrol and thymol poses cytotoxic, genotoxic and DNA-protective effects on human hepatoma HepG2 and Caco-2 cells cultured in vitro. 80 Eugenol and borneol showed cytotoxicity, genotoxicity as well as DNA-damaging in three different cell lines, HepG2 cells, Caco-2 cells and non-malignant human VH10 fibroblasts. 81 Major components of clove (Syzygium aromaticum) essential oil – eugenol (78 %) demonstrates cytotoxic properties towards human fibroblasts and endothelial cells. 82 Knight and Hausen 83 found that among all tested constituent of tea tree oil (limonene, α-terpinene, aromadendrene, terpinen-4-ol, str-cymene, α-phellandrene, d-carvone) only d-carvone caused no allergy reactions. Among 11 patients, all of them was reactive to 1% tea tree oil, six patients reacted to limonene, five to a-terpinene and aromadendrene, two to terpinen-4-ol and one each to str-cymene and α-phellandrene. Prashar et al. 84 demonstrated that lavender (Lavandula angustifolia) oil composed of linalyl acetate (51%) and linalool (35%) is cytotoxic to human skin cells in vitro (endothelial cells and fibroblasts) at a concentration of 0.25% (v/v) and causes membrane damage. Moreover linalyl acetate cytotoxicity was higher than that of the essential oil itself, suggesting suppression of its activity by an unknown factor in the oil. Cytotoxicity of Melaleuca alternifolia oil and its major oxygenated monoterpenes: terpinen-4-ol, 1,8-cineole and α-terpineol were investigated on different human cell lines (HepG2, HeLa, MOLT-4, K-562, CTVR-1). 85 The overall rating for cytotoxicity of tea tree oil and its components was α-terpineol > tea tree oil > terpinen-4-ol > 1,8-cineole and with comparison with the controls used mercuric chloride > tea tree oil > aspirin. Aydm et al. 86 investigated the modulating effects of thyme and its major components (thymol, carvacrol, γ-terpinene) against the oxidative DNA damage induced by H2O2. Concentrations above 0.1 mM thymol and γ-terpinene and 0.05 mM carvacrol significantly induced DNA damage in human lymphocytes, but at the smaller concentrations no additional DNA strand breakage has been observed. At all concentrations studied, γ-terpinene did not show any protective effect against H2O2 induced oxidative DNA damage, but the phenolic compounds thymol and carvacrol at concentrations below 0.2 and 0.1 mM, respectively, significantly reduced the oxidative DNA damage.

Antitumor activity of essential oils and their compounds

Some essential oils and their constituents are known as potential anticancer agents. Aniba rosaeodora essential oil highlights the potential skin anticancer activity against human epidermoid carcinoma cell line (A431) and HaCaT cells, which were killed after addition of essential oils and the same treatments had only a minor cytotoxic effect on transformed normal HEK001 keratinocytes and primary Normal Human Epidermal Keratinocytes (NHEK). 87 Sideritis perfoliata, Satureia thymbra, Salvia officinalis, Laurus nobilis in Pistacia palestina essential oils and some identified terpenes (trans-caryophyllene and α-humulen) inhibit human tumour cell growth (amelanotic melanoma C32, renal cell adenocarcinoma ACHN, hormone-dependent prostate carcinoma LNCaP, MCF-7 breast cancer cell lines). 88 Cinnamaldehyde isolated from the stem bark of Cinnamomum cassia has been shown to inhibit tumour cell proliferation by transduces the apoptotic signal via reactive oxygen species generation, thereby inducing mitochondrial permeability transition and cytochrome c release to the cytosol. 89 On the other hand, there are numerous studies showing the toxicity of essential oils and active components of essential oils, for example, origanum essential oil exhibited high levels of cytotoxicity against four permanent animal cell lines including two derived from human cancers, 90 Melissa officinalis essential oil exhibited cytotoxicity against human cancer cell lines (A549, MCF-7, Caco-2, HL-60, K562) and a mouse cell line (B16F10), 91 Schinus molle essential oil was cytotoxic on breast carcinoma and leukemic cell lines by a mechanism related to apoptosis. 92

Transdermal systemic toxicity of permeation enhancers: essential oils and their compounds

