PLASMA LIPID MODULATING ACTIVITY OF INTRAPERITONEALLY ADMINISTERED AQUEOUS EXTRACT FROM RAW GARLIC: ACUTE STUDIES IN NORMO-LIPIDEMIC RAT

Abstract

ABSTRACT Garlic is a well known medicinal plant which possesses numerous properties as anti-infectious, antitumoral, antioxidant, hypoglycemic or anti-atherosclerotic. Garlic has been shown to lower plasma cholesterol and triacylglycerol levels in chronic experiments using hypercholesterolemic animals or in meta-analysis using humans, although fewer studies failed to show any effect. The active compound was often proposed to be allicin a sulfur aminoacid. We conducted acute experiments on normolipidemic rats and found out that when intraperitoneally administered, aqueous extract of raw garlic is able to lower cholesterol but not triacylglycerol levels. Heat-treated extract and a commercially available preparation were without effect. All these lipid modulating effects were mimicked by a partially purified extract whose rapid onset of action as well as physicochemical properties seems to indicate a nature different from common sulfur-derived amino acids. PRACTICAL APPLICATIONS Chronic high level of plasma lipid constitutes a major risk of cardiovascular diseases and a real public health problem. Considerable interest has focused toward the screening of new compounds able to reduce plasma lipids. For a long time, garlic has been used as a nutritional supplement to lower plasma lipid level. Cholesterol and triacylglycerol-lowering activity from garlic was often attributed to organosulfur compounds as allicin. The present study described strong cholesterol but not triacylglycerol-lowering activity of new compounds different from classical sulfur-derived amino acids. The putative steroid saponin nature is proposed. As garlic lost its beneficial properties upon cooking and is active at very high doses, it could no longer be used as a nutritional supplement. Garlic should rather be envisaged as a convenient source of new cholesterol-lowering compounds as yet to be purified at homogeneity.