Antioxidant and antibacterial activities of various extracts of Inula cuspidata C.B. Clarke stem

Abstract

The objective of the present study includes estimation of total phenolic and total flavonoid contents and evaluation of antioxidant and antibacterial activities of various extracts of Inula cuspidata stem. I. cuspidata belongs to family Compositae; it is an erect shrub, distributed in western Himalaya, usually found growing on steep rocky or precipitous ground.Total phenolic and flavonoid contents were estimated by Folin–Ciocalteu and aluminum chloride method. Antioxidant activity was performed by four methods: DPPH (1,1-diphenyl-2-picryl hydrazyl radical), ferrous chelating activity, reducing power and nitric oxide scavenging activity. These extracts were screened for antibacterial studies using macro-dilution method.Total phenolic and flavonoid contents were found to be highest in methanol extract (69.44 ± 1.12 mg GAE/g, 12.45 ± 0.67 mg QE/g) followed by chloroform (33.53 ± 0.88 mg GAE/g, 1.27 ± 0.51 mg QE/g) and n-hexane (12.25 ± 1.03 mg GAE/g, 0.08 ± 0.43 mg QE/g) extracts. Methanol extract of I. cuspidata exhibited potent antioxidant activity in all the antioxidant assays followed by chloroform and n-hexane extracts. IC50 values of methanol, chloroform and n-hexane extract were found to be 43.35 ± 0.58 µg/mL, 298.08 ± 0.62 µg/mL, 1989.24 ± 0.71 µg/mL for DPPH, 396.63 ± 0.73 µg/mL, 915.29 ± 0.81 µg/mL, 1180.56 ± 0.88 µg/mL for ferrous chelating and 594.68 ± 0.99 µg/mL, 930.55 ± 1.03 µg/mL, 1959.26 ± 1.25 µg/mL for nitric oxide scavenging assays. A strong correlation was found between total phenolic, flavonoid and 1/IC50 values obtained by different antioxidant assays. The correlation coefficient (R) value obtained was more than 0.9 which exhibits a strong correlation.All the extracts showed significant antibacterial activities against Gram positive bacterial strains with minimum inhibitory concentration (MIC) values ranging from 187.5 to 750 µg/mL and moderate to weak inhibition against Gram negative bacteria with MIC values ranging from 750 to 3000 µg/mL. The present study proves the in vitro anti-oxidant and antibacterial activities of different extracts of I. cuspidata stem.