Evaluation of antioxidant and antimicrobial activities of Oenothera biennis, Borago officinalis, and Nigella sativa seedcake extracts

The antioxidant and antimicrobial activities of Oenothera biennis, Borago officinalis, and Nigella sativa seedcake extracts were determined. Seedcakes were subjected to extraction using 50% ethanol (v/v) during 48 h at a solvent temperature of 50A degrees C. The total polyphenol and flavonoid contents were assayed using UV spectrophotometry and the antioxidant activities were determined using DPPH and ABTS testing methods. Extracts were also analyzed for polyphenol content using HPLC. In vitro antimicrobial activities were evaluated using the disc diffusion method and resazurin testing. The ranking of the polyphenol contents and the antioxidant activities of examined seedcake extracts was O. bienis > B.officinalis > N. sativa. The highest antimicrobial activity in both tests was for N. sativa seedcake extracts against Pseudomonas aeruginosa (MIC=300 mg/mL), Escherichia coli (MIC=300 mg/mL), and Staphylococcus aureus (MIC=700 mg/mL).