Hydrogen-rich solvent method enhances the extraction of phenolics, pigments, reducing sugars, organic acids, and vitamin C from cowslip (Primula veris L.) flower

Abstract

Cowslip (Primula veris L.) is an anioxidant-rich plant used for many food and medicinal purposes. In this study, the effect of incorporating hydrogen (H₂) into water (HRW), ethanol (HRE), and methanol (HRM) on the extraction of flavonoids (TFC), phenolics (TPC), and antioxidants (metal chelation, FRAP, DPPH, and ABTS) as well as color (L*, a*, b*, C*, H°), chlorophyll (a, b), lycopene, and β-carotene of wild cowslip flowers was evaluated. The results were submitted to Principal Component Analysis and correlation. Phenolic compounds, organic acids, vitamin C, and sugar content of the extract were analyzed using high-performance reverse phase liquid chromatography (HPLC-DAD/RID). The highest TPC, TFC, and antioxidant activity (metal chelation, FRAP, DPPH, and ABTS) were shown for HRM samples, followed by HRE samples, while the lowest were found for pure solvents. Incorporating H₂ into all solvents significantly increased TPC, TFC, metal chelation, DPPH, and ABTS scavenging activity, as well as b*, C*, H°, chlorophyll, lycopene, and β-carotene values. The levels of some phenolics (catechin, epicatechin, rutin, and quercetin), organic acids (tartaric acid and succinic acid), reducing sugars (maltose, glucose, and fructose), and ascorbic acid increased by 10–90 % when an H₂-rich solvent was used instead of the pure solvent. This is the first report showing the enhanced extraction of organic acids, pigments, and ascorbic acid by hydrogen-rich solvent. The main benefits of the HRS method are its sustainability and high efficiency in extracting bioactive compounds from medicinal plants.