Comparative evaluation of antimicrobial and antioxidant potential of ethanolic extract and its fractions of bark and leaves of Terminalia arjuna from north-western Himalayas, India

The present study was aimed to evaluate the antimicrobial and antioxidant potential of ethanolic extract and its different solvent fractions (chloroform, ethyl acetate, n-butanol and aqueous fraction) of bark and leaves of Terminalia arjuna. The antimicrobial activity was determined by disc diffusion and minimum inhibitory concentration (MIC) methods against six bacterial stains. The antioxidant activity was evaluated by using DPPH, FRAP and Nitric oxide (NO) scavenging assay. The total phenolics and flavonoid content were found to be higher in n-butanolic fraction of bark (294.6 ± 8.1 mg/g GAE and 168.6 ± 12.3 mg/g RE, respectively) and leaves (203.7 ± 7.0 mg/g GAE and 144.8 ± 11.1 mg/g RE, respectively). The maximum antimicrobial activity was shown by n-butanolic fraction of bark and leaves. The zone of inhibition of 15.0 ± 0.7 mm, 15.5 ± 0.7 mm, 15.0 ± 1.5 mm, 15.5 ± 0.7 mm, 15.0 ± 0.7 mm, 15.0 ± 0.7 mm was observed against Bacillus subtilis, Staphylococcus aureus, Eschericia coli, Klebsiella pneumoniae, Pseudomonas aeruginosa and Salmonella typhi respectively. In case of leaves extract, zone of inhibition of 13.5 ± 0.7 mm, 16.5 ± 0.7 mm, 14.0 ± 0.5 mm, 15.0 ± 0.5 mm, 13.5 ± 0.7 mm, 14.0 ± 0.7 mm was observed against B. subtilis, S. aureus, E. coli, K. pneumoniae, P. aeruginosa, S. typhi, respectively. The n-butanol fraction of bark [IC50-4.1 μg/ml (DPPH), 21.0 μM (FRAP), 3.3 μg/ml (NO)] and leaves [IC50-4.8 μg/ml (DPPH), 28.9 μM (FRAP), 3.2 μg/ml (NO)] showed more antioxidant potential as compared to that of crude ethanolic extract, ethyl acetate fraction, chloroform fraction, aqueous fraction and even ascorbic acid. These results clearly indicated comparative antioxidant potential and antimicrobial activity in extracts of bark and leaves of T. arjuna.