Selection of the suitable extraction solvent to improve phenolic content and antioxidant activity in some Algerian black olive varieties

This study aims to investigate the effects of extraction solvent on the extraction of phenolic compounds (total phenolic content; TPC, total flavonoid content; TFC, and total flavonol content; TFLC) and the antioxidant activities (total antioxidant activity; TAA, DPPH radical-scavenging activity; DPPH-RSA, ABTS radical-scavenging activity; ABTS-RSA, ferric reducing power; FRP, and iron chelating activity; ICA) of three Algerian black olive varieties (Aharoune, Bouchouk, and Sigoise) cultivated in the region of Bejaia (Algeria). The results indicated that both cultivar and extraction solvent significantly (p < 0.05) affected the TPC, TFC, TFLC, and the antioxidant activities (TAA, DPPH-RSA, ABTS-RSA, FRP, and ICA). Notably, the TPC of olive fruits showed the highest ranges (2.3–4.2 g GAE/100 g DW) when extracted in 60% acetone, followed by 60% ethanol (2.3–3.8 g GAE/100 g DW) and water (1.9–2.3 g GAE/100 g DW). Pearson correlation analysis showed a good positive linear correlation between phenolic compounds and antioxidant activities, indicating that the phenolic compounds in black olives are the main contributors to their antioxidant potential. These findings support the idea that black olives are a good source of phenolic compounds with high antioxidant activities, namely antiradical scavenger activity, ferric reducing power, and iron chelating activity. Therefore, black olive extracts could serve as valuable natural products beneficial to human health, making them a promising alternative to synthetic antioxidants in various applications, including food, cosmetics, and pharmaceuticals.