Effect of different solvents on biological attributes of olive leaves extracts of newly cultivated varieties:GC–MS based investigations

Abstract

This study investigates the optimal solvents for extraction of bioactives from olive leaves, analyzing the yield, phenolic and flavonoid content, antioxidant, thrombolytic, antimicrobial activities, and chemical profiles of extracts from three olive varieties: Kalamata, Sikitita, and Chietina. During ultrasonic-assisted extraction, the highest extract yield (472.96 mg/g) was achieved with water, while the lowest (224.31 mg/g) antioxidant extract yield was obtained with absolute methanol. On the other hand, aqueous ethanolic extracts (AEEs) demonstrated the highest total phenolics (28.17 mg GAE/g DW) and flavonoids (170.67 mg RE/g DW) contents, along with significant antioxidant activities as measured by 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging and ferric reducing antioxidant power (FRAP) assays. Gas chromatography–mass spectrometry (GC–MS) analysis of these extracts revealed the presence of high-valuebioactive compounds such as oleic acid, β-sitosterol, and 2-methoxy-4-vinylphenol, known for their health benefits. Moreover, hemolytic and thrombolytic activities revealed the safer and health-promoting potential of tested extracts. Carbohydrate analysis identified glucose as the most abundant sugar, while organic acid profiling highlighted tartaric acid as predominant. The AEEs extracts were the most effective against Gram-positive pathogens, particularly Staphylococcus aureus, but were less effective against Gram-negative bacteria. These findings highlight the importance of solvent choice in maximizing the extraction of bioactives and suggest the potential of olive leaf extracts for developing nutraceuticals and functional foods.