Metabolomic profiling of purple corn pericarp phytochemicals and their efficient recovery in deep eutectic solvents with ultrasound-assisted extraction

There is a growing demand for solvents that are renewable, non-toxic, biodegradable, and economically viable for value-added phytochemical extraction. Purple corn pericarp, a cellulosic corn processing industry byproduct, has been documented to be an exceptionally rich source of polyphenolic compounds with potential agro-industrial applications. Nineteen different deep eutectic solvent (DES) formulations were prepared and used in conjunction with ultrasound-assisted for the extraction of anthocyanins, condensed tannins, and flavonoids present in purple corn pericarp. The DESs formed strong intermolecular bonds, and dominant stretching of O–H and C–H bonds was observed during the FTIR analysis. Metabolomic profiling using a UHPLC-MS system identified 36 distinct polyphenolic compounds in pericarp. The ultrasound-assisted extraction of polyphenols in DESs was found to be a highly efficient extraction methodology. Within a short duration of 10 min, 27.41 mg of anthocyanins, 240.37 mg of condensed tannins, and 25.52 mg of flavonoids per g of pericarp, respectively were extracted in DES 13, composed of glycerol and lactic acid (2:1). Extracts retained their bioactivities, demonstrating significant antioxidant potential (Trolox equivalent antioxidant activity) during the DPPH, ABTS and CUPRAC assays. HPLC quantification for distinct anthocyanin forms identified cyanidin-3-glucoside, delphinidin, cyanidin chloride, and peonidin. Caffeic acid, ferulic acid, gallic acid, hesperidin, and chlorogenic acid were the main phenolic acids, whereas the major flavonoids present were epicatechin, naringin and kaempferol. Solvent dependent extraction of individual polyphenols was observed, which was further validated through principal component analysis. An efficient and green extraction methodology for phytochemical recovery from colored corn pericarp has been proposed. • Evaluation of deep eutectic solvents and ultrasound for phytochemical extraction. • UHPLC-MS based metabolomic profiling of purple corn pericarp phytochemicals. • Highly efficient extraction of anthocyanins, condensed tannins and flavonoids. • Extracted phytochemicals retained significant antioxidant activities. • Solvent composition dependent extraction of distinct phytochemicals was observed.