The aim of the present study was to develop a generic analytical method for the identification and quantitation of apolar plant metabolites in biomass using liquid chromatography-photodiode array-accurate mass mass spectrometry (LC-PDA-amMS). During this study, a single generic sample preparation protocol was applied to extract apolar plant metabolites. Compound identification was performed using a single generic screening method for apolar compounds without the need for dedicated fractionation. Such a generic approach renders vast amounts of information and is virtually limited by only the solubility and detector response of the metabolites of interest. Method validation confirmed that this approach is applicable for quantitative purposes. Furthermore, an identification-quantitation strategy based on amMS and molar extinction coefficients was used for carotenoids, eliminating the need for reference standards for each carotenoid. To challenge the validated method, chili peppers (Capsicum frutescens L.) were analyzed to unravel their complex phytochemical composition (carotenoids, glycolipids, glycerolipids, capsaicinoids, lipid-soluble vitamins).

A field experiment was conducted from September 2010 to July 2011 at Research Station Farm of Higher Institute of Agronomy, Chott Mariem, Sousse (Tunisia) in order to evaluate the performance of seven onion varieties: ‘GIZA 6’, ‘Red Amposta’, ‘Z6’, ‘Morada de Amposta’, ‘Yellow Dessex’, ‘Early Yellow Texas Grano 502’ and ‘Keep Red’ against the commonly grown variety ‘Blanc Hâtif de Paris’ under field conditions. The experiment was conducted in a randomized complete block design with three replications. Results obtained showed that onion varieties were significantly different when it comes to the plant and bulb morphological characteristics. Variety ‘Morada de Amposta’ recorded the highest leaf length (68.06 cm), pseudostem diameter (8.63 cm), number of leaves (8.71), plant height (76.95 cm),  in addition to the greatest yields (32.88 t/ha) which were significantly (p≤0.05) increased by respectively 66.2,  88.8,  2.1,  61.2, 63, 27.9  and 28.4%  compared to those obtained from the regular variety ‘Blanc Hâtif de Paris’. Variety ‘Blanc Hâtif de Paris’ was the earliest to maturity and recorded the most preferment bulb weight (155.02 g) and diameter (8.21 cm). ‘Keep Red’ variety had the highest height of the bulb (7.19 cm). Variety ‘Z6’ recorded the minimum data in all measured parameters.