Annona squamosa L. leaves inhibit alpha-melanocyte-stimulating hormone (α-MSH) stimulated melanogenesis via p38 signaling pathway in B16F10 melanoma cells.

BACKGROUND: Annona squamosa L. is a branched shrub, which is believed to be originated from the America and West Indies. Fruits of this plant are commonly known as custard apple, sugar apple, or sweetsops. A number of studies have proven a range of biological activities associated with various parts of A. squamosa. AIMS: The main aim of the present investigation was to evaluate potential inhibitory effects of A. squamosa leaf extract (ALE) on melanogenesis and its underlying mechanisms in B16F10 murine melanoma cells. METHODS: Inhibitory effects of A. squamosa leaf extract (ALE) on melanogenesis were primarily assessed by determining melanin contents. Effects of ALE on tyrosinase activity and the expression of proteins associated with melanogenesis were then determined. GC-MS analysis was carried out to identify the phytochemical profile of A. squamosa leaf extract. RESULTS: Antimelanogenic effects of ALE were found to exert through the inhibition of melanocyte inducing transcription factor (MITF) and activation of p38. GC-MS analysis identified ent-kaur-16-en-19-ol, 18-oxokauran-17-yl acetate, and ß-sitosterol as major phytochemicals. CONCLUSION: To our knowledge, this is the first study on the antimelanogenic effects of A. squamosa leaves, rationalizing the use A. squamosa leaf extract as a natural depigmentation agent for the treatment of skin diseases and the development of cosmetic products with enhanced skin-lightening capabilities.

Sageretia thea fruit extracts rich in methyl linoleate and methyl linolenate downregulate melanogenesis via the Akt/GSK3ß signaling pathway.

BACKGROUND/OBJECTIVES: Sageretia thea is traditionally used as a medicinal herb to treat various diseases, including skin disorders, in China and Korea. This study evaluated the inhibitory effect of Sageretia thea fruit on melanogenesis and its underlying mechanisms in B16F10 mouse melanoma cells. The active chemical compounds in anti-melanogenesis were determined in Sageretia thea. MATERIALS/METHODS: Solvent fractions from the crude extract were investigated for anti-melanogenic activities. These activities and the mechanism of anti-melanogenesis in B16F10 cells were examined by determining melanin content and tyrosinase activity, and by performing western blotting. RESULTS: The n-hexane fraction of Sageretia thea fruit (HFSF) exhibited significant anti-melanogenic activity among the various solvent fractions without reducing viability of B16F10 cells. The HFSF suppressed the expression of tyrosinase and tyrosinase-related protein 1 (TRP1). The reduction of microphthalmia-associated transcription factor (MITF) expression by the HFSF was mediated by the Akt/glycogen synthase kinase 3 beta (GSK3ß) signaling pathway, which promotes the reduction of ß-catenin. Treatment with the GSK3ß inhibitor 6-bromoindirubin-3'-oxime (BIO) restored HFSF-induced inhibition of MITF expression. The HFSF bioactive constituents responsible for anti-melanogenic activity were identified by bioassay-guided fractionation and gas chromatography-mass spectrometry analysis as methyl linoleate and methyl linolenate. CONCLUSIONS: These results indicate that HFSF and its constituents, methyl linoleate and methyl linolenate, could be used as whitening agents in cosmetics and have potential for treating hyperpigmentation disorders in the clinic.

Phytol suppresses melanogenesis through proteasomal degradation of MITF via the ROS-ERK signaling pathway.

Phytol (3,7,11,15-tetramethyl-2-hexadecen-1-ol) is an acyclic monounsaturated diterpene alcohol generated from chlorophyll metabolism that exerts anti-inflammatory, antithrombotic, antimicrobial, and antitumor effects. However, the effect of phytol on melanogenesis and the underlying molecular mechanisms of its inhibition remain unknown. Here, we found that phytol suppressed α-melanocyte-stimulating hormone-induced melanogenesis in B16F10 murine melanoma cells without any toxic effects. Phytol significantly attenuated melanin production by reducing the expression of tyrosinase and tyrosinase related protein 1. Treatment with phytol inhibited the expression of microphthalmia-associated transcription factor (MITF) by phosphorylating extracellular signal-regulated protein kinase (ERK). The ERK inhibitor PD98059 restored MITF expression and prevented the anti-melanogenic effect of phytol. We found that the ERK inhibitor coincidently abrogated MITF ubiquitination and degradation, suggesting that the ERK pathway is involved in phytol-induced ubiquitination of MITF. Furthermore, our data show that reactive oxygen species (ROS) production was increased in cells treated with phytol. Consistently, a ROS scavenger inhibited ERK phosphorylation and restored MITF degradation. Accordingly, the intermediary role of ROS was confirmed in phytol-induced MITF degradation. Taken together, these results demonstrate that phytol stimulates ROS production and modulates ERK-mediated proteasomal degradation of MITF in B16F10 murine melanoma cells. These findings suggest that phytol may have potential to be utilized as a whitening agent in cosmetics and as a therapy for skin hyperpigmentation.

Ethyl linoleate inhibits α-MSH-induced melanogenesis through Akt/GSK3ß/ß-catenin signal pathway.

Ethyl linoleate is an unsaturated fatty acid used in many cosmetics for its various attributes, such as antibacterial and anti-inflammatory properties and clinically proven to be an effective anti-acne agent. In this study, we investigated the effect of ethyl linoleate on the melanogenesis and the mechanism underlying its action on melanogenesis in B16F10 murine melanoma cells. Our results revealed that ethyl linoleate significantly inhibited melanin content and intracellular tyrosinase activity in α-MSH-induced B16F10 cells, but it did not directly inhibit activity of mushroom tyrosinase. Ethyl linoleate inhibited the expression of microphthalmia-associated transcription factor (MITF), tyrosinase, and tyrosinase related protein 1 (TRP1) in governing melanin pigment synthesis. We observed that ethyl linoleate inhibited phosphorylation of Akt and glycogen synthase kinase 3ß (GSK3ß) and reduced the level of ß-catenin, suggesting that ethyl linoleate inhibits melanogenesis through Akt/GSK3ß/ß-catenin signal pathway. Therefore, we propose that ethyl linoleate may be useful as a safe whitening agent in cosmetic and a potential therapeutic agent for reducing skin hyperpigmentation in clinics.

Comparative evaluation of free radical scavenging activities and cytotoxicity of various solvent fractions of Sandong Sageretia thea (Osbeck) M.C. Johnst. branches.

Sageretia thea (Osbeck) M.C.Johnst., an evergreen tender shrub of the Rhamnaceae, has been used as folk medicine and in traditional tea. To the best of our knowledge, this is the first study that investigates the free radical scavenging activity and cell cytotoxicity of S. thea branches. The ethyl acetate fraction and n-butanol fraction were identified to be rich in phenolic compounds exhibiting impressive antioxidant activity after stepwise partitioning of solvent fractions of the methanol extracts of S. thea branches (MB). Among the different human cancer cells tested, maximum cytotoxicity was found in MDA-MB-231 human breast cancer cells with MB, chloroform, ethyl acetate, n-butanol and water fraction. A significant (p<0.05) correlation between antioxidant activities and cytotoxicity exists in each fraction. These results suggest the branches of S. thea can be a valuable source of antioxidants, and they can serve as natural anticancer constituents in nutraceutical and pharmaceutical applications.