A Comparative Study of Antioxidant Activity, Total Phenolic and Flavonoid Contents in Different Parts of Helicteres isora L.

Abstract

Helicteres isora L., commonly known as Indian Screw Tree is a highly valued medicinal plant in South-East Asia. The various phytochemicals like phenols, flavonoids and other antioxidants that impart the medicinal properties in this plant, vary in their composition and concentration in different plant parts. In the present research, the total phenolic content, total flavonoids content and free radical scavenging activity (FRAP and DPPH assay) in fresh and dry sample extracts of leaf, bark, fruit and root of H. isora L., prepared in four different solvents (distilled water, ethanol, methanol and acetone) were studied, and their results compared using Pearson’s Correlation. The plant extracts were also subjected to RP-HPLC for detection and quantitation of naturally occurring phenolic compounds using six phenolic standards (Gallic acid, Vanillin, Catechol, Ferrulic acid, p-coumaric acid and Caffeic acid). The highest total phenolic content (7.22 mg/g GAE) and FRAP value (64.98 mg/g TE) were observed in aqueous dry root extract. The acetone extract of fresh leaf (57.08 mg/g of RE) was found richest in total flavonoids, while the methanolic extract of fresh fruit uniquely exhibited strong free radical scavenging activity as evidenced by the low IC50 value (34.37 mg/ml) in DPPH assay. The RP-HPLC analysis revealed that Catechol and Gallic acid were most abundantly found phenolic compounds in extracts of H. isora L. The total phenolic content showed strong positive correlation with free radical scavenging activity (FRAP and DPPH assays) in both fresh and dry plant parts, suggesting that phenols are the main compounds responsible for the antioxidant activity. The root of H. isora L. was found rich in phenolics and antioxidant capacity indicating its strong potential for medicinal use, followed by fruit, leaf and bark.