Determination of Minerals, Total Phenolic Content, Flavonoids, Antioxidants and Antimicrobial Activities of Ethanolic Extract of Sweet Lupinus angustifolius of Palestine

Aims: To establish the most suitable extraction method for sweet lupine seeds and to determine minerals, phenolic content, flavonoids, antioxidant activity and antimicrobial activities.

Study Design: Known and standard experimental procedures are employed.

Place and Duration of Study: Department of Chemistry, Bethlehem University- Palestine, from January 2019 to March 2019.

Methodology: Seeds were ground and extracted by Soxhlet extractor using ethanol with different percentages (50%, 60%, 70%, 80% and 95%). Sodium, potassium and ferrous ion content were determined. Resistance to bacteria was performed against Escherichia coli and Staphylococcus aureus, while antioxidant activity was determined by FRAP method. Two types of flavonoids were measured: Flavonones and dihydroflavonols via the reaction with 2,4-dinitrophenylhydrazine. Phenolics were determined by the Folin-Ciocalteu method.

Results: 50% ethanol resulted in the highest extract residue (18.6%) while 70% and 60% showed the lowest content (10.0% for both). 80% ethanol extracted sample showed the highest content for sodium (56.51 mg Na/g extract), while 60% and 50% ethanol extracts showed the highest content of potassium (2.25 and 2.33 mg K/g extract, respectively). The maximum concentration of ferrous ion was obtained with 70% ethanol (6.854 mg Fe+2/g extract). 95% ethanolic extract showed the highest antioxidant activity (20.24 mg FeSO4/g extract). Similar results were obtained for total phenolic content and flavonoids: 24.60 mg gallic acid/g extract for phenolics and 116.02 mg rutin/g extract for flavonoids. Extracts showed no bacterial activity against both types of bacteria used.

Conclusion: 95% ethanol extracted samples showed the highest antioxidant activity and the highest flavonoids and phenolic content. Sweet lupine extract did not perform any antimicrobial activity against both Gram positive and Gram negative bacteria.