Evaluation ofNyctanthes arbor-tristisleaf extracts for antioxidant, antibacterial and anticancer potentialsin vitro

Abstract

The bitter leaves of Nyctanthes arbor-tristis are used in traditional systems of medicines for the treatment of rheumatism, sciatica and intestinal worms. The present study was to provide scientific backing to the traditional claims through the in vitro evaluation of the ethanolic, methanolic and aqueous leaf extracts for antioxidant, antibacterial and anticancer potentials. Antioxidant potential was tested by 2, 2-diphenyl-1-picryl-hydrazyl (DPPH) assay based free radical scavenging ability. The scavenging effect of leaf extract and ascorbic standard on the DPPH radical was found to be in the following order: Ascorbic acid> Ethanolic> Aqueous> Methanolic extracts and their IC50 values were found to be 1.6 μg, 25 μg, 34 μg and 38 μg respectively. The antibacterial potential was tested against five strains each of Gram positive and Gram negative bacteria through agar disc diffusion assay. The results showed that the bactericidal potential was higher in aqueous extracts followed by methanolic and ethanolic extracts. The bacterial strains Salmonella typhimurium, Pseudomonas aeroginosa, Klebsiella pneumonia, Escherichia coli, Pseudomonas marginata and Staphylococcus epidermis were found to be more susceptible to the aqueous extract where Micrococcus leuteus, Staphylococcus aureus, Streptococcus pyogenes and Bacillus subtilis were more sensitive to the methanolic extract. The anticancer potential of the extracts was tested using MTT (3-(4,5dimethylthiazol-2-yl)-2,5- diphenyl tetrazolium bromide) based cytotoxic test on the T-cell leukemia (MOLT-4) cells at 24, 48 and 72 hours incubation. Simultaneously the growth inhibition potential of the extracts was tested on mitogen stimulated T-lymphocyte cultures derived from the peripheral blood of healthy individuals. All the extracts exhibited significantly higher cytotoxicity towards cancer cell with increasing time and dose, and at the same time there was a considerable decrease in the level of toxicity observed in normal cells at all the dose and time points. As a measure of genotoxic assessment, micronucleus assay was done in cancer and normal cultures exposed to increasing concentration of different extracts. In both cultures, there was a vast difference between the number of micronuclei induced by the extracts even at the highest tested concentration and the positive control. The results indicated that more elaborate study in this plant may lead to the discovery of new therapeutic agents.