Oxidation resistance 1 is a novel senolytic target

The selective depletion of senescent cells (SCs) by small molecules, termed senolytic agents, is a promising therapeutic approach for treating age‐related diseases and chemotherapy‐ and radiotherapy‐induced side effects. Piperlongumine (PL) was recently identified as a novel senolytic agent. However, its mechanism of action and molecular targets in SCs was unknown and thus was investigated. Specifically, we used a PL‐based chemical probe to pull‐down PL‐binding proteins from live cells and then mass spectrometry‐based proteomic analysis to identify potential molecular targets of PL in SCs. One prominent target was oxidation resistance 1 (OXR1), an important antioxidant protein that regulates the expression of a variety of antioxidant enzymes. We found that OXR1 was upregulated in senescent human WI38 fibroblasts. PL bound to OXR1 directly and induced its degradation through the ubiquitin‐proteasome system in an SC‐specific manner. The knockdown of OXR1 expression by RNA interference significantly increased the production of reactive oxygen species in SCs in conjunction with the downregulation of antioxidant enzymes such as heme oxygenase 1, glutathione peroxidase 2, and catalase, but these effects were much less significant when OXR1 was knocked down in non‐SCs. More importantly, knocking down OXR1 selectively induced apoptosis in SCs and sensitized the cells to oxidative stress caused by hydrogen peroxide. These findings provide new insights into the mechanism by which SCs are highly resistant to oxidative stress and suggest that OXR1 is a novel senolytic target that can be further exploited for the development of new senolytic agents.     

Design and synthesis of lupeol analogues and their glucose uptake stimulatory effect in L6 skeletal muscle cells

Structure modifications of lupeol at the isopropylene moiety have been described via allylic oxidation using selenium dioxide. The antidiabetic efficacy of lupeol analogues were evaluated in vitro as glucose uptake stimulatory effect in L6 skeletal muscle cells. From all tested compounds, 2, 3, 4b and 6b showed significant stimulation of glucose uptake with respective percent stimulation of 173.1 (p <0.001), 114.1 (p <0.001), 98.3 (p <0.001) and 107.3 (p <0.001) at 10 μM concentration. Stimulation of glucose uptake by these compounds is associated with enhanced translocation of glucose transporter 4 (GLUT4) and activation of IRS-1/PI3-K/AKT-dependent signaling pathway in L6 cells. Structure–activity relationship analysis of these analogues demonstrated that the integrity of α,β-unsaturated carbonyl and acetyl moieties were important in the retention of glucose uptake stimulatory effect. It is therefore proposed that naturally occurring lupeol and their analogues might reduce blood glucose, at least in part, through stimulating glucose utilization by skeletal muscles.     

Synthesis and biological evaluation of berberine analogues as novel up-regulators for both low-density-lipoprotein receptor and insulin receptor

Berberine (BBR) is a natural compound with up-regulating activity on both low-density-lipoprotein receptor (LDLR) and insulin receptor (InsR). This one-drug-multiple-target characteristic might be suitable for the treatment of metabolic syndrome. In searching for up-regulators effective for both LDLR and InsR expression, the structure–activity relationship (SAR) analysis for BBR analogues was done. Fourteen BBR analogues were designed, synthesized and biologically evaluated. SAR analysis revealed that appropriate modifications on the phenyl ring A or D of BBR might retain the up-regulatory activities on the expression of both LDLR and InsR. Among these compounds, compound 13a bearing 9-methoxy and 10-hydroxyl on the ring D showed promising activities on either LDLR or InsR gene expression. The 10-hydroxyl of 13a could be an arm to connect proper chemical groups for optimizing drug-bioavailability in vivo. Thus, 13a could be considered to be a parent compound to make pro-drugs for either blood lipids or glucose.     

