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.