Anti-vibrio and antioxidant properties of two weeds: Euphorbia serpens and Amaranthus viridis

Abstract

Euphorbia serpens and Amaranthus viridis are two weed plants, extracts of which were found to be bioactive against antibiotic resistant Vibrio cholerae. Amongst 15 V. cholerae strains studied, 10 were resistant against 6 different antibiotics, such as trimethoprim, polymyxin B sulphate, vancomycin hydrochloride, amoxicillin and ampicillin. Extracts of both the plants were prepared with five different solvents; hexane, dichloromethane, ethyl acetate, ethanol and water. Aqueous extract of E. serpens and ethanolic extract of A. viridis showed maximum anti-Vibrio activity against all the strains of V. cholerae. The anti-Vibrio compounds from both the plants were purified by column chromatography and bioactive fractions were found to be stable at extreme temperature and pH. Minimum Inhibitory Concentration (MIC) of E. serpens and A. viridis were found to be 3.92 and 12.32 mg mL -1, respectively against the most resistant V. cholerae strain in our study. The bioactive fractions were further analyzed by HPLC. Column purified fraction with anti-vibrio activity caused cell wall indentation and cell ruffling on V. cholerae as seen by scanning electron microscopy. Antioxidant content of bioactive fraction of E. serpens and A. viridis was 28.33 and 13.17 mg g -1 of dry weight of extract, respectively as evaluated by TRP assay, 68.93 and 8.65 mg g -1 of dry weight of extract, respectively by FRAP assay and 158 mg g -1 of extract and 55.32 mg g -1 of dry weight of extract, respectively by ABTS assay. The bioactive ingredients in both the plants are essential oil.