Tomato goodies and baddies and types of tomatoes

[Guest guest]

Hi All, I got the impression from two papers that tomatoes are potential

sources of glycoalkaloids, as are also found in potatoes especially when

green, and types of tomatoes makes a big difference. It seems that cherry

tomatoes are best in terms of having fewer glycoalkaloids and more

anti-oxidants. The cluster tomatoes are about half way between the

significantly worse salad and elongated tomatoes, which I had not know of

before. Green tomatoes seem bad in terms of having high levels of

glycoalkaloids. This can reduce body weight but seems to do so through

toxic effects – not something I would like for me.

I can send full-text PDF of both papers. For the first and latest paper I

put in excerpts at first. I attached the abstract for the first paper and

for the second the text without figures (hopefully). The tables may be a

mess in email but I hope for better in the files.

Cheers, Al.

Friedman M.

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

J Agric Food Chem. 2002 Oct 9;50(21):5751-80.

PMID: 12358437 [PubMed - in process]

Tomatine definition: An alkaloid that occurs in the extract of leaves of

wild tomato plants. It has been found to inhibit the growth of various fungi

and bacteria. It is used as a precipitating agent for steroids.

“-Tomatine, a glycoside in which four carbohydrate residues are attached to

the 3-OH group of the aglycon tomatidine, occurs naturally in tomatoes

(Lycopersicon esculentum). Immature green tomatoes contain up to 500 mg

of -tomatine/kg of fresh fruit weight. The compound is largely degraded as

the tomato ripens until, at maturity, it reaches levels in red tomatoes of

~5 mg/kg of fresh fruit weight. Consumers of green tomatoes, high-tomatine

red tomatoes, and tomato products such as pickled green and green fried

tomatoes consume significant amounts of tomatine (1-3)………

Concurrent with the discovery of tomatine, studies were undertaken which

showed that the molecule possessed antibiotic properties against a variety

of fungi and the human pathogens Escherichia coli and Staphylococcus aureus

(4, 9-13). These observations suggested that tomatine may play a major role

in disease resistance in the tomato plant and may be biologically active in

animals and humans……

Effects on Growth of Hamsters. Figure 7D shows weight gains of hamsters fed

green and red tomato diets and control diets fortified with 0.05-0.2%

tomatine for 21 days (24, 267). Green and red tomato feeding resulted in

12-20% lower gain and in lower food consumption compared to control diets.

By contrast, added tomatine did not affect weight gain. Does eating of

tomatoes by humans also result in lower weight gain?……..

Effect on Cholesterol in the Small Intestine and in the Liver. In the course

of studies on the mucosal cholesterol balance in the small intestine of the

rat, it was noted that tomatine removed cholesterol from mucosal cells as

well as the output of cholesterol into the lymph, suggesting that tomatine

may have direct effects on mucosal cell function (302). Related studies

showed tomatine precipitated cholesterol but not bile acids from micellar

solutions in the lumen, affected cholesterol absorption and lipid

metabolism, and induced sterol but not bile acid excretion in the rat (260,

303).

A possible explanation for the tomatine-induced increased cholesterol

synthesis in the liver is that cholesterol in the gastrointestinal tract

forms a complex with tomatine, which is then excreted. The consequence is

that a reduced amount of cholesterol is transported from the intestine to

the liver via the enterohepatic circulation. The liver then compensates by

synthesizing additional cholesterol. Evidently, increasing dietary

cholesterol offsets the tomatine-induced hepatic cholesterol synthesis.

Lowering Plasma LDL Cholesterol and Triglycerides.

The dynamics of cholesterol formation and metabolism in hamsters is similar

to that in humans; therefore, we examined the effect of feeding tomatine as

well as high-tomatine green and low-tomatine red tomatoes on hamster plasma

lipoprotein and triglyceride levels, cholesterol distribution, fecal

excretion of cholesterol, cholesterol metabolites, and bile acids (Figure

7C,D; Tables 9 and 10) (24, 267). Two feeding studies were carried out: (1)

hamsters were fed a 0.2 g of tomatine/100 g of a high saturated fat,

high-cholesterol diet for 3 weeks and (2) hamsters were fed green

(high-tomatine) or red (low-tomatine) freeze-dried tomato powders and diets

containing three concentrations of tomatine. In the first study, plasma LDL

cholesterol decreased by 41%. In the second, 59 and 44% reductions in LDL

cholesterol were induced by the green and red tomatoes, respectively. The

corresponding reductions in plasma triglyceride concentrations were 47 and

31%.

