Protection of human body against the harmful ultraviolet exposure is nowadays more important and interesting. Melanin, a group of bio-pigments, acts as a natural solar filter absorbing and reflecting most of the UV radiation passing through the layer of skin. Over production of the pigments can create a health problem, hyperpigmentation. Tyrosinase is a key enzyme, which catalyzes the conversion of L-tyrosine to L-dihydroxyalanine (L-Dopa), therefore tyrosinase inhibitors are used in various skin preparations due to its pronounced effect on anti-hyperpigment. In this study, an in vitro anti-tyrosinase activity study of the extracts from a hybrid Mulberry plant obtained from Morus alba L. and Morus rotundiloba Koidz, is shown to prove as new source of Thai whitening agent. The presence of betulinic acid, as an anti-inflammatory and anti-tyrosinase activity agent, is also reported. The study develops the technique of HPLC quantitation of betulinic acid and its relation to anti-tyrosinase activity of the whole parts of Thai Mulberry.