Insights into physicochemical traits, bioactive compounds, and antioxidant activity of two lesser-known Iranian melon accessions in developmental stages

Despite the increasing consumption and widespread cultivation of diverse melon accessions across different regions of Iran, the ripening-related compositional changes of several indigenous accessions remain insufficiently characterized. Therefore, this study aimed to investigate and compare the physicochemical characteristics, bioactive compounds, and antioxidant activity of two lesser-known melon accessions (‘Chaghercheh’ and ‘Zamcheh’) across five developmental stages, from fruit set to full ripening at 10-day intervals over two consecutive years. Fruit fresh weight, dimensional attributes, pulp thickness, and pulp percentage increased progressively during fruit development, reaching their maximum values at the final harvest stage. In contrast, fruit firmness, peel thickness, and the percentages of peel and seed decreased continuously throughout ripening. At full maturity, both accessions exhibited the highest total soluble solids and pH values, accompanied by the lowest titratable acidity, resulting in the highest maturity index. Sucrose accumulated substantially from 30 days after fruit set onward, whereas glucose and fructose concentrations gradually declined. During fruit development, total chlorophyll content decreased, while total carotenoid and flavonoid concentrations increased progressively. Likewise, the levels of ascorbic acid, total phenolics, and antioxidant activity increased during ripening, peaked at 30 days after fruit set, and subsequently declined toward the final harvest stage. Significant differences were observed between the two accessions for all evaluated parameters. Overall, the findings demonstrate that both developmental stage and accession identity are major determinants of the physicochemical characteristics, bioactive composition, and antioxidant activity of melon fruit. These results provide valuable insights for optimizing harvest timing to maximize nutritional quality and commercial value. Furthermore, the ‘Chaghercheh’ and ‘Zamcheh’ accessions represent valuable genetic resources with high levels of bioactive compounds and antioxidant activity, highlighting their potential for the development of nutritionally improved melon cultivars and value-added functional food products.