HIGH-PERFORMANCE LIQUID-CHROMATOGRAPHIC DETERMINATION OF THE TOMATO GLYCOALKALOID, TOMATINE, IN GREEN AND RED TOMATOES

A high-performance liquid chromatographic method has been developed to quantify tomatine in green and red tomatoes using UV detection at 205 nm. Extraction was performed by blending tomatoes with tetrahydrofuran-water-acetonitrile-acetic acid (50:30:20:1). C-18 Sep-Paks and alumina were employed for cleanup. Average percent recoveries of tomatine from mature green tomatoes ranged from 77 to 91, while the average percent recoveries from red tomatoes varied from 65 to 114. Tomatine in mature green tomatoes ranged from none detected to 8.79 mg/100 g of fresh weight, while tomatine in red tomatoes varied from none detected to 2.31 mg/100 g of fresh weight. Only 5 of 100 red tomatoes showed detectable levels of tomatine, but 61 of 80 mature green tomatoes had detectable amounts of tomatine. alpha-Solanine was not detected. Mass spectral and HPLC data indicate that there may be other glycoalkaloids in tomatoes besides tomatine, but they appear to be minor. No real differences in the glycoalkaloid levels between nontransgenic and transgenic tomatoes were observed.