EFFECT OF MEDICINAL PLANT EXTRACTS ON THE ANTIMICROBIAL ACTIVITY OF AMOXYCLAVE AND ERYTHROMYCIN AGAINST E. COLI AND S. AUREUS

Development of microbial resistance leads new drug discovery, modification of antibiotics, administration of two or more antibiotics, use of traditional medicinal plants and their combinations with antibiotics. In the present study, 72 medicinal plants extracts were screened to potentiate the antimicrobial with erythromycin and amoxyclave. Among all the medicinal plant, Colebrookea oppositifolia was selected to analyze the synergistic activity with erythromycin and amoxyclave. The class I synergism (increase in the zone of inhibition) was observed in petroleum ether extract of leaves and inflorescence of C. oppositifolia in combination with amoxyclave with the increased zone from 6 +/- 0.2 mm to 8 +/- 0.2 mm and 6 +/- 0.2 mm to 10 +/- 0.2 mm, respectively. The class I synergisms also exhibited in methanol leaf extract of C. oppositifolia in combination with erythromycin and amoxyclave against S. aureus. Interestingly, the methanolic leaf extract (alone) did not show any antibacterial effect against S. aureus, but in combination with erythromycin/amoxyclave enhanced the zone of inhibition from 3 +/- 0.1mm to 9 +/- 0.2 mm and 5 +/- 0.2mm to 9 +/- 0.2mm, respectively. Class II synergism (making drug bactericidal) was exhibited by methanol leaf extract against S. aureus. The sequential fractionation of the methanolic extract using solvent extraction (n-butanol, ethyl acetate) showed the class I synergism in combination with amoxyclave and erythromycin. The solvent fraction of ethyl acetate has increased the zone of inhibition of erythromycin from 4 +/- 0.3 to 11 +/- 0.2 mm and amoxyclave from 8 +/- 0.1 to 12 +/- 0.1 mm against S. aureus. The n-butanol fraction increases the zone of inhibition of erythromycin from 4 +/- 0.1 to 12 +/- 0.2 mm, whereas the zone of inhibition of amoxyclave was increased from 8 +/- 0.1mm to 13 +/- 0.1mm by against S. aureus. The solvent fractions did not show synergism against E. coli. Class II synergism was shown by n-butanol and ethyl acetate fraction, which enhanced the potency of erythromycin by making it bactericidal.