Pumori Saokar Telang

Consultant Dermatologist, Joshi Hospital Maharashtra Medical Foundation, Jehangir Hospital, Apollo Group, Pune, Maharashtra, India


Consultant Dermatologist, Joshi Hospital Maharashtra Medical Foundation, Jehangir Hospital, Apollo Group, Pune, Maharashtra, India
Address for correspondence: Dr. Saokar Pumori Telang, Embellish, the Skin & Laser Clinic, 1st floor Sangam Project, Opp Air India office, at Sangam Ghat, Wellesley Road, Pune, Maharashtra, India. E-mail: moc.liamg
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Vitamin C is a potent antioxidant drug that can be used topically in dermatology khổng lồ treat and prevent changes associated with photoageing. It can also be used for the treatment of hyperpigmentation. Because it is unstable & difficult to lớn deliver into the dermis in the optimum dosage, research is being directed khổng lồ find stable compounds of vi-ta-min C and newer methods of delivery of vi-ta-min C into the dermis.


Keywords: Collagen synthesis, depigmentation, drug formulations, L–ascorbic acid, photo-ageing, vi-ta-min C

INTRODUCTION

Vitamin C (Vit. C) is one of the naturally occurring antioxidants in nature.<1,2> Most plants and animals are able lớn synthesise Vit. C in vivo from glucose. Humans and certain other vertebrates lack the enzyme L-glucono-gamma lactone oxidase required for in vivo synthesis of Vit. C;<3> hence, they must acquire it from natural sources such as citrus fruits, green leafy vegetables, strawberries, papaya & broccoli.<3,4> The word “Ascorbus” means no Scurvy. Traditionally, Vit. C-rich foods lượt thích lemons were carried by sailors on long journeys lớn avoid Scurvy, a disease of bleeding gums. In 1937, Dr. Albert Szent Goyrgi was awarded the Nobel Prize for his work in isolating the Vit. C molecule from red peppers và identifying its role in Scurvy.<4>

L-ascorbic acid (LAA) is the chemically active size of Vit. C. In nature, Vit. C is found in equal parts as LAA và D-ascorbic acid. These are essentially isomeric molecules và are mutually interchangeable.<4> However, only LAA is biologically active & thus useful in medical practice.<2> The absorption of Vit. C in the gut is limited by an active transport mechanism và hence a finite amount of the drug is absorbed despite high oral dosage.<3> Furthermore, bioavailability of Vit. C in the skin is inadequate when it is administered orally.<1,2> The use of topical ascorbic acid is therefore favored in the practice of dermatology.<5>


BIOCHEMISTRY OF vitamin C

Vit. C has a 5-hydrocarbon ring similar lớn that of glucose. With an attached hydrogen ion, LAA becomes a weak sugar acid, similar lớn other alfa hydroxy acids used in dermatology. With a metal ion, it forms a mineral ascorbate. There is a marked interest in synthesis of physiologically active & chemically stable ascorbate molecules as LAA is unstable in nature, especially when exposed to lớn light.


MECHANISM OF kích hoạt OF vitamin C WITH REFERENCE lớn DERMATOLOGY


Vit. C as antioxidant

Vit. C, the most plentiful antioxidant in human skin, forms a part of the complex group of enzymatic và non-enzymatic antioxidants that co-exist khổng lồ protect the skin from reactive oxygen species (ROS). As Vit. C is water soluble, it functions in the aqueous compartments of the cell.<4> When the skin is exposed khổng lồ UV light, ROS such as the superoxide ion, peroxide and singlet oxygen are generated. Vit. C protects the skin from oxidative bao tay by sequentially donating electrons to neutralize the không tính phí radicals. The oxidised forms of Vit. C are relatively non-reactive.<4> Furthermore, they can be converted back lớn Vit. C by the enzyme dehydro ascorbic acid reductase in the presence of glutathione. Exposure khổng lồ UV light reduces the availability of Vit. C in the skin.


UV light, reactive oxygen species (ROS) & skin damage - Vit. C and photoprotection

As mentioned above, the exposure of skin to UV light generates ROS.<3> These radicals have a potential lớn start chain or cascade reactions that damage the cells. The harmful effects of ROS occur as direct chemical alterations of the cellular DNA, the cell membrane và the cellular proteins, including collagen.

