An updated method for isolation, purification and characterization of clinically important antioxidant lignans - Sesamin and sesamolin, from sesame oil

Sesamin and sesamolin are clinically important antioxidant lignans that exhibit anticholestrolemic, antihypertensive and anticancer properties. Chemically they are phenyl propane dimers synthesized as products of secondary metabolism in several plants. The ancient oil crop Sesamum indicum, by far, is the major source of these lignans. Several attempts made earlier for isolation of the lignans under consideration, in pure form, is far from satisfactory resulting in high cost and their rarity in the market. Here we report our results on successful isolation and characterization of the two lignans from commercial sesame oil. A 1:8 mixture of the oil with acetone, on freezing at -80 degrees C, yielded triglycerides and yellow oil. The latter when subjected to a similar treatment but with isooctane at 4 degrees C yielded colourless crystalline product. TLC followed by HPLC revealed that the crystalline product is a mixture of 88% sesamin and 12% sesamolin. The isolated lignan mixture was subjected to semi-preparative HPLC and TLC to result in successful separation of putative sesamin and sesamolin in two independent fractions. Purity of the compounds thus isolated was confirmed by TLC and LC-MS. Structure detail of the isolates was confirmed by NMR. The sesamolin purified in this study was further tested successfully to prove that it can serve as reliable biochemical standard for analysis of lignan diversity among sesame germplasm. Relevance of the method developed for analytical studies and for industrial production of the lignans for therapeutic purpose is discussed. (C) 2014 Elsevier B.V. All rights reserved.