PHYTOCHEMICAL PROFILE, ANTIOXIDANT POTENTIAL AND EXPRESSION OF FLS, GGP GENES IN KIWIFRUIT AT DIFFERENT HARVESTING STAGES AND DURATIONS OF STORAGE

Kiwifruit is recognized as a valuable source of antioxidants, flavonoids, and phenolic compounds, all of which contribute to its health-promoting properties. This study aimed to identify the optimal harvest stage for maximizing beneficial metabolites by quantifying these compounds and analyzing their gene expression profiles. Kiwifruit samples were collected at seven distinct harvesting stages. Total phenolic content (TPC) and total flavonoid content (TFC) were measured, and antioxidant capacity was assessed using HPLC-UV. Expression analysis of flavanol synthase (FLS) and GDP- galactose phosphorylase (GGP) genes was performed via RT-PCR. The results showed that TPC ranged from 0.4 to 1.3 mg of gallic acid equivalents/100 g FW, while TFC ranged from 1.1 to 2.4 mg of quercetin equivalents/100 g FW. Antioxidant activity followed a pattern similar to TPC, peaking at the early harvest stages and declining as maturity progressed. Predominant phenolic compounds included ferulic acid, chlorogenic acid, vanillic acid, vanillin, and p-coumaric acid, while catechin and epicatechin were the primary flavonoids. Quercetin and rutin were detected in smaller quantities in some samples. The FLS gene exhibited increased expression during later harvest stages, whereas expression of GGP gene remained consistently high throughout the different harvesting stages. Immature kiwifruit displayed higher TPC and stronger antioxidant activity, while mature fruit showed increased TFC. These findings provide valuable insights into the metabolic changes and gene expression patterns associated with kiwifruit quality at different harvest stages, offering a foundation for future research and applications in agriculture and food sciences.