Identification of a novel N-caprylhistamine-β-glucoside from tomato fruits and LC-MS/MS-based food screening for imidazole alkaloids

Intestinal Absorption and Metabolism of the Tomato Imidazole Alkaloids N-Caprylhistamine-β-glucoside and N-Caprylhistamine

Histamine-based imidazole alkaloids N-caprylhistamine (HmC₈) and N-caprylhistamine-β-glucoside (HmC₈-Glc) were recently identified as precursors for a tomato biomarker. As studies regarding metabolism and bioavailability are scarce, the present study aimed at the elucidation of intestinal absorption and metabolism using the Caco-2 model and the pig cecum model to mimic human intestinal conditions. The most abundant imidazole alkaloid HmC₈-Glc was neither absorbed nor transferred across cellular barriers but extensively metabolized to HmC₈ in the pig cecum model, whereas the aglycon HmC₈ is subjected to transport and metabolic processes through the Caco-2 monolayer and metabolized to the bioactive neurotransmitter histamine by the intestinal microbiota. Deduced from the combined results of both methods, HmC₈-Glc is not absorbed directly via the intestinal epithelium but requires a metabolic cleavage of the glycosidic bond by the gut microbiota. Because of the high bioavailability of the released HmC₈ and histamine, HmC₈ and its glucoside might also be involved in the intolerance to tomato products by histamine-intolerant consumers.

Pigment-Related Mutations Greatly Affect Berry Metabolome in San Marzano Tomatoes

The study describes the alterations in metabolomic profiles of four tomato fruit mutations introgressed into Solanum lycopersicum cv. San Marzano, a well-known Italian traditional variety. Three lines carrying variants affecting the content of all pigments, high pigment-1 (hp-1), hp-2, pigment diluter (pd), and a combination of Anthocyanin fruit and atroviolaceum (Aft_atv), were selected, and characterized. Biochemical analysis of 44 non-polar, 133 polar, and 65 volatile metabolites in ripe fruits revealed a wide range of differences between the variant lines and the recurrent parent San Marzano. Among non-polar compounds, many carotenoids, plastoquinones, and tocopherols increased in the fruit of high pigment lines, as well as in Aft_atv, whose β-carotene levels increased too. Interestingly, pd displayed enriched levels of xanthophylls (all-trans-neoxanthin and luteoxanthin) but, simultaneously, decreased levels of α-and β-/γ-tocopherols. Looking at the metabolites in the polar fraction, a significant decrease in sugar profile was observed in hp-1, pd, and Aft_atv. Conversely, many vitamins and organic acids increased in the hp-2 and Aft_atv lines, respectively. Overall, phenylpropanoids was the metabolic group with the highest extent of polar changes, with considerable increases of many compounds mainly in the case of Aft_atv, followed by the pd and hp-2 lines. Finally, several flavor-related compounds were found to be modified in all mutants, mostly due to increased levels in many benzenoid, lipid, and phenylalanine derivative volatiles, which are associated with sweeter taste and better aroma. Construction of metabolic maps, interaction networks, and correlation matrices gave an integrated representation of the large effect of single variants on the tomato fruit metabolome. In conclusion, the identified differences in the mutated lines might contribute to generating novel phenotypes in the traditional San Marzano type, with increased desirable nutraceutical and organoleptic properties.

Mass Spectrometry-Based Analysis of Urinary Biomarkers for Dietary Tomato Intake

SCOPE

In this study, the applicability of several β-carboline, imidazole, and steroidal alkaloids as biomarkers for tomato juice intake is evaluated.

METHODS AND RESULTS

Over the course of a 2-week crossover dietary intervention study, 14 volunteers were given low and high doses of tomato juice after 3 days of avoiding tomato-based products. On the day of consumption and the following days, volunteers provided urine samples that were quantitatively analyzed by high-performance liquid chromatography-tandem mass spectrometry. Herein, glucose-derived β-carboline alkaloids are determined as supporting, yet non-specific dietary biomarkers for tomato juice intake. Several imidazole alkaloids represent further biomarkers, which are shown to specifically indicate consumption of tomato juice for 24 h and partly >24 h. Additionally, steroidal alkaloids derived from esculeogenin B are determined to be specific biomarkers for tomato juice detectable for at least 48 h after consumption. The intake of low and high amounts of tomato juice is significantly distinguishable based on the urinary excretion of all determined biomarkers as well.

CONCLUSIONS

The dietary intake of tomato juice is conclusively traceable based on urinary excretion of multiple β-carboline, imidazole, and steroidal alkaloids, and can be determined for up to 48 h after consumption. Furthermore, different intake doses can clearly be distinguished based on their urinary excretion.