Abstract
Mulberry plants have various traditional uses in Thailand, China, Korea and Vietnam. Recently, the root bark of Morus alba L. is used as whitening ingredient in various skin preparations. This paper describes the isolation of two triterpenes from the root bark of a 5 years old hybrid between M. alba L. and M. rotundiloba Koidz., a mulberry sericulture NM60 which is widely grown in Thailand for tea and silk industries. Pentacyclic triterpenes, α-amyrin acetate and betulinic acid, were isolated and identified, their structures were elucidated on the basis of spectroscopic analyses. The antityrosinase activities were tested having the IC50 values of 1.57 mM and 0.50 mM respectively. A validated HPLC technique for betulinic acid was also reported. Linear regression analysis of betulinic acid fell within the range of 61.25-409.15 μg/mL with a linear coefficient of 0.9992. The percentage of recovery is in accordance with that specified by the USP. The limit of detection and limit of quantification were 14.7 and 61.25 μg/mL, respectively. The analysis of the crude methanolic extract revealed 0.14% w/w betulinic acid in the root bark. These findings promote the use of the root bark extract of Thai mulberry hybrid in whitening cosmetics using betulinic acid as a marker and promote further study for the development of antimelanoma agent.