INFLUENCE OF DIFFERENT SOLVENTS ON ANTIBACTERIAL POTENTIAL OF THREE SPECIES OF HIMALAYAN OAKS

The antibacterial property of three Himalayan Oaks species (Quercus floribunda, Q. leucotrichophora and Q. semecarpifolia) in different solvents against eight gram-positive and gram-negative pathogenic bacteria employing disc diffusion method has been investigated. All the test microorganisms were inhibited significantly by Oaks species at 1000 μg/ml. The MIC and MBC values of each extract (where ZOI ≥ 15 mm) were also determined. Q. semecarpifolia exhibited significantly higher antibacterial activity compared to other species. Solvent systems showed species-specific response for extraction of total content (% yield) of dry extract. Maximum yield was found for ethanol extract (3.59-5.79%). Methanol extract of Q. leucotrichophora showed the highest inhibitory activity against all the tested bacteria (16-23 mm) ZOI, followed by acetone extract (17-23 mm), ethanol extract (15-20 mm). Furthermore, methanol and acetone extracts of Q. leucotrichophora showed significant activity against A. tumefaciens and E. chrysanthemi, with MIC values of 15.6-31.25 μg/ml and MBC values of 15.6-125 μg/ml. Q. semecarpifolia showed its highest antibacterial potential against X. phaseoli and E. chrysanthemi whereas extracts of Q. floribunda leaves were found with moderate activity against all the tested bacteria. The chloroform and ethanol extracts have the lowest inhibitory activity (ZOI, 22 mm each). All the tested bacterial strains were found resistant to aqueous extracts of Oaks species. The bacterial inhibitory potential of Q. semecarpifolia was found very close to gentamycin (30 mcg). The present work fully highlighted the utility of three Oaks spp. of Kumaun Himalaya for their antibacterial activities against pathogenic bacteria.