Discovery of Novel Celastrol-Imidazole Derivatives with Anticancer Activity In Vitro and In Vivo

Synthesis and effect of 4-acetylphenylamine-based imidazole derivatives on migration and growth of 3D cultures of breast, prostate and brain cancer cells

In this study, we have synthesized novel 4-acetophenone moiety-bearing functionalized imidazole derivatives containing S-, and N-ethyl substituents and evaluated their anticancer activity. Their anticancer activity was studied against human breast carcinoma (MDA-MB-231), human prostate carcinoma (PPC-1), and human glioblastoma (U-87). Compounds 4, 9, 14, and 22 were identified as the most promising anticancer agents from a series of imidazole derivatives. They showed the highest cytotoxicity by MTT assay against MDA-MB-231, PPC-1 and U-87 cell lines. Compounds 14 and 22 were most selective against PPC-1 and U-87 cell lines, and their EC50 values against these cell lines ranged from 3.1 to 47.2 µM. Most tested compounds showed lower activity against the triple-negative breast cancer MDA-MB-231 cell line. None of the imidazole derivatives possessed an inhibiting effect on the migration of PPC-1 and U-87 cells by 'wound' healing assay. In spheroid assay, the most promising were compounds 14 and 22, especially in PPC-1 3D cultures. They efficiently reduced both the size and the viability of PPC-1 spheroid cells.

Recent drug design strategies and identification of key heterocyclic scaffolds for promising anticancer targets

Cancer, a noncommunicable disease, is the leading cause of mortality worldwide and is anticipated to rise by 75% in the next two decades, reaching approximately 25 million cases. Traditional cancer treatments, such as radiotherapy and surgery, have shown limited success in reducing cancer incidence. As a result, the focus of cancer chemotherapy has switched to the development of novel small molecule antitumor agents as an alternate strategy for combating and managing cancer rates. Heterocyclic compounds are such agents that bind to specific residues in target proteins, inhibiting their function and potentially providing cancer treatment. This review focuses on privileged heterocyclic pharmacophores with potent activity against carbonic anhydrases and kinases, which are important anticancer targets. Evaluation of ongoing pre-clinical and clinical research of heterocyclic compounds with potential therapeutic value against a variety of malignancies as well as the provision of a concise summary of the role of heterocyclic scaffolds in various chemotherapy protocols have also been discussed. The main objective of the article is to highlight key heterocyclic scaffolds involved in recent anticancer drug design that demands further attention from the drug development community to find more effective and safer targeted small-molecule anticancer agents.

Antiproliferative Activities of Cynaropicrin and Related Compounds against Cancer Stem Cells

Glioblastoma (GBM) has a high mortality rate despite the availability of various cancer treatment options. Although cancer stem cells (CSCs) have been associated with poor prognosis and metastasis, and play an important role in the resistance to existing anticancer drugs and radiation; no CSC-targeting drugs are currently approved in clinical practice. Therefore, the development of antiproliferative agents against CSCs is urgently required. In this study, we evaluated the antiproliferative activities of 21 sesquiterpenoids against human GBM U-251 MG CSCs and U-251 MG non-CSCs. Particularly, the guaianolide sesquiterpene lactone cynaropicrin (1) showed strong antiproliferative activity against U-251 MG CSCs (IC50 = 20.4 µM) and U-251 MG non-CSCs (IC50 = 10.9 µM). Accordingly, we synthesized six derivatives of 1 and investigated their structure-activity relationships. Most of the guaianolide sesquiterpene lactones with the α-methylene-γ-butyrolactone moiety showed antiproliferative activities against U-251 MG cells. We conclude that the 5,7,5-ring and the α-methylene-γ-butyrolactone moiety are both important for antiproliferative activities against U-251 MG cells. The results of this study suggest that the α,β-unsaturated carbonyl moiety, which has recently become a research hotspot in drug discovery, is the active center of 1. Therefore, we consider 1 as a potential lead for developing novel drugs targeting CSCs.

