Isolation of new bibenzyl derivatives from Bulbophyllum auricomum and evaluation of their α-glucosidase inhibitory activity

Abstract Bulbophyllum auricomum Lindl., commonly referred to as the 'Royal Thazin' in Myanmar, holds the esteemed status of being the national flower of the country. In our research, we delved into the ethyl acetate extract derived from the pseudobulbs and roots of this plant. This extract exhibited significant inhibitory activity against the α-glucosidase enzyme, prompting a detailed investigation into its active compounds. Our study resulted in the isolation and characterization of several compounds, including a novel natural product named 2-(4-hydroxyphenyl) ethyl 3-(2-hydroxyphenyl) propanoate. Additionally, we identified two previously unreported inseparable isomeric bibenzyls, namely 7-hydroxybatatasin III and 8-hydroxybatatasin III. Furthermore, we isolated six known compounds, including batatasin III, lusianthridin, tristin, phochinenin G, phoyunnanin E, and phoyunnanin C. Significantly, our study unveiled that phochinenin G acts as a reversible noncompetitive inhibitor of the α-glucosidase enzyme. This compound displayed greater inhibitory activity than the standard drug acarbose. GRAPHICAL ABSTRACT