A Bioreductive Prodrug of Cucurbitacin B Significantly Inhibits Tumor Growth in the 4T1 Xenograft Mice Model

Cucurbitacin B and Its Derivatives: A Review of Progress in Biological Activities

The emergence of natural products has provided extremely valuable references for the treatment of various diseases. Cucurbitacin B, a tetracyclic triterpenoid compound isolated from cucurbitaceae and other plants, is the most abundant member of the cucurbitin family and exhibits a wide range of biological activities, including anti-inflammatory, anti-cancer, and even agricultural applications. Due to its high toxicity and narrow therapeutic window, structural modification and dosage form development are necessary to address these issues with cucurbitacin B. This paper reviews recent research progress in the pharmacological action, structural modification, and application of cucurbitacin B. This review aims to enhance understanding of advancements in this field and provide constructive suggestions for further research on cucurbitacin B.

Bitter Phytochemicals as Novel Candidates for Skin Disease Treatment

Skin diseases represent a global healthcare challenge due to their rising incidence and substantial socio-economic burden. While biological, immunological, and targeted therapies have brought a revolution in improving quality of life and survival rates for certain dermatological conditions, there remains a stringent demand for new remedies. Nature has long served as an inspiration for drug development. Recent studies have identified bitter taste receptors (TAS2Rs) in both skin cell lines and human skin. Additionally, bitter natural compounds have shown promising benefits in addressing skin aging, wound healing, inflammatory skin conditions, and even skin cancer. Thus, TAS2Rs may represent a promising target in all these processes. In this review, we summarize evidence supporting the presence of TAS2Rs in the skin and emphasize their potential as drug targets for addressing skin aging, wound healing, inflammatory skin conditions, and skin carcinogenesis. To our knowledge, this is a pioneering work in connecting information on TAS2Rs expression in skin and skin cells with the impact of bitter phytochemicals on various beneficial effects related to skin disorders.

Diselenium-linked dimeric prodrug nanomedicine breaking the intracellular redox balance for triple-negative breast cancer targeted therapy

Triple-negative breast cancer (TNBC) has been regarded as the strongest malignancy in cases of breast cancer with a poor prognosis. The development of effective treatment strategies for TNBC has always been an urgent and unmet need. The intracellular redox balance is essential for maintaining TNBC cell malignancy. Disrupting intracellular redox balance by enlarging reactive oxygen species (ROS) generation and facilitating glutathione (GSH) depletion to amplify intracellular oxidative stress may be an alternative strategy to eliminate TNBC cells. However, inducing ROS generation and GSH depletion concurrently may be challenging. Herein, a diselenium linked-dimeric prodrug nanomedicine FA-SeSe-NPs was developed to break the intracellular redox homeostasis for TNBC targeted therapy. The dimeric prodrug was synthesized by conjugating two cucurbitacin B (CuB) molecules via one diselenium bond, which was subsequently assembled with FA-PEG-DSPE to form the final nanomedicine FA-SeSe-NPs. Using the active targeting potential of folic acid (FA), FA-SeSe-NPs could accumulate in tumor tissue with elevated levels and then be specifically internalized by cancer cells. In the high ROS and GSH conditions of TNBC cells, the diselenium bond can specifically respond to ROS to produce selenium free radicals to increase ROS and react with GSH to generate S-Se bond to deplete GSH. The released CuB further induced ROS production in TNBC cells. The diselenium bond and CuB functioned synergistically to amplify oxidative stress to kill the TNBC cells. Here, we provide a promising strategy to disrupt the intracellular redox balance of cancer cells for effective TNBC therapy.

