Screening for selective thrombin inhibitors in mushrooms

Thrombin is the key serine proteinase of the coagulation cascade and therefore a suitable target for inhibition of blood coagulation. A number of pharmacologically active secondary metabolites from mushrooms have already been isolated, thus providing the rationale for screening for new thrombin inhibitors in mushrooms. In this study, inhibitory activities of mushroom extracts on thrombin and trypsin were measured using the chromogenic substrates H-D-phenylalanine-L-pipecolyl-L-arginine-paranitroaniline dihydrochloride (S-2238) for thrombin and N-benzoyl-D,L-Arg-p-nitroanilide (BAPNA) for trypsin. The inhibitory activities of extracts from 95 Basidiomycete species have been determined. The majority of samples inhibited trypsin and thrombin with various potencies; however, some extracts showed no activity against one or both of the enzymes. An aqueous extract of Gleophyllum odoratum exhibited high inhibitory activity on both thrombin and trypsin (72 and 60%, respectively), while extracts of Clitocybe gibba, Amanita virosa, Cantharellus lutescens, Suillus tridentinus, Hypoloma fasciculare and Lactarius badiosanguineus considerably inhibited thrombin (49, 48, 36, 34, 32 and 31%, respectively) and showed no inhibitory activity on trypsin. The results at this point are promising for further research with the objective of finding an effective and safe thrombin inhibitor.