Toxicity of essential oils and their active constituents to a large extent depends on their concentration and chemical structure. Therefore, fairly toxicological and applicable studies let get a clear answer about their safety and use as enhancers for drug permeation through the skin. On the other hand, essential oils and their constituents can easily penetrate through the skin into the bloodstream however, they are easily excreted from the body with urine and feces. 93-95 Major components of lavender (linalyl acetate and linalol), tea tree (γ-terpinene and terpinen-4-ol), grapefruit (limonene) and cypress oils (α-pinene and 3-carene) from aroma bath showed that their dominant percutaneous absorption were observed after 10–20 min bathing of mice. 93 Limonene from grapefruit oil showed the highest degree of percutaneous absorption, and was detected not only in blood but also in brain and lung after 20 min bathing of mice. Also, main constituents of lavender oil (linalool and linalyl acetale) from massage oil penetrates the skin of a male volunteers, and their maximum concentration were detected in the blood after 20 min. 94 However, 90 min after the end of massage, most of the lavender oil constituents was eliminated from the bloodstream. The disposition of citral from essential oils was studied in male rats after dermal treatments. 95 The study showed that 5 min after the treatment, no unmetabolized citral was detected in their blood. It is worth mentioning that more citral was eliminated in the feces than in the urine. The fact that after application to the skin, essential oils and their components are rapidly metabolized, not accumulated in the organism and fast excreted strongly suggest that they can be successfully use as safe penetration enhancers.


CHEMICALS (frequently not natural but synthetic)

ABSORBED through the skin of animals. NOTE: human skin is far less permeable than animal skin. Benzyl acetate, benzoic acid, camphor, d-carvone, cinnamic acid, coumarin, para- cymene, d-limonene, methyl salicylate, &alpha-phellandrene, terpineol, (&alpha-&beta-pinene & camphene at 150 ml. see para. 3). d-limonene only 3% was absorbed in vitro across isolated human skin, while in rats the figure was 6%. 6 AUTHORS NOTE: One probably gets higher levels of d-limonene in the blood from eating orange flavoured drinks, sweets, cakes, liqueurs, etc.

NOT ABSORBED: linalool within 2 hours of application. 7 d-pulegone in pennyroyal, carvacrol in some thymes and mints, eugenol, isoeugenol & methyl benzoate in clove, tuberose and ylang, fenchone in anise, fennel & some lavenders, geraniol in geranium & palmarosa. Those chemicals in extra bold are considered by some to be the "active" components in our most important essential oils. I do not agree that this is the case, as I consider them to be just a part of the package of chemicals that give essential oils their properties.

Evening primrose (fixed oil) not absorbed through the highly permeable skin of premature babies, but it was thought that water and oil emulsions (creams or lotions) may be more favourably absorbed. 8


Skin serum: What it can and can’t do

Many things improve with age unfortunately, your skin is not one of them. Wrinkles, brown spots, and general dullness often start to creep in as the years tick by. To reverse these problems many women are turning to a skin serum. Serums are light, easily absorbed oil- or water-based liquids that you spread on your skin. They typically come in small bottles with a dropper, and you only need a few drops to treat your whole face.

A skin serum is not a moisturizer, like a lotion or cream, says Dr. Abigail Waldman, instructor of dermatology at Harvard Medical School. Rather, they are highly concentrated formulations that are designed to sink into the skin quickly, delivering an intensive dose of ingredients that can address common skin complaints. “I definitely recommend serums for anyone who is concerned about aging. It’s a really good way to get extra anti-aging effects, more than your typical moisturizer and sunscreen,” says Dr. Waldman.

How do you choose and use a skin serum?

Serums are typically applied to skin after cleansing but before moisturizing, says Dr. Maryam M. Asgari, associate professor in the department of dermatology at Harvard Medical School. Some serums have one main ingredient, while others, including those that target the signs of aging, are combination formulas. “I use and recommend serums that have a combination of vitamin C, vitamin E, and ferulic acid,” says Dr. Waldman. “There is good literature that shows that vitamin C in particular can prevent brown spots, reverse damage from ultraviolet rays, and stimulate the growth of new collagen.”

Other good skin serum options to target wrinkles are those with antioxidants including tea polyphenols and resveratrol. Retinol, which reduces inflammation, is another good option, as is niacinamide.

If you are looking to fight blotchiness and discoloration, look for formulas that can brighten and lighten dark patches, including kojic acid and glycolic acid. If your skin is dry, tight, and flaky, find a skin serum that contains vitamin E, niacinamide, and glycolic acid. Also look for ceramides, which are fatty molecules that help hold the skin together and keep moisture from escaping. Other good options are serums that contain hyaluronic acid, or those with collagen peptides, epidermal growth factors, or stem cells.

Are all skin serums created equal?

