Investigation of aminomethyl indole derivatives as hyaluronidase inhibitors

Hyaluronidase inhibitors are of potential therapeutic value for the treatment of a variety of diseases, such as cancer, arthrosis, or bacterial infections. Potent and selective hyaluronidase inhibitors are not known so far, and current approaches to the development of hyaluronidase inhibitors are limited. Elevated levels of hyaluronan (HA) are connected with most malignant tumours. Therefore, the search for drugs modulating the hyaluronidase activity became very important. In the present study, a new series of aminomethyl indole derivatives (AMIDs) were tested for inhibition of bovine testes hyaluronidase (BTH). In vitro assays were performed using stains-all at pH 7 and Morgan-Elson reaction at pH 3.5. Among the AMIDs, 3-[(4-methylpiperazin-1-yl)methyl]-5-phenyl-1H-indole (9) was found to be active with 23% inhibition at 50 microM and pH 7. All the other inhibitors showed less activity at pH 3.5 and pH 7. These activity results demonstrated that compounds with phenyl substitution at position 5 have higher activity. The results confirmed that more lipophilic compounds have better inhibition against the hyaluronidase enzyme.

Comparative studies on conventional and microwave synthesis of some benzimidazole, benzothiazole and indole derivatives and testing on inhibition of hyaluronidase

We have synthesized twelve 2-substituted benzimidazole, benzothiazole and indole derivatives using on both microwave irradiation and conventional heating methods. The microwave method was observed to be more beneficial as it provides an increase of yield from 3% to 113% and a 95 to 98 % reduction in time. All compounds were tested by a stains-all assay at pH 7 and by a Morgan-Elson assay at pH 3.5 for hyaluronidase inhibitory activity at a concentration of 100 microM. The most potent compound was 2-(4-hydroxyphenyl)-3-phenylindole (12) with an IC(50) value of 107 microM at both pH 7 and 3.5.

New potent indole derivatives as hyaluronidase inhibitors

Because of the physiologic importance of hyaluronidases, the identification of potent and selective inhibitors of hyaluronidases has become increasingly important. A variety of assay methods have been used for such a purpose, i.e. classical turbidimetric, viscometric and colorimetric. In this study, a modified enzymatic assay has been used to obtain a microtiter plate-based sensitive activity screening. All inhibitors were tested in a stains-all assay at pH 7 and in a Morgan-Elson assay at pH 3.5. Among the tested compounds, 1, 2, 3, 6, 7, 8, 16, 17 and 18 showed good inhibition of more than 50%, so the IC(50) values of these derivatives were determined in the range of 25-41 microm. The IC(50) value of the most active hyaluronidase inhibitor Vcpal (6-palmitoyl-L-ascorbic acid) was measured as 8.36 microm. All inhibitors including Vcpal showed twofold less activity at pH 3.5 in a Morgan-Elson assay. Examination of substituent effects on the activity showed that para-positions of benzamide needs to be chlorinated or fluorinated to obtain good inhibitory effect. It was found that the introduction of a p-fluoro benzyl ring in the indole nitrogen has a positive effect for the inhibitory effects of both indole-2- and 3-carboxamide derivatives.