The fact that tomatine alone reduces both dietary cholesterol

bioavailability and endogenous cholesterol and that our calculations show

that the amount reduced is equivalent to the amount consumed suggests that

tomatine forms an insoluble complex with cholesterol from both dietary

cholesterol and from endogenous cholesterol produced by the liver. Liver

cholesterol enters the digestive tract via the enterohepatic circulation.

Although we do not know much about the dynamics of this event, it probably

does not occur under the acid conditions of the stomach, because in vitro

studies show that protonation of the ring nitrogen of tomatine prevents

complex formation with cholesterol (57). Complex formation probably takes

place in the alkaline environment of the duodenum. Whether acid or enzyme

(glycosidase)-catalyzed hydrolysis of tomatine occurs in vivo is not known.

The fact that the high-tomatine green tomatoes are more effective in

lowering plasma cholesterol and triglycerides than low-tomatine red tomatoes

suggests that tomatine in green tomatoes contributes to the

cholesterol-lowering effects. Red tomatoes are also a potent hypolipidemic

food for hamsters, so obviously other components of tomatoes must be

involved in inducing the observed hypolipodemias. These could include fiber,

free amino acids, protein, sugars, and antioxidants. In fact, an additional

study (304) showed that feeding hamsters l0% cellulose-containing diets

supplemented with cholesterol levels of 0.025, 0.05, or 0.2% resulted in

plasma LDL concentrations of 121, 175, and 326 mg/dL, respectively. The

corresponding values with 10% red tomato diets were much lower: 64, 90, and

102 mg/dL. The tomato diets also reduced plasma triglyceride but not HDL

(good) plasma cholesterol levels. The fecal content of cholesterol,

coprostanol, and bile acids supports the hypothesis that the major pathway

by which tomatine induces lowering of cholesterol is by complex formation

described earlier. The mechanism of the triglyceride lowering effect is not

known.

Tomatine was used to measure cholesterol esters in the plasma of 30 patients

suffering from diabetes mellitus and in 10 patients with cirrhosis of the

liver (305). Both diseases were associated with a decrease in plasma

cholesterol. It was also used to measure the cholesterol content of plasma

HDL and to separate mixtures of five oxidation products of cholesterol

(306).

Removal of Cholesterol from Butteroil. Micich et al. (307, 308) covalently

attached tomatine to a resin via acetal or ester linkages at an average

value of 0.14 mM of tomatine/g of polymer. Passage of hexane solutions of

cholesterol or cholesterol-containing butteroil through the tomatine-bound

resin resulted in removal of cholesterol, which was left attached to the

tomatine on the column. The resin could be regenerated by extraction of the

bound cholesterol with acetone or ethyl acetate. This method has the

potential for practical use to reduce the cholesterol content of foods.

Conclusions and Outlook

Glycoalkaloids may have evolved in nature to protect selected plants against

bacteria, fungi, insects, and animals. It is striking that both green

tomatoes and tomato leaves have a very high glycoalkaloid content, which

makes them undesirable to eat because the green fruit and leaves not only

taste bitter to animals but may not be safe to phytopathogens. An unanswered

question involves the respective contributions of -tomatine and

dehydrotomatine to host-plant resistance of tomato plants and whether the

two tomato glycoalkaloids act synergistically both in the plant and in the

diet. ……...