Not all serums work the same. How well they work depends on the active ingredients, the formulation, the vehicle, and the stability of the compound, says Dr. Asgari. The prices of serums vary from less than $20 to hundreds of dollars. “To be honest, I don’t think price makes a difference,” says Dr. Waldman. More important than price are the ingredients in the serum — so the best practice is to read labels to find the best formulation for your needs.

Caveats when using a skin serum

“Powerful ingredients can irritate sensitive skin,” says Dr. Asgari. “Always test a small area before you apply a skin serum widely.” And use caution when combining acid-containing serums with other products that also contain acids. For example, your skin may get irritated if you use a serum with vitamin C (which is acidic) and as well as a retinol cream, or if you use a retinol serum along with a prescription retinol cream.


Mechanism of Fat Absorption in Human Body (With Diagram) | biologija

Most dietary fat of either vegetable or animal origin comprises of triglycerides in which glycerol is com­bined in low-energy ester linkages with three fatty acids and the fatty acids are of even number of carbon atoms. Fatty acids are both saturated and unsaturated which are almost entirely palmitic and stearic in case of former and in case of the latter oleic and linoleic acids. These are long-chain fatty acids. Milk fat contains 3 -10% (C4 – C14 acids) contributing shorter-chain fatty acids.

Since fats are insoluble in water and immiscible in chyme, so fat neither is absorbed as such nor is digested by lipase (due to lack of contact with lipase) to fatty acid and glycerol for absorption. Emulsification of fat by different emulsifying agent is required for preparing it suitable for both digestion and absorption and this process (emulsification) possible in small intestine where bile salt and other agents are present.

Bile salts themselves are relatively weaker than the mixture of bile salts and a polar body—lecithin, lysolecithin or monoglycerides as emulsifying agent. The latter two are produced by the action of pancreatic lipase on lecithin or triglycerides. Thus the enzymic action tends to stabilize the emulsion.

So fat digestion and absorption do not occur in stomach significantly which is devoid of emulsifying agent but natural (milk fat) or artificial emulsions are digested in the stomach. Recent studies account for many aspects of fat absorption better than previous supposition.

Aspects of Fat Absorption:

It has been observed that:

(1) Fatty acid is absorbed more readily than any other components, i.e., triglycerides, I-monoglycerides, 2-monoglycerides, diglycerides and free fatty acids (which are formed in the sample collected near- the duodeno-jejunal junction) and

(2) The hydrolysis occurring in the lumen is faster than the absorption of free fatty acid.

(3) There is spontaneous migration of fatty acids from one alcohol group to another in the glycerol.

The chief products of luminal hydrolysis of triglycerides are 2-monoglycerides and free fatty acid. Glycerol and 1-monoglycerides are quantitatively less important while fat is undergoing digestion and absorption. The fat is distributed among the emulsified fat droplets, micells (small), hydrated polymolecular aggregates and molecular solution. Micells of intestine contain three major components as bile salts, monoglycerides and fatty acids.

The salts spontaneously aggregate with monoglycerides and form micells when the concentration of bile salts attains a certain value known as critical micellar concentration. Since the concentration of conjugated bile salts remains always higher than the critical micellar concentration (at ordinary circumstances), the mono­glycerides rapidly form micells as soon as they are liberated from triglycerides by lipase actively with bile salt.

As the micelle once formed it dissolves free fatty acid, cholesterol and fat-soluble vitamins and dissolution varies directly up to a limit with the amount of monoglyceride contained in it. But the unconjugated bile salt has got higher critical micellar concentration for which fat absorption is inhibited when bile salts are deconjugated in the gut.

The inhibition of absorption of fat (due to de-conjugation) is for the inability of micellar solution at this condition of holding monoglycerdies and free fatty acids liberated from lipolysis and thereby these are precipitated and become unavailable for absorption.

Lipid molecules in solution can diffuse into the epithelial cells through its lipoprotein membrane. So the metabolic machinery contained in the endoplasmic reticulum of the cell takes up monoglycerides and free fatty acid and rapidly synthesizes them into triglycerides. Diffusion gradient from lumen to cell down which free fatty acid and monoglycerides flow is present till the completion of absorption.

The gradient is produced by immediate replacement of monoglycerides and free fatty acids in the solution from the micellar phase as they leave the luminal solution and consequently the luminal solution remains saturated with free fatty acid and monoglycerides. Of the fat digestion products, the monoglycerides and fatty acids are separated from micells to be absorbed in the duodenum and jejunum and conjugated bile salts only in the terminal ileum.

