Improving the Polyphenol Profile, Antioxidant and Antiglycation Activity of Onion Outer Scales with Chamomile Treatment

Research background. The outer scales of common onion (Allium cepa L.) are often discarded as biological waste but they can be an interesting source of polyphenols with antioxidant and antidiabetic properties that can be used in the food and pharmaceutical industries. Experimental approach. The aim of this study is to use dried chamomile (Matricaria chamomilla L.) flowers containing 6 % flavonoid apigenin in the form of a water extract to improve the polyphenol profile, and the antioxidant and antiglycation activity of onion outer scales. “Red Carmen” onion bulbs with roots were exposed to deionized water (control) and chamomile water extract (test treatment) in a phytotron (23 °C/16 h day/8 h dark). Fourier transform infrared (FTIR) analysis was performed on dried, pulverised outer scales and chamomile. Pure standards of polyphenols (apigenin, quercetin and caffeic acid) were also used for FTIR spectral comparison. Results and conclusions. Total hydroxycinnamic acids (THA), total flavonols (TFL), antioxidant activity (2,2’-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid (ABTS) and Fe(III) reducing antioxidant power (FRAP)), and inhibition of bovine serum albumin (BSA) by onion scale extract were measured in the initial, salivary, gastric and intestinal phases. Chamomile treatment increased THA, TFL, antioxidant (FRAP) and antiglycation activity (BSA method) in almost all in vitro digestion phases. Treating onions with chamomile water extract is an effective method for enriching biological waste, as confirmed by FTIR analysis. Enriched onion scales are a good source of bioaccessible polyphenols with high antioxidant (ABTS>85 % and FRAP>95 %) and moderate antiglycation activity (43–62 %). Novelty and scientific contribution. The enrichment of the phytochemical composition and biological potential of onions highlights the potential applications of this technique for health and nutritional purposes. Since the method does not require genetic modification but relies on natural absorption mechanisms and stress induction, it could become a valuable tool for enriching the nutritional and therapeutic composition of herbs. These results provide a foundation for future research, which should further elucidate the mechanisms of transmission, long-term effects, and potential industrial applications of this phenomenon.