Antioxidant and Antibacterial Activity of Ludwigia octovalvis on Escherichia coli O157:H7 and Some Pathogenic Bacteria

Ludwigia octovalvis (Jacq.) P. H. Raven (Family: Onagraceae) is traditionally used to treat skin diseases, diarrhea and flatulence. This study assayed twelve extracts of L. octovalvis for their total phenolic content (TPC), antioxidant and antibacterial activity. The highest TPC at 264.76 ± 0.23 GAE mg/g dry weight and antioxidant activity (evaluated by 2, 2-diphenyl-1-picrylhydrazyl and ferric reducing antioxidant power assays) at 1080.84 ± 6.07 μM TE/mg dry weight and 1256.88 ± 5.38 μM TE/mg dry weight, respectively, were detected in 80% methanol extract of the leaf. A strong correlation between TPC and antioxidant activities of both assays was observed (r > 0.98). Eighty percent methanol extract of the leaf gave the lowest minimum inhibitory concentration (MIC, 62.5 μg/mL) and minimum bactericidal concentration (MBC, 125.0 μg/mL) against Escherichia coli O157:H7, Escherichia coli ATCC 25922 and Bacillus spizizenii (ATCC 6633), while 80% methanol extract of the root gave similar MIC and MBC values against Pseudomonas aeruginosa (ATCC 27853). Our findings suggest that leaf of L. octovalvis as a possible new source of natural mixture of antioxidant and anti-E. coli O157:H7.