Submitted to: Journal of Agricultural and Food Chemistry
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/11/2010
Publication Date: 6/18/2010
Publication URL: DOI:10.1021/jf100162
Citation: Choi, S.H., Kim, H.J., Lee, I.S., Kozukue, N., Levin, C.E., Friedman, M. 2010. Changes in free amino acid, chlorophyll, carotenoid, phenolic, and glycoalkaloid content in tomatoes during 11 stages of growth, and inhibition of cervical, lung, and lymphoma human cancer cells by green tomato extracts. Journal of Agricultural and Food Chemistry. 58:7547-7556. Interpretive Summary: As part of an effort to discover new plant-derived antimicrobial compounds, we participated in a collaborative study with Korean university scientists on changes in tomato constituents during growth of tomato fruit on the vine. The results of the present study indicate complex dynamics in the biosynthesis of free amino acids and other nutrients, pigments, and secondary metabolites during multiple stages of ripening of the tomato fruit during growth. Novel aspects include analysis of free amino acids, two chlorophylls, 12 phenolic compounds, and two glycoalkaloids in 11 stages of tomato ripening, the demonstration that extracts from different ripening stages differ widely in inhibitory activities against human normal and cancer cells, and the observation that several extracts exhibited very high inhibitory effects against cervical and lung cancer cells. Because tomatine is also reported to inhibit viruses, we hypothesize that high-tomatine red tomatoes may increase resistance of tomato plants against the yellow curl virus, the cause of the most devastating plant disease in the world. Because the findings in the present study relate to potential health benefits of tomatoes, they could stimulate further research in plant sciences as well as more detailed evaluation of the biological and nutritional activity of the evaluated compounds.
Technical Abstract: Tomato (Lycopersicon esculentum) plants synthesize nutrients, pigments, and secondary metabolites that benefit nutrition and human health. The concentrations of these compounds are strongly influenced by the maturity of the tomato fruit on the vine. Widely consumed Korean tomato variety Doturakworld were analyzed for changes in the content of amino acids, glycoalkaloids, chlorophylls, phenolic compounds, and carotenoids at 11 stages (S1 to S11) of ripeness. The results show that (a) the total content (in mg/100 g FW) of the free amino acids and other nitrogen containing compounds in the extracts ranged from about 41 to 85 in the green tomato extracts S1-S7, then increased to 250.5 (S9) in the red extracts, followed by a decrease to 124.4 in S11 red extracts; (b) tomatoes harvested during the S1 contained 5.72 mg of chlorophyll a and b per 100 g fresh pericarp, then decreased continuously to 1.14 mg/100 g for S11; (c) the concentration (in µg/100 g FW) of lycopene in the S8 red extract of 315.0 increased to 897.0 in S10; (d) the total initial concentration of up to 12 phenolic compounds of ~2,000 µg/100 g FW continuously decreased with maturity, especially in S7 to S11 red tomatoes; and (e) tomatoes harvested during S1 contained 48.2 mg of dehydrotomatine per 100 g FW, then continually decreased to 1.5 in S7, with no detectable levels in S8 to S11. The corresponding a-tomatine content decreased from S1 (360.9) to S8 (13.8). MTT cell assay IC50 values showed that inhibitory activities of green tomato extracts against normal cells were generally lower than against the cancer cells and that human cervical and lung cancer cells are highly susceptible to inactivation. The possible significance of the results for plant physiology and the diet are discussed.