Oxidative stress also triggers certain cellular events mediated by transcription factors such as ROS tăng cấp transcription factor activator protien-1 (AP-1) that increases matrix metalloprotienase (MMP) production, leading to collagen breakdown.<3> Oxidative căng thẳng induces nuclear transcription factor kappa B (NFk
B). This produces a number of mediators that contribute to lớn inflammation & skin ageing.<3> ROS also increase the elastin m
RNA cấp độ in dermal fibroblasts. This may explain the elastotic changes observed in photoaged skin.<2>

Antioxidants are necessary for neutralizing the ROS formed due to UV exposure.<2> It is important to chú ý that Vit. C is equally effective against both UVB (290-320 nm) và UVA (320-400 nm).<2,5> Repeated small doses of UVA penetrate 30-40-times deeper into the dermis as against UVB, which mostly affects the epidermis. UVA mutates & destroys collagen, elastin, proteoglycans & other dermal cellular structures.<2> Thus, UVA causes skin ageing and possibly melanoma formation. UVB causes sunburn, ROS, epidermal mutations and skin cancer. Sunscreens when properly applied prevent UV-induced erythema và thymine dimer mutations that contribute to cutaneous carcinogenesis. However, sunscreens block only 55% of the không tính phí radicals produced by UV exposure. Photoageing can be prevented by prevention of UV-induced erythema, sunburn cell formation và inducing collagen repair.<2> to lớn optimize UV protection, it is important to lớn use sunscreens combined with a topical antioxidant. Vit. C does not absorb UV light but exerts an UV-protective effect by neutralizing không tính tiền radicals, while this effect is not seen with sunscreens. Under laboratory conditions, it has been shown that application of 10% topical Vit. C showed statistical reduction of UVB-induced erythema by 52% and sunburn cell formation by 40-60%.<3>

Although Vit. C alone can provide photoprotection, it works best in conjunction with vitamin E (Vit. E), which potentiates the action of Vit. C four-fold. Hydrophilic Vit. C helps regenerate Vit. E, a liphophilic antioxidant.<1,3,5,6> Thus, Vit. C & Vit. E together protect the hydrophilic & lipophilic compartments of the cell, respectively. Vit. C & Vit. E synergistically limit chronic UV damage by significantly reducing both cell apoptosis và thymine dimer formation.<3,6>

A combination of 0.5% ferulic acid (a potent antioxidant of plant origin) with 15% Vit. C & 1% Vit. E can increase the efficacy of Vit. C eight-fold.<3> It was noted that this triple combination was very useful for the reduction of acute & chronic photodamage, & could be used for prevention of skin cancer in the future.<3>


Vit. C & collagen synthesis

Vit. C is essential for collagen biosynthesis. It has been proposed that Vit. C influences quantitative collagen synthesis in addition lớn stimulating qualitative changes in the collagen molecule.<2> Vit. C serves as a co-factor for the enzymes prolysyl and lysyl hydroxylase, the enzymes that are responsible for stabilizing và cross-linking the collagen molecules.<2> Another mechanism by which Vit. C influences the collagen synthesis is by stimulation of lipid peroxidation, và the sản phẩm of this process, malondialdehyde, in turn stimulates collagen ren expression.<2>

Vit. C also directly activates the transcription of collagen synthesis and stabilizes procollagen m
RNA, thereby regulating collagen synthesis.<2,3> Signs & symptoms of Scurvy, a deficiency disease of Vit. C, are due to lớn impaired collagen synthesis. Clinical studies have shown that the topical use of Vit. C increases collagen production in young as well as aged human skin.<3,6>


Vit. C as a depigmenting agent

When choosing a depigmenting agent, it is important to lớn differentiate between substances that are toxic lớn the melanocyte and substances that interrupt the key steps of melanogenesis. Vit. C falls into the latter category of depigmenting agents. Vit. C interacts with copper ions at the tyrosinase-active site and inhibits action of the enzyme tyrosinase, thereby decreasing the melanin formation. Vit. C also acts on the perifollicular pigment.<5,7,8> However, Vit. C is an unstable compound. It is therefore often combined with other depigmenting agents such as soy và liquorice for better depigmenting effect.<7>


