Stability of lipid constituents in radiation processed fenugreek seeds and turmeric: role of phenolic antioxidants.

Impact of radiation processing on the lipid profile of fenugreek and turmeric was investigated. Oleic and linoleic acid were the dominant fatty acids with an appreciable amount of linolenic acid in both cases. Gamma-irradiation did not bring about any significant changes in the fatty acid profile of these spices despite a high content of unsaturation. The ability of aqueous methanolic extract of both spices with high phenolic content to prevent lipid peroxidation suggests a possible role of phenolic constituents in preventing lipid radiolysis. Among the phenolics identified, kaempferol-3-O-alpha-L-rhamnoside, kaempferol 3,7-O-alpha-L-dirhamnoside, quercetin 3,7-O-alpha-L-dirhamnoside, and 3-O-alpha-L-rhamnosyl quercetin are reported here to occur in fenugreek for the first time. The role of phenolic antioxidants in preventing lipid oxidation in the above spices is discussed.