New antifungal scaffold derived from a natural pharmacophore: Synthesis of α-methylene-γ-butyrolactone derivatives and their antifungal activity against Colletotrichum lagenarium

Thirty new and thirty-four known analogues were designed and synthesized to improve the potential use of the α-methylene-γ-butyrolactone ring, a natural pharmacophore. All structures were confirmed by ¹H and ¹³C NMR, MS, and single-crystal X-ray diffraction analyses. The results of antifungal and cytotoxic activity indicated that the synthesized analogues showed significant inhibitory activity and limited selectivity. Compound 45 exhibited the highest antifungal activity with IC₅₀ = 22.8 μM but moderate cytotoxic activity with IC₅₀ = 28.5 μM (against BGC823 cell line) and 7.7 μM (against HeLa cell line). Analysis of structure–activity relationships revealed that the incorporation of an aromatic ring into the β, γ positions of the lactone ring improved antifungal activity, and that the introduction of electron-withdrawing groups into the aromatic rings increased the activity compared with electron-donating groups. The above results identified 4-phenyl-3-phenyl-2-methylenebutyrolactone (33) as a lead scaffold for discovering and developing novel and improved crop-protection agents.     

New triazinoindole bearing thiazole/oxazole analogues: Synthesis, α-amylase inhibitory potential and molecular docking study

New triazinoindole bearing thiazole/oxazole analogues (1–21) were synthesized and characterized through spectroscopic techniques such as HREI-MS, ¹H and ¹³C NMR. The configuration of compound 2i and 2k was confirmed through NOESY. All analogues were evaluated against α-amylase inhibitory potential. Among the synthesized analogues, compound 1h, 1i, 1j, 2a and 2f having IC₅₀ values 1.80 ± 0.20, 1.90 ± 0.30, 1.2 ± 0.30, 1.2 ± 0.01 and 1.30 ± 0.20 μM respectively, showed excellent α-amylase inhibitory potential when compared with acarbose as standard (IC₅₀ = 0.91 ± 0.20 µM). All other analogues showed good to moderate inhibitory potential. Structural activity relationship (SAR) has been established and binding interactions were confirmed through docking studies.     

Synthesis and activity evaluation of a series of cholanamides as modulators of the liver X receptors

The Liver X receptors (LXRs) are members of the nuclear receptor family, that play fundamental roles in cholesterol transport, lipid metabolism and modulation of inflammatory responses. In recent years, the synthetic steroid N,N-dimethyl-3β-hydroxycholenamide (DMHCA) arised as a promising LXR ligand. This compound was able to dissociate certain beneficial LXRs effects from those undesirable ones involved in triglyceride metabolism. Here, we synthetized a series of DMHCA analogues with different modifications in the steroidal nucleus involving the A/B ring fusion, that generate changes in the overall conformation of the steroid. The LXRα and LXRβ activity of these analogues was evaluated by using a luciferase reporter assay in BHK21 cells. Compounds were tested in both the agonist and antagonist modes. Results indicated that the agonist/antagonist profile is dependent on the steroid configuration at the A/B ring junction. Notably, in contrast to DMHCA, the amide derived from lithocholic acid (2) with an A/B cis configuration and its 6,19-epoxy analogue 4 behaved as LXRα selective agonists, while the 2,19-epoxy analogues with an A/B trans configuration were antagonists of both isoforms. The binding mode of the analogues to both LXR isoforms was assessed by using 50?ns molecular dynamics (MD) simulations. Results revealed conformational differences between LXRα- and LXRβ-ligand complexes, mainly in the hydrogen bonding network that involves the C-3 hydroxyl. Overall, these results indicate that the synthetized DMHCA analogues could be interesting candidates for a therapeutic modulation of the LXRs.     

Structural modifications of coumarin derivatives: Determination of antioxidant and lipoxygenase (LOX) inhibitory activity

In the present project, a series of coumarin analogues, were synthesised and evaluated for their antioxidant and soybean lipoxygenase inhibitory activity. A variety of structural modifications on the coumarin scaffold revealed interesting structure–activity relationships concerning the different biological assays. Prenyloxy-coumarins 9 and 10 displayed the best combined inhibition of lipid peroxidation and soybean lipoxygenase. Thiocoumarins 11 and 14 were identified as potent lipoxygenase inhibitors whereas hydrazone analogues 15 and 16 were efficient DPPH radical scavengers.     