Development of novel celastrol-ligustrazine hybrids as potent peroxiredoxin 1 inhibitors against lung cancer

The disruption of oxidation-reduction equilibrium through inhibiting reactive oxygen species (ROS) clearance or enhancing ROS production has emerged as a novel and promising strategy for cancer therapy. Herein, a series of celastrol-ligustrazine hybrids were designed and synthesized as effective ROS promoters, and their biological activities were further evaluated. Among them, compound 7e stood out as the most potent peroxiredoxin 1 (PRDX1) inhibitor (IC50 = 0.164 μM), which was significant super to the recognized PRDX1 inhibitor Conoidin A (IC50 = 14.80 μM) and the control compound celastrol (IC50 = 1.622 μM). Furthermore, 7e dramatically promoted intracellular ROS accumulation, and inhibited the proliferation, invasion and migration of cancer cells besides inducing apoptosis in vitro. Additionally, 7e suppressed the key signaling pathways (AKT and ERK) and promoted the expression of apoptosis-related proteins (cleaved caspase-3/8 and cleaved PARP) in A549 cells, which resulted in the prevention of tumor progression. Most importantly, compound 7e (TGI = 77.47%) showed more considerable in vivo antitumor efficacy and less toxicity than celastrol (TGI = 71.00%). Overall, this work indicates 7e as the most potential PRDX1 inhibitor and may be a promising candidate for the therapy of lung cancer.

Discovery of Michael reaction acceptors from the leaves of Ailanthus altissima by a modified tactic

Structural characteristics-guided investigation of Ailanthus altissima (Mill.) Swingle resulted in the isolation and identification of seven undescribed potential Michael reaction acceptors (1-7). Ailanlactone A (1) possesses an unusual 1,7-epoxy-11,12-seco quassinoid core. Ailanterpene B (6) was a rare guaianolide-type sesquiterpene with a 5/6/6/6-fused skeleton. Their structures were determined through extensive analysis of physiochemical and spectroscopic data, quantum chemical calculations, and single crystal X-ray crystallographic technology using Cu Kα radiation. The cytotoxic activities of isolates on HepG2 and Hep3B cells were evaluated in vitro. Encouragingly, ailanaltiolide K (4) showed significant cytotoxicity against Hep3B cells with IC50 values of 1.41 ± 0.21 μM, whose covalent binding mode was uncovered in silico.

Brønsted Acid-Catalyzed Synthesis of 1,2,5-Trisubstituted Imidazoles via a Multicomponent Reaction of Vinyl Azides with Aromatic Aldehydes and Aromatic Amines

A facile and efficient approach to the synthesis of 1,2,5-trisubstituted imidazoles is developed via a multicomponent reaction under metal-free catalysis. Under Brønsted acid catalysis, the desired products can be obtained from readily available vinyl azides, aromatic aldehydes, and aromatic amines without generating any toxic waste. The convenient operations and high functional group compatibility indicate that this approach offers an attractive alternative method for the synthesis of imidazole derivatives.

Discovery of semisynthetic celastrol derivatives exhibiting potent anti-ovarian cancer stem cell activity and STAT3 inhibition

The hallmark of ovarian cancer is its high mortality rate attributed to the existence of cancer stem cells (CSCs) subpopulations which result in therapy recurrence and metastasis. A series of C-29-substituted and/or different A/B ring of celastrol derivatives were synthesized and displayed potential inhibition against ovarian cancer cells SKOV3, A2780 and OVCAR3. Among them, compound 6c exhibited the most potent anti-proliferative activity and selectivity, gave superior anti-CSC effects through inhibition of the sphere formation and downregulation of the percentage of CD44⁺CD24^- and ALDH⁺ cells. Further mechanism research demonstrated that compound 6c could attenuate the expression of STAT3 and p-STAT3. The results suggested that the inhibition of celastrol derivative 6c on ovarian cancer cells may be related to resistance to cancer stem-like characters and regulation of STAT3 pathway.

Synthesis and Biological Activity Screening of Newly Synthesized Trimethoxyphenyl-Based Analogues as Potential Anticancer Agents

A group of novel trimethoxyphenyl (TMP)-based analogues were synthesized by varying the azalactone ring of 2-(3,4-dimethoxyphenyl)-4-(3,4,5-trimethoxybenzylidene)oxazolone 1 and characterized using NMR spectral data as well as elemental microanalyses. All synthesized compounds were screened for their cytotoxic activity utilizing the hepatocellular carcinoma (HepG2) cell line. Compounds 9, 10 and 11 exhibited good cytotoxic potency with IC₅₀ values ranging from 1.38 to 3.21 μM compared to podophyllotoxin (podo) as a reference compound. In addition, compounds 9, 10 and 11 exhibited potent inhibition of β-tubulin polymerization. DNA flow cytometry analysis of compound 9 shows cell cycle disturbance at the G2/M phase and a significant increase in Annexin-V-positive cells compared with the untreated control. Compound 9 was further studied regarding its apoptotic potential in HepG2 cells; it decreased the level of MMP and Bcl-2 as well as boosted the level of p53 and Bax compared with the control HepG2 cells.