Influence of Extraction Parameters on the Yield of Total Phenolic Compounds from Grape ( Vitis vinifera L .) Seeds

Abstract

Background: The scientific literature has developed general approaches to assess the content of phenols in raw plant materials. However, the conditions for extracting and analyzing these compounds can vary significantly between plant species. Using suboptimal extraction conditions may lead to the degradation of target substances and reduced extraction efficiency. Therefore, selecting optimal methods for extracting and analyzing polyphenols is crucial to ensure accuracy and efficiency. Objectives: This study aimed to investigate the influence of various factors on the extraction of phenolic compounds from Georgian grape (Vitis vinifera L.) seeds, with the goal of developing an optimized extraction method. Methods: Phenolic compounds were extracted from the raw material using ultrasound-assisted extraction (UAE). The total phenolic content was determined using the Folin-Ciocalteu reagent, which forms a blue complex with phenols in an alkaline medium. The solutions' absorbance was measured spectrophotometrically at the appropriate wavelength for quantification. Results: The maximum yield of phenolic compounds (95.969 mg/g GAE) was achieved under the following extraction conditions: solvent—70% ethyl alcohol, particle size: 0.3-0.5 mm, raw material-to-solvent ratio: 1:20, temperature: 60°C, duration: 30 minutes, and double extraction cycle. Conclusions: These findings provide a solid foundation for efficiently extracting phenolic compounds from grape seeds. This optimized method has potential applications in the food, pharmaceutical, and cosmetic industries, contributing to the valorization of residues from wine production.