Discovery of Triazolyl Derivatives of Cucurbitacin B Targeting IGF2BP1 against Non-Small Cell Lung Cancer

Cucurbitacin B (CuB) is a potent but toxic anticancer natural product. Herein, we designed and synthesized 2-OH- and 16-OH-modified CuB derivatives to improve their antitumor efficacy and reduce toxicity. Among them, derivative A11 had the most potent antiproliferative activity against A549 lung cancer cells (IC50 = 0.009 μM) and was approximately 10-fold more potent than CuB, while the cytotoxicity of A11 toward normal L02 cells was about 10-fold less potent, indicating a much wider therapeutic window than CuB. Derivative A11 directly binds to the insulin-like growth factor 2 mRNA-binding protein 1 (IGF2BP1) protein with a KD value of 2.88 nM, which is about 23-fold more potent than CuB, leading to the decreased expression of downstream apoptosis- and cell cycle-related proteins. More importantly, A11 exhibited much more potent anticancer efficacy in an A549 xenograft mouse model with a TGI rate of 80% and a superior in vivo safety profile than that of CuB.

TfOH-Catalyzed Cascade C-H/N-H Chemo-/Regioselective Annulation of Indole-2-carboxamides with Benzoquinones for the Construction of Anticancer Tetracyclic Indolo[2,3-c]quinolinones

An efficient TfOH-catalyzed cascade C-H/N-H annulation of indole-2-carboxamides with benzoquinones has been developed for the synthesis of tetracyclic indolo[2,3-c]quinolinones. This reaction exhibits excellent chemo-/regioselectivity, achieving functionalization of the C-3 of indole and N-H of the amide moiety to form the new C-C and C-N bonds. Various expected products were synthesized from readily available starting materials in good to high yields with a wide substrate scope and good functional group tolerance. Among all synthetic products, 3d showed the most potent cytotoxicity toward the 4T1 cancer cell line with an IC₅₀ value of 0.62 ± 0.05 μM. In vivo study demonstrated that 3d remarkably suppressed 4T1 xenograft tumor growth without body weight loss.

Research advances in NQO1-responsive prodrugs and nanocarriers for cancer treatment

NAD(P)H: quinine oxidoreductase (NQO1) is a class of flavoprotein enzymes commonly expressed in eukaryotic cells. It actively participates in the metabolism of various quinones and their in vivo bioactivation through electron reduction reactions. The expression level of NQO1 is highly upregulated in many solid tumor cells compared with that in normal cells. NQO1 has been considered a candidate molecular target because of its overexpression and bioactivity in different tumors. NQO1-responsive prodrugs and nanocarriers have recently been identified as effective objectives for achieving controlled drug release, reducing adverse reactions and improving clinical efficacy. This review systematically introduces the research advances in applying NQO1-responsive prodrugs and nanocarriers to cancer treatment. It also discusses the existing problems and the developmental prospects of these two antitumor drug delivery systems.

Analgesic Effect of SH003 and Trichosanthes kirilowii Maximowicz in Paclitaxel-Induced Neuropathic Pain in Mice

Pacliatxel is a taxol-based chemotherapeutic drug that is widely used to treat cancer. However, it can also induce peripheral neuropathy, which limits its use. Although several drugs are prescribed to attenuate neuropathies, no optimal treatment is available. Thus, in our study, we analyzed whether SH003 and its sub-components could alleviate paclitaxel-induced neuropathic pain. Multiple paclitaxel injections (cumulative dose 8 mg/kg, i.p.) induced cold and mechanical allodynia from day 10 to day 21 after the first injection in mice. Oral administration of SH003, an herbal mixture extract of Astragalus membranaceus, Angelica gigas, and Trichosantheskirilowii Maximowicz (Tk), dose-dependently attenuated both allodynia. However, when administered separately only Tk decreased both allodynia. The effect of Tk was shown to be mediated by the spinal noradrenergic system as intrathecal pretreatment with α₁- and α₂-adrenergic-receptor antagonists (prazosin and idazoxan), but not 5-HT_1/2, and 5-HT₃-receptor antagonists (methysergide and MDL-72222) blocked the effect of Tk. The spinal noradrenaline levels were also upregulated. Among the phytochemicals of Tk, cucurbitacin D was shown to play a major role, as 0.025 mg/kg (i.p.) of cucurbitacin D alleviated allodynia similar to 500 mg/kg of SH003. These results suggest that Tk should be considered when treating paclitaxel-induced neuropathic pain.