The bile salts being insoluble in the cell membrane (due to their charge) must be actively transported. The rate of their absorption is proportional to their solubility and hence the more soluble monoglycerides are absorbed first and then follow other substances in the order of their solubility, viz., long-chain fatty acid, cholesterol, short and medium-chain fatty acids.

And the triglycerides of these acids are absorbed without passing through the micellar phase since they are relatively solution as well as in the cell membrane. Fat aggregation does not take place in the space between the microvilli and endoplasmic reticulum when fat re-synthesis occurs. Lysolecithin enters into the mucosal cell as such and its base is separated there by phosphodiesterase and its fatty acid by lysophosphatidase and finally glycerol and phosphate are separated by non-specific phosphatase.

Within the cells monoglycerides without further hydrolysis (of long-chain fatty acid) are resynthesized to triglycerides or phospholipids. The shorter-chain fatty acid ester is hydrolised by lipase (intracellular) and not those of long-chain fatty acids, (i.e., dietary fat). Mucosal cells can synthesis long-chain fatty acid, i.e., stearic acid (C18) from acetic acid as well as palmitic acid (C16) to stearic acid (C18) with acetic acid.

Glycerol liberated in the lumen by hydrolysis of triglycerides is partly oxidized in mucosal cell to CO2 and partly goes to liver for its conversion to glycogen and remaining is utilized in the re-synthesis of triglycerides. The glycerol required for the re-synthesis of triglycerides is also derived from glucose (glycolytic path). Resynthesized fat is absorbed into the lymph.

Intracellular Fat Transport:

After re-synthesis, the fats are accumulated more in the apical cells of the tip of villi than at the sides and they are restricted in the supranuclear part of the cell. It appears first as discrete particles in the endoplasmic reticulum. Microsomes derived from the reticulum contain enzymes which resynthesize triglycerides.

So fat is seen to be deposited in the reticulum. Re-synthesis and absorption take place simultaneously. The entire reticulum is filled with fat droplets and then the fat moves to the supranuclear part of the cell acquiring along its way an envelope of phospholipid and protein and finally they are expelled from the sides of the cell at or below the level of the nucleus.

Droplets of fat known as chylomicron is formed (aggregation of fat molecules) before the delivery of resyn­thesized fat into lymph.

The droplets are enclosed in a membrane, composed of small amount of protein, free cholesterol and sat­urated triglycerides in a monolayer of phospholipid. The fat in the chylomicron reflects the composition of ingested fat (dietary) partly since long-chain fatty acids of the dietary fat are added to mucosal cells for re-syn­thesis whereas most of short and medium-chain fatty acids and some glycerol are shunted to portal blood. Water-soluble components of fat diffuse into capillaries of the villi which are fenestrated.

The gap in the fenestra formed by an uninterrupted basement membrane envelope the endothelium and the fenestrae are possible gateway for entry of water-soluble compounds into the capillary blood Chylomicron cannot enter the fenestrae due to its particle size. It enters the lacteals through open channels existing between interstitial spaces and the lymphatic lumen. Although the endothelial wall of lacteals is relatively thick but there is absence of envel­oping basement membrane and presence of intercellular space. The fat droplets pass through these spaces.

(The cells forming the walls of the lacteal contain many vesicles which may be capable of carrying fat droplets across them due to their pinocytotic property.)


Vaseline Intensive Care Dry Skin Lotion

Ingredients from packaging: ACTIVE INGREDIENT: ETHYLHEXYL P-METHOXYCINNAMATE (SPF 5). OTHER INGREDIENTS: WATER, GLYCERIN, STEARIC ACID, GLYCOL STEARATE, SUNFLOWER SEED OIL, SOYA STEROL, LECITHIN, TOCOPHERYL ACETATE, RETINYL PALMITATE, DIMETHICONE, GLYCERYL STEARATE, CETYL ALCOHOL, TEA, MAGNESIUM ALUMINUM SILICATE, FRAGRANCE, CARBOMER, STEARAMIDE AMP, CORN OIL, METHYLPARABEN, DMDM HYDANTOIN, IODOPROPYNYL BUTYLCARBAMATE, DISODIUM EDTA, PG, BHT, TITANIUM DIOXIDE, YELLOW NO. 10.

By selecting organic and natural products for yourself and your family, you are taking a big step toward a healthier lifestyle. The developing organs of babies and children are particularly sensitive to chemicals so it is especially important to use safe products for your youngsters. Down to Earth has a wide selection of natural and organic body care products. Look for even more in the near future as our team is working hard to ensure that DTE carries the purest products available.


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