Onion (Allium cepa L.) as a food with interesting nutritional profile for health promotion

INSANI, E.M.; SALOMÓN, V.M.; MIGNAQUI, A.C.; PAZOS, A.A.; PIGHIN, D.G.; GALMARINI, C.

Zilina. Eslovaquia

Conferencia; International Scientific Conference on Nutraceuticals and Functional Foods. Food and Function 2009.; 2009

Bioactive food components are defined as those which have a positive effect on human health when they are consumed in the frame of a balanced diet. The three mayor types of bioactive compounds present in onions are polyphenols, non-digestible oligosaccharides –fructan type- and sulphur-containing compounds. Epidemiological studies highlighted the importance of onions for the prevention of chronic diseases due to their bioactive compounds content. The aim of this work was to evaluate parameters of health promotion and of nutritional interest in onion. Polyphenols and oligosaccharides (Total and three authentic FOS) were determined by HPLC; Total phenolic content by Folin-Ciocalteau; Total Antioxidant Status (TAS) by the decolorization assay of the ABTS●+ radical cation and the Aminoacidic profile by Ion-exchange chromatography. Valcatorce-INTA, an argentine germplasm onion was selected for this study because this variety was employed for further bioactivity studies in wistar rats (see another abstract presented). Juice of a representative number of bulbs (edible part) was obtained by a juice extractor. Results showed the following polyphenolic profile (µg/g fresh onion): Catechin 0.18±0.04; Epicatechin ND; Epigallocatechin 14.73±2.8; Epigallocatechin-gallate 0.94±0.18; Epicatechin-gallate 2.19±0.16; Kaempherol aglycone 0.08±0.03; Total Kaempherol 0.46±0.16; Quercetin aglycone 3.42±0.47; Total Quercetin 17.62±0.54 and Chlorogenic Acid 0.17±0.06. Total Phenols (mgGAE/g fresh onion) was 466.02±22.28. TAS showed a value of 170,14±6,12 mM. Three FOS were quantified (mg/g fresh onion) using authentic standards (Wako, Chemical Co.): 1-Kestose 2,64±0,39, Nystose 1,36±0,27 and Fructo-Furanosyl-Nystose 0,85±0,04. Moreover, in order to determine the whole content of oligosaccharides present in the onions, an alternative method according to Hoebregs, 1997 was applied. Briefly, free Glucose, Fructose and Sucrose were determined by HPLC in basal and after acid hydrolysis of the samples and the value obtained was 7,29±1,56 mg/g fresh onion. Regarding the aminoacidic content, it was observed 531,00±4,49 for Total, 95,15±0,81 for Essential and 208.45 free aminoacids (all µg/g fresh onion). Onion is a food that presents a remarkable combination of bioactive compounds. Therefore, it would be interesting to study each one present in this vegetable more in detail as well as their combined effect on human health.