Tomatine toxicity

This primary mode of action of tomatine, that involves the formation of complexes with membrane sterols is similar to that described for polyene antibiotics [2, 4], and results in pore formation and loss of membrane integrity. This mode of action is supported by the reduced activity of tomatine on sterol-free bacteria and Oomycete fungi such as Pythium and Phytophthora [15, 28], and the strongly reduced toxicity of hydrolysis products of the glycoalkaloid which fail to bind sterols [57]. 

The a-tomatine (Fig. 9.11) is the major glycoalkaloid present in the leaves, stems, and immature fruit of tomato plants. It is reported to be potentially toxic and also is reported to exert antifungal activity and to inhibit the growth of fruitworm and other insects (Friedman et al., 1994). The method consists of lyophilization of the tomatoes followed by grinding and sieving. The extraction is aqueous and reversed-phase C-18 is the sorbent used for the isolation of the a-tomatine. 

There is a tendency for laymen to think of chemicals as being only man-made, and to characterize them as toxic, as if every natural chemical was not also toxic at some dose. Even a recent NRC/NAS report (28) states "Advances in classical plant breeding.. . offer some promise for nonchemical pest control in the future. Nonchemical approaches will be encouraged by tolerance revocations if more profitable chemical controls are not available.. .." The report was particularly concerned with some pesticides used on tomatoes. Of course, tomatine, one of the alkaloids in tomatoes, is a chemical too, and was introduced from the new world 400 years ago. It has not been tested in rodent cancer bioassays, is present at 36,000 pg/lOO g tomato, and is orders of magnitude closer to the toxic level than are man-made pesticide residues found on tomatoes. 

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