Cytotoxic Potential of a-Azepano- and 3-Amino-3,4-SeCo-Triterpenoids.

Semi-synthetic triterpenoids, holding an amino substituted seven-membered A-ring (azepano-ring), which could be synthesized from triterpenic oximes through a Beckmann type rearrangement followed by a reduction of lactame fragment, are considered to be novel promising agents exhibiting anti-microbial, alpha-glucosidase, and butyrylcholinesterase inhibitory activities. In this study, in an attempt to develop new antitumor candidates, a series of A-ring azepano- and 3-amino-3,4-seco-derivatives of betulin, oleanolic, ursolic, and glycyrrhetinic acids were evaluated for their cytotoxic activity against five human cancer cell lines and non-malignant mouse fibroblasts by means of a colorimetric sulforhodamine assay. Azepanoallobetulinic acid amide derivative 11 was the most cytotoxic compound of this series but showed little selectivity between the different human tumor cell lines. Flow cytometry experiments showed compound 11 to act mainly by apoptosis (44.3%) and late apoptosis (21.4%). The compounds were further screened at the National Cancer Institute towards a panel of 60 cancer cell lines. It was found that compounds 3, 4, 7, 8, 9, 11, 15, 16, 19, and 20 showed growth inhibitory (GI50) against the most sensitive cell lines at submicromolar concentrations (0.20-0.94 µM), and their cytotoxic activity (LC50) was also high (1-6 µM). Derivatives 3, 8, 11, 15, and 16 demonstrated a certain selectivity profile at GI50 level from 5.16 to 9.56 towards K-562, CCRF-CEM, HL-60(TB), and RPMI-8226 (Leukemia), HT29 (Colon cancer), and OVCAR-4 (Ovarian cancer) cell lines. Selectivity indexes of azepanoerythrodiol 3 at TGI level ranged from 5.93 (CNS cancer cell lines SF-539, SNB-19 and SNB-75) to 14.89 for HCT-116 (colon cancer) with SI 9.56 at GI50 level for the leukemia cell line K-562. The present study highlighted the importance of A-azepano-ring in the triterpenic core for the development of novel antitumor agents, and a future aim to increase the selectivity profile will thus lie in the area of modifications of azepano-triterpenic acids at their carboxyl group.

4-Benzyloxylonchocarpin and Muracatanes A-C from Ranunculus muricatus L. and Their Biological Effects.

Ranunculus muricatus L. is a spiny fruit buttercup that is used in various traditional medicinal systems. In the current investigation of R. muricatus, the new chalcone 4-benzyloxylonchocarpin (1), the new anthraquinone muracatanes A (2), the new-to-nature anthraquinone muracatanes B (3), and the new naphthalene analog muracatanes C (4) were isolated, in addition to the three previously reported compounds, 4-methoxylonchocarpin (5), ß-sitosterol (6), and ß-sitosterol ß-D-glucopyranoside (7). Their structures were elucidated using 1D (1H and 13C) and 2D (COSY, HSQC, and HMBC) NMR spectroscopy and HR-ESI-MS. Chalcone 1 showed potent acetylcholinesterase inhibitory effects with Ki of 5.39 µM and Ki' of 3.54 µM, but none of the isolated compounds showed inhibitory activity towards butyrylcholinesterase. Anthraquinone 3 illustrated α-glucosidase inhibitory effects with IC50-values of 164.46 ± 83.04 µM. Compound 5 displayed moderate cytotoxic activity towards ovarian carcinoma (A2780, IC50 = 25.4 µM), colorectal adenocarcinoma (HT29, IC50 = 20.2 µM), breast cancer (MCF7, IC50 = 23.7 µM), and thyroid carcinoma (SW1736, IC50 = 26.2 µM) while it was inactive towards pharynx carcinoma (FaDu: IC50 > 30 µM).

Synthesis of new boswellic acid derivatives as potential antiproliferative agents.

