We previously reported the antifungal, antioxidant, and vasodilator effects of Ryudai gold (RD) and isolated some potentially active compounds. Here, we aimed to identify other active compounds present in RD and investigate their pharmacological effects, in terms of antioxidant, and inhibitory activities against skin disease-related enzymes, pancreatic α-amylase, and lipase enzymes. The methanol extract of RD rhizomes was subjected to repeated fractionation by silica gel column, Toyopearl HW-40F column, and high-performance liquid chromatography to obtain a pure compound. The isolated compound was characterized by analyzing its spectroscopic data, particularly nuclear magnetic resonance spectra. Inhibitory activities against α-amylase, pancreatic lipase, elastase, collagenase, xanthine oxidase, and tyrosinase were evaluated to investigate its potential antidiabetic, antiobesity, and enzyme inhibitory effects. Antioxidant activity was evaluated using 2,2-diphenyl-1-picrylhydrazyl-scavenging, reducing power, and 2-deoxyribose degradation assays. The purified compound was recognized as 4-methylene-8-hydroxybisabola-2,10-diene-9-one, a new compound. The content of this compound was 0.068 μmol/g or 0.016 mg/g of dry RG powder. Our results suggested that 4-methylene-8-hydroxybisabola-2,10-diene-9-one exhibited antidiabetic, antiobesity, enzyme inhibitory, and antioxidant activities by inhibiting their respective enzymes activity. 4-methylene-8-hydroxybisabola-2,10-diene-9-one could be a promising candidate therapeutic agent or a lead compound for the development of new synthetic drugs.
Keywords: Antidiabetic; Antiobesity; Antityrosinase; NMR; Turmeric.