Polyphenolic compounds have been classified find more into several groups, including hydroxybenzoic acids, hydroxycinnamic acids, coumarins, xanthones, stilbenes, antraquinones, lignans and flavonoids (Manach et al., 2005). The largest and best known group among the polyphenolic compounds are flavonoids. The basic skeleton of flavonoid molecule consists of 15 carbon atoms (formula C6–C3–C6) forming the two benzene rings (A- and B-ring), between which there is a three-carbon unit (C3) closed in the heterocyclic pyran or pyrone ring (C-ring). Flavonoids are divided into six subgroups: anthocyanins, flavanols, flavanones, flavones, flavonols and isoflavones

(Ullah and Khan, 2008). In our study we tested 20 polyphenolic compounds occurring most abundantly in nature and belonging to the main group of polyphenols (Fig. 6) at the highest used concentration of 1,000 μM. The results, presented in Table 1, demonstrate that of all polyphenolic compounds examined in this study, only six belonged to the flavonoid class [cyanidin, quercetin, silybin, cyanin, (+)-catechin and (−)-epicatechin] and had inhibitory effect on thrombin activity (the strongest effect showed cyanidin and quercetin). According to our observations, flavonoids which inhibit thrombin amidolytic activity Quisinostat mw belong to flavanols,

Selleck Sotrastaurin flavonols anthocyanins (aglycones with –OH substituents at the position of R1 and R2 in the B-ring). Only silybin has a methoxy group at the R1 position. These results are consistent with data presented by Mozzicafreddo et al. (2006). They also reported that flavonoids showed an inhibitory effect on thrombin amidolytic activity. Jedinák et al. (2006) demonstrated that silybin and quercetin strongly inhibited thrombin’s ability to hydrolyze N-benzoyl-phenylalanyl-valyl-arginine-paranitroanilide Fenbendazole (IC50 for silybin was 20.9 μM, and for quercetin 30.0 μM, respectively at 0.6 mM substrate concentration). In their study these flavonoids also showed very strong inhibitory effect on trypsin and urokinase amidolytic activity (for trypsin, silybin IC50 was 3.7 μM and quercetin IC50 was 15.4 μM, while for urokinase, silybin

IC50 was 21.0 μM and quercetin IC50 was 12.1 μM). We also studied the effect of DMSO on thrombin activity at the same concentration as used in the case of polyphenolics dissolved in this solvent. After 5 % DMSO treatment, we did not observe any influence on thrombin activity. Fig. 6 Chemical structures of polyphenolic compounds used in the study. Chemical formulas were downloaded from http://​pubchem.​ncbi.​nlm.​nih.​gov/​ as InChI. The visualization of chemical formulas was performed using ChemBioDraw Ultra Software from ChemBioOffice® Ultra 12.0. suite The most important function of thrombin is its proteolytic activity against fibrinogen and platelet PAR receptors. Thrombin has much higher affinity to these molecules, than to smaller compounds such as the chromogenic substrate (Crawley et al., 2007).