C vitamin

Ta tema vsebuje 16 odgovorov, ima 5 glasov, in jo je nazadnje posodobil/a Profile photo of Nina Nina 6 let, 8 mesecev nazaj.

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  • #3599
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    Nina
    Upravitelj

    C vitamin ali askorbinska kislina je vodotopen vitamin. V obliki iona- kot askorbat, deluje antioksidativno, lovi proste radikale. Pomemben je tudi pri sintezi kolagena in pri zaviranju pigmentacije.
    Za vgrajevanje v kozmetične izdelke je vitamin C neprimeren, ker je zelo nestabilen- pod vplivom svetlobe, zraka se pretvori v neaktivno obliko. V kozmetičnih izdelkih se zato ponavadi uporabljajo estri vitamina C z maščobnimi kislinami, npr. askorbil palmitat.

    VITAMIN C

    #23894
    Profile photo of Nina
    Nina
    Upravitelj

    Na kratko: kožni pigment melanin (dve vrsti: feumelanin in eumelanin) nastaja iz aminokisline tirozin (to sintezno pot sestavlja več stopenj).

    Vitamin C zavira pigmentacijo na večih mestih v sintezni poti melanina, in sicer:
    1. zavira encim tirozinazo, ki je v dveh stopnjah ključna za pretvorbo aminokisline tirozin v naslednje intermediate (ki se po večih stopnjah spremenijo v melanin)
    2. spreminja določene intermediate v tej sintezni poti in tako še dodatno blokira nastanek melanina
    3. spreminja (reducira) že sintetiziran melanin v svetlejšo obliko

    KRATKA SHEMA

    DOLGA SHEMA

    Upam, da tole nisem preveč zakomplicirala.. :einstein: :blush2:

    #23895
    Profile photo of nejka
    nejka
    Član

    Kaj veš, kako vpliva vitamin C na sintezo kolagena? :flower2:

    #23896
    Profile photo of Nina
    Nina
    Upravitelj

    Sinteza kolagena (poenostavljen prikaz):

    1. osnovna veriga PROKOLAGEN (to še ni kolagen) je sestavljena iz različnih aminokislin
    2. na določene aminokisline prokolagena se pripnejo -OH skupine
    3. na te -OH skupine se vežejo sladkorji, nastane trojna vijačnica
    4. ta trojna vijačnica se izloči iz celice kot TROPOKOLAGEN
    5. iz tropokolagena nastanejo KOLAGENSKA VLAKNA

    Druga točka: hidroksiliranje (to je pripenjanje -OH skupin) je odvisno od prisotnosti vitamina C.

    #23897
    Profile photo of nejka
    nejka
    Član

    Hvala! Vse jasno. :flower2:

    #23898
    Profile photo of nejka
    nejka
    Član

    Imam še eno vprašanje glede C vitamina. :blush1:
    Vitamin C fosfat in vitamin C glukozid sta derivata C vitamina in baje zelo obstojna, drži?

    #23899
    Profile photo of Nina
    Nina
    Upravitelj

    Ja, derivati vitamina C so bolj obstojni. Vitamin C deluje sicer kot antioksidant samo v obliki iona (askorbata), vendar je v prosti obliki zelo slabo obstojen. C vitamin se iz vezane oblike sprosti po aplikaciji na kožo.

    #23900

    Najprej pohvale za tak strokoven forum :flower2: sicer sem pa na internetu brala, da se da narediti tudi tak homemade serumcek z vitamnom c.. voda+vitamin c v prahu (baje se ga da v lekarni, dm-u dobit)..+verjetno še nekaj alkalnega, da ni tok kisel ph? in to naneseš na kožo..
    Pa me zanima, Nina, če je to ok? oziroma če ima vitamin c v taki obliki učinek?

