Evaluation of Phytochemical and in vitro Antimicrobial Effects of Solanum lycopersicum Linn. (Tomato) on Oral Thrush and Human Cariogenic Pathogens

Aims: Study on the evaluation of phytochemical and antimicrobial effects of tomato Solanum lycopersicum (L.) on oral thrush and human cariogenic pathogens was designed to determine the antimicrobial effect of tomato extracts, and to identify the common phytochemical constituents of tomato that may be inhibitory to oral pathogens.

Place and Duration of Study: Fresh tomato fruit samples were collected from Samaru market, Zaria in the month of November and December 2015, and analyzed at Microbiology Laboratory, Nigerian Institute of Leather and Science Technology Zaria, Kaduna.

Methodology: Cold maceration extraction using methanol and water was adopted. All the extracts were subjected to standard phytochemical qualitative screening for the presence or absence of various primary and secondary metabolites. Antimicrobial susceptibility was carried out by agar-well diffusion technique. The antimicrobial susceptibility test of Solanum lycopersicum (tomato) fruit extracts against selected bacterial (Streptococcus mutans, Bacillus subtilis) and yeast (Candida albicans) pathogens capable of causing oral thrush and dental caries was carried out. Ciprofloxacin and Econazole were used as positive controls. The Minimum Inhibitory Concentrations (MICs) were determined in three concentrations; 100 mg/ml, 50 mg/ml and 25 mg/ml of each extract. Mean zone of inhibition was used to measure the antimicrobial potential of tomato fruit extracts against the test organisms. The microbial isolates were obtained from the Department of Medical Microbiology, Ahmadu Bello University, Zaria.

Results: Alkaloids, flavonoids, glycosides, saponins, tannins, steroids, phlabotannins, terpenoids and tannins are present in tomato fruit extract, but, anthraquinones and phlabotannins are absent in methanolic extract. While, the only phytochemical that was not detected in the aqueous extract is anthraquinones. Highest antibacterial activity was recorded on Bacillus subtilis at the concentrations of 100 mg/ml and 50 mg/ml for aqueous and methanolic extracts respectively. Candida albicans and Streptococcus mutans showed resistance to the various extracts at various concentrations used. The MIC of 100mg/ml was recorded on Bacillus subtilis, whereas all other test organisms showed relative resistance to various concentrations of the extracts used.

Conclusion: Tomato fruit contains phytochemicals that showed promising antimicrobial effect on oral thrush and cariogenic pathogens. The tomato extract recorded antimicrobial effect against Bacillus subtilis with MIC of 100 mg/ml. The methanolic extract was the most active that could compete favourably with the conventional antibiotic (ciprofloxacin) at higher concentrations, which suggests that possible new drug candidates can be harnessed from the tomato fruit against oral thrush and cariogenic pathogens.