Assessment of Bioactive Compounds, Soluble Sugars, Antioxidant Activity, and Yield of the Onion Cultivar Hamilton F1 Grown by Direct Sowing

Abstract Onion ( Allium cepa L.) is the most widely cultivated species of the genus Allium and one of the most consumed vegetables globally. With the aim of supporting onion cultivation practices and breeding programs, this study examined the main classes of bioactive compounds, soluble sugars, antioxidant properties (measured via TAC, CUPRAC, DPPH • and ABTS •+ assays) and yield indicators of the widely grown onion cultivar Hamilton F1 (Bejo Zaden BV, Warmenhuizen, Netherlands) under the agroecological conditions of Vojvodina, Serbia. The onion was established by direct sowing in 4 × double-row strips, using a randomized block design with three replications. Extraction was performed with 80% methanol in order to prevent protein extraction and potential interferences with phenolics. The results revealed that total phenolic content (TPC), total flavonoid content (TFC), and soluble sugars content (SSC) were 0.76 mg/g GAE, 0.29 mg/g QE, and 106.9 mg/g Glc, respectively. The highest antioxidant activity was observed in TAC and ABTS •+ assays, with values of 6.57 mg/g AAE and 3.67 µmol/g TE, respectively. The content of total hydroxycinnamic acid derivatives was below the detection limit. The dry matter content was 8.11%. Additionally, the total yield of the Hamilton F1 onion was 108.01 t/ha, with a first-class yield of 104.4 t/ha and a high proportion of marketable bulbs. The results indicate that the Hamilton F1 cultivar is characterized by a considerable content of the examined bioactive compounds that contribute to better agronomic traits, including improved performance under stress conditions, longer storage potential and greater disease tolerance. From consumers’ perspective, these compounds provide also health benefits. The findings emphasize the potential of Hamilton F1 as a reliable option for farmers and highlight the importance of breeding programs focused on developing onion cultivars with similar or improved functional properties, combining high yield potential with enhanced nutritional value.