Zanthoxylum zanthoxyloides leaf extracts demonstrate antimicrobial effect on selected oral pathogens

Background: Oral infections continue to be a major health problem and may be associated with conditions such as colorectal cancer, gum bleeding, toothache, preterm birth among pregnant mothers, arterial hardening, myocardial infarction and stroke. Yet available conventional treatments for oral infections are not only expensive and sometimes harmful but also ineffective compared to cheap and readily available plant-based ethnodentistry therapies because of increased resistance by microorganisms. This has necessitated the need to explore plant-based medicine for the purposes of controlling oral infection. Objective: The study assessed anti-microbial activity of three extract fractions of Zanthoxylum zanthoxyloides (Z. zanthoxyloides) leaf, which has long been used as chewing stick to maintain oral hygiene, against three selected oral pathogens: Lactobacillus acidophilus (L. acidophilus), Aggregatibacter actinomycetemcomitans (A. actinomycetemcomitans), and Candida albicans (C. albicans). Materials and Methods: The crude extract of Z. zanthoxyloides leaf was prepared, and increasing concentrations of each extract fraction and respective standard antibiotics were tested against the growth of each selected oral pathogen by using serial broth dilution. After 24 hours culturing, absorbance of each test broth was measured spectrophotometrically at 450 nm. Percentage inhibition by each extract fraction, vehicle and standard antibiotics: Fluconazole (FLUCO), amoxicillin and metronidazole (AMOX&MET), and ciprofloxacin (CIPRO) against C. albicans, A. actinomycetemcomitans and L. acidophilus respectively, were determined indirectly from absorbance values by proportions relative to an untreated standard broth. The IC50 of each drug was determined from log concentration - response curve whilst minimum inhibitory concentration (MIC) of each fraction was determined using scatter plot with line of best fit. Results: The extract fractions produced concentration-dependent inhibition of growth. Except in the case of Lactobacillus acidophilus where growth inhibitory effect of the extract fractions was lower compared to standard antibiotic (ciprofloxacin), for the remaining pathogens, the extract fractions produced comparable growth inhibitory effects at higher (in the case of Candida albicans) and lower (in the case of Aggregatibacter actinomycetemcomitans) concentrations relative to standard antibiotics (Amoxacillin & Metronidazole and Fluconazole). Conclusion: Z. zanthoxyloides leaf extracts have anti-microbial activity against the three studied oral pathogens; thus, it can be explored for active anti-microbial agents against oral infections in which the studied pathogens may be implicated.