Determination of bioactive compounds in ten cultivars of onions from Aragón and Castilla y León

Abstract

Onion (Allium cepa L.) is one of the most important agricultural crops worldwide. The onion has high content of bioactive compounds and by this it is a food with healthy proprieties. The onion has two groups of compounds with these proprieties: S-alk(en)yl-cysteine sulphoxides (ACSOs), which are also flavour precursors, and non-sulfur compounds. In non-sulfur compounds, there are: flavonoids (mainly flavonols), fructans and saponins. Quercetin and its derivatives are the most important flavonols. Onion is an excellent source of quercetin, which is known to have various health benefits. The aim of this study was: cultivar selection according to the quantity of some bioactive compounds with healthy benefits. In this study, ten local onion landraces were supplied by the Vegetable Germplasm Bank in Zaragoza (BGHZ) Centro de Investigacion y Tecnologia Agroalimentaria (CITA) of Zaragoza (Spain), and these correspond to two Spanish autonomous communities: “Aragon” and “Castilla y Leon”. The ten onion cultivars were grown in a greenhouse (CITA) under the same conditions of time, temperature, climate, soil and nutrient supply. The samples were processed as follows: the two outer layers were removed (dry brown layers), cut and the central part were minced and frozen. The pyruvic acid content, total polyphenols, quercetin, antioxidant capacity, pH and soluble solids were evaluated. In relation to the pyruvic acid content in the different cultivars studied, it was found that all of them showed little pungency and can be classified as sweet. The cultivar ‘BGHZ-3096’ (“Cebolla Pequena”, Teruel) presented the highest content in total polyphenols, quercetin and antioxidant capacity, and the highest soluble solids content, of all the cultivars analyzed.