Synthesis and evaluation of vitamin D3 analogues with C-11 modifications as inhibitors of Hedgehog signaling

Previous structure-activity relationship studies have provided potent and selective analogues of vitamin D3 as inhibitors of the Hedgehog (Hh) signaling pathway. These analogues contain both modified A- and seco-B ring motifs, and have been evaluated for anticancer therapeutic potential. To continue our studies on this scaffold, a new series of compounds were synthesized to explore additional interactions and spatial constraints. These compounds incorporate functional groups of varying size and hydrophobicity at the C-11 position. While large hydrophobic moieties (9c–e) resulted in significant loss of Hh inhibition, smaller or more flexible moieties (9a, 11) maintain anti-Hh activity. These results call for additional and continued studies to identify the binding pocket to better understand these structure-activity relationships.     

Discovery of hybrid Hsp90 inhibitors and their anti-neoplastic effects against gefitinib-resistant non-small cell lung cancer (NSCLC)

Heat shock protein 90 (Hsp90) represents an attractive cancer therapeutic target due to its role in the stabilization and maturation of many oncogenic proteins. We have designed a series of hybrid Hsp90 inhibitors by connecting the resorcinol ring of VER-49009 (2) and the trimethoxyphenyl ring of PU3 (3) using structure-based approach. Subsequent testing established that compound 1f inhibited gefitinib-resistant H1975 cell proliferation, brought about the degradation of Hsp90 client proteins including EGFR, Met, Her2 and Akt and induced the expression of Hsp70. The design, synthesis, and evaluation of 1f are described herein.     

Synthesis and biological activity of ester and ether analogues of α-galactosylceramide (KRN7000)

α-Galactosylceramide (αGalCer, KRN7000) has been identified as a modulator of immunological processes through its capacity to bind iNKT cells mediated by CD1d molecules. Some analogues in while the amide group in αGalCer is replaced with ester or ether groups were synthesized from d-arabinitol or l-ribose to evaluate their ability to activate iNKT cells. Ester analogues 30a, 31a, and 61 showed activity for IFNγ and IL-4 production of iNKT cells, while ether (31b) and 4-methoxy ester (76) analogues of α-galactosylceramide were not active for iNKT cells.     

Synthesis and activity evaluation of benzoylurea derivatives as potential antiproliferative agents

3-Haloacylamino benzoylureas (3-HBUs) consist of a new family of tubulin ligands that kill cancer cells through mitotic arrest. In exploring the structure–activity relationship (SAR), 17 analogues defined through variations of formylurea at the 1-position of the aromatic ring were synthesized. SAR analysis revealed that (i) the p–π conjugation between the aromatic ring and formylurea was essential; (ii) suitable aryl substitutions at the N′-end increased anticancer activity with a mechanism different from that of parent compounds; and (iii) introduction of pyridyl at the N′-end provided an opportunity of making soluble salts to improve bioavailability. Among the analogues, 16c bearing 3,4,5-trimethoxyphenyl and 16g bearing 2-pyridyl at the N′-end showed an enhanced activity and were active in hepatoma cells that were resistant to tubulin ligands including the parent compounds. Furthermore, 16c and 16g killed cancer cells with a mechanism independent of mitotic arrest, indicating a change of action mode.     

Synthesis and biological evaluation of novel triptolide analogues for anticancer activity

Three types of novel triptolide analogues with 9,11-olefin (3–5), five-membered unsaturated lactam ring (6–7) or A/B cis ring junction (8–14) were synthesized. Although with 9,11-olefin instead of 9,11-β-epoxide, compound 4a was much more active than the parent natural triptolide (1) with the lowest IC₅₀ value of 0.05 nM for SKOV-3 cells, clearly challenging the traditional viewpoint on the necessity of 9,11-β-epoxide group of triptolide. In addition, structure–activity relationships for three classes of compounds were studied.     

Inhibitory effects of ethacrynic acid analogues lacking the α,β-unsaturated carbonyl unit and para-acylated phenols on human cancer cells

A series of ethacrynic acid analogues, lacking the α,β-unsaturated carbonyl unit, was synthesized and subsequently evaluated for their ability to inhibit the migration of human breast cancer cells, Hs578Ts(i)8 as well as of human prostate cancer cells, C4-2B. These cell lines provide a good model system to study migration and invasion, since they represent metastatic cancer. Our studies show that ethacrynic acid analogues with methyl substituents at the aromatic ring demonstrate no inhibitory effect on the migration of both cancer cell lines, whereas a precursor in the synthesis of these ethacrynic acid analogues (II-1, a para-acylated m-cresol) is an excellent inhibitor of the migration of both cancer cell lines.     

