Characterization of nutraceutical components in tomato pulp, skin and locular gel

Abstract

Nutraceutical properties of tomato fruits (Solanum lycopersicum L.) were investigated, focusing on selected secondary metabolites: glycoalkaloids and polyphenols (hydroxycinnamic acids and flavonoids). Three tomato varieties were studied: Red Round-Smooth, Cherry, and Camone (as whole fruits), and subsequently, portions of Camone fruits (skin, pulp and locular gel) were characterized. Particular attention was devoted to the locular gel portion, a by-product material from the tomato processing industry. Quantification of α-tomatine and dehydrotomatine was carried out by reverse phase liquid chromatography coupled with electrospray ionization tandem mass spectrometry (HPLC–ESI-MS/MS). The contents of α-tomatine and dehydrotomatine in the Camone locular gel were 38.73 ± 3.32 and 4.90 ± 0.01 mg/kg dw, respectively, resulting about ten times higher than in the skin; just traces were revealed in the pulp. Samples were also assayed for antioxidant activity (TEAC, Trolox Equivalent Antioxidant Capacity) via ABTS and DPPH radical quenching, and selected targeted polyphenols were also quantified via HPLC–ESI-MS/MS. Chlorogenic and caffeic acids were the main hydroxycinnamic acids in all the varieties, while rutin was the most abundant flavonoid.