Rotenoids and coumaronochromonoids from Boerhavia erecta and their biological activities: In vitro and in silico studies

Abstract

Boerhavia erecta is a tropical plant that is widely used in folk medicine. Roots of this plant are applied as a diuretic, stomachic, anthelminthic, febrifuge, and expectorant. The whole plant has been used for treating gastrointestinal, liver, and infertility problems. More than 40 metabolites have been identified in its leaves, roots, and the aerial parts. Among them, isoflavonoids such as rotenoids and coumaronochromonoids are major components. Some of these compounds exhibited potent cytotoxicity, COX inhibition and opioid and cannabinoid receptor. However, little is known about the inhibition of α-glucosidase enzyme of these compounds. As part of our ongoing search for α-glucosidase inhibitors from Vietnamese medicinal plants, we conducted bioactive-guided isolation of the aerial part of Boerhavia erecta. Twelve known compounds were isolated and elucidated, including boeravinone M (1), boeravinone G (2), boeravinone P (3), boeravinone B (4), boeravinone E (5), boeravinone A (6), boeravinone H (7), 9-O-methyl-4-hydroxyboeravinone B (8), boeravinone T (9), boeravinone J (10), boeravinone C (11), and 10-demethylboeravinone C (12). Isolates 2–5, 7, and 12 showed potent α-glucosidase inhibition, which is stronger than acarbose, a positive control. Among them, compound 5 showed strongest inhibition with IC50 value of 85.1 µM. A kinetic study indicated that 5 was a mixed-type inhibitor. Compound 5 was determined to be a potential inhibitor of the α-glucosidase enzyme based on in silico molecular docking mode. Compounds were tested for cytotoxicity against K562 and antimicrobial activity against antibiotic-resistant, pathogenic bacteria Enterococcus faecium, Staphylococcus aureus, and Acinetobacter baumannii. Only compounds 4 and 12 showed moderate activity against K562 cell line. As regards antimicrobial activity, compounds 6 and 10 showed strong inhibition toward Enterococcus faecium. In silico studies of cytotoxicity and antimicrobial activity were also performed, indicating that in vitro and in silico data were consistent.