Novel hybrids of brefeldin A and nitrogen mustards with improved antiproliferative selectivity: Design, synthesis and antitumor biological evaluation.

A series of novel conjugates of brefeldin A (11a-c, 12a-c and 13a-c) were obtained by introducing a variety of nitrogen mustards at 4-OH or 7-OH position to explore more efficacious and less toxic antitumor agents. The antiproliferative activities were tested against three cancer cell lines (HL-60, PC-3 and Bel-7402) and one multidrug resistant cell line Bel-7402/5-FU. Among them, compound 11a was the strongest derivative with IC50 values of 4.48, 9.37, 0.2 and 0.84 µM, respectively, and more potent than nitrogen mustards. Though the antiproliferative potency was weaker than the lead compound brefeldin A, 11a displayed lower toxicity than brefeldin A (IC50 < 0.001 µM) with an IC50 of 9.74 µM against normal human liver L-O2 cells, showing good selectivity between normal and malignant liver cells. The mechanism studies confirmed that 11a could induce apoptosis, arrest cell cycle at the G1 phase and lead to mitochondrial dysfunction in Bel-7402 cells at submicromolar concentrations. Furthermore, 11a induced the intrinsic apoptotic mitochondrial pathway in Bel-7402 cells, evidenced by the enhanced expression of the pro-apoptotic protein Bax, cyto-c and p53, and the reduced expression of the anti-apoptotic protein Bcl-2. The caspase-9 and -3 levels were also up-regulated.

Nitric oxide-releasing derivatives of brefeldin A as potent and highly selective anticancer agents.

A series of NO-donating mono- or diester derivatives of brefeldin A were designed, synthesized and biologically evaluated. Some derivatives exhibited potent antiproliferative activity with low IC50 values. The most potent NO-donating hybrid 13b exhibited stronger cytotoxicity against human prostate cancer PC-3 cells, human colon carcinoma HT-29 cells and human liver cancer HepG-2 cells than BFA with IC50 values of 25 nM, 160 nM and 180 nM, respectively. More importantly, compound 13b showed good selectivity between human normal and tumor liver cells with selectivity index of 33. Additionally, 13b released higher levels of NO in HepG-2 cells than L-02 cells. Further mechanism concerning cellular apoptosis showed that 13b induced apoptosis and S phase cell cycle arrest in HepG-2 cells. Incubation with 13b increased the number of HepG-2 cells with collapsed mitochondrial membrane at low concentrations in dose-dependent manner. In addition, by using the Human Apoptosis Protein Array kit, several apoptosis-related proteins, including HO-1, HO-2 and survivin, were found to be markedly downregulated by 13b in HepG-2 cells. Furthermore, in western blot assay, 13b increased the expression of Bax, Cyt c and caspase 3, and reduced the relative levels of Bcl-2, Bcl-xl and pro-caspase 3 in HepG-2 cells.

Synthesis, Cytotoxicity and Antimicrobial Activity of New Enmein-type Kauranoid Diterpenoid Derivatives.

BACKGROUND: Recently, we devoted to disclosing the antibacterial activities of enmein-type 6,7-seco-ent-kauranoid derivatives. OBJECTIVE: Eleven new enmein-type diterpenoid derivatives with different substituents and drug-like properties were designed and synthesized. METHOD: The antimicrobial activities against E. coli, S. aureus, B. subtilis and M. albicans were disclosed. The antiproliferative activities against human cancer Bel-7402, K562, MGC-803 and CaEs-17 cells and non-cancerous L-02 cells were also measured by MTT method. RESULTS: The results revealed that enmein-type diterpenoids showed more promising activities against tested gram-positive bacteria than gram-negative bacterium and fungus. Compound 9 with R of 2-quinolyl group exhibited the strongest antimicrobial activities with MIC values of 7.81 µg/ml and 0.98 µg/ml against S. aureus and B. subtilis, respectively. All the target derivatives exhibited superior cytotoxic activities to compounds 1 and 2 against tumor cells, and slight selectivity between cancerous cells and normal liver cells. Compound 12 with R of 3-(2-chloropyridyl) group and IC50 values of 0.7 µM, 0.9 µM, 0.8 µM and 2.0 µM agaist four tumor cells, respectively, was selected for further mechanism study in Bel-7402 cell line. CONCLUSION: Compound 12 could induce S phase cell cycle arrest and apoptosis at low concentrations via mitochondria-related pathways. The effects of compound 12 on some apoptosis related proteins showed that CDK2 was up regulated and ATM and cyclin A1 were down-regulated which confirmed the apoptosis and cell cycle effects.

