The phytochemical profiles of Morus australis roots, stems and twigs were firstly compared by
HPLC analysis. It was found that Morus australis stem extract mainly contained one known
tyrosinase inhibitor, oxyresveratrol, while its root and twig extract might contain some
unknown potential tyrosinase inhibitors. The root extract of Morus australis was further
investigated in this study. One new compound, austraone A, together with 21 known
compounds, was isolated and their structures were identified by interpretation of MS and NMR
data. In the tyrosinase inhibitory testing, some of them, such as oxyresveratrol, moracenin D,
sanggenon T, and kuwanon O, exhibited stronger tyrosinase inhibitory activities than that of
kojic acid. These results suggested the Morus australis root extract as a good source of natural
tyrosinase inhibitors with a great potential to be used in foods as anti-browning agents and in
cosmetics as skin-whitening agents.