Evaluation of antimicrobial, antioxidant and cytotoxic activities of methanolic extracts of Lagerstroemia speciosa leaves and barks

Methanolic extracts of Lagerstroemia speciosa leaves (MLL) & barks (MBL) have been evaluated for their antimicrobial, antioxidant & cytotoxic activity. Antimicrobial activity of the extracts was evaluated against 11 Gram-positive, Gram-negative bacteria and 3 fungi using disk diffusion technique. Kanamycin (30μg/disc) was used as standard. Antioxidant potentiality of the extracts was investigated on DPPH scavenging activity, Total antioxidant capacity, Reducing ability as well as total phenolic contents. Cytotoxic study was done by brine shrimp lethality bioassay and vincristin sulphate was used as standard. In antimicrobial study, the average zone of inhibition exhibited by MLL & MBL (each 500μg/disc) was 10-20 mm & 12-21mm respectively. In DPPH scavenging activity, IC50 value was found 27.89 ± 0.83µg/ml,21±0.61 µg/ml and 16.76 ± 1.11μg/ml for MLL, MBL and standard ascorbic acid, respectively. Total antioxidant capacity was found 398.37 ± 0.22 mg/g and 346.37 ± 4.02 mg/g equivalent of ascorbic acid for MLL & MBL, respectively. Reducing ability was found concentration dependent for both the extracts. The total phenolic content was found 71.06 ± 2.01 and 60.65 ± 2.16 mg/g equivalent of gallic acid for MLL & MBL, respectively. The cytotoxicity exhibited by MLL was promising with LC50 value 9.602μg/ml, comparing with the LC50 (6.25 μg/ml) values of standard vincristin sulphate as a positive control. The results suggest into the plant extracts could be used as a potential therapeutics in many pathological conditions.