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Variation in Antioxidant Activity, Total Phenolics, and Nitrate in Spinach

There is increasing interest in the determination of antioxidant and nitrate levels in vegetables. Antioxidant activity and total phenolic content of 24 spinach (Spinacia oleracea L.) genotypes that had smooth, savoy or semi-savoy leaves were determined. Nitrate content, as an unfavorable parameter in spinach, was evaluated. Mean values of antioxidant capacity, total phenolics, and nitrate of leaves and petioles were 40.87 and 16.11 μmol Trolox·g−1 dry weight, 11.03 and 3.19 mg GAE·g−1 dry weight, and 80.40 and 721.32 mg·kg−1 dry weight, respectively. There was a significant and positive correlation between antioxidant activity and total phenolic content in leaves (R 2 = 0.8349) and petioles (R 2 = 0.7657). Genotypes with smooth leaves had higher values of antioxidant capacity and total phenolic content. Nitrate content of smooth-leaved genotypes was comparable to semi-savoy- and savoy-leaved genotypes. The best genotypes were selected by cluster analysis. Leaf type, genotype, and plant part are important sources of variability in the antioxidant capacity and nitrate content. The best smooth-leaved types without petioles can be used to increase the quality of spinach.