Dehydrotomatine content in tomatoes

A variety of methods are used to analyze tomato glycoalkaloids. Because no single method has gained wide acceptance,the extraction and analysis of tomatine by HPLC with pulsed amperometric detection (PAD) was previously optimized for standard and transgenic tomatoes and processed tomato products. In the course of these studies it was discovered that commercial tomatine contained a second glycoalkaloid, which was named 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 red and green tomatoes. Both the absolute concentration of dehydrotomatine 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 weight. 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 and senescent leaves and calyxes, 10 for green fruit, 14 for small stems and flowers, and 23 for roots and large stems. The corresponding values for 15 different tomato varieties ranged from similar to 3 to 10%. This study demonstrates the advantages of the highly sensitive HPLC-PAD method for DT and TMT. The possible significance of these findings for plant and food sciences is discussed.