Synergistic effects of chlorogenic acid and γ-aminobutyric acid on postharvest quality, antioxidant defense, and capsaicin synthesis in pepper fruit

Postharvest pepper fruit ( Capsicum annuum L.) quality is often compromised by oxidative stress, weight loss, and color degradation. Thus, in this study, the effects of chlorogenic acid (CGA), γ-aminobutyric acid (GABA), and their combination (CGA + GABA) on postharvest quality are investigated over a during 12-day storage period at 20 °C. All treatments reduced weight loss, preserved color, and enhanced antioxidant defense by increasing the activity of key enzymes, including superoxide dismutase, catalase, peroxidase, and ascorbate peroxidase. The combined CGA + GABA treatment further stimulated enzymes involved in capsaicin and phenolic compound biosynthesis, such as phenylalanine ammonia-lyase and capsaicin synthase, resulting in increased capsaicin content and higher levels of phenolic acids, including cinnamic acid and p-coumaric acid. Additionally, CGA + GABA upregulated the expression of CGA and amino acids like proline and glutamine, indicating improved stress tolerance. These findings highlight the potential of CGA and GABA as eco-friendly treatments to improve the postharvest quality and marketability of peppers. • CGA + GABA treatment significantly reduces weight loss and preserves color in postharvest pepper fruit. • CGA + GABA enhances antioxidant capacity by increasing key enzyme activities. • CGA + GABA stimulates capsaicin biosynthesis through the activation of phenylpropanoid pathway enzymes. • CGA + GABA increases amino acid levels, improving stress tolerance and metabolic stability in stored peppers.