Antioxidant Potential, Phenolics Content and Antimicrobial Attributes of Selected Medicinal Plants

Abstract

The bioactive extracts recovered from Curcuma longa (stem), Mentha aquatica (stem and leaves), Emblica officinalis (fruits), Nigella sativa (seeds), and Glycyrrhiza glabra (stem) using methanol and ethanol, were appraised for antioxidant (total flavonoid contents, total phenolic contents, DPPH free radical scavenging ability, inhibition of linoleic acid peroxidation and reducing power) and antimicrobial attributes. Total phenolics (16.89 ± 0.18 - 25.06 ± 0.31g GAE/100g) and total flavonoids (1.96 ± 0.07 - 13.54 ± 0.18 CE g/100g) contents of aqueous methanol extracts of tested plant materials were significantly (p < 0.05) lower than that of aqueous ethanol extracts (13.87 ± 0.12 - 28.63 ± 0.34 g GAE/100g) and (2.20 ± 0.10 - 8.71 ± 0.24 CE /100g), respectively. The percent inhibition of linoleic acid per oxidation by crude ethanol extracts of plants was in the range of 48.72 ± 1.24 - 70.79 ± 1.57 and crude methanol extract 35.90 ± 1.28 - 61.54 ± 2.14, while the range of DPPH free radical scavenging activity of ethanol extracts was (58.36 ± 1.98 - 80.55 ± 3.07) and methanol extracts (39.55 ± 1.52 - 79.64± 2.33). The reducing power of the tested extracts obtained by ethanol (at the concentration of 10 mg/mL) ranged 1.11 ± 0.12 – 1.53 ± 0.18 while for methanol extracts 0.98 ± 0.11 – 1.39 ± 0.12. Among the attributes analyzed, total phenolics, total flavonoids, and DPPH free scavenging activity were found to be varied significantly in all the tested medicinal plants. The extracts from all plants showed good antimicrobial potential against a penal of bacteria, including E. coli, P. multocida and S. aureus, and fungi including A. niger, A. flavus, A. alternate, and G. lucidium. Overall, the tested samples were found to be a good source of natural antioxidant and antimicrobial agents and thus can be explored for potential functional food and nutra-pharmaceutical applications.

Keywords

• medicinal flora
• antioxidant components
• solvent extraction
• colorimetric assays