Food and biomedical scientists, including nutritionists and microbiologists,

are challenged to further define beneficial effects of -tomatine and

dehydrotomatine and hydrolysis products in the human diet in lowering

cholesterol and triglycerides, in enhancing the immune system, in cancer

chemotherapy, and in protecting against virulent fungi, bacteria, viruses,

and protozoa………

Table 9. Effect of Green and Red Tomato Diets on Plasma Cholesterol and

Triglycerides in Hamsters Fed for 21 Days

Mg/dL

Tomato VLDL LDL HDL Total Triglycerides LDL/HDL

Control 139 52 130 313 627 0.41

Green 77 21 130 228 333 0.17

Red 98 29 112 240 432 0.26

VLDL, very low density lipoprotein; LDL, low-density lipoprotein; HDL,

high-density lipoprotein.

(Adapted from References 24 [Feeding tomatoes to hamsters reduces their

plasma low-density lipoprotein cholesterol and triglycerides Friedman,

Mendel; Fitch, T. E.; Levin, C. E.; Yokoyama, W. H. Journal of Food Science

(2000), 65(5), 897-900] and 267 [PMID: 10942315 [PubMed - indexed for

MEDLINE]]) "

Leonardi C, Ambrosino P, Esposito F, Fogliano V.

Antioxidative activity and carotenoid and tomatine contents in different

typologies of fresh consumption tomatoes.

J Agric Food Chem. 2000 Oct;48(10):4723-7.

PMID: 11052724 [PubMed - indexed for MEDLINE]

Alan Pater, Ph.D.; Faculty of Medicine; Memorial University; St. 's, NF

A1B 3V6 Canada; Tel. No.: (709) 777-6488; Fax No.: (709) 777-7010; email:

apater@...

1: J Agric Food Chem 2002 Oct 9;50(21):5751-80

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

Friedman M.

Western Regional Research Center, Agricultural Research Service, U.S. Department

of Agriculture, 800 Buchanan Street, Albany, California 94710.

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.

PMID: 12358437 [PubMed - in process]

1: J Agric Food Chem 2002 Oct 9;50(21):6182-6187

Antioxidant Activity of Grains.

Adom KK, Liu RH.

Institute of Comparative and Environmental Toxicology and Department of Food

Science, Cornell University, Stocking Hall, Ithaca, New York 14853-7201.

Epidemiological studies have shown that consumption of whole grains and

grain-based products is associated with reduced risk of chronic diseases. The

health benefits of whole grains are attributed in part to their unique

phytochemical composition. However, the phytochemical contents in grains have

been commonly underestimated in the literature, because bound phytochemicals

were not included. This study was designed to investigate the complete

phytochemical profiles in free, soluble conjugated, and insoluble bound forms,

as well as their antioxidant activities in uncooked whole grains. Corn had the

highest total phenolic content (15.55 +/- 0.60 & mgr;mol of gallic acid equiv/g

of grain) of the grains tested, followed by wheat (7.99 +/- 0.39 & mgr;mol of

gallic acid equiv/g of grain), oats (6.53 +/- 0.19 & mgr;mol of gallic acid

equiv/g of grain), and rice (5.56 +/- 0.17 & mgr;mol of gallic acid equiv/g of

grain). The major portion of phenolics in grains existed in the bound form (85%

in corn, 75% in oats and wheat, and 62% in rice), although free phenolics were

frequently reported in the literature. Ferulic acid was the major phenolic

compound in grains tested, with free, soluble-conjugated, and bound ferulic

acids present in the ratio 0.1:1:100. Corn had the highest total antioxidant

activity (181.42 +/- 0.86 & mgr;mol of vitamin C equiv/g of grain), followed by

wheat (76.70 +/- 1.38 & mgr;mol of vitamin C equiv/g of grain), oats (74.67 +/-

1.49 & mgr;mol of vitamin C equiv/g of grain), and rice (55.77 +/- 1.62 & mgr;mol

of vitamin C equiv/g of grain). Bound phytochemicals were the major contributors

to the total antioxidant activity: 90% in wheat, 87% in corn, 71% in rice, and

58% in oats. Bound phytochemicals could survive stomach and intestinal digestion

to reach the colon. This may partly explain the mechanism of grain consumption

in the prevention of colon cancer, other digestive cancers, breast cancer, and

prostate cancer, which is supported by epidemiological studies.

PMID: 12358499 [PubMed - as supplied by publisher]