Ultrasound-assisted liquid-liquid extraction followed by ultrahigh pressure liquid chromatography for the quantification of major carotenoids in tomato

Lycopene and β-carotene, the main carotenoids present in different tomatoes varieties (gordal, cherry, roma and campari) of Solanum lycopersicum L. (Solanaceae), were investigated using ultrasound-assisted liquid-liquid extraction (LLUSAE) followed by ultra-high pressure liquid chromatography with PDA detection (UHPLC-PDA) analysis. Experimental parameters influencing the LLUSAE were optimized using an univariate design, resulting in a 30-min ACN/MeOH extraction by sonication of a lyophilized sample, followed by PSA/C18/MgSO4 clean-up and fast centrifugation before UPLC analysis. Using this greener methodology, high recoveries (above 97%), good linearity (r2 > 0.98) and improved sensitivity, with limits of detection and quantification of 24.0 and 80.0 ng/mL for lycopene and 3.0 and 9.9 ng/mL for β-carotene, respectively, were obtained. This sensitivity is about five times better than previously reported in literature, making LLUSAE/UHPLC-PDA a promising strategy for lycopene and β-carotene quantification in tomato and eventually in other matrices. The carotenoids studied, lycopene and β-carotene, were found at highest concentrations in the gordal tomato variety, followed by cherry, roma and campari (727.1, 342.2, 267.2 and 218.2 μg/g and 80.4, 44.0, 45.7 and 44.0 μg/g for lycopene and β-carotene, respectively). Additionally, an exponential increase of both carotenoids occurs during ripening and mainly in the skin and locular cavity of the gordal variety. These results provide further evidences of the potential of tomatoes as an interesting source of lycopene and β-carotene.