Abstract
More understanding of the risk-benefit effect of the glycoalkaloid tomatine is required to be able to estimate the role it might play in our diet. In this work, we focused on effects towards intestinal epithelial cells based on a Caco-2 model in order to analyze the influence on the cell monolayer integrity and on the expression levels of genes involved in cholesterol/sterol biosynthesis (LDLR), lipid metabolism (NR2F2), glucose and amino acid uptake (SGLT1, PAT1), cell cycle (PCNA, CDKN1A), apoptosis (CASP-3, BMF, KLF6), tight junctions (CLDN4, OCLN2) and cytokine-mediated signaling (IL-8, IL1β, TSLP, TNF-α). Furthermore, since the bioactivity of the compound might vary in the presence of a food matrix and following digestion, the influence of both pure tomatine and in vitro digested tomatine with and without tomato fruit matrix was studied. The obtained results suggested that concentrations <20 µg/mL of tomatine, either undigested or in vitro digested, do not compromise the viability of Caco-2 cells and stimulate cytokine expression. This effect of tomatine, in vitro digested tomatine or in vitro digested tomatine with tomato matrix differs slightly, probably due to variations of bioactivity or bioavailability of the tomatine. The results lead to the hypothesis that tomatine acts as hormetic compound that can induce beneficial or risk toxic effects whether used in low or high dose.
Highlights
Glycoalkaloids are steroidal secondary metabolites present in plants of the Solanum genus, including potato (Solanum tuberosum L.) and tomato (Solanum lycopersicum L.), which play a role in plant resistance against fungi, bacteria, virus and insects [1,2].Tomatine is a mixture of two glycoalkaloids called α-tomatine and dehydrotomatine generally found in all parts of tomato plants (Figure 1)
In order to understand whether tomato glycoalkaloid (α-tomatine and dehydrotomatine) content could be altered after ingestion, in vitro digestion assays were carried out
The percentage of dehydrotomatine observed in the samples of in vitro digested tomatine spiked into tomatoes (T) (53.5 ± 18.1) was higher than that detected in the samples of in vitro digested pure tomatine (A) (26.0 ± 6.2)
Summary
Tomatine is a mixture of two glycoalkaloids called α-tomatine and dehydrotomatine generally found in all parts of tomato plants (Figure 1). Tomatine is degraded in the fruit: immature green tomatoes can contain up to 500 mg/kg of fresh weight (FW), while red ripe tomatoes up to 5 mg/kg (FW) [3]. Glycoalkaloid content, whose biosynthesis involves gene cluster coding for glycosyltransferases, dehydrogenase and reductase, is inversely proportional to the weight and the diameter of the fruit, and it is not correlated to the position of the fruit on the stem. The amount of glycoalkaloid in the fruits, as well as in the other parts of tomato. Molecules 2018, 23, 644 plants, is highly variable and depends on cultivar and growing conditions [4].
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