Novel nitric oxide-releasing spirolactone-type diterpenoid derivatives with in vitro synergistic anticancer activity as apoptosis inducer.

Herein, we reported the cytotoxicity, NO-releasing property, and apoptosis induced ability of two series of novel nitric oxide-releasing spirolactone-type diterpenoid derivatives (10a-f and 15a-f). All the title compounds were more potent than oridonin (7) and parent compound (9 or 14) against human tumor Bel-7402, K562, MGC-803 and CaEs-17 cells. SARs were concluded based on above data. Compound 15d exhibited the strongest antiproliferative activity with the IC50 of 0.86, 1.74, 1.16 and 3.75µM, respectively, and could produce high level (above 25µM) of NO at the time point of 60min. Further mechanism evaluation showed that 15d could induce S phase cell cycle arrest and apoptosis at low micromolar concentrations in Bel-7402 cells via mitochondria-related pathways. It was expected that the remarkable biological profile of the synthetic NO-releasing spirolactone-type diterpenoid analogs make them possible as promising candidates for the development of anticancer agents.

Oridonin, a Promising ent-Kaurane Diterpenoid Lead Compound.

Oridonin belongs to ent-kaurane tetracyclic diterpenoid and was first isolated from Isodon species. It exhibits inhibitory activities against a variety of tumor cells, and pharmacological study shows that oridonin could inhibit cell proliferation, DNA, RNA and protein synthesis of cancer cells, induce apoptosis and exhibit an antimutagenic effect. In addition, the large amount of the commercially-available supply is also very important for the natural lead oridonin. Moreover, the good stability, suitable molecular weight and drug-like property guarantee its further generation of a natural-like compound library. Oridonin has become the hot molecule in recent years, and from the year 2010, more than 200 publications can be found. In this review, we summarize the synthetic medicinal chemistry work of oridonin from the first publication 40 years ago and share our research experience of oridonin for about 10 years, which may provide useful information to those who are interested in this research field.

Antiproliferative activity and apoptosis inducing effects of nitric oxide donating derivatives of evodiamine.

The first series of nitric oxide donating derivatives of evodiamine were designed and prepared. NO releasing ability of all target derivatives was evaluated in BGC-823, Bel-7402 and L-02 cells. The cytotoxicity was evaluated against three human tumor cell lines (Bel-7402, A549 and BGC-823) and normal human liver cells L-02. The nitrate derivatives 11a and 11b only exhibited moderate activity and furoxan-based derivatives 13a-c, 14a and 14b showed promising activity. 13c showed good cytotoxic selectivity between tumor and normal liver cells and was further investigated for its apoptotic properties on human hepatocarcinoma Bel-7402 cells. The molecular mode of action revealed that 13c caused cell-cycle arrest at S phase and induced apoptosis in Bel-7402 cells through mitochondria-related caspase-dependent pathways.

Antitumor and Antibacterial Derivatives of Oridonin: A Main Composition of Dong-Ling-Cao.

Isodon rubescens has been used as a traditional green tea for more than 1000 years and many medicinal functions of I. rubescens are also very useful, such as its well-known antitumor and antibacterial activities. Oridonin, a bioactive ent-kaurane diterpenoid, is the major ingredient of this medicinal tea. Herein, 22 novel oridonin derivatives were designed and synthesized. The antibacterial activity was evaluated for the first time. Compound 12 was the most promising one with MIC of 2.0 µg/mL against B. subtilis, which was nearly 3-fold stronger than positive control chloromycetin. The antiproliferative property was also assayed and compound 19 showed stronger activity than taxol. The apoptosis-inducing ability, cell cycle arrest effect at S phase and influence of mitochondrial membrane potential by 19 in CaEs-17 cancer cells were first disclosed. Based on the above results, the cell apoptosis induced by compound 19 in CaEs-17 cells was most probably involved in the intrinsic apoptotic pathway.