Sun's Uv Assault: A Growing Threat
For years, we have known that chronic UV exposure results in DNA damage, photoaging, hyperpigmentation and skin cancer. Specifically, UVA exposure generates harmful compounds known as reactive oxygen species (ROS), including singlet oxygen, hydrogen peroxide and hydroxyl free radicals. These ROS react with the skin's DNA, proteins, lipids and saccharides, causing oxidative damage that can lead to injured blood vessels, structural damage to the DNA, an impaired immune system and cell death – or, in plain English, wrinkles, loss of elasticity, age spots and skin cancer.
While ROS are wreaking their havoc on the skin's keratinocytes (the predominant cells comprising the epidermal layer) and fibroblasts (the dermal cells responsible for generating connective tissue), the sun's UVB rays are depleting the skin of its natural antioxidants, rendering it defenseless against the sun's UV-induced free radicals. This leads to a cascade of even more damaging events, ultimately resulting in the degradation of yet more collagen and elastin.
Fortunately, we have antioxidants – the best antidote to the sun's mayhem. In recent years, one specific class of antioxidants known as phenolics have received significant regard among the antioxidant category for their ability to protect the skin before, during and after UV exposure.
Pre- And Post-Treating Skin With Phenolics
Formulators often integrate vitamins C, E and beta-carotene into pre- and post-treatment skin care to help fortify the skin's defenses against UV-induced free radicals. But phenolics, representing one of the richest sources of the plant-based antioxidant family, may be capable of protecting the skin at even greater levels and in different ways against the sun's assault. Indeed, many phenolic flavonoids such as quercetin, luteolin and catechins offer more effective antioxidants than what vitamins C and E and beta-carotene can offer single-handedly.
With approximately 8,000 naturally occurring compounds to their name, phenolics encompass phenolic acids, flavonoids and polyphenols and are naturally abundant in fruit (namely berries, citrus, grapes, apples, apricots, cherries and plums) and vegetables (such as onions, broccoli, tomatoes, lettuce, olives, cabbage and eggplant). Coffee beans, tea, grains and even red wine also offer plentiful sources of phenolic acids, flavonoids and polyphenols.
Phenolics, particularly polyphenols, exhibit health benefits ranging from antiviral, antibacterial, immune-stimulating, anti-inflammatory and anti-carcinogenic activity. Even after the skin has absorbed its fair share of ROS, the flavonoids and phenolic acids of these ingredients are hard at work, scavenging the free radicals, chelating metal ions such as iron and copper, and inhibiting the activities of damaging enzymes in
One of the most well-known phenolic ingredients – resveratrol – rose to fame in 2004 when its cancer-fighting and heart-protective benefits were lauded widely by the mainstream press. Today, skin care chemists continue to turn to this potent antioxidant for its free radical-scavenging and anti-inflammatory benefits. Sourced from the skin and seeds of grapes, peanuts and berries, resveratrol has proven itself as a significant inhibitor of UVB-induced skin edema when topically applied to mice. In fact, pre-treatment of resveratrol resulted in a decrease of UVB-induced hydrogen peroxide and leukocytes, a marker of UV-induced oxidative stress, according to a study published in Frontiers in Bioscience.
Most recently, a 2011 European Journal of Pharmacology study demonstrated resveratrol's ability to increase the viability of human keratinocytes following UVA exposure and protect them from UVA stress while upregulating antioxidant enzyme activity.
Green and Black Tea Polyphenols
Another widely used antioxidant and anti-inflammatory source, green and black tea (Camelia sinensis) offer one of the best, most proven natural defenses against the sun's harmfulUV rays. Tea provides polyphenols such as epigallocatechin-3-gallate (EGCG). Many published studies have proven tea's anti-inflammatory and anti-carcinogenic abilities at even multiple stages of cancer formation in mice.
Green tea polyphenols, in particular, have been shown to protect the skin against UVB-induced edema (swelling) and erythema (redness), lipid peroxidation (the "stealing" of electrons which leads to free radical production), depletion of enzymes essential to the skin's antioxidant defense system and more.
