Toxicological, Bioassay-Guided Fractionation and Antibacterial Activity of Methanol Stem Extract of Terminalia microptera on Oral Bacteria Pathogens

Abstract

The search for new lead compounds with improved therapeutic activity is ongoing due to microbial resistance to the currently available drugs. This study was aimed at evaluating the toxicological, bioassay-guided fractionation and antibacterial activity of methanol stem extract of Terminalia microptera on oral bacterial pathogens. Quantitative phytochemical determination was carried out using spectrophotometric method, acute and sub-chronic toxicity study was carried out following Lorke’s and Organization for Economic Co-operation and Development (OECD) guidelines. Fractionation and antibacterial activity of the extract (20, 30 and 40 mg/mL) against Klebsiella pneumoniae Pseudomonas aeruginosa, Micrococcus luteus, Streptococcus mutans, Streptococcus pneumoniae and Streptococcus pyogenes were carried out following standard protocol. The extract contains phenols, flavonoids, tannins, alkaloids and saponins at varying concentration range. Acute toxicity study of the extract gave an LD50 of 1386 mg/kg. Sub-chronic toxicity study of the extracts revealed that the extracts have no significant effect (p>0.05) on the body weight, haematological, biochemical and renal parameters of the rats. The mean zones of inhibition of the extract and fractions revealed a significant (p<0.05) spectrum of activity ranging between 13.33–25.33mm and 15.50–24.00mm, respectively. Column chromatography of ethyl acetate sub-fraction of the extract yielded 4 fractions (TME1-4) and their antibacterial sensitivity test showed a spectrum of activity that ranged between 6.50- 25.50mm against the tested bacterial isolates. GC-MS analysis of the fractions revealed 13 compounds in T. microptera. The current study revealed the pharmacological significance and safety of T. microptera. However, uncontrollable use of the extract without adequate dose regulation should be discouraged.