Chemical and biological study of the seeds of Eragrostis tef (Zucc.) Trotter

Abstract

A chemical study of the red type of the seeds of Eragrostis tef (Zucc.) Trotter (Poaceae) led to the isolation of seven compounds from its ethanol extract, namely β-sitosterol (1), β-amyrin-3-O-(2′-acetyl(glucoside (2), β-sitosterol-3-O-β-D-glucoside (3), naringenin (4), naringenin-4′-methoxy-7-O-α-L-rhamnoside (5), eriodictyol-3′,7-dimethoxy-4′-O-β-D-glucoside (6) and isorhamnetin-3-O-rhamnoglucoside (7), which are reported for the first time in the genus Eragrostis. This is the first report for the isolation of compounds (2) and (6) in nature. The isolated compounds were identified using different spectroscopic methods (EIMS, UV, 1H NMR, 13C NMR, HMQC and HMBC). A proximate analysis revealed the high nutritive value of the seeds: carbohydrates (57.27%), protein (20.9%), essential amino acids (8.15%) with major leucine and lysine (1.71 and 1.35%, respectively), vitamin B1 (1.56 mg/100 g) and potassium and calcium (32.4 and 9.63%, respectively). The seeds yielded 22% w/w of fixed oil rich in unsaturated fatty acids (72.46%), among which oleic acid, was predominant (32.41%), followed by linolenic acid (23.83%). The ethanolic extract and fixed oil of the seeds exhibited anti-hyperlipedaemic and anti-hyperglycaemic activities. Oral administration of the fixed oil for 10 days resulted in a rise in serum calcium levels in rats.