A-Tomatine in tomatoes

Other common phytoalexins in food materials are pisatin, cinnamylphenols, glyceolin, phaseolin [13401 -40-6] (14), and 5-deoxykieritol in peas, beans, soybeans, and lima beans viniferin in grapes momilactones and ory2alexins in rice a-tomatine in tomato lubimen in eggplant and capsidiol in green peppers. 

SchonbeckE, SchlosserE (1976) Preformed substances as potential protectants. In Heitefuss, R, WiUiams, PH (eds) Physiological plant pathology. Springer, Berlin, pp. 653-678 Pegg GE, Woodward S (1986) Synthesis and metabohsm of a-tomatine in tomato isoUnes in relation to resistance to Verticillium albo-atrum. Mol Plant Microbe Interact 28 187 Eord JE et al (1977) The detoxification of a-tomatine by Fusarium oxysporum f.sp. lycopersici. Phytochemistry 16 544... 

The P-glycoside of tomatidenol in tomatoes, called dehydro-tomatine, accompanies a-tomatine in tomatoes. Dehydrotoma-tine and a-tomatine contain bound lycotetraose. The (25S)-stereoisomer tomatidine (10-48), also known as 5,6-dihydro-tomatidenol, is an aglycone of the main tomato glycoalkaloid a-tomatine (10-52). a-Tomatine also occurs in small amoimts in some potato species and some other species of the genus Solanum. 

Fig. 2.1 Strucnires of some common saponins. The strucnires of some of the saponins described in the text are shown, including aescin from horse chesnut, avenacin A-1 and avenacoside A from oat, and a-tomatine from tomato. The glucose molecule enclosed in square brackets in the structure of avenacoside A highlights the glucose moiety that is cleaved off by hydrolysis by glycosidases in disrupted oat leaf tissue, leading to the fungitoxic 26-desglucosyl avenacoside A. Redrawn from [94]...

Recently, new methods have been developed for very precise quantification of tomatine in tomato plants [13, 48-50]. Thus, Friedman and Levin, used HPLC with a pulse amperometric detection method, for the direct analysis of tomatine in different parts of tomato plants. They found 0.134 % in roots, 0.287 % in stems, 0.567% in calyxes, 0.64% in leaves and 0.745% in flowers [13]. 

Barbour, J. D. and G. G. Kennedy, Role of steroidal glycoalkaloid a-tomatine in host-plant resistance of tomato to Colorado potato beetle, J. Chem. Ecol., 17, 989-1005 (1991). 

FIGURE 10.12 High-performance liquid chromatograms of a-tomatine in field-grown (A) ripe red tomatoes and (B) unripe green tomatoes. Conditions Column, Supelcosil LC-ABZ mobile phase 25% ACN, 15% MeOH, 100 mM sodium phosphate (monobasic) pH 3. (Reprinted from Friedman, M., Levin, C.E., and McDonald, G.M., J. Agric. Food Chem., 42, 1959-1964, 1994.)... 

Kozukue, N. Han, J.-S. Lee, K.-R. Friedman, M. Dehydrotomatine and a-Tomatine Content in Tomato Fruits and Vegetative Plant Tissues. J. Agric. Food Chem. 2004, 52, 2079-2083. 

The existence of tomatinases in fungal-tomato pathogens supports the idea that tomatine may play a role in resistance to fungal attack because these enzymes seem to act specifically on tomatine. Such a role is also supported by the finding that at least in F. oxysporum f. sp. lycopersici, tomatinase is produced during infection both in roots and stems... 

Analysis of tomatine contents in tomato plants showed that the glycoalkaloid is present in all organs [7, 40-42]. There is a significant variation in the reported tomatine content of particular plant organs. For example, Tukalo (1958) found, in terms of dry weight, 0.86-1.9% tomatine in leaves, 0.3-0.6% in stems and roots and 0.93-2.2% in fully... 

Although several authors claimed that the glycoalkaloid tomatine is not present in sufficient concentrations in roots or stems to play a major role in resistance to Fusarium oxysporum f. sp. lycopersici [7, 57, 88], the fact that tomatinase is induced in tomato plants during infection, strongly suggests that the enzyme may have a specific role in pathogenicity of tomato plant by F. oxysporum f. sp lycopersici. 

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. 

Friedman, M., Levin, C. E., and McDonald, G. M. 1994. a-Tomatine determination in tomatoes by HPLC using pulsed amperometric detection, J. Agricul. Food Chem., 42 1959-1964. 

If the role of -tomatine in resistance to L. deceml lneata is verified, It should be relatively easy to select for high levels of foliar -tomatine In a tomato breeding program because the genetic variation in -tomatine is controlled by the segregation of 2 codominant alleles at a single locus (28). One possible limitation on the utility of -tomatine-mediated resistance to L. deceml lneata is... 

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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