In a report published in Free Radical Biology & Medicine, researchers demonstrated green and black tea's ability to scavenge the ROS hydrogen peroxide and inhibit UV-induced DNA damage. Green tea polyphenols also have the ability to induce apoptosis (cell death) in human cancer cells.
Ferulic and Caffeic Acids
Grains, fruits and vegetables not only provide a great source of vitamins A, C, E and B; they also yield ferulic and caffeic acids, both of which have demonstrated the ability to protect the skin's phospholipidic membranes from UV-induced peroxidation. Ferulic acid, in particular, has exhibited strength in protecting human skin from UVB-induced erythyma and proven its worth as a potent UV absorber in many lotions and sunscreens.
One of the most common flavonoids, quercetin serves the skin as a powerful antioxidant when integrated into a pre- and post-sun skin care regimen. Found in apples, grapes, lemons, onions, broccoli, kale, cottonseed and the herb gingko biloba, quercetin diminishes the harmful effects of UV light. In a study published in Clinical and Experimental Dermatology, researchers demonstrated that the flavonoid has the ability to protect the skin's antioxidant systems glutathione peroxidase, glutathione reductase, catalase and superoxide dismutase against
Another common plant-based flavonoid, apigenin may help prevent UVA- and UVB-induced skin cancers, according to two studies published in Anticancer Research and Carcinogenesis. In those studies, tumor incidence decreased with a topical application of apigenin, which is derived from herbs like endive and clove, fruits like apples and cherries, vegetables, and beverages like tea and wine.
It turns out soybeans not only offer a great phytoestrogenic and protein source for vegans and menopausal women, but its valuable phytonutrient genestein has also been shown to inhibit UVB-induced tumors in mice, according to a study published in Carcinogenesis.
Further, a 2001 study published in Photochemistry and Photobiology demonstrated how a topical application substantially inhibited UVB-induced hydrogen peroxide production and contact hypersensitivity and lowered the inflammatory edema reaction in mice.
Rosemary and sage's main constituent, carnosic acid, is not only a potent antioxidant but also touts wide-ranging chemoprotective effects against carcinogens as demonstrated in a study published in the Journal of the National Cancer Institute of Medicine. A separate study published in Free Radical Biology & Medicine found human fibroblasts that were pre-treated with carnosic acid resulted in suppression of metalloproteinase-1 (MMP) mRNA, a damaging enzyme caused by UVA irradiation and a biomarker of photoaging.
Widely used as medicine in Europe for 2,000 years, silymarin has been used most commonly for treating liver diseases. However, silymarin, a standardized extract derived from the seeds of the milk thistle, may also have chemoprotective activity against skin cancer, according to several published papers.
Topical application is thought to significantly inhibit UVB-induced skin edema and formation of sunburn and apoptotic cells, the destructive cells that cause cell death. It is also known to protect against the formation of UVB-induced cyclobutane-pyrimidine dimers (CPDs), pre-mutagenic lesions found in DNA and the primary cause of melanoma, according to the animal study published in Frontiers in Bioscience.
In a 2007 Czech study, silymarin was shown to extensively reduced depletion of GSH, the body's natural antioxidant, glutathione; ROS production; and lipid peroxidation in irradiated cells. In this report, silymarin also significantly decreased formation of UVA-induced DNA damage.
One of the plant kingdom's most formidable defense systems against predators and UV radiation has also proven useful to humans in protecting our skin against the ravages of the sun. Tannins offer potent antioxidant activity against free radical damage, resulting in a lowered risk of skin cancer and premature aging. When applied topically or injected, tannins have demonstrated the ability to reduce hydrogen peroxide production, decrease tumor incidence and delay their appearance in the skin of mice.
The rich tannin content in the root extract Sanguisorba officinalis L. may explain why the topical application of this extract has resulted in reduced wrinkle formation and preservation of skin elasticity, as shown in an animal study published in Biological & Pharmaceutical Bulletin.
