Effects of hydroxybenzyl alcohols on melanogenesis in melanocyte-keratinocyte co-culture and monolayer culture of melanocytes

Natural products in cosmetics

The global cosmetics market reached US$500 billion in 2017 and is expected to exceed US$800 billion by 2023, at around a 7% annual growth rate. The cosmetics industry is emerging as one of the fastest-growing industries of the past decade. Data shows that the Chinese cosmetics market was US$60 billion in 2021. It is expected to be the world's number one consumer cosmetics market by 2050, with a size of approximately US$450 billion. The influence of social media and the internet has raised awareness of the risks associated with the usage of many chemicals in cosmetics and the health benefits of natural products derived from plants and other natural resources. As a result, the cosmetic industry is now paying more attention to natural products. The present review focus on the possible applications of natural products from various biological sources in skin care cosmetics, including topical care products, fragrances, moisturizers, UV protective, and anti-wrinkle products. In addition, the mechanisms of targets for evaluation of active ingredients in cosmetics and the possible benefits of these bioactive compounds in rejuvenation and health, and their potential role in cosmetics are also discussed.

Anti-Melanogenesis Effects of Lotus Seedpod In Vitro and In Vivo

Melanogenesis has many important physiological functions. However, abnormal melanin production causes various pigmentation disorders. Melanin synthesis is stimulated by α-melanocyte stimulating hormone (α-MSH) and ultraviolet (UV) irradiation. Lotus seedpod extract (LSE) has been reported as possessing antioxidative, anti-aging, and anticancer activities. The present study examined the effect of LSE on melanogenesis and the involved signaling pathways in vitro and in vivo. Results showed that non-cytotoxic doses of LSE and its main component epigallocatechin (EGC) reduced both tyrosinase activity and melanin production in the α-MSH-induced melanoma cells. Western blotting data revealed that LSE and EGC inhibited expressions of tyrosinase and tyrosinase-related protein 1 (TRP-1). Phosphorylation of p38 and protein kinase A (PKA) stimulated by α-MSH was efficiently blocked by LSE treatment. Furthermore, LSE suppressed the nuclear level of cAMP-response element binding protein (CREB) and disturbed the activation of melanocyte inducing transcription factor (MITF) in the α-MSH-stimulated B16F0 cells. The in vivo study revealed that LSE inhibited melanin production in the ear skin of C57BL/6 mice after exposure to UVB. These findings suggested that the anti-melanogenesis of LSE involved both PKA and p38 signaling pathways. LSE is a potent novo natural depigmenting agent for cosmetics or pharmaceutical applications.

Vitiligo and Hashimoto's thyroiditis: Autoimmune diseases linked by clinical presentation, biochemical commonality, and autoimmune/oxidative stress-mediated toxicity pathogenesis

Vitiligo (VL) is a chronic autoimmune pigmentation disorder characterized by destruction of melanocytes. The condition is associated with several other autoimmune diseases, but autoimmune thyroid diseases, especially Hashimoto's thyroiditis (HT), is the most prevalent organ-specific autoimmune disease with a co-morbidity up to 34%. Among the many hypotheses that have been proposed for the pathogenesis of both diseases, autoimmunity and oxidative stress-mediated toxicity in melanocytes or thyrocytes, respectively, have been the most widely accepted - with autoimmunity being the presumed consequence of oxidative stress-mediated toxicity. However, the predominant etiologic basis for impairment of redox balance has rarely been studied. The two autoimmune diseases are not only linked by a concordance of clinical presentations and an autoimmune/oxidative stress-mediated toxicity pathogenesis but also by an apparent biochemical commonality. The target molecules produced in the thyroid and skin, i.e., thyroxine and melanin, respectively, are derived from the same primordial parent molecule, tyrosine. On the basis of these similarities between Hashimoto's thyroiditis and vitiligo, specifically with respect to the activation of oxidative stress, we propose a novel hypothesis accounting for the destruction of melanocytes or thyrocytes in VL and AT. We suggest a new therapeutic regimen of quinone derivatives to combat ROS-induced autoimmunity resulting from this common biochemical etiologic error.

