No abstract

Proteases play a key role in a variety of pathologies, including cancer, pancreatitis and thrombosis. Low molecular inhibitors can act as drugs to combat these pathologies. Twelve natural phenolic compounds and one alkaloid were evaluated. Quercetin was used as a standard in the in vitro tests on serine proteases (trypsin, thrombin and urokinase). Salicin showed a highly selective effect with a value of IC50 = 11.4 microm for thrombin, suggesting it may be a suitable lead structure for developing thrombin inhibitors and thus for perspective thrombolytics. Interesting results were also observed for hyperoside with IC50 = 8.3 microm for urokinase. The flavonoid skeleton seems to be a suitable structure for investigating urokinase inhibitors as prospective drugs for cancer therapy. A very high inhibitory activity on trypsin was observed for the flavonoid silybin (IC50 = 3.7 microm), indicating a prospective structure on which to base possible polyphenolic trypsin inhibitors.

Proteases play a regulatory role in a variety of pathologies including cancer, pancreatitis, thromboembolic disorders, viral infections and many others. One of the possible strategies how to combat with these pathologies seems to be the use of low molecular inhibitors. Natural products were evaluated in the in vitro antiprotease assay on serine proteases (trypsin, thrombin and urokinase) and on the cysteine protease cathepsin B. We found interesting results for -ursolic acid isolated from Salvia officinalis, which significantly inhibited all tested proteases in vitro in the micromolar range. -Ursolic acid showed the strongest inhibition activity to urokinase (IC 50 = 12 μm) and cathepsin B (IC 50 = 10 μm) as proteases included in tumour invasion and metastasis indicated possible anticancer effectivity. Therefore, we tested the ability of -ursolic acid at doses of 50, 75 and 100 mg/kg given i.p. to inhibit lung colonization of B16 mouse melanoma cells in vivo. We found, that -ursolic acid significantly decreased the number of B16 colonies in the lungs of mice at the dose 50 mg/kg (p Ͻ 0.05).

The aspartic protease of HIV-1 represents a valid therapeutic target of antiviral agents suitable for the treatment of AIDS. We have designed peptidomimetic inhibitors for this enzyme with a hydroxyethylenediamine core, based on a molecular modeling approach that predicts the effectiveness of the designed compounds in terms of computed enzyme-inhibitor complexation Gibbs free energies. This structurebased molecular design was then combined with a synthetic strategy that couples stereochemical control with full flexibility in the choice of the central core side chains and of the flanking residues. A series of peptidomimetic inhibitors was thus assembled from readily available amino acids and carboxylic acids and -Phe-ω[CH2-(r/s)CHOH]-Phe- cores. The IC50 values for these compounds ranged from 3 nM to 80 μM, allowing a QSAR analysis and identification of factors that determine the inhibition potency of the compounds. Predicted ADME-related properties of the inhibitor candidates span a range of pharmacokinetics profiles, which allows selection of a potent and bioavailable lead compound for further development

Medicinal mushroom Ganoderma lucidum, well recognized natural product that have been used in the traditional Chinese medicine, is currently used as a popular dietary supplement. Here, we show that an oral application of G. lucidum triterpene extract (GLT) suppressed colon carcinogenesis induced by the food‐borne carcinogen (2‐Amino‐1‐methyl–6‐phenylimidazol[4,5‐b]pyridine [PhIP]) and inflammation (dextran sodium sulfate [DSS]) in mice. PhIP and DSS induced formation of colonic tumors, whereas GLT treatment significantly decreased the number of tumors. Furthermore, GLT suppressed focal hyperplasia and aberrant crypt foci (ACF) formation. These anti‐proliferative effects of GLT were confirmed by the decreased staining with Ki‐67 in colon tissues. PhIP/DSS‐induced colon inflammation was demonstrated by the significant shortening of the large intestine, whereas GLT treatment reversed the shortening of colon lengths to the levels comparable to the control group. Moreover, PhIP/DSS‐induced infiltration of macrophages was significantly reduced in colon tissue in animals treated with GLT. Our data suggest that GLT could be considered as an alternative dietary approach for the suppression of the food‐borne carcinogen‐ and inflammation‐induced colon carcinogenesis.Supported by P50 AT00477 from NCCAM and the NIH Office of Dietary Supplements.