Phytochemical analysis and comprehensive evaluation of antimicrobial and antioxidant properties of 61 medicinal plant species

Plants are rich source of therapeutic compounds that have tremendous applications in pharmaceutical industry. To find new sources of antimicrobial and antioxidant agents, methanol/chloroform and aqueous extracts of 61 medicinal plants were evaluated systematically. Antimicrobial activity was assessed against six bacterial and five fungal strains, while natural antioxidants were studied using reducing power (RP), total antioxidant capacity (TAC) and 2,2-diphenyl-1-picrylhydrazyl (DPPH) free radical scavenging assay. Six plants exhibited broad spectrum antibacterial activity while two exerted significant antifungal activity. Total phenolic content (TPC) of the samples varied from 20.2 to 85.6 mg/g dry weight (DW) in M/C extracts and 5.5 to 62.1 mg/g DW in aq. extracts, expressed as gallic acid equivalents (GAE). Total flavonoid content (TFC) varied from 2.9 to 44.5 mg quercitin equivalent (QE)/g DW of sample for M/C extracts and 2.4 to 37.1 mg QE/g DW for aq. extracts. The results showed that antioxidant activities of plant species varied to a great extent not only among extracts (M/C and aq.) but also between the assays used for antioxidant evaluation. Significant linear correlation (p< 0.01) of TPC with antioxidant activities suggested their contribution to antioxidant activity. Using high performance liquid chromatography coupled with diode array detector (HPLC-DAD), gallic acid and rutin were detected in most of plant extracts with significant antioxidant activities. Study identifies plants with antimicrobial and antioxidant properties which could be used for isolation of desired therapeutic compounds and to develop infusions, nutriceuticals and pharmaceuticals. (C) 2015 Production and hosting by Elsevier B.V. on behalf of King Saud University.