Abstract
Consumption of onion has been associated with reduced incidence of chronic diseases. Phenolic, organosulfur and carbohydrate compounds present are largely responsible for these effects. This study examined compositional variation for health-enhancing compounds in a genetically diverse collection of onion cultivars. Total antioxidant activity and aroma profiles were characterized. Significant variation in bulb concentration for total and individual phenolic compounds, thiosulfinates, carbohydrates, and total and soluble solids was found. The range of variation was particularly large (>50-fold difference between the cultivars with the highest and lowest content) for fructo-oligosaccharides (FOS) and the polyphenols quercetin, epigallocatechin gallate and epicatechin gallate. Amino acid profiles varied significantly as well with substantial variation (~10 fold) observed in both total and essential amino acids. Total antioxidant activity was positively correlated with polyphenols content, and quercetin in particular (r = 0.83), suggesting a major contribution from phenolic compounds to onion antioxidant properties. Significant positive correlation was also found between solids and thiosulfinates content (r = 0.74) and between solids and FOS (r = 0.81), suggesting a dilution/concentration effect for organosulfur compounds and FOS in onion bulbs. The present study revealed broad variation for health-enhancing compounds content in onion germplasm, which can be exploited in breeding programs aiming at increasing onion nutraceutical value.
Highlights
Consumption of Allium species, such as onion (A. cepa L.), has been associated with reduced incidence of cardiovascular disease [1] and some types of cancer [2]
Positive and significant correlation was found between pyruvate and dry matter content (r = 0.71; P < 0.0001), suggesting a dilution/concentration effect due to cultivar differences in bulb water content (Table 1). In agreement with these results, Galmarini et al [12] reported significant positive phenotypic and genetic correlations between pyruvate levels, Dry Matter (DM) and onion-induced antiplatelet activity (OIAA) in onion F3 families, which were genetically unrelated to the materials used in our study. These results suggest that the increase in water content associated with low-DM onions may be responsible for diluting solids and organosulfur compounds associated with onion pungency and antiplatelet activity
We provide evidence–for the first time- that EN data can effectively be used for discriminating among onions cultivars grown under the same environmental conditions, as well as for characterizing onion germplasm based on their aroma profiles, a relevant trait for fresh onion consumers
Summary
Consumption of Allium species, such as onion (A. cepa L.), has been associated with reduced incidence of cardiovascular disease [1] and some types of cancer [2]. These general health-protective effects may be attributed to a few well-demonstrated biological properties of alliums, such as antiplatelet, antioxidant, anti-inflammatory, anti-tumor and hypolipidemic activities [3]. Polyphenols contribute to controlling oxidative stress [4] Their consumption has been associated with reduced risk of developing some chronic diseases of high prevalence [5]. Quercetin is the predominant polyphenol in onion bulbs [7]
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