Comparative study of the in vivo acute toxicity, phytochemical analysis, in vitro antimicrobial, antiplasmodial and cytotoxic activities of leaves, stem bark and roots of Guibourtia tessmannii

Abstract

Guibourtia tessmannii (Harms) J. Leonard’s is use traditionally in the treatment of sexually transmitted diseases (gonorrhea), hypertension, typhoid fever, female infertility and malaria. This study aimed to assess the comparative antibacterial, antifungal, antiplasmodial and cytotoxic activities of G. tessmannii methanolic leaves, root bark, root wood, stem bark extracts. The antimicrobial activity was evaluated by the method of microdilution. The antimalarial activity was carried out on the 3D7 strain of Plasmodium falciparum, the cytotoxic activity on human HeLa cells, the acute toxicity on Wistar rats according to the modified OECD 423 guidelines. The stem bark extract proved to be the most active with good antibacterial activity with MIC values equal to 256 µg/mL for S. aureus and K. pneumonia strains, average antibacterial and fungal activities with an MIC equal to 512 µg/mL on bacterial and fungal strains/isolates namely N. gonorrhoeae, S. typhi and C. albicans, thereby justifying the use of G. tessmannii in the traditional pharmacopoeia to treat certain conditions such as gonorrhea, typhoid fever, female infertility linked to infections. This extract was had bactericidal properties (MMC/MIC < 4). None of the 4 extracts showed a significant inhibition of P. falciparum 3D7 cells growth, and thus no antimalarial activity was observed at 50 µg/ml. The HeLa cells viability was reduced by 2% (leaves), 6% (root wood), 34% (root bark) and 44% (stem bark) at 50 µg/ml and therefore no IC50 was determined. All four extracts presented an LD50 greater than 5000 mg/kg. Phytochemical analysis revealed the presence of triterpenes including saponins, and phenolic compounds such as flavonoids and anthraquinones. Anthocyanins were only found in the leaves extract. Coumarins and alkaloids were absent.