Total Phenol/Flavonoid Content, Antibacterial and DPPH Free Radical Scavenging Activities of Medicinal Plants

The general desire to replace antibiotics and synthetic antioxidants with natural plants extracts has gained importance in recent years. This approach may be associated with the negative health effects of synthetic antioxidants and antibiotic resistance. Due to these controversial issues, in this study, free radical scavenging activity, Total Phenolic Content (TPC), Total Flavonoid Content (TFC), and antimicrobial activity of Methanolic Extracts (ME) from Teucrium polium, Smyrnium cordifolium Boiss, Mentha longifolia, and Nectaroscordum tripedale leaves were compared with Crocus sativus tepals. The antioxidant activity of these extracts was investigated in comparison with BHA, BHT, and alpha-tocopherol by DPPH method. Antimicrobial activities were determined by paper disc agar diffusion method against S. aureus (Gram positive) and E. coli 0157: H7 (Gram negative). Results showed that C. sativus tepals contained the highest TPC (37.36 mg GAE g(-1)) and TFC (138.52 mg Q g(-1)). Also, radical scavenging activity of C. sativus tepals ME (87.33%) was significantly higher than the other extracts; and it was the same as BHA and alpha-tocopherol statistically. In addition, a significant relationship between radical scavenging activity and TPC (R= 0.964) and TFC (R= 0.806) was found, illustrating the major role of these compounds in antioxidant activity of the mentioned plants. Antibacterial activity of N tripedale leaf extract and C. sativus tepal extract against the two abovementioned pathogens were the highest among all the studied herbal extracts (P< 0.05). Moreover, Results of antimicrobial activities were also strongly correlated to free radical scavenging activity and TPC, which indicates the importance of these factors on antimicrobial properties of the five studied medicinal herbs.