Résumé
Objective: To determine the thin-layer chromatography (TLC) fingerprint profiles and to evaluate the in vitro antioxidant activity of ethanol extracts of Muntingia calabura (M. calabura) leaves and stems. Methods: The leaves and stems were extracted using ethanol as solvent. The TLC separation of the phytochemical constituents of the leaf and ethanol extracts was carried out in ethyl acetate: n-hexane and chloroform: ethyl acetate mobile phase systems. Distinct spots were visualized under visible light, UV 254 nm, UV 366 nm and after spraying with vanillin-sulfuric acid. The 2,2-diphenyl-1-picrylhydrazyl free-radical scavenging assay was used to evaluate the antioxidant activity of the extracts. Results: Both the leaf and stem ethanol extracts at 4 mg/mL exhibited 2,2-diphenyl-1-picrylhydrazyl inhibition of more than 90%, relative to gallic acid. The results of TLC showed that the degree of resolution between the constituent spots was comparable be-tween the two mobile phase systems using the different visualization wavelengths. Under the 254 nm visualization, few spots were observed in leaf and stem extracts. Visualization at 366 nm yielded the greatest number of observable spots of various colors in both leaf and stem extracts. More spots were visualized upon post-derivatization with vanillin-sulfuric acid in the TLC chromatograms using chloroform: ethyl acetate mobile phase, compared to those in ethyl acetate:n-hexane mobile phase. Conclusions: M. calabura exhibited very high antioxidant activity in its leaves and stems ethanol extracts, both of which are used in traditional medicine. The TLC results demonstrated the presence of diverse secondary metabolites in the leaf and stem ethanol extracts, indicating that the antioxidant activity, including other bioactivities may be attributed to these phytochemical constituents. This paper has reported for the first time the TLC fingerprinting of M. calabura using visible light, UV 254 nm, UV 366 and post-derivatization with vanillin-spray to visualize separate spots on TLC plates.
Résumé
Objective: To determine the bioactive phytochemicals and antimicrobial activity of leaf and stem ethanolic extracts from Muntingia calabura L. (M. calabura). Methods: Dried leaves and stems of M. calabura were extracted with 95%ethanol. The antibacterial and antifungal activities of the extracts were examined using the disc diffusion assay. The minimum inhibitory concentration (MIC) of each extract showing antimicrobial activity was determined. The dried extracts were subjected to phyto-chemical screening to determine the presence of bioactive components. Total phenolic and flavonoid contents were also determined by the Folin-Ciocalteu method and the aluminum chloride method, respectively. Results: Varying degrees of antimicrobial activity were exhibited by the leaf and stem extracts against Pseudomonas aeruginosa (P. aeruginosa), Salmonella typhimurium, Staphylococcus aureus (S. aureus), Bacillus subtilis, and Candida albicans (C. albicans), with minimal activity against Escherichia coli. Based on the MIC, the extracts showed the highest activity against C. albicans, S. aureus and P. aeruginosa. Phytochemical screening revealed the presence of sterols, flavonoids, alkaloids, saponins, glycosides and tannins in the leaf extract; however, no triterpenes were detected. In the stem extract, triterpenes were detected along with relative amounts of flavonoids, saponins, glycosides and tannins. Alkaloids and sterols were absent in the stem extract. Conclusions: M. calabura leaf and stem ethanol extracts are potential sources of anti-bacterial agents against P. aeruginosa and S. aureus. This study reports for the first time the high degree of antifungal activity of M. calabura ethanolic extract, especially against C. albicans.