Screening of some Bangladeshi medicinal plants for in vitro antioxidant, antimicrobial and insecticdal activities

Abstract

Screening of some Bangladeshi medicinal plants for antioxidant , antimicrobial , insecticidal activity and analysis of some of their chemical contents were undertaken in the present study. The medicinal plants studied were Mikania cordata and Mucuna pruriens. Literature survey revealed some reports on biological and chemical work done with different parts of these two medicinal plants. However no detailed studies have been reported. In addition previously no work was done on insecticidal activity of these plants and this is also the first report on polyphenol and flavonoid contents in different parts of these plants. Sixteen methanol and chloroform extracts were obtained from different parts of these two medicinal plants. The antioxidant activity was performed by using DPPH free radical scavenging assay. The methanol extract of M. cordana root and shoot showed highest antioxidant activity (19.95 and 28. 18 μg/ml, respectively) compared to that of the reference sample, ascorbic acid (12.58 gglml). The antimicrobial activity was conducted by using agar disc diffusion method. Among the 16 extracts, only the chloroform extract of leaf and flower of M cordana exhibited moderate antimicrobial activity against most of Gram positive and Gram negative organisms. None of extracts of M. pruriens showed antimicrobial activity compared to the standard kanamycin. But interestingly the chloroform extract of seed of M. pruriens showed significant insecticidal activity against Sitofillus oryzae within 30 minutes after treatment followed by methanol extract of seed pulp of M. pruriens. Analysis of total polyphenol and flavonoid contents of all 16 extracts of two medicinal plants showed that the highest concentration of polyphenol (872.94 ± 4.85 mg/g of galic acid equivalent) was present in the methanol extract of leaf of M. cordata and highest concentration of flavonoid (913.39 ± 12.38 mg/g quarcetin equivalent)) was present in the chloroform of the shoot of this plant. The methanol extract of the roots of M. pruriens showed the highest concentration of polyphenol ((398.98 ± 10.20 mg/g gailic acid equivalent) and the chloroform extract of the roots of these plant showed the highest concentration of flavonoid ( 1644.90 t 11.63 mg/g quarcetin equivalent). On the basis of the observed bioassay and phenol and flavonoid profiles, different parts of the two plants may be further studied for development antibacterial, antifungal and insecticidal preparations.