Phytochemical and biological studies of the hydroethanolic extract of Pteleopsis suberosa and Piliostigma thonningii used in herbal medicine in Togo

Abstract Background The emergence of multidrug-resistant isolates to conventional antibiotics calls for the search for other active molecules. The aim of this study was to evaluate the antimicrobial activity of Pteleopsis suberosa and Piliostigma thonningii, two Togolese medicinal plants used to treat vaginal, pulmonary, gastric and skin infections. Methods The total hydroethanolic extracts of the various organs were obtained by maceration. Qualitative phytochemistry of the extracts was performed using staining methods to identify the main chemical groups. The total flavonoid content was quantified using a spectrophotometric assay. Two methods were used to assess antioxidant activity: the phosphomobyldate reduction method and the FRAP test. The solid-well diffusion method and the microplate microdilution method were used to evaluate the antimicrobial activity of the study extracts. Results The highest hydroethanol extraction yield was obtained with P. thonningii trunk bark extract (22.67%). The results revealed the presence of tannins, saponosides, alkaloids, phenols, triterpenes and reducing sugars. The highest total flavonoid content was found in P. thonningii leaves, with 313.82 µg Eq routine/mg ES. P. suberosa leaves showed high in vitro antioxidant activity with 90.70 EAA/g ES and 430.50 µmol Eq FeSO4/mg ES. The largest inhibition zone diameter was observed with the P. thonningii trunk bark extract against the C. albicans strain (20 mm). P. suberosa trunk bark and both organs (leaves and trunk bark) of P. thonningii showed a low MIC of 1.562 mg/ml on S. aureus strains. Conclusion The present study supports the local use of both plants for pathologies caused by the microbial strains studied. However, further research is needed to isolate and identify the chemical molecules responsible for the observed activities, and to study the toxicity of the two plants.