SEPARATION AND CHARACTERIZATION OF LIPOPHILIC EXTRACTS FROM BARLEY STRAW

Abstract

Barley straw was extracted with toluene-ethanol (2:1, vol/vol), chloroform, methyl tert-butyl ether (MTBE), hexane-acetone (2:1, vol/vol), and dichloromethane for 12 hours in a Soxhlet. The 51 individual compounds in 5 lipophilic extracts were separated by gas chromatography. Free fatty acids (15.18–38.20%), sterols (1.41–10.42%), waxes (3.45–11.87%), steryl esters (5.04–24.70%), and triglycerides (1.16–10.03%) were identified as the major 5 classes of lipids in the barley straw extracts. Minor components such as diglycerides (0.07–0.89%) and resin acids (0.12–0.57%) were also verified from the straw lipophilic extracts. Nonlipids detected from the barley straw extracts were composed of minor amounts of phenolic compounds (0.17–2.05%), noticeable amounts of azelaic and maleic acids (0.48–15.06%), and some quantities of co-extracted polysaccharides, ash, or salts. Of the individual compounds in each group, 16 free fatty acids, 5 steryl esters, 3 sterols, 3 triglycerides, and 2 waxes were quantitatively determined. Extraction with MTBE gave the lowest yield of total extracts (1.19%) but contained the highest amounts of lipophilic extracts (81.04%), which were enriched with steryl esters (24.70%), free fatty acids (23.60%), waxes (11.22%), sterols (10.42%), and triglycerides (10.03%). In contrast, extraction with 2:1 toluene-ethanol produced the highest quantities of total extracts (3.92%) but of the lowest purity of the lipid substances (49.69%) and were comprised mainly of free fatty acids (38.20%) and nonlipid substances such as maleic and azelaic acids (15.06%), phenolic compounds (1.89%), and noticeable amounts of released polysaccharides, ash, or salts.