Tomatoes, a major food source for humans, accumulate a variety of secondary metabolites including phenolic compounds, phytoalexins, protease inhibitors, and glycoalkaloids. These metabolites protect against adverse effects of hosts of predators including fungi, bacteria, viruses, and insects. Because glycoalkaloids are reported to be involved in host-plant resistance, on the one hand, and to have a variety of pharmacological and nutritional properties in animals and humans, on the other, a need exists to develop a better understanding of the role of these compounds both in the plant and in the diet. To contribute to this effort, this integrated review presents data on the history, composition, and nutrition of tomatoes, with special focus on the assessment of the chemistry, analysis, composition, nutrition, microbiology, and pharmacology of the tomato glycoalkaloids comprising alpha-tomatine and dehydrotomatine; their content in different parts of the tomato plant, in processed tomato products, and in wild and transgenic tomatoes; their biosynthesis, inheritance, metabolism, and catabolism; plant-microbe relationships with fungi, bacteria, viruses, insects, and worms; interactions with ergosterol and cholesterol; disruption of cell membranes; tomatine-induced tomatinases, pantothenate synthetase, steroid hydroxylases, and cytokines; and inhibition of acetylcholinesterase. Also covered are tomato-human pathogen relationships and tomatine-induced lowering of plasma cholesterol and triglycerides and enhancement of the immune system. Further research needs in each of these areas are suggested. The overlapping aspects are discussed in terms of general concepts for a better understanding of the impact of tomato glycoalkaloids in the plant in general and in food in particular. Such an understanding can lead to the creation of improved tomatoes and to improved practices on the farm and in the consumption of tomatoes.

Tomato glycoalkaloids: role in the plant and in the diet.

Potatoes, tomatoes, and aubergines are all species of the Solanum genus and contain a vast array of secondary metabolites including calystegine alkaloids, phenolic compounds, lectins, and glycoalkaloids. Glycoalkaloids have been the subject of many literature papers, occur widely in the human diet, and are known to induce toxicity. Therefore, from a food safety perspective further information is required regarding their analysis, toxicity, and bioavailability. This is especially important in crop cultivars derived from wild species to prevent glycoalkaloid-induced toxicity. A comprehensive review of the bioactivity of glycoalkaloids and their aglycones of the Solanum species, particularly focused on comparison of their bioactivities including their anticancer, anticholesterol, antimicrobial, anti-inflammatory, antinociceptive, and antipyretic effects, toxicity, and synergism of action of the principal Solanum glycoalkaloids, correlated to differences of their individual molecular structures is presented.

Bioactivities of glycoalkaloids and their aglycones from Solanum species.

(1981). Naturally Occurring Toxic Alkaloids in Foods. CRC Critical Reviews in Toxicology: Vol. 9, No. 1, pp. 21-104.

Naturally occurring toxic alkaloids in foods.

The purpose of exploring the potential naturally occurring toxic hazards in food plants is not to persuade a person to avoid these common foods. Rather, it is important to put some perspective on these chemicals (natural pesticides) in our foods, and to clearly show that their toxicology, which is unknown in most cases, needs to be better understood. Many natural pesticides function similarly to synthetic pesticides or other biohazard chemicals. The natural pesticide concentration in our foods may be as much as 10,000 times higher than that of synthetic pesticide residues (Ames 1983). In some cases, these natural chemicals are prime candidates to be monitored by plant producers and plant breeders.

Natural Pesticides and Bioactive Components in Foods

The steroidal glycoalkaloid α-tomatine

The clinical attractiveness of antibiotic agents, as typified by penicillin and streptomycin, lies in their ability to effect striking and specific bacteriostatic action in vivo without the simultaneous production of severe toxic symptoms. However, since penicillin and streptomycin are limited in their usefulness because of their ineffectiveness against certain important groups of pathogenic organisms, the search for new antibiotic agents continues in the hope that additional substances having sufficiently low toxicity will be found whose high antibiotic activity against the penicillinand streptomycin-resistant organisms will permit their therapeutic use in the conquest of the diseases caused by these pathogens. Although the fungi, including Actinomyces and related forms, and bacteria have been the most fruitful sources of antibiotic agents, antibiotic activity has also been attributed to the juices of certain green plants. Many plant families have been examined for antibiotic activity (Osborn, 1943; Huddleson et al., 1944; Lucas and Lewis, 1944; Seegal and Holden, 1945), and several plant constituents that possess antibiotic activity have been isolated in crystalline form. Among these antibiotic agents are a substance from garlic (Allium sativum) that has been tentatively identified as the sulfoxide of diallyl disulfide (Cavallito, Buck, and Suter, 1945); a substance from common burdock (Arctium minus) that has not been identified but which appears to be a lactone having the empirical formula C15H2006 (Cavallito, Bailey, and Kirchner, 1945); and a substance designated "crepin" from Crepis taraxacifolia that has the empirical formula C14H1604 (Heatley, 1944). It is the purpose of this paper to describe some of the antibiotic properties of what is believed to be a new antibiotic agent from a plant source. This substance occurs in the tomato plant and has been designated "tomatin." Tomatin has not yet been crystallized, but preparations of sufficient potency have been obtained to warrant a preliminary investigation of its antibiotic spectrum. Because of the probable impurity of the tomatin preparation used in the present investigation, the data to be presented have only qualitative or, at best, semi-

S. P. Doolittle

Papers

Partial Antibiotic Spectrum of Tomatin, an Antibiotic Agent from the Tomato Plant.