Alkaloids isolated from leaves of Prosopis juliflora against Xanthomonas pathovars

Abstract

Aqueous extract, different solvent extracts and isolated constituents of leaves of Prosopis juliflora (Sw.) DC. (Fabaceae) were assayed for antibacterial activity by cup diffusion method against three phytopathogenic Xanthomonas pathovars viz., Xanthomonas axonopodis pv. malvacearum, X. a. pv. phaseoli and X. campestris pv. vesicatoria associated with angular leaf spot of cotton, common blight of bean and bacterial spot of tomato respectively and 14 human pathogenic bacteria. Aqueous, methanol and ethanol extracts showed significant antibacterial activity against all pathovars of Xanthomonas and the activity varied among 14 human pathogenic bacteria. Methanol extract was subsequently fractioned and monitored by bioassay leading to the isolation of active fraction and confirmed as alkaloids by further phytochemical analysis. The active fraction recorded highly significant antibacterial activity in vitro (MIC 6, 5 and 4 µg/ml for Xanthomonas pathovars and 3 and 5 µg/ml against Staph. aureus and Strep. faecalis) compared with synthetic antibiotics such as Bact-805 and K-cycline tested at the recommended dosage for phytopathogenic bacteria and Gentamycin and Streptomycin discs for human pathogenic bacteria.