The effect of harvest time and varieties on total phenolics, antioxidant activity and phenolic compounds of olive fruit and leaves.

ABSTRACT

The effect of harvest periods on total phenol, antioxidant activity, individual phenolic compounds of fruit and leaves of Tavsan Yüregi, Memecik, Edremit, Ayvalik and Gemlik olive varieties grown in Turkey were investigated. The highest total phenol (317.70 mg/100 g and 2657.81 mg/100 g) were observed in Tavsan Yüregi olive fruit and Ayvalik leaves harvested in December, respectively. The highest antioxidant activities (83.84%) were determined in Edremit fruit harvested in August and 83.33% in either Edremit olive leaves harvested in November and Tavsan Yüregi leaves harvested in December. The olive fruit contained gallic acid ranging from 7.18 mg/100 g (August) to 35.85 mg/100 g (December) in case of Ayvalik and 2.09 mg/100 g (November) to 21.62 mg/100 g (December) in Edremit. Gemlik olives showed higher gallic acid contents compared to the other varieties, however it depended significantly on harvest time in all cases. 3,4-Dihydroxybenzoic acid contents ranged from 33.11 mg/100 g (October) to 25.17 mg/100 g (September) in Memecik olives; 12.17 mg/100 g (August) to 33.11 mg/100 g (December) in case of Tavsan Yüregi olives depending on harvest time. The 3,4-dihydroxybenzoic acid contents of Memecik leaves ranged between 122.25 mg/100 g (September) to 196.58 mg/100 g (August) and that of Tavsan Yüregi leaves changed between 99.38 mg/100 g (November) and 179.90 mg/100 g (August). The leaves of these two varieties contained significantly (p < 0.01) higher 3,4-dihydroxybenzoic acid contents than other varieties. The highest gallic acid (144.83 mg/100 g) was detected in Memecik leaves (September) whereas lowest were found in Gemlik leaves collected in October.