NATURAL SKIN-LIGHTENING AGENTS

SKIN DARKENING PROCESS

Skin darkening is due to an increased production and accumulation of melanin or an increased number of melanocytes. Melanin are dark colored pigments produced by special skin cells, called melanocytes. Hyperpigmentation can be inherited or, more often, acquired by a number of causes including photo-aging, hormonal changes (contraceptives, pregnancy, menopause), repeated and prolonged exposure to the sun, and chronic skin irritations, inflammation or skin diseases. Dark skin areas may be of cosmetic relevance especially if they occur in the face or other uncovered body areas. Many efforts have been devoted to screening and testing recognized and putative depigmenting agents. In addition, physical therapies, such as lasers, are currently under investigation to treat hyperpigmentation.

SKIN WHITENERS MODE OF ACTION

• Inhibit melanotropin (MSH) activity: Undecylenoyl-Phenylalanine.
• Inhibit tyrosinase synthesis: Tretinoin.
• Inhibit tyrosinase activity: Bearberry Extract, Arbutin, Kojic Acid, Hydroquinone, Aleosin, Azelaic Acid.
• Inhibit UV-induced melanin synthesis: Vitamin C & Vitamin E, Chamomile Extract.
• Removal of pigmented skin cells: Alpha-hydroxy Acids (Glycolic Acid, Salicylic Acid, Lactic Acid), Liquiritin.

DEPIGMENTING (SKIN-WHITENING) AGENTS

The production of melanin in the melanocytes is a highly complicated process involving a variety of proteins, enzymes, and amino acids. Consequently, there are several possibilities where the synthesis of melanin can be inhibited or decreased. The depigmenting compounds that are currently used achieve depigmentation by one of the following mechanisms. The ideal depigmenting compound should have a potent, rapid and selective bleaching effect on hyperactivated melanocytes, carry no short- or long-term side-effects and lead to a permanent removal of undesired pigment. Two depigmenting components that fulfill these criterias include undecyl-phenylalanin and bearberry extract combined with vitamin C that inhibit the activity of melanotropin (MSH). As MSH stimulates the production of melanin at multiple steps, inhibition of MSH is therefore a powerful method to depigment the skin. In fact, this mixture has been shown to inhibit the melanin synthesis in melanocytes at a much higher degree than kojic acid or arbutin, two other widely used skin whiteners. The potency of inhibition is about in the range of hydroquinone which, however, has been suggested by the FDA to be removed from the market due to hazards seen with long-term treatments (currently, products that contain up to 2% hydroquinone are sold in the U.S. without a prescription, and up to 4% with a prescription

ANTIOXIDANTS SKIN WHITENING ACTIVITY

Antioxidants very useful active ingredients for the manufacturing of cosmetics. Generally, antioxidants interrupt oxidation reactions and prevent the effects of oxygen radicals (e.g. peroxides) both processes known to damage the integrity and function of various natural substances. Antioxidants are useful in two ways: On the one hand they prevent degradation of natural ingredients (proteins, sugars, lipids) in the cosmetic product. On the other hand antioxidants protect the skin cells from being damaged and slow down the aging process. Antioxidants have been shown to boost the skin's radiance, minimize age spots, sun spots, and fine lines.

• Coenzyme Q10 Antioxidant with Anti-Aging & Anti-Wrinkle Properties
• Vitamin A (retinol palmitate) Vitamin with Regenerating & Anti-Wrinkle Properties
• Vitamin C (L-ascorbic acid) Water-Soluble Antioxidant, High Active Vitamin C
• Vitamin C (L-ascorbyl palmitate) Fat-Soluble Antioxidant, High Stability Vitamin C
• Vitamin C (magnesium ascorbyl phosphate) Highly Stable & Water-Soluble Vitamin C
• Vitamin E (d-alpha tocopherol) Effective Anti-Inflammatory & Antioxidant Properties
• Vitamin E (dl-alpha tocopheryl acetate) Effective Anti-Inflammatory & Antioxidant Properties
• Olive leaf extract Natural Free Radicals Protector
• Green Tea Extract Natural Antioxidant & Collagen Protector
• White Tea Extract Antioxidant & Anti-Inflammatory

ALPHA & BETA HYDROXY ACIDS EXFOLIATING AGENTS

Alpha hydroxy acids (AHA's) work mainly as an exfoliant. They cause the cells of the epidermis to become "unglued" allowing the dead skin cells to slough off, making room for regrowth of new skin. AHA's may even stimulate the production of collagen and elastin, and are reported to improve wrinkling, roughness, and mottled pigmentation of photodamaged skin after months of daily application. Alpha hydroxy acids found in skin-care products work best in a concentration of 5% to 8% and at a pH of 3 to 4. Beta hydroxy acid, salicylic acid, is a topical exfoliant that can reverse some of the effects of photoaging such as fine wrinkles and discolored skin. Currently, salicylic acid is the only beta hydroxy acid used as an exfoliant.

Alpha-hydroxy acids (AHAs) are naturally occurring organic carboxylic acids such as, for example, glycolic acid, a natural constituent of sugar cane juice, lactic acid, found in sour milk and, tomato juice, or citric acid, found in various citric fruits. Topical formulations incorporating these acids are now frequently used or prescribed by dermatologists and they are also present in a wide range of cosmetic products.
Mechanism of action AHAs exfoliate dead skin cells and moisturize the skin. Their main action is to facilitate degradation of the binding structures between cells leading to an increased des-quamation of the horny skin cells and an increased regeneration. There is also as an increase in the skin’s content of natural hyaluronic acid (which holds 1000x times its weight in water) which explains the moisturizing effect of AHAs. In addition, this might be also one of the causes of increased skin ‘plumpness’. By normalizing cohesion of the horny cells, the upper skin layer is somewhat thinned, smoother and more flexible (even at low relative humidity), and the formation of dry flaky scales is reduced. The overall result is skin which looks and feels better. Claims that AHAs reverse photodamage and reduce wrinkles, brown spots and roughness are somewhat controversial and are currently being reviewed by the CTFA (Cosmetic, Toiletry and Fragrance Association), the FDA and the FTC (Federal Trade Comission). Several aspects concerning the mechanism of action of AHAs are still unknown. In particular, little is known about the correlation between the structural and functional changes in the upper skin layer induced by AHA treatment. Several studies have suggested that treatment with AHAs produce significant reversal of epidermal and dermal markers of photo-aging.

Therapeutic Use

The dermatological use of AHAs is critical – is it to be used as a cosmeceutical, a dermatologic application or as a chemical peel? It is known that the formulation is more important than concentration alone. In particular, the bioavailability of the AHA is a major determinant. For example, a high concentration of AHA near neutral pH is ineffective because the AHAs are inactive at neutral pH. At the other extreme, at low pH even small concentrations of AHAs can be very effective because a major amount of the AHAs is available and active In brief, the more free acid in a formulation, the more biologically active are AHAs. An expert panel of the CIR (US Cosmetic Ingredient Review) concluded:

Summary of AHAs Properties

• Exfoliation (desquamation of horny cells)
• Moisturization (reducing water loss)
• Anti-wrinkle effect
• Skin-whitening effect
• Smoothing effect
• nImproves skin texture & tone• Unblocks & cleans pores