RESUMO
OBJECTIVE: To isolate α-mangostin (AMG) from the peels of mangosteen (Garcinia mangostana L.), grown in Vietnam, and to investigate antibiofilm activity of this compound against three Staphylococcus aureus (S. aureus) strains, one of which was methicillin-resistant S. aureus (MRSA) and the other two strains were methicillin-sensitive S. aureus (MSSA). METHODS: AMG in n-hexane fraction was isolated on a silica gel column and chemically analyzed by HPLC and NMR. The antibiofilm activity of this compound was investigated by using a 96-well plate model for the formation of biofilms. Biofilm biomass was quantified using crystal violet. The viability of cells was observed under confocal microscopy using LIVE/DEAD BacLight stains. Biofilm composition was determined using specific chemical and enzyme tests for polysaccharide, protein and DNA. Membrane-damaging activity was assayed by measuring the hemolysis of human red blood cells in presence of AMG. RESULTS: The results indicated that the isolated AMG, with a purity that exceeded 98%, had minimal inhibitory concentrations in the range of 4.6-9.2 µmol/L for the three strains tested. Interestingly, the MSSA strains were more sensitive to AMG than the MRSA strain. Minimal bactericidal concentrations were 2-fold higher than the minimal inhibitory concentration values for the three strains, indicating that AMG was a bactericidal compound. AMG also prevented biofilm formation effectively, albeit that again the MRSA strain was the most resistant. Interestingly, biofilms of the MRSA strain contained protein as a main component of the extracellular matrix, whereas this was polysaccharide in the MSSA strains. This might relate to the resistance of the MRSA 252 strain to AMG. Assays using human red blood cells indicated that AMG caused significant membrane damage with 50% of cell lysis occurred at concentration of about 36 µmol/L. CONCLUSIONS: Our results provide evidence that the isolated AMG has inhibitory activity against biofilm formation by S. aureus, including MRSA. Thus, isolated AMG proposes a high potential to develop a novel phytopharmaceutical for the treatment of MRSA.
RESUMO
OBJECTIVE: To evaluate the anti-inflammatory activity of methyl ferulate (MF) isolated from the roots of Stemona tuberosa (S. tuberosa) Lour (Stemonaceae) in lipopolysaccharide activated macrophage cells. METHODS: Methanol extracts of a root powder of S. tuberosa were prepared for isolation of a potential anti-inflammatory agent using ultrasound extraction combined with repeated chromatography on silica gel. After the quantitative analyses, anti-inflammatory activity of the isolated compound was evaluated by measurement of cytokine release, NO generation, expression of cyclooxygenase-2 and phosphorylation of mitogen activated protein kinases including p38 and c-Jun NH2-terminal kinase using quantitative kits and Western blotting with specific antibodies. RESULTS: The isolation process yielded a potential anti-inflammatory compound with a purity level of 99% determined by high performance liquid chromatography. The compound was identified as MF by using nuclear magnetic resonance. MF strongly inhibited the release of pro-inflammatory cytokines from macrophages, including IL-6, TNFα, IFNγ, yet it did not affect the anti-inflammatory cytokine IL-10. Phosphorylation of p38 and c-Jun NH2-terminal kinase were clearly reduced in MF-treated macrophages stimulated with lipopolysaccharide. cyclooxygenase-2 expression and NO generation by macrophages were also suppressed when the cells were treated with MF. CONCLUSIONS: The data suggested that MF is a possible inhibitor of the mitogen activated phosphor kinase pathway and could be a potential anti-inflammatory agent isolated for the first time in medicinal plant S. tuberosa.