Induction of ferroptosis in human nasopharyngeal cancer cells by cucurbitacin B: molecular mechanism and therapeutic potential

Cucurbitacin B (CuB) is a widely available triterpenoid molecule that exhibits various biological activities. Previous studies on the anti-tumour mechanism of CuB have mostly focused on cell apoptosis, and research on the ferroptosis-inducing effect has rarely been reported. Herein, we first discovered the excellent cytotoxicity of CuB towards human nasopharyngeal carcinoma cells and elucidated its potential ferroptosis-inducing mechanisms. Morphology alterations of mitochondrial ultrastructure, as observed via transmission electron microscopy, showed that CuB-treated cells undergo ferroptosis. CuB caused intracellular accumulation of iron ions and depletion of glutathione. Detailed molecular mechanism investigation confirmed that CuB both induced widespread lipid peroxidation and downregulated the expression of GPX4, ultimately initiating a multipronged mechanism of ferroptosis. Furthermore, CuB exhibited anti-tumour effects in vitro by inhibiting cellular microtubule polymerization, arresting cell cycle and suppressing migration and invasion. Finally, CuB significantly inhibited tumour progression without causing obvious side effects in vivo. Altogether, our study highlighted the therapeutic potential of CuB as a ferroptosis-inducing agent for nasopharyngeal cancer, and it provided valuable insights for developing effective anti-tumour agents with novel molecular mechanisms derived from natural products.

Stimulus-cleavable chemistry in the field of controlled drug delivery

This review comprehensively summarises stimulus-cleavable linkers from various research areas and their cleavage mechanisms, thus provides an insightful guideline to extend their potential applications to controlled drug release from nanomaterials.

Synthesis and biological evaluation of NQO1-activated prodrugs of podophyllotoxin as antitumor agents

Podophyllotoxin (PPT), a toxic polyphenol derived from the roots of genus Podophyllum, had been reported with strong inhibition on both normal human cells and tumor cells, which hindered the development of PPT as the candidate antitumor agent. In the present work, multiple NQO1-activatable PPT prodrugs were synthesized for reducing normal cell toxicity and keeping tumor cell toxicity. The antiproliferative activities in vitro showed prodrug 3 was greatly selectively toxic to tumor cells over-expressing NQO1, taxol-resistant A549, hypoxia A549 and HepG2, and lower damage to normal cells in comparison with podophyllotoxin, prodrug 1 and 2. As elucidated by further mechanistic research, prodrug 3 was activated via NQO1 to efficiently while gently produce cytotoxic PPT units and kill tumor cells. In additions, in vivo study revealed that 3 significantly suppressed cancer growth in HepG2 xenograft models without obvious toxicity. Therefore, this NQO1-activatable prodrug delivery system exhibits good biosafety and provides a novel strategy for the development of drug delivery systems.

New triterpenoid saponin glycosides from the fruit fibers ofTrichosanthes cucumerinaL

Five new triterpenoid saponin glycosides, trichocucumerisides A–E (1–5), together with eleven known compounds (6–16) were isolated from Trichosanthes cucumerina fruit fibers. The structures of the new compounds were elucidated by detailed analysis of NMR and mass spectroscopic data as well as chemical reactions. The anti-inflammatory study against nitric oxide (NO) production in lipopolysaccharide (LPS)-stimulated RAW264.7 cells shows that compounds 7 and 9 exhibited stronger NO inhibitory activity, with IC₅₀ values of 3.0 and 2.7 μM, respectively, with comparison to positive references Celecoxib and aminoguanidine (IC₅₀ values 75.7 and 75.0 μM, respectively). Compounds 7 and 9 also possessed a greater selectivity index (SI) of approximately 3–4-fold activity than that of the positive references.

The new glycosides 1–5, together with eleven known compounds were isolated. Two compounds exhibited more potent anti-inflammatory activity than Celecoxib and aminoguanidine reference compounds.