DEHYDROTOMATINE CONTENT IN TOMATOES

A variety of methods are used to analyze tomato glycoalkaloids. Becaus e no single method has gained wide acceptance,the extraction and analy sis of tomatine by HPLC with pulsed amperometric detection (PAD) was p reviously optimized for standard and transgenic tomatoes and processed tomato products. In the course of these studies it was discovered tha t commercial tomatine contained a second glycoalkaloid, which was name d dehydrotomatine. This study demonstrates that the HPLC-PAD assay can be used to measure both the dehydrotomatine (DT) and a-tomatine (TMT) content of parts of the tomato plant and of low- and high-tomatine re d and green tomatoes. Both the absolute concentration of dehydrotomati ne and the percent dehydrotomatine in the mixture of the two extracted glycoalkaloids, defined as [DT/(DT + TMT) x 100], varied widely. The DT content of red tomatoes ranged from 0.05 to 0.42 mg/kg of fresh wei ght. The corresponding range for green tomatoes was from 1.7 to 45 mg/ kg. The percent DT for the tomato plant parts was about 7 for fresh an d senescent leaves and calyxes, 10 for green fruit, 14 for small stems and flowers, and 23 for roots and large stems. The corresponding valu es for 15 different tomato varieties ranged from similar to 3 to 10%. This study demonstrates the advantages of the highly sensitive HPLC-PA D method for DT and TMT. The possible significance of these findings f or plant and food sciences is discussed.