Variability in phytochemical and nutritional attributes of Iranian red onion (Allium cepa L.) landrace as potential nutraceutical resources

Allium cepa L. (onion) is recognized for its nutraceutical and therapeutic potential. Six Iranian landraces (Azarshahr, Rey, Dorcheh, Ghom, Zanjan, and Qorveh) were evaluated for edible quality, energy value, and phytochemical composition in a randomized complete block design with three replications to identify nutritionally and antioxidatively superior genotypes. Significant differences were observed among landraces. Azarshahr showed the lowest moisture (79.94 ± 3.82%) and highest crude fiber (2.34 ± 0.21%), carbohydrate (14.23 ± 1.62%), energy (71.88 ± 5.13 kcal/100 g), and magnesium (1.05 ± 0.11 mg/100 g DW). Dorcheh, Ghom, and Rey had the highest ash, protein, and fat, respectively. Qorveh contained the highest levels of most minerals, while Zanjan was richest in sodium. Among five major phenolic acids, gallic acid was most abundant in Dorcheh (61.43 mg/g DW), and chlorogenic acid lowest in Zanjan (0.37 mg/g DW). Dorcheh and Azarshahr had the highest phenolic and flavonoid contents and antioxidant activity, whereas Rey had the highest vitamin C (4.1 mg/100 g DW). Azarshahr also had the highest sucrose, glucose, and fructose levels. These findings highlight Iranian red onion landraces as valuable sources of bioactive compounds with strong antioxidant activity, suitable for breeding and functional food applications.