M. Friedman et al., ALPHA-TOMATINE DETERMINATION IN TOMATOES BY HPLC USING PULSED AMPEROMETRIC DETECTION, Journal of agricultural and food chemistry, 42(9), 1994, pp. 1959-1964
As part of a program to control the biosynthesis of glycoalkaloids, we
used an improved HPLC method with pulsed amperometric detection (PAD)
to measure the alpha-tomatine content of store-bought and field-grown
, including transgenic, red, and green tomatoes. The HPLC method respo
nded linearly to alpha-tomatine in the range 0.125-12.5 mu g, suggesti
ng a lower limit of detection of about 125 ng of alkaloid. Recoveries
from tomato extracts spiked with alpha-tomatine ranged from 97 to 107%
. alpha-Tomatine and a new glycoalkaloid tentatively identified as deh
ydrotomatine, whose molecular mass determined by mass spectrometry is
2 Da less than that of alpha-tomatine, separated well on the HPLC colu
mn. The ratio of alpha-tomatine to dehydrotomatine in commercially ava
ilable standards was approximately 10:1. The alpha-tomatine content of
ripe red tomatoes ranged from 0.03 to 0.6 mg/100 g of fresh weight. T
he corresponding values for unripe green tomatoes ranged from 4 to 17
mg/100 g of fresh weight. These results show that the ratio of alpha-t
omatine content for the highest concentration in green tomatoes to the
lowest value in red tomatoes is more than 500. The difference in alph
a-tomatine content of transgenic and nontransgenic tomatoes, at the sa
me level of ripeness, was negligible. Possible applications of the HPL
C-PAD method are discussed.