In the current investigation, a series of heterocyclic derivatives of boswellic acids were prepared along with new monomers of 3-O-acetyl-11-keto-ß-boswellic acid (AKBA, 1) 11-keto-ß-boswellic acid (KBA, 2) and several new bis-AKBA and KBA homodimers and AKBA-KBA heterodimers. The effects of these compounds on the proliferation of different human cancer cell lines, viz., FaDu (pharynx carcinoma), A2780 (ovarian carcinoma), HT29 (colon adenocarcinoma), and A375 (malignant melanoma), have been evaluated. Thus, KBA homodimer 21 effectively inhibited the growth of FaDu, A2780, HT29, and A375 cells with EC50 values below 9 µM. In addition, compounds 7, 8, 11, 12, 15, 16, and 17 also exhibited cytotoxic effects for A2780, HT29, and A375 cancer cells. In particular, the pyrazine analog 8 was highly cytotoxic for A375 cancer cells with an EC50 value of 2.1 µM.

Design, synthesis and cytotoxicity of BODIPY FL labelled triterpenoids.

Several triterpenoid acids (betulinic, oleanolic, ursolic, glycyrrhetinic) and triterpene betulin were used as starting material to synthesize BODIPY FL adducts, and these compounds were screened for their cytotoxic activity employing several human tumor cell lines. The cytotoxicity of the compounds strongly depended on the chosen spacer between the triterpenoid core and the BODIPY FL unit. Thus, 3-O-acetyl-betulinic acid derived BODIPY FL conjugate holding an ethylendiamine spacer was cytotoxic for human breast adenocarcinoma cells MCF7 but not cytotoxic for all other cell lines.

Synthesis and Cytotoxicity Evaluation of DOTA-Conjugates of Ursolic Acid.

In this study, we report the synthesis of several amine-spacered conjugates of ursolic acid (UA) and 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid (DOTA). Thus, a total of 11 UA-DOTA conjugates were prepared holding various oligo-methylene diamine spacers as well as different substituents at the acetate units of DOTA including tert-butyl, benzyl, and allyl esters. Furthermore, three synthetic approaches were compared for the ethylenediamine-spacered conjugate 29 regarding reaction steps, yields, and precursor availability. The prepared conjugates were investigated regarding cytotoxicity using SRB assays and a set of human tumor cell lines. The highest cytotoxicity was observed for piperazinyl spacered compound 22. Thereby, EC50 values of 1.5 µM (for A375 melanoma) and 1.7 µM (for A2780 ovarian carcinoma) were determined. Conjugates 22 and 24 were selected for further cytotoxicity investigations including fluorescence microscopy, annexin V assays and cell cycle analysis.

The cytotoxicity of oleanane derived aminocarboxamides depends on their aminoalkyl substituents.

Several oligo-methylene diamine derived carboxamides of oleanolic and maslinic acid have been prepared, and substitutions of the terminal primary amine as well as variations of the length of alkyl chain of the diamine moiety were made. Biological evaluation of their cytotoxic activity was performed using photometric sulforhodamin B assays employing a panel of different human cancer cell lines. These experiments showed most of the carboxamides to be cytotoxic with EC50 values below 10 µM. Prolongation of the alkyl chain length initially reduced EC50 values to a minimum, but a decrease in cytotoxicity was observed for longer alkyl chains. Variation of substituents at the terminal nitrogen atom, however, did not influence EC50 values at all. Noteworthy results were obtained particularly for compounds 4, 6 and 23 as indicated by EC50 values lower than 2 µM, and in case of a maslinic derivative 23 even an increased tumor/non-tumor cell selectivity was observed. These compounds were further investigated using fluorescence microscopy and flow cytometry analysis, which revealed 6 to show indications of apoptosis.

2,4-Disubstituted Quinazoline Derivatives Act as Inducers of Tubulin Polymerization: Synthesis and Cytotoxicity.