Anti-inflammatory action of Vit. C

As stated earlier, Vit. C inhibits NFk
B, which is responsible for the activation of a number of pro-inflammatory cytokines such as TNF-alfa, IL1, IL6 và IL8.<2,3> Therefore, Vit. C has a potential anti-inflammatory activity và can be used in conditions lượt thích acne vulgaris và rosacea. It can promote wound healing và prevent post-inflammatory hyperpigmentation.<2,3>


TOPICAL FORMULATIONS OF vi-ta-min C

Vit. C is available in the market as a variety of creams, serum and transdermal patches. Of these, only the serum contains active Vit. C in an almost colorless form. It is unstable and, on exposure khổng lồ light, gets oxidized to Dehydro Ascorbic Acid (DHAA), which imparts a yellow color. The stability of Vit. C is controlled by maintaining a p
H of less than 3.5. At this p
H, the ionic charge on the molecule is removed và it is transported well across the stratum corneum.<3,5,9>

From a clinical point of view, it is important to chú ý that the efficacy of the Vit. C serum is proportional to the concentration, but only up to lớn 20%.<3> The half-life in the skin after achieving maximum concentration is 4 days. A persistent reservoir of Vit. C is important for adequate photoprotection, & can be achieved by regular 8-hourly applications.<1,5> As UV light lowers tissue Vit. C levels, topical Vit. C is best used after exposure to UV light và not prior.<1–3> A combination of tyrosine, zinc & Vit. C has been shown to lớn increase the bioavailability of Vit. C 20-times vis-à-vis using just Vit. C.<2>

A variety of creams with Vit. C derivatives are available in the market. As a dermatologist, it is important to lớn know that not all preparations are physiologically effective. Some are not delivered into the dermis in an adequate quantity, while others vì not chemically convert to the biologically active size of Vit. C in the skin.<1,2,4>

Magnesium ascorbyl phosphate (MAP) is the most stable & preferred ascorbyl ester. This lipophilic molecule is easily absorbed into the skin, & the rate-limiting step for absorption is its release from the vehicle, and not the rate of diffusion across the stratum corneum as one might suppose. Bản đồ has a hydrating effect on the skin và decreases transepidermal water loss. It is also a miễn phí radical scavenger that is photoprotective và increases collagen production under laboratory kiểm tra conditions.<1,3> Other useful stable esterified derivatives are:


Disodium isostearyl 2-0 L-ascorbyl phosphate (VCP-IS-Na), another reliable and popular derivative of Vit. C with a C8 alkyl chain attached to the stable ascorbyl moiety. This ensures increased permeability across the epidermis
Tetraisopalmitoyl ascorbic acid, a lipophilic provitamin and sodium ascorbate, are derivatives under research.

ADVERSE REACTIONS OF TOPICAL vi-ta-min C

Topical Vit. C is largely safe to lớn use on a daily basis for long durations. It can safely be used in conjunction with other common topical anti-ageing agents such as sunscreens, tretinoin, other antioxidants & alfa hydroxy acids such as glycolic acid. Minor adverse reactions include a yellowish discoloration of the skin, hypopigmented hair and staining of clothes, which occur due lớn oxidative changes of Vit. C. Once applied, Vit. C cannot be fully washed or wiped off the skin. Rarely, stinging, erythema và dryness are observed after use of topical Vit. C. These can easily be treated using a moisturiser. Care must be taken while applying Vit. C around the eyes.<1,2>

Urticaria & erythema multiforme, following the use of topical Vit. C, have been documented.<1> The toxic doses of Vit. C that lead lớn cellular apoptosis under laboratory conditions are 100-200-times the daily recommended dose, giving Vit. C a very high safety profile.<1>


