|First Hypothesized in 1956 by Dr. Denham Harman, the free radical theory of aging is now the most widely accepted theory regarding the etiology of skin aging.
Both internal and external oxidative stressors create inflammatory pathways characterized by the formation of free radicals, which are highly reactive molecules with unpaired electrons. Left unchecked, free radicals can cause severe cellular damage to cell membrances, lipids, proteins, and DNA. Free radicals that are known to cause DNA damage, lipid peroxidation, and inflammation are also believed to cause skin aging.
Antioxidants are substances that protect cells from endogenous oxidative stress,which is a natural byproduct of cellular energy production. Antioxidants also offer protection from exogenous stressors, such as UV radiation from the sun, air pollution, cigarette smoke, ozone, and even oxygen itself.
The damage accumulation theory of aging suggests that a lifetime buildup of damage caused by unchecked free radicals is a primary mechanism leading to the manifestations of aging. The almost universal acceptance of both the free radical theory and the damage accumulation theory helps explain the intense interest of modern medicine in the capacities of antioxidants.
By scavenging and eliminating free radicals, antioxidants balance and thwart the deleterious effects of the free radical-mediated inflammatory pathways promoted by oxidative stress.
Several antioxidants are used as ingredients in topical skin care formulations,
including vitamins C and E, lycopene, grape seed extract, green tea, coenzyme
Q10, and alpha-lipoic acid. Each offers distinct advantages, but they all pose
similar challenges in terms of harnessing their potency in topical products.
C. Although there is a dearth of research evaluating the effects of
ascorbic acid (vitamin C) on wrinkles, one such study has garnered a good deal
of attention. The topical application of Cellex C serum for 3 months was shown
to reduce the size of wrinkles in a study of 19 patients (Arch. Otolaryngol.
Head Neck Surg. This study was not blinded, as a significant percentage of the
participants experienced stinging on the treated side of the face. Vitamin C
is known to play an important role for the skin: It has been shown to increase
collagen synthesis in neonatal and adult fibroblasts when added to the culture
C preparations have proven to be disappointing, however. Most preparations are
unstable upon exposure to UV light and air, which renders them useless. Also,
most topical vitamin C products, even the stable ones, fail to penetrate the
E. The topical application of a tocopherol (vitamin E) has been shown
to confer significant protection against UV-induced damage to animal skin.
Although immunostimulatory and anti-inflammatory effects have been ascribed
to vitamin E, several studies have cited adverse reactions to topical vitamin
E. A sun protection factor of 3 topical application of vitamin E, which is believed
to have the capacity to marginally absorb light (Cosmet. Dermatol.) It appears
likely, however, that vitamin E requires the interaction of other antioxidants
to provide any photoprotective effect.
Q10. A powerful antioxidant that combats free radical stress and assists
in energy production, coenzyme Q10 is found in all cells. By inhibiting lipid
peroxidation in plasma membrances thus limiting free radical formation coenzyme
Q10 is believed to prevent oxidative stress-induced apoptosis.
Coenzyme Q10 plays an important role in the energy-producing adenosine triphosphate
pathways present in the mitochondria of each cell in the body. Energy production
is an important component of cellular metabolism that is thought to diminish
in efficiency with age. Coincidentally, levels of coenzyme Q10 also decline
with age. Supplementation with this coenzyme is believed to have potential to
stem the decline in energy production associated with senescence and illness.
A preponderance of clinical work with coenzyme Q10 has evaluated its systemic
administration. However, topical coenzyme Q10 has been shown to penetrate the
viable layers of the epidermis and lower the level of oxidation, measured by
weak photon emission, and reduce wrinkle depth. In the same study, the coenzyme
suppressed expression of collagenase in human fibroblasts following UVA irradiation.
These results suggest that topical coenzyme Q10 may effective in preventing
the deleterious effects of ultraviolet radiation exposure.
extract. By inducing vascular endothelial growth factor expression
in keratinocytes, grape seed extract in one study appeared to exhibit the potential
to confer beneficial results in dermal wound healing and related skin problems.
