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Aims The aim of this study was to identify components of the Withania somnifera that could show anti-virulence activity against Streptococcus mutans biofilms. Methods and results The anti-acidogenic activity of fractions separated from W. somnifera was compared, and then the most active anti-acidogenic fraction was chemically characterized using gas chromatography-mass spectroscopy. The effect of the identified components on the acidogenicity, aciduricity and extracellular polymeric substances (EPS) formation of S. mutans UA159 biofilms was evaluated. The change in accumulation and acidogenicity of S. mutans UA159 biofilms by periodic treatments (10 min per treatment) with the identified components was also investigated. Of the fractions, n-hexane fraction showed the strongest anti-acidogenic activity and was mainly composed of palmitic, linoleic and oleic acids. Of the identified components, linoleic and oleic acids strongly affected the acid production rate, F-ATPase activity and EPS formation of the biofilms. Periodic treatment with linoleic and oleic acids during biofilm formation also inhibited the biofilm accumulation and acid production rate of the biofilms without killing the biofilm bacteria. Conclusions These results suggest that linoleic and oleic acids may be effective agents for restraining virulence of S. mutans biofilms. Significance and impact of the study Linoleic and oleic acids may be promising agents for controlling virulence of cariogenic biofilms and subsequent dental caries formation.

Summary In order to understand the mechanism of fibrin deposition in the synovia during the progression of rheumatoid arthritis (RA), activities of coagulation factors, fibrinolytic enzymes, and corresponding inhibitors were measured in synovial fluid of 12 RA patients. Almost all of the synovial fluid (SF) fibrinogen molecules were found to be fragmented and some portions of the molecule that were slightly affected were found to be in a complex with albumin molecules. Immunohistochemical analysis showed deposits of insoluble fibrin in synovial membranes and pannus, in levels related to the progression of disease. Coagulation factor VII, VIII, X, XII, and XIII activities in SF were found to be 30 to 50% of plasma levels but factors II and V activities were less than 25% of plasma levels. Protein C and antithrombin III activities in SF were 30% of plasma levels. However, the two orders of magnitude, higher level of thrombin-antithrombin III (TAT) complex in SF than in plasma, suggests a steady activation of coagulation cascade in synovia. The observed increased levels of fibrinogen, TAT complexes, Bβ 15–42 peptide and plasminogen activator inhibitor-1 (PAI-1) in plasma are consistent with the systemic inflammatory state of RA patients. Although a 30% decrease in plasma levels of α2-plasmin inhibitor activity, and a 2-fold higher level of PAI-1 activity in SF were found, the presence of D-dimer and Bβ 15–42 peptide in SF suggests an active participation of plasmin in the fibrino(geno)lysis. In addition, elevated levels of elastase-α1-proteinase inhibitor complexes and of thrombin-increasable fibrinopeptide A in SF suggest the participation of leukocyte elastase in fibrin(ogen)olysis as well.