Abstract

INVESTIGATION OF PHYTOCHEMICALS, ACUTE TOXICITY STUDIES AND ANTIMICROBIAL ACTIVITY OF TECTONA GRANDIS (TEAK) LEAF EXTRACT: A MEDICINAL PLANT COMMONLY USED IN GHANA

Nestor Tordzagla*, Francis Kwaku Dzideh Amankwah and Stephen Antwi

ABSTRACT

Plant species have been used traditionally to treat many microbial infections due to their medicinal properties. This study aimed to evaluate phytochemicals, acute toxicity effects and antimicrobial activity of methanolic leaf extract of Tectona grandis. The toxicity studies of Tectona grandis extract was carried out in Sprague-Dawley rats (N= 6). The antimicrobial assays were done using bacterial strains S. aureus ATCC 25923, E. faecalis, E. coli, P. aeruginosa, MRSA, E. coli ESLB, S. typhi, S. typhimurium, N. gonorrhoeae, K. pneumomiae, B. cereus, and a fungal strain C. albicans. The determination of minimum inhibition concentrations (MIC) and minimum bactericidal concentrations (MBC) were carried out by broth dilution method using 96 well plates. The MIC values of the extract ranged from 1.562 mg/mL to 12.50 mg/mL. Moreover, the MBC values obtained against all the bacteria ranged from 6.25 mg/mL to 100 mg/mL. The synergistic effect of the extract and ciprofloxacin was very remarkableagainst S. typhi, MRSA, S. typhimurium and N. gonorrhoeae with MIC values of 0.390 μg/mL, 0.781 μg/mL, 0.781 μg/mL, and 0.781 μg/mL respectively. Preliminary acute toxicity studies of methanolic extract of Tectona grandis leaves at doses of 500, 1000, 2000, 3000, and 5000 mg/kg indicated no serious adverse effects that could result in death of the experimental animals. This suggests that the LD50 value of the extract could exceed 5000 mg/kg, meaning the methanolic extract of Tectona grandis leaf is nontoxic. Hence, Tectona grandis leaf is a potential source of a novel antibacterial agent.

Keywords: Tectona grandis, antimicrobial activity, phytochemicals, acute toxicity, medicinal plants.