Arbutin—A potent antioxidant that is found naturally in cranberries, wheat, pears, and blueberry and bearberry leaves, arbutin is thought to be less cytotoxic than hydroquinone. It inhibits the activity of tyrosinase, inhibits melanosome maturation and converts to hydroquinone in the skin, allowing for a controlled release—which results in less irritation than hydroquinone.
Azelaic acid—Naturally sourced from cultures of Pityrosporum ovale, grain products and castor beans or by the oxygenation of oleic acid (found in milk), azelaic acid has an antiproliferative and cytotoxic effect on melanocytes while sparing surrounding healthy cells. It also inhibits tyrosinase activity, DNA synthesis and mitochondrial activity.
Hydroquinone—Hydroquinone is typically engineered in a lab, but can be found naturally in wheat, berries, coffee and tea. It works by inhibiting DNA and RNA synthesis, suppressing the binding of copper and tyrosinase—decreasing the formation of melanosomes, increasing the degradation of melanosomes and inducing melanocyte-specific cytotoxicity.
Kojic acid—Derived from rice, soy and mushrooms, kojic acid may cause irritation in some skin types, although less frequently than hydroquinone. It inhibits melanogenesis by chelating the copper bound to tyrosinase, rendering it useless. It also decreases the number of melanosomes and dendrites, and is useful in treating hyperpigmentation due to its ability to inhibit nuclear factor-kappa B (NF-kB) activation in keratinocytes, mitigating inflammatory response.
L-ascorbic acid (vitamin C)—Derived from many botanical sources, notably citrus fruit and corn, L-ascorbic acid is an anti-inflammatory and antioxidant agent that stimulates collagen production and converts dopaquinone back to L-DOPA, preventing melanin formation.
Lactic acid—Derived from sour milk and sugars, lactic acid works as a moisturizer and antimicrobial agent. It increases the exfoliation of melanin-filled keratinocytes and suppresses the formation of tyrosinase.
Licorice extract—Licorice extract can be naturally derived or engineered. It inhibits tyrosinase activity of melanocytes without cytotoxicity, UVB–induced hyperpigmentation and erythema, and has strong anti-inflammatory properties.
Morus bombycis root extract (mulberry)—A potent antioxidant and anti-inflammatory agent that inhibits the L-DOPA oxidase activity of tyrosinase, studies show a 50% reduction in tyrosinase activity following an application of Morus bombycis root extract.
Phenylethyl resorcinol—An engineered resorcinol derivative, phenylethyl resorcinol is an antioxidant that has demonstrated results comparable to kojic acid and hydroquinone without any potential for topical irritation. It works by inhibiting the conversion of tyrosinase to L-DOPA.
Retinoids (vitamin A)—Retinoids stimulate collagen, elastin and glycosaminoglycan production, and inhibit tyrosinase activity, decrease the amount of melanosomes produced, inhibit the transfer of melanin from melanocytes to keratinocytes and enhance the penetration of actives through the stratum corneum.
Undecylenoyl phenylalanine—Another engineered ingredient, undecylenoyl phenylalanine prevents the synthesis the melanocyte-stimulating hormone (MSH).