B. Rodríguez Galdón

Flavonoids in onion cultivars (Allium cepa L.).

Total phenol and flavonoid contents were analyzed by HPLC coupled with a diode array detector in 5 traditional onion cultivars from Tenerife (Guayonje, San Juan de la Rambla, Carrizal Alto, Carrizal Bajo, and Masca) and a commercial cultivar (Texas Early Grano 502). Five quercetin chemical species (isoquercetin, quercetin diglucoside, quercetin monoglucoside 1, quercetin monoglucoside 2, and free quercetin) and kaempferol were identified and quantified in the onion samples. Quercetin monoglucoside 1 and quercetin diglucoside were the major flavonoids accounting for 80% of the total quercetin content. The mean quercetin monoglucoside 1: quercetin diglucoside ratio (QMG/QDG) was 1: 2.2. There were differences between the onion cultivars in the cases of total phenol, quercetin diglucoside, isoquercetin, QMG/QDG ratio, and kaempferol. The Texas cultivar had a higher QMG/QDG ratio and a higher kaempferol content than the traditional cultivars. The correlation study showed significant correlations between the analyzed phenolic components.

Fatty acid profile in varieties of chestnut fruits from Tenerife (Spain) Perfil de ácidos grasos en variedades de castañas procedentes de Tenerife (España)

Total fat and fatty acids (FA) were determined in chestnut samples belonging to 21 different chestnut varieties. Total saturated, monounsaturated, polyunsaturated acids and the relationships between them, such as oleic/linoleic and linoleic/linolenic, were calculated. The predominant FAs in the fat of chestnuts were linoleic acid (43.4 ± 4.1% of total FA), oleic acid (30.5 ± 4.8% of total FA), palmitic acid (14.7 ± 1.7% of total FA), and linolenic acid (6.76 ± 2.02% of total FA). These FA represent ≥ 90% of the total FA in all the varieties investigated. Considerable differences were observed in many FA and in their relationships according to the variety. The influence of the production zone only significantly affected the content of arachidic acid. Correlations between oleic acid with linoleic (r = −0.743) and linolenic (r = −0.593) acids were observed thereby indicating metabolic relationships between them. Se determinó el contenido de grasa total y de ácidos grasos en muestras de castañas pertenecientes a 21 variedades diferentes. Asimismo, se calcularon otros parámetros tales como ácidos grasos saturados, monoinsaturados, poliinsaturados, y relaciones oleico/linoleico y linoleico/linolénico. Los ácidos grasos predominantes en la grasa de castañas fueron linoleico (43,4 ± 4,1% del total de ácidos grasos), oleico (30,5 ± 4,8% del total de ácidos grasos), palmítico (14,7 ± 1,7% del total de ácidos grasos) y linolénico (6,76 ± 2,02% del total de ácidos grasos). Estos ácidos grasos representan más del 90% de los ácidos grasos totales en todas las variedades investigadas. Se observaron diferencias en los contenidos de muchos ácidos grasos y sus relaciones en función de la variedad. El área de producción sólo afectó de forma significativa el contenido de ácido araquídico. Se establecieron algunas correlaciones significativas entre los ácidos grasos, destacando las existentes entre el ácido oleico con el ácido linoleico (r=−0.743) y con el ácido linolénico (r=−0.593), lo que pone de manifiesto las relaciones entre ellos.

Capacidad antioxidante de diferentes variedades de cebolla Antioxidant capacity of different onion cultivars

The total antioxidant activity (expressed as mmol Trolox/kg of fresh onion) was determined in six cultivars of onions produced in Tenerife in order to find out differences between them. The decrease of absorbance, at 734 nm, of an ABTS (2.2´-azino-bis-3-ethylbenzothiazoline-6-sulfonic acid) diamonium salt solution in presence of the onion sample was measured. The antioxidant activity of the onion decreases significantly from the external leaves to the internal leaves. The mean antioxidant activity of all the onion samples analyzed was 0.579 ± 0.304 mmol/kg, ranging between 0.349 ± 0.084 mmol/kg and 0.696 ± 0.371 mmol/kg. The Guayonje cultivar presented the highest mean value 0.696 ± 0.371 mmol/kg, with significant differences with respect to the San Juan de la Rambla (0.349 ± 0.084 mmol/kg) and Texas (0.398 ± 0.058 mmol/kg) cultivars, which presented the lowest antioxidant activities. Besides, it was observed that the red color of the onion was related with a higher antioxidant activity.