Phenolic Content and Antioxidant Activities of Green Walnuts Harvested at Different Periods on the Lake Van Coast

Abstract

Walnut (Juglans regia L.) is a nut with high nutritional and economic values. Walnut is commonly used as a functional ingredient in several traditional food products and as a natural source of phytochemicals in pharmacy and cosmetics. Walnut harvested in the immature periods, known as milk walnut, have been used in formulation of some traditional foods. In this study, phenolic composition and antioxidant activities of green walnuts (immature) harvested from 3 different districts (Van Center, Edremit, and Gevas) around Lake Van in 4 different periods (1st June, 15th June, 30th June, and 15th July) were investigated. The total phenolic content, DPPH, and ABTS values of green walnuts were 17842.26-6907.83 mg GAE kg-1, 208.8-49.03 and 208.48-66.97 mmol TE g-1, respectively. Juglone, gallic acid, neochlorogenic acid, and rutin common phenolic compounds were determined in green walnut samples. While the highest total phenolic content and antioxidant activity were observed in green walnuts harvested on 1st June, the highest juglone was determined in samples collected on 30th June. As a result, it was determined that green walnut had high antioxidant activity and phenolic content, especially juglone. The harvesting period considerably affect the phenolic contents of samples. © 2019, Centenary University. All rights reserved.