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Phytochemical evaluation, in-vitro radical scavenging and antioxidant activities of aqueous leaf extract of Heen Bovitiya (Osbeckia octandra L. (DC.) grown in Sri Lanka
Sujeewa Krishanthi Hettihewa and Pilippenge Dinithi Sanketha Ananda Silva

Abstract
Osbeckia octandra L. (DC.) is an endemic plant which belongs to the family Melastomataceae and highly used in Sri Lankan Ayurvedic medicine. The aim of the present study was to evaluate total phenolic (TP), flavonoid (TF) contents, in-vitro radical scavenging activity and antioxidant activity of aqueous extract obtained from Osbeckia octandra L. (DC.) (Heen bovitiya) leaves. The crude aqueous extract was prepared by soaking method in the dark conditions from oven dried Heen bovitiya leaves collected from Galle District in Sri Lanka. The freeze dried powder of the crude extract was obtained and subjected to preliminary phytochemical tests. TP and TF contents of extract were determined by Folin-Ciocalteu assay and Aluminum chloride colorimetric method respectively. In-vitro antioxidant activity was determined using 2,2-diphenyl- 1-picrylhydrazyl (DPPH) and ferric reducing antioxidant power (FRAP) assays. Results of the preliminary phytochemical screening exhibited the presence of phenolic compounds, flavonoids, tannins, terpenoids, phytosterols, saponins, alkaloids, carbohydrates, proteins and amino acids. TP and TF contents of aqueous extract were calculated as 5356.501±59.552 mg Gallic acid equivalents (GAE)/100 g dry weight (DW) of leaves and 2004.514±2.206 mg Catechin equivalents (CAE)/100 g DW of leaves. Radical scavenging and antioxidant capacities for the aqueous extract were 11.279±0.516 mmol Trolox equivalents/100 g DW and 33.366±0.674 mmol Fe(II) equivalents/100 g DW of leaves. Results revealed that O. octandra leaves have a high TP and TF content which is exhibited through its promising antioxidant activity. Hence, it was concluded that O. octandra is a medicinally important herb with remarkable antioxidant activity which could be used to address pathological states related to oxidative stress.

Keywords: Antioxidant; Total flavonoid; Total phenolic; Osbeckia octandra L. (DC.)