Author(s):

Md Hamiduzzaman, Ishrat Jahan, Sayma Afroz Santa and Mazharul Islam Bhuiyan

Abstract:
Plants are the sources of variety of important secondary metabolites, in which some are often used as antioxidants. Hence, the objective of this study is to evaluate the free radical scavenging activity, total flavonoid and total phenolic content of underground tuber and aerial fruits (used as vegetable) of Dioscorea alata to get an idea about in-vitro oxidative stress reduction activity. Shade dried powders of tubers and fruits were extracted with solvents having different polarity for experimental assay procedure. Additionally, tuber and fruits were boiled with water to get hot water extract to make it simulation with traditional cooking method. Due to the different solvent polarity, antioxidant capacity (IC₅₀ values), total phenolic content and total flavonoid content varied significantly. It was observed that aqueous soluble fraction possessed highest antioxidant capacity (lowest IC₅₀ value= 31.89 μg/ml for tuber and 47.69 μg/ml for fruits) in comparable with standard BHT having IC₅₀ value 20.39 μg/ml); total phenolic content 37.80 and 29.15 mg of gallic acid equivalent/gm of extract for tuber and fruits respectively; total flavonoid content 10.56 and 9.67 mg of quercetin/gm of extract for tuber and fruits respectively. It is also mentionable that hot water extract revealed significant free radical scavenging activity (IC₅₀ value 27.65 μg/ml for tuber & 41.9 μg/ml for fruits), total phenolic content (43.56 and 37.85 mg of GAE/gm of extract for tuber and fruits) and total flavonoid content (15.78 & 13.56 mg of GAE/gm of extract for tuber and fruits). Antioxidant capacity, total phenolic and total flavonoid content of tuber and fruits were strongly positively correlated with significant P values (P <0.01). Presence of significant phenolic compounds and flavonoids along with highest antioxidant capacity concluded that tubers and fruits of D. alata those are taken as vegetable can significantly reduce oxidative stress in human subject.

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