Analyzing amino acid profiles of herbal decoctions: understanding their antioxidant potential and role in functional beverages

Herbal decoctions are widely consumed for their health benefits and flavour. These beverages are known for their natural antioxidant properties, primarily linked to their phytochemical and nutrient content, including amino acids. This study investigated the amino acid composition of four multicomponent decoctions (with nine to twenty-eight different plants), focusing on their antioxidant potential and relevance to chronic disease prevention. The main objective was to analyze the amino acid profiles of selected decoctions to evaluate their contribution to oxidative stress reduction and their role as functional beverages. After an aqueous extraction with boiling water, decoctions were lyophilized before re-dissolution in water for derivatization using OPA/3-MPA and FMOC-Cl. Analysis was performed using high-performance liquid chromatography with fluorescence detection (HPLC-FLD). Antiradical activity, a reliable indicator of oxidative stress reduction, was evaluated using 2,2-diphenyl-1-picrylhydrazyl (DPPH•), 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid (ABTS•+) and nitric oxide radical (•NO) assays. The results revealed that all decoctions contain high levels of histidine (2.31 ± 0.18 μg/g to 5.75 ± 0.55 μg/g) and arginine (10.0 ± 0.7 μg/g to 32.5 ± 2.2 μg/g). Both amino acids are essential in free radical scavenging and oxidative stress reduction and in preventing chronic diseases such as cardiovascular disorders, diabetes, and obesity. A decoction with 28 components exhibited the highest activity against ABTS•+ and •NO, while the 14-component decoction showed the highest DPPH• scavenging capacity. Furthermore, two decoctions contained cysteine (0.99 ± 0.09 μg/g and 1.78 ± 0.83 μg/g), an important amino acid with potent antioxidant properties due to its ability to interact with redox reactions. Additionally, glutamine, a precursor for glutathione synthesis and essential for antioxidant defence, was present in all the samples. Multicomponent decoctions offer functional beverages with amino acid-driven antioxidants, supporting oxidative stress reduction and health promotion. They support sustainable food systems and serve as dietary strategies for chronic disease prevention and management, highlighting their potential in nutrition-based health interventions.