Evaluation of in vitro antioxidant property and phytochemical contents in different genotypes of fenugreek (Trigonella foenum graecum L.)

Abstract

Polyphenol content and antioxidant activity in methanolic extracts of 10 fenugreek (Trigonella foenum graecum. L) genotypes from north India were evaluated, using different in vitro assays, together with total carotenoid, alpha-tocopherol and total ascorbate content. The antioxidant activity was evaluated using total antioxidant activity (Phosphomolybdenum method), ferric reducing antioxidant power (FRAP) assay, 1,1-diphenyl-2-picrylhydrazyl (DPPH) assay, 2,2'-azinobis (3-ethylbenzothiazoline)-6-sulphonate (ABTS) assay, hydroxy radical scavenging assay, superoxide radical scavenging assay, nitric oxide scavenging and beta-carotene-linoleate bleaching assay. The total phenol content (TPC) varied from (48.766 +/- 0.042 mg GAE g(-1) extract) in RMt-303 to (36.204 +/- 0.371 mg GAE g(-1) extract) in UM-265. RMt-303 also showed higher flavonoid (4.682 +/- 0.105 mg QE g(-1) extract), alpha-tocopherol (171.918 +/- 11.722 mu g g(-1) dry wt.) and total ascorbate content (359.884 +/- 30.886 mu g g(-1) dry wt.). Higher free radical scavenging activity, viz., ABTS radical (IC50 = 303.380 +/- 4.170 mu g ml(-1) extract), superoxide radical (IC50 = 152.040 +/- 3.290 mu g ml(-1) extract) and nitric oxide scavenging (IC50 = 142.160 +/- 0.320 mu g ml(-1) extract) was observed in RMt-1. The genotypes showed significant difference (p >= 0.05) with respect to phytochemical content and corresponding antioxidant activity. The phytochemicals, viz., alpha-tocopherol and total ascorbate content within the genotypes showed a significant positive correlation (i.e., 0.517 and 0.546) with antioxidant activity (TAA) exhibited by the genotypes. Significant positive correlation (0.659) was observed between phenol and flavonoid content within the genotypes. The findings of the present investigation clearly show variation in phytochemical content and antioxidant activity among fenugreek genotypes. Thus, variation in antioxidant property among the genotypes may be attributed to the variation in phytochemical content which may be due to genetic differences among the fenugreek genotypes.