Isolation and Structural Elucidation of Coumarin and Flavonoids from Citrus grandis Linn. (Tubtim Siam Pomelo) and Their Biological Activities

Abstract

Natural products from plants have the potential to exert antioxidant, anti-tyrosinase, antibacterial, and cytotoxic activities and have been widely used as ingredients in cosmetics, medicines, or supplementary food. Several types of secondary metabolites from the Citrus genus have been reported to exhibit interesting biological activity. Due to this lack of studies and biological activity of compounds from related species, it was considered important to investigate Citrus grandis Linn. (Tubtim Siam Pomelo) to be studied. The objective of this research was to isolate and elucidate the structures of chemical constituents and to evaluate their biological activity from the peels of C. grandis Linn. A coumarin (1) and 3 flavonoids (2 - 4) were isolated from the peels of C. grandis Linn. The structures of these compounds were elucidated by analyses of spectroscopic data as well as comparison of their spectroscopic data with the previously published data. Compounds 1 - 4 have been evaluated for antioxidant, anti-tyrosinase, antibacterial and cytotoxic activities. Compound 2 showed the highest inhibition in DPPH and tyrosinase with IC50 values of 0.219 ± 0.011 and 0.033 ± 0.002 mg/mL, respectively. Interestingly, compound 1 - 4 were the first time being isolated from Tubtim Siam Pomelo. HIGHLIGHTS Chemical constituents from grandis Linn. (Tubtim Siam Pomelo) have not been reported Coumarin and flavonoids have been isolated from acetone extract (-) meranzin hydrate, 5-demethoxynobiletin, tangeretin and naringin were isolated for the first time from Tubtim Siam Pomelo Four compounds exhibited good antioxidant and anti-tyrosinase activities GRAPHICAL ABSTRACT