In human volunteers,
topical application of grape seed extract has been shown to enhance the sun
protection factor. Data suggest that grape seed extract is a significantly more
potent scavenger of free radicals than either vitamin C or E. The bioflavonoids
in grape seed extract appear to promote the body`s ability to absorb vitamins,
creating a symbiotic atmosphere for other nutrients.
Green tea is included in various skin care products because of the purported
antioxidant and anti-inflammatory effects of polyphenols that occur naturally
in the green tea leaf. The polyphenols have been shown to modulate the biochemical
pathways important in cell proliferation, inflammatory responses, and responses,
and responses of tumor promoters.
of green tea has actually been shown to increase green tea phenol levels in
skin as indicated by tapestripping analysis. Numerous studies support continuing
interest in and use of green tea.
when high levels of green tea are placed in a moisturizing vehicle, the cream
often turns brown. One company(Topix) has avoided this problem by making their
cream brown to begin with.
acid. Water and lipid-soluble lipoic acid is a potent antioxidant and
a promising option in the treatment of aging skin.. It is believed to be effective
in treating inflammatory diseases, and may slow the pace of skin aging.
Lipoic acid is
absorbed in a stable form. After entrance into cells, however, it is immediately
converted to its byproduct, dihydrolipoic acid, which has a stronger antioxidative
effect. The topical application of 3% lipoic acid in a lecithin base on human
skin has been shown to decrease erythema caused by UVB twice as fast as lecithin
base alone. This suggests that lipoic acid could potentially reduce the effects
of photoaging or even thwart carcinogenesis.
Lipoic acid is
another in the long line of antioxidants that show promise, but lack double-blind
clinical trials showing their efficacy in available products. Lipoic acid can
be irritating to those with sensitive skin.
Naturally present in human blood and tissues, lycopene is a non-provitamin A
carotenoid. It is best known as the pigment primarily responsible for the characteristic
red color of tomatoes.
Lycopene is now
drawing attention for its potential potency as an antioxidant. Lycopene may
play a role in reducing oxidative damage to tissues, as suggested by a study
in which a 31%-46% decrease in skin lycopene concentration was observed following
a single intense exposure (three times the minimal erythema does) of solar simulated
light on a small area of the volar arm.
In a separate study
of oral consumption of lycopene, both lycopene and B-carotene failed to confer
photoprotective effects to human dermal fibroblasts. Their stability was enhanced,
however, by the presence of vitamin E, which contributed to the suppression
of metalloproteinase-1 mRNA expression. This suggests that to deliver the benefits
of lycopense in topical products, it may be necessary to combine the carotenoid
with other antioxidant active ingredients. The literature is rife with evidence
of the efficacy of ingested lycopene, but there is a paucity of double-blind,
case-control studies evaluating the efficacy of topical products.
Millions of people are likely aware of many of the topical antioxidants currently
marketed, given how popular the use of “antiaging” cosmeceuticals
containing such ingredients has become. Most consumers are clueless, however,
as to how to rate the effectiveness of such formulations, as scant scientific
date exist on the wide range of skin care products that contain highly touted
Until now, there
have been no standard methods for comparing the relative efficacy of different
antioxidants in a fashion readily accessible to consumers.
Pharma Cosmetix Research, a cosmeceutical research and development company,
has produced a protocol of in vitro and in vivo studies designed specifically
to address the need to standardize efficacy measurement of topical antioxidants.
In much the same way that the sun protection factor provides a measuring stick
enabling the user to estimate the level of UV protection to expect from a sunscreen
product, Pharma Cosmetix Research’s environmental protection factor (EPF)
is designed to provide the product user with an estimate of the level of oxidative
/ environmental stress protection to expect from an antioxidant skin care product.
In all of the antioxidant efficacy protocols, each antioxidant substance is
scored, and the results are totaled for each antioxidant on an equal weighted
basis. The over all total score for each antioxidant reflects the overall stress
protection capacity, or EPF, of the antioxidant.
The bottom line is that EPF is to antioxidant environmental protection efficacy
what SPF is to sunscreen UV protection efficacy. Consumers will now have a simple
way to rate antioxidant strength and compare the efficacy of topical antioxidant