New 3-tetrazolyl-ß-carbolines and ß-carboline-3-carboxylates with anti-cancer activity.

The synthesis and in vitro anticancer activity of novel ß-carbolines is reported. New tryptamines have been prepared via hetero-Diels-Alder reaction of nitrosoalkenes with indoles and used to prepare functionalized ß-carbolines by the Pictet-Spengler approach. These included 6-substituted-ß-carboline-3-carboxylates and 3-(1H-tetrazol-5-yl)-ß-carbolines, whose synthesis is reported for the first time. Carboline-3-carboxylates derived from l-tryptophan methyl ester were also prepared. The structural diversity that was achieved allowed the discovery of impressive activities against a range cancer cell lines with the selectivity depending on the type of substitution pattern of the ß-carboline core. We have identified at least one ß-carboline derivative with GI50 ≤ 1  µM for each of the following human tumor cell lines: glioblastoma (U251), melanona (UACC-61), breast (MCF-7), ovarian expressing multiple-drug-resistance phenotype 4 (NCI-ADR/RES), renal (786-0), lung (NCI-H460), ovarian cancer (OVCAR-3), leukemia (K-562) and colon (HT29). These results demonstrated that the new ß-carboline derivatives are very promising anticancer agents.

Synthesis and evaluation of novel hybrids ß-carboline-4-thiazolidinones as potential antitumor and antiviral agents.

A series of novel hybrids ß-carboline-4-thiazolidinones were synthesized and evaluated for their in vitro antitumor activity against human cancer cell lines and for antiviral activity towards Herpes simplex virus type-1 (HSV-1). From the N'-(2-ylidene-4-thiazolidinone)-ß-carboline-3-carbohydrazide series (9-11), compounds 9c and 11d were the most active, showing growth inhibition 50% (GI50) values less than 5 µM for all cell lines tested. Compound 9c, bearing the 4-dimethylaminophenyl group at C-1 of ß-carboline was selected for further investigation concerning cell death and cell cycle profile, focusing on the human renal adenocarcinoma cell line 786-0. Treatments with 25 µM of compound 9c induced cell death after 15 h of treatment, characterized by phosphatidylserine exposure and loss of membrane integrity. Moreover, treatment with 12.5 µM promoted a sub-G1 arrest, which indicates cell death. Derivatives of the N-(2-substituted-aryl-4-thiazolidinone)-ß-carboline-3-carboxamide series (18-23) showed a potent activity and high selectivity for glioma (U251) and ovarian (OVCAR-3) cancer cell lines. Also, some ß-carboline-4-thiazolidinone hybrids showed potent antiviral activity against Herpes simplex virus type-1. The N-(2-substituted-aryl-4-thiazolidinone)-carboxamide moiety in 18, 19 and 22 confer a potent anti-HSV-1 activity for these derivatives, which presented EC50 values of 0.80, 2.15 and 2.02 µM, respectively. The assay results showed that the nature of 4-thiazolidinone moiety and of the substituent attached at the 3- and 1- position of ß-carboline nucleus influenced the antitumor and antiviral activities.