French Maritime Pine Bark Extract
French maritime pine bark extract, also known as Pycnogenol®, is a blend of phenols and polyphenols (i.e. catechin and epicatechin) and phenolic acids (i.e. caffeic, ferulic and gallic). Demonstrating stellar free radical-scavenging abilities, Pycnogenol boosts the production of antioxidant enzymes and has been shown to significantly prevent UV-induced erythema, according to studies published in International Journal of Clinical Pharmacology and Therapeutics and Free Radical Biology & Medicine.
Grape Seed Extract
Rich in a compound known as oligomeric proahtocyanidins (OPCs), grape seeds protect the skin against inflammation and carcinogenic activity while also providing a broad-reaching anti-aging function. Grape seed extract has demonstrated the ability to prevent UVB- and UVC-induced lipid peroxidation.
Studies have shown grape seeds to be a more effective antioxidant than vitamins C and E alone. In fact, Canada's Food Research Group reported that grape seed OPCs provide 20 times the antioxidant power of vitamin E and 50 times the potency of vitamin C. The report, published in the winter 2003 issue of Journal of Medicinal Food noted that grape seed extract protects the body against sun damage by bonding with collagen to help maintain skin's cell health and elasticity.
From ancient to modern times, pomegranates have been favored as medicine, largely for their rich ellagic acid content. This potent free radical scavenger helps replenish the body's natural stores of the antioxidant glutathione, which further helps protect the skin's DNA. Pomegranate's ellagic acid also fortifies cell membranes to defend against free radical damage and water loss while inhibiting damaging enzymes that can upset the skin's healthy cell turnover.
Numerous in vitro and in vivo studies have shown pomegranate offers a strong anti-inflammatory, antioxidant and
anti-carcinogen activity in skin. A study published in the Journal of Agricultural and Food Chemistry found that five to 60 mg/L of a standardized pomegranate fruit extract protected human skin fibroblast cells from cell death following exposure to UVA and UVB radiation; whereas, a higher dosage of 500 to 10,000 mg/L significantly reduced UV-induced ROS levels and increased intracellular antioxidant levels.25 In addition, a small independent study found that adding pomegranate extract to sunscreen boosted the SPF by 20 percent.
The beneficial free radical-scavenging abilities of vitamin C have been well documented for years. But in 1996, researchers at the North Carolina Biotechnology Center reported an interesting discovery: Vitamins C and E have the ability to boost a sunscreen's protection against UV damage. While vitamin E is most effective at defending the skin against UVB exposure, vitamin C protects significantly better against an UVA assault. When vitamin C or a combination of vitamins C and E is formulated with a commercial UVA sunscreen, an "apparently greater than additive protection" is demonstrated, the researchers reported in the Acta Dermato Venereologica. "These results confirm the utility of antioxidants as photoprotectants but suggest the importance of combining the compounds with known sunscreens to maximize photoprotection," the authors noted.
And as published in the International Journal of Toxicology and elsewhere, researchers have reported ascorbic acid's photoprotective qualities prior to UV exposure.
However, the instability and relatively short shelf life of water-soluble ascorbic acid has made formulation with this vitamin antioxidant challenging for many. In contrast, tetrahexyldecyl ascorbate (BV-OSC) provides a stable, oil-soluble form of vitamin C with many benefits. BV-OSC provides potent
antioxidant, DNA protection, UV protection, MMP inhibition, collagen synthesis and skin whitening activity. At the same concentration, BV-OSC has been shown to maintain a higher penetration in the skin even when compared to ascorbic acid at levels 25 times that of BV-OSC.29
In collagen synthesis studies, a 0.1 percent level of BV-OSC added to a fibroblast culture resulted in a 50 percent proliferation of cells. At the same level, BV-OSC reduced melanogenesis by more than 80 percent in an in vitro test.
The antioxidant activity of BV-OSC also has a longer incubating time in the skin when compared to its water-soluble counterpart. In studies, BV-OSC's reduction ratio for stable radical reducing activity measured 18.7 percent, 52 percent and 98.1 percent, respectively, after three hours, 24 hours and 42 hours. On the other hand, ascorbic acid's reduction ratio neared the 100 percent mark after only 30 minutes. Thus, BV-OSC would appear to offer longer-term UV protection in the sun. In addition, this stable vitamin C increases cell viability by up to 30 percent compared to pure ascorbic acid, giving the skin an edge when faced with UV exposure.
