Comparison of Phenolic Compounds and Antioxidant Properties of Black Grape Extract, Concentrate and Residual

Grape fruit contains high amounts of phenolic compounds which are used in healthy food diets. Phenolic compounds as effective antioxidants are able to protect biological systems from damage of free radicals. In this research black grape samples were obtained from research center of Gorgan. Total phenolic content was determined using Folin-Ciocalteau method. Total flavonoides content was determined according to dewanto et al. Also antioxidant properties were investigated by scavenging percent of DPPH and superoxide. Ultimately some of the most important phenolic compounds were separated by HPLC followed by quantification. Results showed that total phenolics and total flavonoides of methanolic extract of this grape species were amounted to 54.3 +/- 5.1 (g gallic acid/100g dry basis) and 130 +/- 15 (mg quercetin/g dry basis) respectively. Results showed that phonlic content and antioxidant properties of the grape fruit are higher than those of concentrate and residual. Results of HPLC analysis showed that in all studied samples, catechine flavonoids had the most concentration. Also there was a trace amount of rezoraterol in all samples. Moreover black grape residual had a significant amount of phenolics content and antioxidant properties which can be used in food formulation.