BACKGROUND: During last recent years number of anti-tubulin agents were introduced for treatment of diverse kind of cancer. Despite of their potential in treatment of cancer, drug resistance and adverse toxicity such as peripheral neuropathy are some of the negative criteria of anti-tubulin agents. METHODS: Twenty seven quinazoline derivatives were synthesized using a multicomponent reaction. The cytotoxicity of compounds 1-27 was tested in SRB assays employing five different human tumor cell lines. Effect of two of active compounds on tubulin polymerization was also checked using a commercially available assay kit. Molecular modelling studies were also performed using autodock tools software. RESULTS: SRB assays showed that compounds 2, 9, 16 and 26, being highly cytotoxic with IC50 values ranging between 2.1 and 14.3µM. The possible mode of action of compounds, 2, 9, 16 and 26, and the taxol binding site of the protein tubulin, an important goal for antimitotic drugs, was also studied by molecular docking, which showed reasonable interactions with tubulin active site, followed by investigation of the effects of compounds 9 and 16 on the polymerization of tubulin. The results showed the tested compounds to be highly active as inducers of tubulin polymerization. CONCLUSION: Altogether, with respect to obtained results, it is attractive and beneficial to further investigation on quinazoline scaffold as antimitotic agents.

Transformation of asiatic acid into a mitocanic, bimodal-acting rhodamine B conjugate of nanomolar cytotoxicity.

Based on their biological activity natural products continue to represent optimal lead structures for the development of novel drug candidates. We focused on the syntheses of several derivatives of the triterpene asiatic acid and on the evaluation of their cytotoxic activity in a photometric sulforhodamin B assay. Especially, benzamide 2 and rhodamine B conjugate 11 show a distinct cytotoxicity for several human tumor cell lines, e.g. EC50 (A2780) = 110 ±â€¯1 nM and EC50 (A2780) = 8 ±â€¯2 nM, respectively. Interestingly, compound 11 showed for two human tumor cell lines (HT29 and 518A2) non-linear, bimodal dose-response relationships.

Syntheses of C-ring modified dehydroabietylamides and their cytotoxic activity.

Due to their auspicious pharmacological efficacy as future drug candidates, natural products have been attracting scientific interest for centuries. An interesting field of research concerns the natural product class of terpenes. In this regard, a multitude of studies have already shown their promising biological potential. Therefore, a set of 27 derivatives of the diterpene dehydroabietylamine was synthesized, focusing on C-ring modifications and the derivatization of the amino moiety at C-18. Subsequent screening of the compounds in colorimetric sulforhodamine B-assays revealed an in vitro cytotoxicity especially towards malignant cell line MCF7. Particularly, 12-hydroxy-N-(isonicotinoyl)dehydroabietylamine and N-(4-methoxybenzoyl)dehydroabietylamine showed good cytotoxic activities (EC50 (MCF7) = 4.3 ±â€¯0.2 µM and EC50 (MCF7) = 4.5 ±â€¯1.5 µM, respectively) and significant selectivities (SI = 6.2 and SI = 8.8, respectively) towards malignant cell lines.

Homopiperazine-rhodamine B adducts of triterpenoic acids are strong mitocans.

Parent pentacyclic triterpenoic acids such as ursolic-, oleanolic, glycyrrhetinic, betulinic and boswellic acid were converted into their acetylated piperazinyl amides that were coupled with rhodamine B. SRB assays to evaluate their cytotoxicity showed all of these triterpene-homopiperazinyl-rhodamine adducts 16-20 being highly cytotoxic for a panel of human tumor cell lines even in nanomolar concentrations while being significantly less cytotoxic for non-malignant cells. Interestingly enough, these compounds were even more cytotoxic than previously prepared piperazinyl analogs, thus making the homopiperazinyl spacer a very interesting scaffold for the development of biologically active compounds. Extra staining experiments showed that the cytostatic effect of compounds 18 and 20 onto A2780 cancer cells is due to their ability to act as a mitocan.