Abstract
In this study, the bioactive properties and phenolic constituents of different grape seeds grown in Turkey were investigated. Total phenolic and flavonoid contents of grape seeds varied between 1,120.83 mgGAE/100 g (Tarsus beyazi) and 3,485.24 mgGAE/100 g (Buzgulu) to 10,087.13 mg/100 g (Topacik) and 47,013.06 mg/100 g (Eksikara),respectively. Antioxidant activity values of grape seeds were determined between 79.22%(Kizil uzum-Sik Dimrit) and 90.24% (Buzgulu-Konya). In general, the total phenolic contents of Buzgulu (Gulnar-Mersin), Miski, Iri Akuzum, Buzgulu (Konya), Ispitiren, Gokuzum, Irikara, Dimrit and Muftalma grape seeds were above 2,000 mgGAE/100 g. While (+)-catechin values of seeds are determined between 30.70 (Devegozu-Black) and 410.42mg/100 g (Ispitiren),1,2-dihydroxybenzene amounts of extracts were found between 31.43 (Devegozu-Black) and 1,211.00 mg/100 g (Honusu). While apigenin-7-glucoside values of grape seed extracts vary between 42.22 (Dimrit) and 293.58 mg/100 g (Kara Dimrit), quercetin contents of seeds changed between 91.79 (Dimrit) and 466.44 mg/100 g (Dimrit-Siyah). A large variation of amounts of phenolic constituents depending on grape seed varieties was observed.
Practical applications Grapes are one of the fruits with the highest phenolic compound content. Therefore, grape seed obtained as a by-product during the production of boiled juice, wine and juice is a good source of polyphenols. In the grape processing industries, these by-products emerge as potential waste, which is a problem for the environment. Grape seeds, which are obtained in large amounts in the fruit juice, jam, marmalade, boiled fruit juice industries as grape by-products, are a good source of antioxidants and phenolic components.