    #23901
    Profile photo of timnala
    timnala
    Udeleženec

    Tocno to, sem hotla vprasat..sem zasledila to kao kuro z vitaminom C..kupi se pa v prahu v DMu..in si ga nanasas na obraz.
    Me pa tudi zanima kolk je to ok in ce ja, kako se sploh to pripravi :read:


    vir

    #23902
    Profile photo of Nina
    Nina
    Upravitelj

    Odvisno v kakšni obliki je vitamin C v tem prahu…ampak jaz sem malo skeptična. Se mi zdi, da bi pri taki stvari bilo potrebno več parametrov prej preverit preden to naneseš na kožo – najprej sploh določit koncentracijo (tudi glede na to v kakšni obliki je vit.C), potem pa še ta reč s pHjem…morali bi pH zmerit, ker kar tako na pamet nima smisla dodajat karkoli za uravnavanje. Razen če kje obstajajo recepture, ki so že preverjene in je vse preračunano…
    kakšne so pa količine, ki jih navajajo po netu..?

    #23903

    je kar nekaj nekaj takih “receptov” na netu :P recimo:
    Make your own Vitamin C serum

    The recipe makes an approximate 10% concentration of vitamin C serum, using simple ingredients you can buy from your local Chemist store. The advantages of doing it yourself – apart from the obvious – ‘it will save you a lot of money’ is that you can make it fresh, store it in your refridgerator and know that it will not have oxidised- so in fact you will get fresh active product onto your skin. It is best only to make up small quantities at a time, to ensure it is always fresh and unoxidised.

    Take care- these are active ingredients At this concentration it will have a relatively low ph, and in some people this will be too irritating for the skin. If this is the case, try making a half or even quarter concentration to start with. Use this for a week or two until you know you skin is tolerating this, and then slowly increase to a higher concentration. If after you apply it, you find your skin is tingling excessively, wash off immediately.

    The recipe is divided into active ingredient, the one that has been shown to stimulate collagen, reduce fine lines and wrinkles and protect against sun damage and a simple base formula. Any product you buy over the counter with active ingredients consists of this.

    Vitamin C serum Active Ingredient : 1-1.2 grams Vitamin C (L-ascorbic acid) (approximately 1/4 teaspoon) (The active ingredient must be L-ascorbic acid, not vitamin C tablets, or calcium Ascorbate) This can also be purchased from Skin Actives.

    Base Ingredients. 5 ml glycerine (1 teaspoon) 5ml water (1 teaspoon) You should be able to buy both the L-ascorbic acid and glycerine from your chemist store.

    Process. 1. Dissolve 1gram of L-ascorbic acid in 5 ml of water (preferably distilled), in small glass container using a stirrer. Make sure it is fully dissolved before proceeding to next step.

    2. Add 5 ml of glycerine and mix.

    3. Put in a sealable jar, (not clear glass as this allows light in, and light degrades vitamin C.) Store in cool dry place.

    Voila – your own fresh vitamin C serum. Apply to skin once per day to start with (preferably at night), and increase to twice daily if tolerated. (vir:http://www.natural-skin-care-info.com/vitamin-c-serum.html)

    Tole sem pa nasla na enem izmed slovenskih forumov
    Najboljša koncentracija je 20% raztopina in pH od 3,5 do 4,5.

    Torej – voda, L-askorbinska kislina in soda bikarbona ali mešanica alkalnih mineralov (oboje za zbijanje kislosti oz. višanje pH-ja). V Sanolabroju nabavite pH lističe in mešajte Smile

    Vsak pripravek naredite tik preden ga nanesete na obraz, ne puščajte ga niti za uro. Vitamin C hitro oksidira in oksidiran pripravek povzroča ravno obratno od željenega – torej pospešuje oksidacijo oz. staranje.

