Antimicrobial properties of tomato leaves, stems, and fruit and their relationship to chemical composition

Authors: Tam, Christina; NGUYEN, KEVIN - University Of The Pacific; NGUYEN, DANIEL - University Of The Pacific; HAMADA, SABRINA - University Of The Pacific; KWON, OKHUN - University Of The Pacific; KUANG, IRENE - University Of The Pacific; GONG, STEVEN - University Of The Pacific; ESCOBAR, SYDNEY - University Of The Pacific; LIU, MAX - University Of The Pacific; KIM, JIHWAN - University Of The Pacific; HOU, TIFFANY - University Of The Pacific; TAM, JUSTIN - University Of The Pacific; CHENG, LUISA - Former ARS Employee; Kim, Jong Heon; LAND, KIRKWOOD - University Of The Pacific; Friedman, Mendel

Submitted to: BMC Complementary Medicine and Therapies
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/17/2021
Publication Date: 9/13/2021
Publication URL: https://handle.nal.usda.gov/10113/7504415
Citation: Tam, C.C., Nguyen, K., Nguyen, D., Hamada, S., Kwon, O., Kuang, I., Gong, S., Escobar, S., Liu, M., Kim, J., Hou, T., Tam, J., Cheng, L., Kim, J., Land, K.M., Friedman, M. 2021. Antimicrobial properties of tomato leaves, stems, and fruit and their relationship to chemical composition. BMC Complementary Medicine and Therapies. 21. Article 229. https://doi.org/10.1186/s12906-021-03391-2.
DOI: https://doi.org/10.1186/s12906-021-03391-2

Interpretive Summary: Infection by the parasitic protozoan Trichomonas vaginalis in humans causes the sexually transmitted disease trichomoniasis, reported to be the most common non-viral transmitted infection in the world. Tritrichomonas foetus are reported to cause the disease of trichomonosis in farm animals (cattle, bulls, and pigs), as well as in domestic animals (cats and dogs). In cows, the disease causes failed pregnancies and infected cows are usually culled. In domesticated cats, the disease infects the gastrointestinal tract, causing diarrhea, and is transmitted by the oral-fecal route. Because of increasing rates of clinical resistance to the widely used drug metronidazole, new treatments are needed to replace or to complement current available therapies. The need for new treatments is illustrated by a publication from the National Institute of Allergy and Infectious Diseases, National Institute of Health (NIH) that emphasizes the need for new therapeutics to help overcome the global epidemic of sexually transmitted infections, including trichomoniasis As part of an effort to discover the efficacy of safe food extracts and their bioactive constituents against pathogenic trichomonads, we previously reported on the anti-trichomonad effects of potato and tomato glycoalkaloids, potato peels, and of black tea and other food-compatible compounds and extracts against three trichomonad parasites. To help meet the need to develop new effective therapeutic agents, the objective of the present study was to evaluate anti-trichomonad, antibacterial, and anti-fungal properties of powders prepared from leaves, stems, and tomatoes harvested from a growing plant, and correlate this inhibitory activity to their composition of a separate set of test powders, as determined using high performance-liquid chromatography/mass spectrometry. The results of the described efforts suggest that several tomato-plant-derived powders, especially powders prepared from tomato leaves, could potentially replace or enhance the therapeutic potency of metronidazole. The tomato leaf powders merit clinical studies to determine their efficacy in infected humans, cattle, and cats.

Technical Abstract: We previously reported that the tomato glycoalkaloid tomatine inhibited the growth of Trichomonas vaginalis strain G3, Tritrichomonas foetus strain D1, and Tritrichomonas foetus-like strain C1 that cause disease in humans and farm and domesticated animals. The increasing prevalence of antibiotic resistance requires development of new tools to enhance or replace medicinal antibiotics. Wild tomato plants were harvested and divided into leaves, stems, and fruit of different colors: green, yellow, and red. Samples were freeze dried and ground with a handheld mill. The resulting powders were evaluated for their potential anti-microbial effects on protozoan parasites, bacteria, and fungi. A concentration of 0.02% (w/v) was used for the inhibition of protozoan parasites. A high concentration of 10% (w/v) solution was tested for bacteria and fungi as an initial screen to evaluate potential anti-microbial activity and results using this high concentration limits its clinical relevance. Natural powders derived from various parts of tomato plants were all effective in inhibiting the growth of the three trichomonads to varying degrees. Test samples from leaves, stems, and immature ‘green’ tomato peels and fruit, all containing tomatine, were more effective as an inhibitor of the D1 strain than those prepared from yellow and red tomato peels which lack tomatine. Chlorogenic acid and quercetin glycosides were present in all parts of the plant and fruit, while caffeic acid was only found in the fruit peels. Any correlation between plant components and inhibition of the G3 and C1 strains was not apparent, although all the powders were variably effective. Tomato leaf was the most effective powder in all strains, and was also the highest in tomatine. Salmonella enterica bacteria showed a minor susceptibility while Bacillus cereus bacteria and Candida albicans fungi both showed a significant growth inhibition with some of the test powders. The powders inhibited growth of the pathogens without affecting beneficial lactobacilli found in the normal flora of the vagina.