The rhizomes of Tulbaghia violacea Harv. used in Eastern Cape of South Africa for the treatment of heart diseases and several human ailments was investigated for antioxidant activity. The phytochemical content and toxicity of the fresh and dried rhizomes was also evaluated. Antioxidant activity was determined by spectrophotometric methods such as 2, 2-diphenyl-2-picrylhydrazyl (DPPH), hydrogen peroxide and lipid peroxidation scavenging activities and ferric reducing power assay. Toxicity evaluation was carried out using brine shrimps cytotoxicity test. Results obtained indicated that methanolic extract of the fresh rhizomes contained higher concentration of flavonoid, flavonol, phenolics, tannin and proanthocyanidin than dried sample. Antioxidant studies revealed that the two extracts exhibited potent antioxidant activities in concentration dependent manner. The fresh extract had higher radicals scavenging activity than the dried extract with 50% inhibition of DPPH, hydrogen peroxide and lipid peroxidation at a concentration of 35.0 ± 0.12, 19.3 ± 0.11 and 17.9 ± 0.15 µg/ml, respectively. The dried extract demonstrates lower ferric reducing ability with an absorbance of 0.61 when compared with fresh extract (0.79), butylated hydroxytoluene (BHT) (1.80) and rutin (1.20) standard at 50 µg/ml. The fresh and dried methanolic extracts of the plant exhibited high degree of cytotoxic activity with IC50 values of 18.18 and 19.24 µg/ml, respectively. The results obtained in this present study indicated that the rhizome of T. violacea may serve as potential source of natural antioxidant, antimicrobial and anticancer agents.
Key words: Tulbaghia violacea, antioxidant activity, free radicals, polyphenolic compounds, cytotoxicity.
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