Extraction Method and Evaluation of Phenolics, Flavonoids, Antioxidant activity, Antimicrobial Activity and Minerals of Bitter Lupinus albus in Palestine

Abstract

In this paper, extraction methods for bitter Lupinus albus seeds are described. Samples were either soaked with water (thereafter soaked) or used without soaking (thereafter unsoaked) and were exposed to Soxhlet extraction using commercial ethanol (~95 %), 80 %, 70 %, 60 % and 50 % ethanol. Yields of extractions were 12.5 %, 23.9 %, 12.6 %, 16.1 % and 16.6 % for soaked samples, and 11.6 %, 20.9 %, 19.3 %, 20.5 % and 25 % for unsoaked samples, respectively. 50 % ethanol extracted samples showed the highest sodium concentration (14.186 mg.g-1), 60 % ethanol extracts showed highest potassium concentration (8.76 mg.). Redox titration showed higher concentration of Fe+2 in all unsoaked samples. All samples showed very good antimicrobial activity against Gram positive bacteria (Staphylococcus aureus) but were weakly active or had no activity against Gram negative bacteria (Escherichia coli). FRAP method for the determination of antioxidant activity showed higher antioxidant activity for the soaked samples than the unsoaked ones. Total phenolics showed very similar results for soaked and unsoaked samples. Finally, contents of two of the flavonoids (flavonones and dihydroflavonols) were measured spectrophotometrically against Rutin as standard. Soaked samples demonstrated higher content than those of the unsoaked ones.