Chiang Mai Journal of Science

Plants belonging to genus Scutellaria (Lamiaceae) possess different pharmacological properties. S.lindbergii Rech.f is a species from this genus that is found in Iran and Afghanistan. The present study aimed to detrmine total phenolic and flavonoid contents together with antimicrobial and antioxidant activities of methanol, ethyl acetate and dichloromethane extracts of the aerial parts of S.lindbergii. Total flavonoid contents were detected using 2% aluminum chloride and expressed as quercetin equivalents (QE). Total phenolics were determined using Folin-Ciocalteu method and expressed as tannic acid equivalent (TAE). The antimicrobial activities of the three mentioned extracts were determined against standard strains of Staphylococcus aureus, Bacillus cereus, Pseudomonas aeruginosa, Escherichia coli and Candida albicans by broth macro-dilution method. Antioxidant activities of the extracts were determined using two model systems, the thiobarbituric acid reactive species (TBARS) and 2,2^´-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging assays. Vitamin E was used as standard in TBARS assay while vitamin C and BHT served as standards in DPPH assay. Total flavonoid and phenolic contents ranged between 33.72-82.32 mg QE/g of dry material and 47.12-80.64 TAE/g, respectively. The results showed that MIC and MCC for the most sensitive strain, S. aureus, was 6.25 mg/mL for methanol extract. In DPPH assay, the methanol extract was more effective than two other extracts. The IC_50s for radical scavenging activity of methanol, ethyl acetate and dichloromethane extracts were 3.03, 4.69 and 16.73 mg/mL respectively. In TBARS method, ethyl acetate extract was more effective than the two other extracts. The highest antioxidant activity of ethyl acetate extract was 36.0% at 4 mg/mL, whereas that of methanol extract was 37.0% at 16 mg/mL and dichloromethane extract was 33.0% at 8 mg/mL. In antimicribial assays, ethyl acetate extract was found as the most effective extarct and S. auerus as the most sensitive strain. In conclusion, S. lindbergii extracts were found to possess moderate antioxidant and antibacterial capacity.