Another popular vitamin C choice for pre-UV treatments is magnesium ascorbyl phosphate (MAP), a stable ascorbate ester that has demonstrated the ability to delay skin tumor formation in mice when applied after exposure to UV radiation. MAP also has melanin suppression capabilities, as seen clinically in 19 of 34 patients with melasma and solar lentigos (pigmented spots), according to a report published in Journal of the American Academy of Dermatology.
A number of newer, innovative ingredients have also hit the skin care market, stocking the chemist's formulary with treatments perfected for pre- and post-UV exposure.
One of the more intriguing ingredients to come about in years, light-activated photosomes use a patented delivery system and technology inspired by blue algae, which over time have developed a natural resistance to extreme sunlight and UV. Like the plankton in the ocean, the skin benefits from these photosomes by using the energy from visible light to help repair UV damage. The enzymes in the photosomes absorb visible light to cleave the damaged DNA's cyclobutane pyrimidine dimers and reverse the damage. By applying to skin before or after sun exposure, this novel ingredient is shown to reverse the UV-induced damage upon exposure to photoreactivating light and penetrate the keratinocytes with liposomes that release DNA-repairing enzymes.
Dermox SRC, a unique blend of bamboo silica, helps replenish the body's natural depletion of silica and thus stimulate the skin's chondroblasts to produce chondroitin and hyaluronic acid. In addition to bamboo, this proprietary complex is comprised of pea extract – which helps the skin generate collagen and elastin – and glucosamine (a natural skin exfoliator that also stimulates the dermal fibroblasts for a smoother complexion). In clinical studies, Dermox SRC resulted in more than a 45 percent improvement in reducing lines and wrinkles compared to a 4.7 percent improvement with a base gel over a four-week period. In addition, Dermox displayed superior collagen-stimulating activity compared to ascorbic acid.
This proprietary ingredient comprised of caprylic/capric triglyceride and teprenone helps UV-stressed skin weather normal signs of UV-induced signs of aging, including wrinkles, dehydration, age spots and a broken barrier function. Renovage helps stabilize the cells' telomere function, the end "fuses" of our chromosomes that protect our DNA's vital cell data and maintain proper cell division. This oil-soluble ingredient also maintains cell communication and metabolism and can delay cell senescence and extend cell lifespan by one-third. In a simple blind study of 24 mature-aged women, a twice daily application of a cream containing three percent Renovage resulted in up to 58 percent moisturization, 46 percent epidermal barrier integrity improvement and 56 percent improvement in UV sun spots over six months.
Finally, certain ingredients can significantly improve the quality of sunscreens by enhancing the water resistance, spreadability, transparency, SPF and dispersion of the active ingredients. For example, the SPD series, a dispersion of fine titanium dioxide and zinc oxide in a cyclopentasiloxane blend, offers a stable, low-viscosity welcome addition to transparent sunscreens.
While much focus has been placed on the role of sunscreens in preventing UV damage, there is a wealth of data supporting the benefit of new, innovative proprietary ingredients as well as time-proven vitamins and phenolics. As consumers sharpen their savvy to these skin-friendly ingredients, all will continue to enjoy a greater presence on the backs of labels in pre- and post-UV skin treatments now and in the future.
Sam Dhatt was born and raised in India. He achieved a MS in Chemistry and an MBA in Marketing and Finance. Dhatt's introduction as a leader in innovative technology begins with his work in 1992 with alpha hydroxy acids, which was in its infancy at the time. Then in 1995, he started his own cosmetics research and development company, Allure Cosmetics, Inc. In addition, Allure Cosmetics, Inc. also supplies hair care, foot care, spa products, cosmetic accessories and makeup to their 700 clients worldwide. In 1999, Dhatt opened another company, DermaQuest® Skin Therapy.