Nizip Yaglık olive leaves ( Olea europaea L.) collected at different seasons and altitudes: Enzyme inhibition, antioxidant activities and phenolic compound profiles

This study aimed to evaluate the antioxidant activity (DPPH, ABTS, CUPRAC, and iron-reducing power methods) phenolic component profiles (by LC-MS/MS), and cholinesterase enzyme inhibition of Nizip Yagl & imath;k olive leaf extracts. The leaves were collected from the Nizip district of Gaziantep province at three different altitudes and during four different seasons. The winter season Kocatepe location extract (W3), at a concentration of 160 mu g/ mL, demonstrated the highest antioxidant activity among all olive leaf extracts. The major components identified by LC-MS/MS analysis were cynaroside (luteolin-7-glucoside) and quinic acid among fifty-three components, with the highest concentration found in the summer season Kocatepe location extract (SU3, 18.986 mg/g) and the autumn season Kerzin location extract (A1, 14.147 mg/g) respectively. Fingerprint phytochemical analysis was also performed for four compounds (3-hydroxytyrosol, oleuropein, diosmin, verbascoside) on the extracts. Oleuropein and verbascoside were determined as 56.738 mg/g in the winter season Kocatepe location (W3) extract and 8.853 mg/g in the spring season Kerzin location (S1) extract, respectively. The spring season I(center dot)kizce location extract (S2, IC50: 10.16 mu g/mL) exhibited the strongest inhibition on the AChE enzyme, while the spring season Kocatepe location extract (S3, IC50: 7.73 mu g/mL) exhibited the highest inhibition on the BChE enzyme. The study concluded that olive leaves have increased antioxidant and enzyme inhibition potential, especially when harvested in the winter and spring seasons and at higher altitudes. These findings suggested that Nizip Yagl & imath;k olive leaves could be valuable for therapeutic drug production and pharmacological research due to their rich phenolic content and high antioxidant activity.