Lipid extraction of tissues with a low-toxicity solvent

Abstract

An improved method for extracting the lipids from tissues consists of the use of hexane:isopropanol, followed by a wash of the extract with aqueous sodium sulfate to remove nonlipid contaminants. This method has a number of advantages over the common usage of chlorofomnmethanol. The solvents are somewhat less toxic, interference in processing by proteolipid protein contamination is avoided, the two phases separate rapidly during the washing step, the solvent density is low enough to permit centrifugation of the homogenate as an alternative to filtration, the solvents are cheaper, and the washed extract can be applied to a chromatographic column with continuous monitoring of the elution in the far ultraviolet region. The new extraction method is inefficient for the extraction of gangliosides. Biochemists wishing to extract lipids from tissues have in the past paid rather little attention to questions of danger to their health or to the health of people living downstream from their sewage treatment plants. Recent findings from public health studies and animal experiments have implicated a wide variety of organic solvents in the production of tumors, through exposure in the work place or in drinking water. It therefore seems appropriate to review lipid extraction techniques as a potential health hazard. While many solvents have been recommended [for reviews see Refs. (l-3)], the most popular is the chloroform:methanol (CM)' system of Folch et al. (4) and its various modifications. Chloroform can produce tumors in animals (5) and methanol is well known for its damage to the visual system. A choice of solvents for lipid extraction should be made on the basis of several additional factors: volatility (for ready removal later), freedom from toxic or reactive impurities (to avoid reaction with the lipids), ability to form a two-phase system with water (to remove nonlipids), extraction power for undesired components (proteolipid proteins, small molecules), price, range of extraction power for the different lipid classes, and ultraviolet transparency for subsequent column chromatography and monitor-1 Abbreviations used: HIP, hexane:isopropanol, usually in the ratio 3:2. CM, chloroform: methanol, usually in the ratio 2: 1.

Milk fat depression and energy balance in stall-fed dairy goats supplemented with increasing doses of conjugated linoleic acid methyl esters

“…The milk fatty acids were extracted according to Hara and Radin (1978), using a 3 : 2 (v/v) mix of hexane and isopropanol (18 ml/g of extracted fat) followed by a solution of sodium sulfate 67 g/l (12 ml/g of extracted fat). Fatty-acid methyl esters (FAME) were obtained by base-catalyzed transmethylation using a freshly prepared methylation reagent (0.4 ml of 5.4 mol/l of sodium methoxide solution plus 1.75 ml methanol).…”

Hypoglycemia prevents increase in lactic acidosis during reperfusion after temporary cerebral ischemia in rats

“…Acidosis was assessed as an injury mechanism in vivo in previous 31 P MRS studies of global ischemia. 8,45 In cats made hypoglycemic before ischemia, the observed reduction in pH i was attenuated both during ischemia and early during reperfusion.…”

“…There were no significant differences between the groups. (b) Time course of changes in intracellular pH (pH i ) (mean ± SD) measured by 31 P MRS in normoglycemic and hypoglycemic rats. The difference between groups during ischemia is not statistically significant.…”

“…Lipids were extracted from tissue specimens. 28,[30][31][32][33] Cholesterol and total FFAs were separated by thin layer chromatography. [34][35][36] The linearity of the detector response was checked with known standards of fatty acid methyl esters.…”

“…4 During global ischemia in rats, ATP depletion was greater under hypoglycemic than normoglycemic conditions. 1 In this study, we used in vivo 31 P and 1 H MRS to study the time course of changes in energy metabolism during 30 min of temporary global ischemia and 5.5 h of reperfusion in rats with insulin-induced hypoglycemia. In order to assess the effect of ischemic lactic acidosis on delayed cytotoxic tissue injury, these findings were correlated with free fatty acid (FFA) and excitory amino acid levels, cation concentrations, and water content at death after 5.5 h of reperfusion.…”