Antibacterial activity of leaf extracts of seven grape cultivars against six strains of bacteria

Background: Grape (Vitis spp.) is one of the most widely grown fruit crops in the world. It contains large amounts of phenolic compounds which have antimicrobial properties. Many efforts have been done to discover new antimicrobial compounds from various kinds of natural sources to benefit mankind. The current study is aimed to evaluate the antimicrobial properties of the methanolic extract of different cultivars of grapes against six bacterial strains.Methods: In the present study, the antibacterial activity of different concentrations (25, 50 and 100mg/mL) of methanolic leaf extracts of seven cultivars of grape (Red Globe, Autumn Royal, Crimson, Thompson, Sundarkhani, Perlette and King’s Ruby) was tested against six strains of bacteria (Proteus sp., Streptococcus viridans, Escherichia coli, Pseudomonas sp., Staphylococcus aureus and Clostridium septicum) using agar well diffusion method.Results: The methanolic leaf extract of all the cultivars showed significant antibacterial activity, suppressing the growth of all the six bacterial strains tested. The inhibition zones against the different bacteria ranged from 12.6 mm to 29.6 mm. The highest zones of inhibition were produced by Proteus sp. (29.6 mm), Pseudomonas sp. (27 mm), Staphylococcus aureus (27 mm), E. coli (26 mm), Streptococcus viridans (23.3 mm) and Clostridium septicum (21.0mm) at 100 mg/mL concentrations of different cultivars.Conclusion: This study confirms that Vitis vinifera methanolic leaf extracts have inhibitory activity against all the tested microorganisms and is worthy of further investigation.Keywords: Vitis vinefera; Antibacterial activity; Proteus sp.; Streptococcus viridans; E. coli; Pseudomonas sp.; MRSA; Clostridium septicum; Agar well diffusio