Investigation of the anti-osteoporotic activity of Edgeworthia papyrifera and Edgeworoside A and anti-melanogenic activity of Rhizoma arisaematis

Abstract

Natural products have been considered a rich source of new drugs, nutraceuticals and cosmeceuticals for decades. Efforts on discovering new bioactive ingredients with drug-like benefits from natural products have been aided greatly by the availability of natural product-derived libraries (collection of crude mixtures, fractions, and purified compounds). In this thesis, a library of extracts derived from 4,200 plants native to Korea was exploited to identify candidates for anti-osteoporosis agents and anti-melanogenic agents. The approach to discover candidates for anti-osteoporosis agents involves a series of assays that utilize biomarkers for osteoclast and osteoblast differentiation: the library was screened for the ability to inhibit RANKL-induced NF-κB (nuclear factor–kappa B) expression in RAW 264.7 osteoclatic cells, to modulate the activity of alkaline phosphatase in MC3T3-E1 osteoblastic cells, and to enhance the deposition of extracellular calcium in osteoblasts in vitro. These efforts in conjunction with a dereplcation technology led to identification of Edgeworthia papyrifera and edgeworoside A which exhibited a desired bioactivity profile in vitro. In an animal model of post-menopousal osteoporosis, E. papyrifera was demonstrated to improve all of the osteoporosis relevant parameters, suggesting that E. papyrifera and edgeworoside A may be used as functional ingredients in health supplements to increase bone strength and as therapeutics to treat osteoporosis. Identification of candidates for anti-melanogenic agents involves a series of tests that utilize α-MSH-stimulated melanogenesis in vitro and quantification of tyrosinase and TRP1 expression in B16F1 cells. The efforts led to identification of Rhizoma arisaematis that inhibited biosynthesis of melanin and expression of tyrosinase and TRP1 in α-MSH-treated B16F1 cells. The anti-melanogenic effect of R. arisaematis was mediated through activation of autophagy in B16F1 cells, and pharmacological inhibition of autophagy reduced the anti-melanogenic activity of R. arisaematis in α-MSH-treated B16F1 cells. Further analyses of R. arisaematis using three-dimensional skin substitutes and in a human clinical trial revealed that it significantly suppressed pigmentation and exerted whitening effects on human skin. These observations serve as a basis for further elaboration of R. arisaematis for the development of functional skin care products.