Flavonoids from Maytenus buchananii as potential cholera chemotherapeutic agents

Maytenus buchananii is worldwide distributed small evergreen tree traditionally used as anti-tumor, anti-ulcer, anti-inflammatory, and as antimicrobial. The column chromatography of the MeOH extract of M. buchananii leaves followed by purification of different fractions led to the isolation of nine known flavonoids. Their structures were elucidated on the basis of spectrum analysis, and by comparison with those from the literature. The antibacterial activity was assessed by performing minimum inhibitory concentration (MIC), minimum bactericidal concentration (MBC) and the time-kill kinetic study while the antioxidant activity was determined by the 1,1-diphenyl-2-picrylhydrazyl (DPPH) and trolox equivalent antioxidant capacity (TEAC) assays. All of the extracts/compounds showed antibacterial activity against the strains of Gram-positive bacteria, Staphylococcus aureus, and Gram-negative multi-drug resistance bacteria, Vibrio cholerae (causative agent of cholera) and Shigella flexneri (causative agent of shigellosis). Compounds 2 (MIC = 32 to 128 μg/mL) and 6 (MIC = 16 to 64 μg/mL) showed the largest antibacterial activities with the best MIC (16 μg/mL) recorded with compound 6 on S. aureus. The results of both DPPH and TEAC assays found compounds 3 (EC50 = 1.38 μg/mL; TEAC = 89.69 μg/mL), 5 (EC50 = 1.56 μg/mL; TEAC = 90.93 μg/mL) and 6 (EC50 = 1.42 μg/mL; TEAC = 89.76 μg/mL) to exhibit the most antioxidant activity. Results obtained from this study may help to exploit the use of the M. buchananii leaf extracts and some of their flavonoid compounds as pharmacological ingredients for promoting health, especially for cholera/shigellosis and chronic diseases associated with oxidative stress.