Phytochemical screening and in vitro antimicrobial activity of Calycobolus heudelotii stem

Calycobolus heudelotii (Baker ex Oliv.) Heine is a native plant from West Tropical Africa. Stems are used in folk medicine of Guinea-Bissau for inflammations, skin allergies and wounds [1]. First work previously performed was a preliminary botanical analysis of the stem [2]. Here we present results from an antimicrobial activity study of C. heudelotii stem methanol extract and a preliminary phytochemical screening. The minimum inhibitory concentration (MIC) was determined by the broth dilution method against Candida albicans ATCC 10231, Enterococcus faecalis ATCC 435628, Escherichia coli ATCC 25922, Pseudomonas aeruginosa ATCC 27853, Micrococcus luteus ATCC 10240 and Staphylococcus aureus ATCC 25923. The phytochemical screening was made by thin layer chromatography (TLC) and high performance liquid chromatography with ultraviolet diode array detection (HPLC-UV-DAD). In the range of tested concentrations (3200 to 15.62µg/ml), the extract show antimicrobial activity against all tested strains (MIC between 625 and 156.3µg/ml) except against S. aureus. The highest activity (MIC of 156.3µg/ml) was demonstrated against M. luteus. Phenolic compounds are the major constituents of the extract, as shown by TLC and HPLC-UV-DAD profile, and include phenol acid derivatives like chlorogenic acid. β-sitosterol is also detected. Alkaloids, present in other Convolvulaceae, are absent in this extract. Further chemical, toxicological and bioactivity studies are underway to prove other traditional uses and to check the safety of this medicinal plant.