Skin, the human body’s largest organ is always under the influence of internal and external factors and reacts to those factors by modifying the constitutive pigmentation pattern. It is well documented that darker skin is dramatically more resistant to the damaging effects of UV, such as photocarcinogenesis and photoaging, still people often express a desire to “lighten” skin tone and reduction in the appearance of hyperpigmented spots. Both physicians and dermatology patients are searching for long-term topical skin care solutions to address the problem of hyperpigmentation. Depigmenting agents such as hydroquinone, corticosteroids, kojic acid, although are highly effective but can raise several safety concerns for example, ochronosis, atrophy, carcinogenesis, and other side effects with long-term exposure. Depigmenting agents function by means of antioxidant or anti-inflammatory activities.
An understanding of the benefits of natural and botanical extracts provides opportunities to develop new products to address pigmentation problems. Active compounds isolated from plants, such as arbutin, aloesin, gentisic acid, flavonoids, hesperidin, licorice, niacinamide, polyphenols etc. are more potent inhibitors of melanin formation than hydroquinone and kojic acid and also not associated with cytotoxicity.
Plants such as Indigenous kinnickinnick, Aloe vera, Panax ginseng, Morus alba, and Gingko are a rich source of anti-hyperpigmentry agents such as polyphenols, flavonoids and triterpenoids etc. that show their effect as antioxidant and skin whitening agents. Polyphenols are a class of compound that have antioxidant capacity and are found widely within plants. The inhibition of melanogenesis has been observed with many types of polyphenol plant extracts. Proanthocyanidins, classified as polyphenols, exist in red wine and cranberry juice; grape seeds are another especially rich source. The antioxidative activities of proanthocyanidins were found to be much stronger than the activity of vitamin C or E in aqueous systems. Ellagic acid is another natural polyphenol that is widely found in fruits and vegetables. Isoflavones including glycitein, daidzein, genistein and 6,7,4′-trihydroxyisoflavone has been identified as a potent tyrosinase inhibitor even stronger than kojic acid.
Hesperidin is a bioflavonoid existing extensively in the peel and membranes of citrus fruits has potent ability to inhibit melanin synthesis without cytotoxicity. In addition, hesperidin also protect against UVA-induced damage of fibroblasts and oxidative damage of collagen. Thus, hesperidin offers potential skin-lightening benefits, including improved overall skin tone and antiyellowing effects. Niacinamide, found widely in many root vegetables and yeasts, have demonstrated reduction in hyperpigmented lesions and increased skin lightness after 4 weeks of use.
Leaves of Indigenous kinnickinnick (bearberry) are a rich source of arbutin, a naturally occurring β-D-glucopyranoside derivative of hydroquinone. Topical treatment with α-Arbutin for 12 weeks resulted in a significant reduction in overall skin lightness and improvement of solar lentigines in a population of light-skinned or dark-skinned individuals, respectively. α-Arbutin has widely replaced arbutin as the chosen skin-lightening agent in topical skin preparations because it is more effective and stable in producing the desired effects on human skin. The topical application of Aloesin, a compound isolated from the aloe plant, on UV-irradiated human volar forearm (four times a day for 15 days) showed pigmentation suppression in a dose-dependent manner. Aloesin, along with arbutin, was observed to synergistically inhibit melanin production.
Mulberry (Morus alba) leaves are rich source of mulberroside and several phenolics and flavonoids, such as gallic acid and quercetin and fatty acids, such as linoleic acid and palmitic acid. Research studies revealed that, Mulberroside F (moracin M-6, 3′-di-O-beta-D-glucopyranoside), showed inhibitory effects on tyrosinase activity and on melanin formation in melan-a cells. This compound also exhibited superoxide scavenging activity that is involved in the protection against auto-oxidation, suggesting a role for Morus alba as a component of lightening cosmetics.
Ginseng, being rich source of P-coumaric acid, is very effective in suppressing tyrosinase activity and melanin content and can play an important role as a skin-lightening agent. Ginkgo leaves are rich in flavones glycosides, mostly quercetin and kaempferol derivatives and have shown potent free radical scavenger activity when applied to the skin. Similarly, Licorice extracts have several active compounds that may stimulate or suppress melanogenesis. Glabridin, glabrene, isoliquiritigenin licuraside, isoliquiritin, and licochalcone A are the main ingredient in the licorice extract that inhibits tyrosinase activity and cause depigmentation.
Source
Wenyuan Zhu, Jie Gao, The Use of Botanical Extracts as Topical Skin-Lightening Agents for the Improvement of Skin Pigmentation Disorders, Journal of Investigative Dermatology Symposium Proceedings, Volume 13, Issue 1, 2008, Pages 20-24, ISSN 1087-0024, https://doi.org/10.1038/jidsymp.2008.8.