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Abstract

Trigonella foenum-graecum is an annual plant in the family Fabaceae. The distinctive cuboid-shaped, yellow to amber coloured fenugreek seeds are frequently encountered in the cuisines of the Indian subcontinent. In this study, Trigonella foenum-graecum is used as an experimental matrix. Ultrasound-assisted extraction (UAE) of total flavonoids from Trigonella foenum-graecum is studied with dual wavelength UV-VIS spectrophotometer. Effects of various factors including ratio of material to liquid, ultrasonic time, methanol concentration and extraction times on extraction yield of total flavonoids are evaluated. Then, optimization of total flavonoid compound (TFC) extraction from Trigonella foenum-graecum seed is investigated using response surface methodology (RSM) in this paper. Statistical analysis of the experiments indicated that Ratio of material to liquid and methanol concentration significantly affected TFC extraction (p < 0.01). The Box-Behnken experiment design shows that polynomial regression models are in good agreement with the experimental results, with the coefficients of multiple determination of 0.9758 for TFC yield. The optimal conditions for maximum TFC yield are 70% methanol, 50min and 30 (v/w) liquid to solid ratios with a 2 time extraction time. Extracts from these conditions showed a moderate antioxidant value from 1,1-diphenyl-2-picrylhydrazyl (DPPH) assay, Ferric chloride reducing assay and hydrogen peroxide reducing assay. Fenugreek flavonoids have direct and potent antioxidant activities, might be developed and utilized as natural antioxidant.