    Ker vitamin C deluje pod kožo še 72 ur po nanosu, je dovolj tudi, če pripravek nanašate vsak tretji večer, vendar nikoli pogosteje kot na 24 ur.
    Edina pomanjkljivost je ta, da je askorbinska kislina vodotopni vitamin C, koža pa potrebuje še topnega v maščobi (npr. ascorbyl palmitate). (vir:http://www.diva.si/forum/viewtopic.php?t=9225&postdays=0&postorder=asc&start=885)

    #23904
    Profile photo of Nina
    Nina
    Upravitelj

    1. recept – 10% je maksimalno, kar bi jaz doma home made mešala..če se tega lotite, bolje, da začnete z manj. Shranjevanje nima smisla – bolje uporabiti takoj..ne vemo, kaj se s tem izdelkom dogaja in kako je stabilen..potrebne bi bile stabilnostne študije, zato se mi zdi bolj varno, da se takega izdelka ne shranjuje (pa še vit. C je glede obstojnosti problematičen).

    Tole sem pa nasla na enem izmed slovenskih forumov
    Najboljša koncentracija je 20% raztopina in pH od 3,5 do 4,5.

    Torej – voda, L-askorbinska kislina in soda bikarbona ali mešanica alkalnih mineralov (oboje za zbijanje kislosti oz. višanje pH-ja). V Sanolabroju nabavite pH lističe in mešajte Smile

    Vsak pripravek naredite tik preden ga nanesete na obraz, ne puščajte ga niti za uro. Vitamin C hitro oksidira in oksidiran pripravek povzroča ravno obratno od željenega – torej pospešuje oksidacijo oz. staranje.

    Ker vitamin C deluje pod kožo še 72 ur po nanosu, je dovolj tudi, če pripravek nanašate vsak tretji večer, vendar nikoli pogosteje kot na 24 ur.
    Edina pomanjkljivost je ta, da je askorbinska kislina vodotopni vitamin C, koža pa potrebuje še topnega v maščobi (npr. ascorbyl palmitate)

    2. recept – 20% je preveč, kar tako dodajati, mešati in s pH listki meriti pH ni dobro, ker lahko v želji po desaganju pravega pHja dodate preveč ene ali druge sestavine! Najprej raztopiti vit. C…potem preveriti pH…potem pa če je potrebno dodati kaj za zvišanje pHja.
    Postara glih ne :silly: , postane pa neaktiven. Askorbil palmitat je obstojnejši – vitamin C pa je vedno topen v vodi in ne v maščobah :wink1: . Askorbil palmitat razpade na vitamin C po nanosu..in koža v vsakem primeru dobi “enak” vitamin C (torej vodotopen).

    #23905

    Z vsem dolžnim spoštovanjem do gospe Nine, bi v korist ostalim uporabnikom vseeno dodala nekaj popravkov in opozorila na nepravilne trditve:

    @nina wrote:

    Postara glih ne :silly: , postane pa neaktiven.

    Oxdized and denatured ascorbic acid is not the anti-inflammatory, anti-aging, collagen-sparking primary antioxidant listed on the label — it’s an extract of rotten oranges: a rancid mix. Such ascorbic acid is not in a reduced state of potential — not simply less than it was at genesis — it is something more and different.
    Cigarettes manufacturers list “tar” alone as an ingredient in their products, but governments often spell out the real-world truth of that tar for the smoker in an additional panel detailing the categories into which 1000s of bio-available chemicals emerge once that tar is oxidized (burnt by heat in the presence of air).
    The skin has no choice but to convert oxidized ascorbic acid back into usable ascorbic acid, just as the lungs must somehow process any smoke forced into them.
    Degraded topical ascorbic acid engages progressively exhausting glucose-powered metabolic processes within the skin which burn up alpha lipoic acid, glutathione (refer Glutathione: Anti-Aging and Anti-Glycation of Skin), proline and other elements of its synergistic antioxidant system.
    Just a few days’ obtuse ascorbic acid use is enough to secure permanent damage.
    The more biologically viable the skin is to begin with the more reserves it has available to process poor materials and methods to delay readily visible changes.
    Clinically, the foolhardy look of oxidized-C users’ skins is easier to spot than smoker’s skin.
    The grey, stressed, retrained appearance is from the opposite pole of correctly employed fresh ascorbic acid, which produces incomparable photoluminescence
    .

