Common bean (Phaseolus vulgaris L.) is a major food crop in Africa and its production is plagued by diseases that reduce the potential yield, thus threatening food security. This study evaluated compounds from Hagenia abyssinica for bioactivity against bean bacterial pathogens Xanthomonus axonopodis pv. phaseoli and Pseudomonus savastanoi pv. phaseolicola. One triterpenoid, 1,3,19-trihydroxy-2-oxo-12-ursen-28-oic acid (1) and two flavans namely, 3,3’,4’,5’-tetrahydroxyflavan (2) and 3,3’,4’,5,7-pentahydroxyflavan (3) were isolated from the bark of H. abyssinica. Structures of the compounds were elucidated based on nuclear magnetic resonance (NMR) and high-resolution electrospray ionization mass spectra (HRESIMS) data analysis. These compounds and the ethyl acetate extract were evaluated against the bean pathogens using agar disc diffusion method. The ethyl acetate crude extract showed activity against the two pathogens with minimum inhibitory concentrations of 1.25 mg/mL. Compound 1 showed good activity against X. axonopodis pv. phaseoli and P. savastanoi pv. phaseolicola with minimum inhibitory concentrations of 5 and 1.25 mg/mL, respectively, whereas compounds 2 and 3 showed modest activity. This study demonstrated that compound 1 and the ethyl acetate crude extract from H. abyssinica have good activity against the two bean pathogens and can be used in the development of biopesticides to control bean diseases.
Key words: Bean pathogens, bioactive compounds, Hagenia abyssinica, Xanthomonus axonopodis pv. phaseoli, Pseudomonus savastanoi pv. phaseolicola.
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