A preliminary study of growth characteristics of melanocytes co-cultured with keratinocytes in vitro

To clarify the characteristic growth of melanocytes (MCs) and Keratinocytes (KCs) in vitro and discuss the mechanism of culturing autologous melanocytes in the treatment of vitiligo. Epidermis cells derived from normal skin tissues were isolated and cultured in vitro. Melanocytes in DOPA staining were observed. The expression level of markers in MCs was detected by qRT-PCR and the percentage of MCs and KCs were detected by flow cytometry. Cells derived from normal skin tissues mainly included KCs, MCs, and fibroblasts. There were significant differences between the percentage of KC, MC, fibroblasts (P < 0.05), and the expression of Microphthalmia-associated transcription factor (P < 0.05) and Tyrosinase-related protein-2 (P < 0.05) in the second, 10th, 20th, and 30th day. Significant differences were also found between the average numbers of MC stained by DOPA (P < 0.05) and the average percentage of MCs in the 10th, 20th, and 30th Day (P < 0.05). But there were no significant differences between the average percentage of KCs in the 10th, 20th, and 30th Day (P > 0.05) detected by flow cytometry. The number of MCs co-cultured with KCs in vitro reached the maximum in the 20th Day and this co-cultured model may contribute to the growth of MCs which could be used in the treatment of vitiligo.

The hunt for natural skin whitening agents

Skin whitening products are commercially available for cosmetic purposes in order to obtain a lighter skin appearance. They are also utilized for clinical treatment of pigmentary disorders such as melasma or postinflammatory hyperpigmentation. Whitening agents act at various levels of melanin production in the skin. Many of them are known as competitive inhibitors of tyrosinase, the key enzyme in melanogenesis. Others inhibit the maturation of this enzyme or the transport of pigment granules (melanosomes) from melanocytes to surrounding keratinocytes. In this review we present an overview of (natural) whitening products that may decrease skin pigmentation by their interference with the pigmentary processes.

Antioxidant activity and free radical scavenging reactions of hydroxybenzyl alcohols. Biochemical and pulse radiolysis studies

Comparative studies on free radical scavenging by isomers of hydroxybenzyl alcohols (HBAs) were carried out to understand the molecular mechanisms involved in the antioxidant action. Using rat liver mitochondria as model systems, we have examined the radioprotective and antioxidant effects of hydroxybenzyl alcohols. Apart from their ability to scavenge free radicals and ferric reducing power, HBAs have shown good protection against radiation and oxidative stress. Using peroxyl radicals as initiator of reactive oxygen species (ROS), studies were carried out to evaluate antioxidant properties of HBAs against rat liver mitochondrial membrane components such as lipid and protein. Our results show that HBAs are potent inhibitor of lipid peroxidation and protein oxidation thus suggesting their role as free radical scavengers. In the presence of HBAs, restoration of depleted activity of Mn-SOD has also been investigated. In the presence of 2-hydroxybenzyl alcohol (2-HBA) complete restoration in the activity of Mn-SOD was observed on exposure to 2,2'-azobis(2-amidinopropane) dihydrochloride (AAPH). Free radical scavenging ability of HBAs were found to be comparable to alpha tocopherol. Pulse radiolysis technique has been used to study the reactions of HBAs with various biologically relevant reactive species such as hydroxyl radical (OH) and trichloromethyl peroxyl radical (CCl3O2). HBAs could scavenge OH radical giving initially OH-adducts which in turn decays to phenoxyl radicals. Reactions of phenoxyl radicals of HBAs with ascorbic acid have been also studied. Redox potential of HBAs has been evaluated with cyclic voltammetry. Studies clearly suggest a structural reactivity correlation between radical scavenging and antioxidant properties of these isomers of HBA. Among the 3 isomers of HBAs, 4-HBA and 2-HBA are found to have better radical scavenging and antioxidant properties than 3-HBA.

Bibliography. Current world literature

This bibliography is compiled by clinicians from the journals listed at the end of this publication. It is based on literature entered into our database between 1 February 2008 and 31 January 2009 (articles are generally added to the database about two and a half months after publication). In addition, the bibliography contains every paper annotated by reviewers; these references were obtained from a variety of bibliographic databases and published between the beginning of the review period and the time of going to press. The bibliography has been grouped into topics that relate to the reviews in this issue.