Thesis Abstract

The present study was designed to estimate the total phenolic and flavonoid contents and to evaluate the in vitro antioxidant activities of both the methanol extract and the various solvent fractions of the whole plant, Desmodiumramosissimum. Qualitative phytochemical screening showed the presence of various bioactive components such as phenolics, flavonoids and tannins. The quantitative analyses of total phenolic content (TPC) and total flavonoid content (TFC) were carried out spectrophotometrically using Folin-Ciocalteu phenol reagent and aluminum chloride method, respectively. Ethyl acetate fraction followed by n-butanol fraction exhibited high total antioxidant activity, DPPH radical scavenging ability as well as ferric ion reducing ability when compared to all other solvent fractions including the methanol extract. The presence of these flavonoid and phenolic compounds might contribute to the antioxidant properties observed in these fractions. In order to support this observation, the relationship between the antioxidant content using various models revealed that TPC exhibited a strong correlation with ferric ion reducing potential (FIRP) and total antioxidant capacity (TAC) with R2 vmalues of 0.995 and 0.980, respectively; but a weak relationship with 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical with R2 value of 0.877. However, aqueous fraction showed a strong relationship between DPPH and its concentration compared to other fractions. This showed that various solvent extracts possess unique chemical constituent of plant with various antioxidant capacity. Free radicals were scavenged by the extract and solvent fractions in a concentration-dependent manner within the range of the given concentrations (25-1000 mg/l) in all models. The findings from this study show that methanol extract and the solvent fractions of Desmodiumramosissimum G. Don contained phenolics, flavonoids and tannins which exhibited antioxidant properties.

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