Phytochemical Analysis of Extracts from Waste of Technical Grape Varieties and Pomegranate Peel Processed in South Kazakhstan

The food industry is interested in utilizing active compounds from agri-food waste to produce healthy products and promote sustainability and resource efficiency. This study aimed to conduct a phytochemical analysis of grape pomace derived from Vitis vinifera wine grape varieties Saperavi and Cabernet Sauvignon, as well as pomegranate (Punica granatum L.) peel of the Nar-Shirin variety, which are widely processed in South Kazakhstan. The extraction processes were simple and employed water and ethanol, two food-grade solvents widely used in green extraction due to their low toxicity and compatibility with food applications.Among the extraction methods tested, aqueous–alcoholic extraction demonstrated the highest efficiency in recovering total phenolic content (TPC), yielding 225.5 ± 1.46 mg GAE/g extract from pomegranate peel, 153.9 ± 1.25 mg GAE/g extract from Cabernet Sauvignon pomace, and 98.6 ± 0.83 mg GAE/g extract from Saperavi pomace. Phenolic profiling of the aqueous–alcoholic extract was performed using ultra-high-performance liquid chromatography coupled with quadrupole time-of-flight tandem mass spectrometry (HPLC-Q-TOF MS/MS). The total ion chromatograms revealed the presence of predominant phenolic compounds in all analyzed samples. Key identified constituents in grape pomace included kaempferol 3-O-β-D-xylofuranoside, kaempferol 3-O-β-glucopyranoside-7-O-α-rhamnopyranoside, quercetin-3-O-α-L-arabinoside, genistin, and megastigmane glycoside. In pomegranate peel, compounds such as myricetin, 5-(2Z,8Z)-pentadecadien-1-yl-1,3-benzenediol were identified for the first time. These findings highlight the rich phenolic composition of grape pomace and pomegranate peel’s extracts and support their potential as valuable sources of bioactive compounds for food, pharmaceutical, and industrial applications.