Evaluation of the Antioxidant and Biological Properties of Muscadine Grape Seed Extracts

Abstract

The objectives of this research were i) to optimize extraction of phenolic compounds from muscadine grape seeds using food grade solvents, ii) to characterize and quantify the phenolic compounds present in Carlos muscadine grape seed extracts, iii) to assess the oxidative stability of the grape seed extract, iv) to evaluate the antimicrobial activity of the optimal muscadine grape seed extract, and v) to evaluate the effect of muscadine grape seed extract on MCF-10A breast cells.

Carlos muscadine grape seeds were manually removed from the skin and pulp, then freeze-dried or oven-dried. Phenolic compounds were extracted from muscadine grape seeds using a Dionex Accelerated Solvent Extractor 200 following a two factor composite design. The two factors were solvent and temperature. Ethanol in combination with water and ethyl acetate in combination with water were evaluated in this research. Solvent percentages ranged from 35% to 95% and temperature ranged from 75C to 150C. Optimal extraction conditions were determined using the Folin-Ciocalteu and oxygen radical absorbance capacity assays. Identification and quantification of the phenolic compounds were determined by high performance liquid chromatography with mass spectroscopy.

The optimal extraction conditions for the highest recovery of phenolic compounds consisted of the freeze-dried seeds extracted with 65% ethanol and 35% water at 150°C, with total phenolic and oxygen radical absorbance capacity values of 5.87 mg GAE⁄g and 60.32 M-TE⁄g of seeds, respectively. The four major phenolic compounds quantified in the muscadine grape seed extract were epicatechin, catechin, gallic acid and ellagic acid. Oxidative stability index of the muscadine grape seed extract resulted in an induction period of 4.6 hours. In the antimicrobial study, both muscadine grape seed extract and ellagic acid inhibited the growth of E. coli 0157:H7, Listeria monocytogenes, and Salmonella typhimurium at 104 cfu⁄ml. These research findings show that muscadine grape seed extracts contain phytochemicals with antioxidant and antimicrobial properties that can be used in applications including food ingredients, food supplements and other nutraceutical applications.