FUTURE DEVELOPMENTS

As Vit. C is hydrophilic, there is a marked interest khổng lồ find methods of efficient transepidermal delivery of the stable active compound. If antioxidants could be delivered in high concentration through the stratum corneum barrier, then a dermal reservoir of protective antioxidant could be increased and thus photoprotection would be enhanced.<5> As stated earlier, the use of stable lipophilic esterified derivatives of Vit. C is being explored for the purpose.<5,8,10–13> Extensive research is underway to investigate microspheres, nanoparticles và multilayered microemulsions for graded topical delivery. Trials have been performed with Vit. C and Vit. E in the same multilayered emulsions together.<6> Both electroporation and iontophoresis have been used to lớn enhance penetration of Vit. C into the dermis.<11,14,15> Application of Vit. C lớn the treated skin surface after microdermabrasion & CO2 or Er-Yag resurfacing increases the transepidermal penetration of Vit. C 20-times.<2,16> It has also been observed that Vit. C is a good priming agent and a post-operative agent for the prevention of erythema following tia laze resurfacing. Smokers have been found khổng lồ have low Vit. C levels in the dermis, akin khổng lồ UV-damaged skin. Smoking-related skin ageing is another area where efficacy of Vit. C is being explored. Another very useful application of Vit. C may be striae, where a study has shown that daily application of Vit. C combined with 20% glycolic acid over 3 months can significantly improve striae.<9>


CONCLUSION

To summarize, Vit. C is a naturally occurring drug with multiple desirable effects. With an excellent safety profile, it finds increasing use in photoageing, hyperpigmentation, tissue inflammation and promotion of tissue healing. Ongoing research has been directed toward improving its delivery into the dermis for stimulating collagen production và scavenging không lấy phí radicals. Vit. C thus holds promise as a mainstream drug in future dermatology practice.

The experts have spoken, và this list of vitamin C-spiked serums is sure to leave your skin looking healthier and more radiant with each passing day.

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The best vitamin C serums are among the most potent skin-care products you can have in your collection for tackling some of the most common skin-care concerns — from dullness & discoloration khổng lồ fine lines & uneven skin texture. Serums contain the highest concentrations of the brightening ingredient (also known as ascorbic acid or L-ascorbic acid) but there are plenty of other ways to find it, too: in fruits lượt thích oranges and papaya, of course, but also in a slew of other skin-care products like moisturizers, eye creams, & face masks.

"Vitamin C is a potent antioxidant that's a key component to many skin-brightening regimens, as it interferes with pigment production & keeps inflammation at bay," explains board-certified dermatologist Joshua Zeichner, MD, the director of cosmetic và clinical research at Mount Sinai’s Department of Dermatology in new york City.

Because of its antioxidant properties, vitamin C-enhanced options are also ideal as day serums, since they're well-equipped lớn protect your skin against any environmental aggressors that you'll experience when you step out of the house. Dr. Zeichner says that vitamin C neutralizes không lấy phí radicals, which are molecules found in external factors lượt thích air pollution và sunlight. This may help protect the skin from pre-cancerous changes due to UV light exposure, he explains. (However, you always still need to wear sunscreen, no matter what you have layered underneath in terms of skin care.) and since không tính phí radicals can speed up signs of aging, vi-ta-min C helps with fending off fine lines they cause, too.

Their help for youthful-looking skin doesn't just stop there though. Because vitamin C is highly acidic, when it's used topically, "the skin is triggered khổng lồ heal itself by accelerating elastin and collagen production," new york City-based dermatologist Howard Sobel, MD, previously explained to lớn us, which helps to plump and firm skin, while preventing premature aging of the skin. Think of it as the ideal daytime counterpart to the retinol or acids you might be using at night to lớn smooth over your skin, speed up cellular turnover, & treat acne scars left over from pesky breakouts.

Another reason why it's always used in brightening products is that vitamin C contains a property that inhibits your skin's melanin production, which is what causes skin discoloration like dark spots và hyperpigmentation, new york City-based board-certified dermatologist Patricia Wexler, MD, previously told gdtxdaknong.edu.vn. Over time, she says that vi-ta-min C can help prevent dark spots from forming in the first place. It's also a

Now that you know what it does, we've rounded up some of the best topical skin-care products containing vi-ta-min C to lớn help you achieve glowy skin — & all the rest of those feel-good benefits. Read on for the best vitamin C serums for all skin types that are sure lớn leave you glowing.

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