The Modulation of Melanogenesis in B16 Cells Upon Treatment with Plant Extracts and Isolated Plant Compounds

Plants are a rich source of secondary metabolites that exhibit numerous desired properties. The compounds may influence the biology of melanocytes, pigment cells that produce melanin, by modulating numerous signaling pathways, including cAMP/PKA, MAPKs and PI3K/AKT. Its downstream target is microphthalmia-associated transcription factor, responsible for the expression of the tyrosinase enzyme, which plays a major role in melanogenesis. Therefore, this literature review aims to provide insights related to melanogenesis modulation mechanisms of plant extracts and isolated plant compounds in B16 cells. Database searches were conducted using online-based library search instruments from 2012 to 2022, such as NCBI-PubMed and Google Scholar. Upregulation or downregulation of signaling pathways by phytochemicals can influence skin hypo- and hyperpigmentation by changing the level of melanin production, which may pose a significant cosmetic issue. Therefore, plant extracts or isolated plant compounds may be used in the therapy of pigmentation disorders.

Terpenoids with Special Pharmacological Significance: A Review

Terpenoids are a very prominent class of natural compounds produced in diverse genera of plants, fungi, algae and sponges. They gained significant pharmaceutical value since prehistoric times, due to their broad spectrum of medical applications. The fragrant leaves of Eucalyptus trees are a rich source of terpenoids. Therefore this review starts by summarizing the main terpenoid compounds present in Eucalyptus globulus, E. citriodora, E. radiata and E. resinifera and describing their biosynthetic pathways. Of the enormous number of pharmaceutically important terpenoids, this paper also reviews some well established and recently discovered examples and discusses their medical applications. In this context, the synthetic processes for (–)-menthol, (–)- cis-carveol, (+)-artemisinine, (+)-merrilactone A and (–)-sclareol are presented. The tricyclic sesquiterpene (–)-englerin A isolated from the stem bark of the Phyllanthus engleri plant ( Euphorbiaceae) is highly active against certain renal cancer cell lines. In addition, recent studies showed that englerin A is also a potent and selective activator of TRPC4 and TRPC5 calcium channels. These important findings were the motivation for several renowned research labs to achieve a total synthesis of (–)-englerin A. Two prominent examples – Christmann and Metz – are compared and discussed in detail.