Extraction, separation and characterisation of sesame oil lignan for nutraceutical applications

Abstract

Nutraceutical aspects of sesame oil (SO) are well reported. However, an efficient process for commercial production has not yet been reported. In this study we have aimed at separating lignans from SO aiming at use as nutraceuticals. SO was Subjected to sequential extraction with methanol under selected conditions of temperature (70 degrees C, time (100 min) and solvent:oil ratio (1: 1). Under the optimised conditions, the yields of pooled methanolic extract concentrate and residual oil were 10.09 +/- 1.0 g and 89.2 +/- 1.0 g. respectively. On HPLC analysis, the methanol concentrate showed a total lignan content of 9.32 +/- 0.19% (6.54 +/- 0.12% sesamin and 2.78 +/- 0.31% sesamolin). The concentrate was subjected to low temperature crystallization (4 degrees C) for the separation of lignan crystals and 51% of the lignans in the oil with 94.4% purity. The crystal-removed methanolic concentrate was saponified and purified; the total lignan content (sesamin and sesamolin) in the unsaponifiable matter (USM) was 64%. The distribution of sesamin and sesamolin in the purified USM was in the proportion 46:54, unlike that in the pure crystals (84:16). Lipid classes (triglycerides, TG: free fatty acids, FFA: diglycerides, DG; monoglycerides, MG; polar lipid, PL) in SO, methanolic extract concentrate and residual oil were separated using thin-layer chromatography (TLC). The amounts of lipid classes were determined by relating the total area of the fatty acid peaks to the area of the peak for internal standard (methyl heptadecanoate), using gas chromatography (GC). The process reported here describes a simple and less Cumbersome procedure to produce lignans with high yield and purity for nutraceutical applications.