ARS | Publication request: Free amino acid, protein, and phenolic content and antioxidative and cancer cell-inhibiting activities of extracts of 11 greenhouse-grown tomato varieties and 13 tomato-based foods

Submitted to: Journal of Agricultural and Food Chemistry
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: November 9, 2011
Publication Date: November 9, 2011
Citation: Choi, S., Kim, H., Kim, H., Lee, I., Kozukue, N., Levin, C.E., Friedman, M. 2011. Free amino acid, protein, and phenolic content and antioxidative and cancer cell-inhibiting activities of extracts of 11 greenhouse-grown tomato varieties and 13 tomato-based foods. Journal of Agricultural and Food Chemistry. 2011,59:12801-12814.

Interpretive Summary: Widely cultivated and consumed tomatoes are fruity edible vegetables of the species Lycopersicon esculentum cerasiforme. Tomatoes are a good source of vitamins and bioactive phenolic compounds and flavonoids. However, the nature and amounts of biosynthesized bioactive compounds are strongly influenced by the choice of agronomic practices, and environment (soil fertility, climate), genotype, and stage of ripeness. To minimize environmental, agronomic, and ripeness effects, the present study evaluated the composition and antioxidative and cancer-cell-inhibiting effects of extracts from 11 tomato varieties grown and harvested under identical conditions in a greenhouse. For comparison, we included 13 store-bought, widely consumed tomato foods. These consisted of six whole, cut, and peeled tomatoes, one paste, one sauce, three ketchups, and three juices. Our findings emphasize the substantial variation in free amino acid, protein, and in individual and total phenolic content found among the test substances. The data suggest that consumers have a choice in selecting varieties and foods with a high content of phenolic compounds and high antioxidative and anticarcinogenic effects. Because individual phenolics may exhibit different health-promoting effects, knowledge of both composition and concentrations of bioactive compounds of tomatoes can benefit consumers.

Technical Abstract: Tomato (Lycopersicon esculentum) plants synthesize nutrients, pigments, and bioactive compounds that benefit nutrition and human health. The nature and concentrations of these compounds are strongly influenced by the agronomic practices, environmental conditions, tomato size, and maturity of the fruit on the vine. To minimize environmental effects, extracts of 11 freeze-dried greenhouse-grown Korean tomato varieties weighing from 12.1 to 233.9 g/fruit as well as 13 tomato-based foods (six whole, cut, and peeled tomatoes; three ketchups; three juices; one sauce) were analyzed for 20 free amino acids, 9 nitrogen-containing metabolites, and 15 individual phenolic compounds by HPLC and LC-MS, and for total phenolic content by colorimetry. The extracts were also investigated for antioxidative activities using FRAP and DPPH methods, and by the MTT assay to measure the induction of cell death in normal human liver (Chang), normal lung (Hel299), lung cancer (A549) and lymphoma (U937) cells. Protein content (N × 6.25 in g/100 g fresh wt) of fresh tomatoes range from 0.88 (Dotaerang Gold) to 1.72 (Tiger). The total content of other analytes (in mg/100 g dry wt) in 24 tomatoes and tomato foods range as follows (lowest:highest value): free amino acids (1394.5:7142.3); essential amino acids (161.9:887.0); asparagine (10.8:70.2); metabolites (343.6:1365.0); individual phenolics (22.2:627.5); total phenolics (426.0:882.7). FRAP values (mole mol Fe 2+/100 g) for tomatoes ranged from 1.2 to 4.5 and for foods from -1.2 (pro-oxidant effect) to 1.9. DPPH values (IC50, µg/mg) for tomatoes ranged from 159.2 to 496.8 and for foods from 366.3 to 2940.6. Small tomatoes had higher content of bioactive compounds/100 g dry wt than the large ones. The results suggest that consumers can select tomatoes and foods with a high a content of health-promoting bioactive compounds. The dietary significance of the results is discussed.