    Individuals who insist on using rancid C are not realistic cosmetic patients, they are users treating psychological needs distinct from those of their skin, just as 40% or more of smokers are mentally ill and use cigarettes to forestall feelings of unpleasantness.

    Oxidized ascorbic acid produces considerable harm from its first application when skin care users insist on forcing habitual and failed skin care theories and practices onto the ingredient.

    Oxidized ascorbic acid accelerates skin aging by:
    • fostering decreased collagen synthesis;
    • encouraging increased collagen breakdown;
    • creating a skin environment characterized by enhanced metalloproteinase activity, responsible for rapid and unnecessary depletion of:
    o peptides;
    o growth factors;
    o antioxidant nutrients and
    o a plethora of other biologically essential molecules too poorly understood to warrant extensive modification to their volume and function.

    Vir: Melbourne Dermatology

    @nina wrote:

    Askorbil palmitat je obstojnejši – vitamin C pa je vedno topen v vodi in ne v maščobah :wink1: . Askorbil palmitat razpade na vitamin C po nanosu..in koža v vsakem primeru dobi “enak” vitamin C (torej vodotopen).

    Ascorbyl palmitate

    Ascorbyl palmitate is the most widely used fat-soluble derivative of vitamin C in skin care. It is nonirritating and more stable than vitamin C. Furthermore, ascorbyl palmitate is a fat-soluble antioxidant and is at least as effective as vitamin E in protecting the skin from lipid peroxidation (a key type of free radical damage in the skin). Unfortunately, it appears that the concentrations of ascorbyl palmitate achievable in skin care formulas do not boost collagen synthesis as much as vitamin C.

    Vir: smartskincare.com

    #23906
    Profile photo of Nina
    Nina
    Upravitelj

    @anotherexpert wrote:

    Z vsem dolžnim spoštovanjem do gospe Nine, bi v korist ostalim uporabnikom vseeno dodala nekaj popravkov in opozorila na nepravilne trditve:

    @nina wrote:

    Askorbil palmitat je obstojnejši – vitamin C pa je vedno topen v vodi in ne v maščobah :wink1: . Askorbil palmitat razpade na vitamin C po nanosu..in koža v vsakem primeru dobi “enak” vitamin C (torej vodotopen).

    Ascorbyl palmitate

    Ascorbyl palmitate is the most widely used fat-soluble derivative of vitamin C in skin care. It is nonirritating and more stable than vitamin C. Furthermore, ascorbyl palmitate is a fat-soluble antioxidant and is at least as effective as vitamin E in protecting the skin from lipid peroxidation (a key type of free radical damage in the skin). Unfortunately, it appears that the concentrations of ascorbyl palmitate achievable in skin care formulas do not boost collagen synthesis as much as vitamin C.

    Vir: smartskincare.com

    Pozdravljeni na forumu :)
    Z vsem spoštovanjem do vašega truda..moram vseeno poskrbeti, da mamo na arsu točne podatke :wink1:
    Mislim, da vsak, ki se spozna na sestavine ve, da je vitamin C vodotopna spojina. Kemijska formula je kakršna je. Derivati vitamina C niso enako vitamin C!! – derivate pa uporabljamo zato, da so bolj obstojni, da so topni v lipidih itn. Askorbil palmitat ni vitaminC, ampak je derivat (natančneje ester) vitamina C.
    Če sem še jaz malo pikra :cool: – noben strokovnjak ne bi na moje pisarije odvrnil s citatom, kako je vitamin C fat-soluble…in ga zamenjeval z askorbil palmitatom.

    Zgornji del pa obljubim da pregledam jutri…danes je že malo pozno..

    #23907

    Iz teksta sem (očitno napačno) razbrala, da zanikate, da je ascorbyl palmitate topen v maščobi. Moja napaka.

Za objavo odgovora morate biti prijavljeni.

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