Synthesis and biological evaluation of novel biaryl type α-noscapine congeners

Natural α-noscapine, a known antitussive drug, is also now known to possess weak anticancer efficacy with relatively safe toxicity profile. In this study, we report synthesis and evaluation of novel biaryl type α-noscapine congeners designed by adding aryl unit to the tetrahydroisoquinoline part of natural α-noscapine core. Palladium catalyzed Suzuki cross coupling of 9-bromo α-noscapine with aryl boronic acids was employed using mild and inexpensive reagents to attain desired noscapinoids 5a–g in excellent yields. Screening anti-proliferative activity for new noscapinoids 5b–g, on human cancer cell lines resulted three compounds 5b, 5d and 5f as potent analogues, active against human breast epithelial (MCF-7), human cervix cancer (HeLa) and human lung adenocarcinoma epithelial (A549) cell lines.     

Design,synthesis, and characterization of novel apigenin analogues that suppress pancreatic stellate cell proliferation in vitro and associated pancreatic fibrosis in vivo

Accumulating evidence suggests that activated pancreatic stellate cells (PSC) play an important role in chronic pancreatitis (CP), and inhibition of the activated PSC is considered as a potential strategy for the treatment and prevention of CP. Herein, we disclose our findings that apigenin and its novel analogues suppress the proliferation and induce apoptosis in PSC, which reduce the PSC-mediated fibrosis in CP. Chemical modifications of apigenin have been directed to build a focused library of O-alkylamino-tethered apigenin derivatives at 4′-O position of the ring C with the attempt to enhance the potency and drug-like properties including aqueous solubility. A number of compounds such as 14, 16, and 24 exhibited potent antiproliferative effects as well as improved aqueous solubility. Intriguingly, apigenin, new analogues 23 and 24 displayed significant efficacy to reduce pancreatic fibrosis even at a low dose of 0.5 mg/kg in our proof-of-concept study using a preclinical in vivo mouse model of CP.     

Synthesis and structure–activity relationship studies of MI-2 analogues as MALT1 inhibitors

Recent studies revealed that MALT1 is a promising therapeutic target for the treatment of ABC-DLBCL. Among several reported MALT1 inhibitors, MI-2 as an irreversible inhibitor represents a new class of ABC-DLBCL therapeutics. Due to its inherent potential cross-reactivity, further structure–activity relationship (SAR) study is imperative. In this work, five focused compound libraries based on the chemical structure of MI-2 are designed and synthesized. The systematic SARs revealed that the side chain of 2-methoxyethoxy has little impact on the activity and can be replaced by other functionalized groups, providing new MI-2 analogues with retained or enhanced potency. Compounds 81–83 with terminal hydroxyl group as side chain displayed enhanced activities against MALT1. Replacement of triazole core with pyrazole is also tolerant, while structural modifications on other sites are detrimental. These findings will facilitate further development of small-molecule MALT1 inhibitors.     

Evaluation of structural effects on 5-HT2A receptor antagonism by aporphines: Identification of a new aporphine with 5-HT2A antagonist activity

A set of aporphine analogs related to nantenine was evaluated for antagonist activity at 5-HT_2A and α_1A adrenergic receptors.With regards to 5-HT_2A receptor antagonism, a C2 allyl group is detrimental to activity. The chiral center of nantenine is not important for 5-HT_2A antagonist activity, however the N6 nitrogen atom is a critical feature for 5-HT_2A antagonism.Compound 12b was the most potent 5-HT_2A aporphine antagonist identified in this study and has similar potency to previously identified aporphine antagonists 2 and 3. The ring A and N6 modifications examined were detrimental to α_1A antagonism. A slight eutomeric preference for the R enantiomer of nantenine was observed in relation to α_1A antagonism.     

Structure–activity relationships of N-substituted 4-(trifluoromethoxy)benzamidines with affinity for GluN2B-containing NMDA receptors

GluN2B subtype-selective NMDA antagonists represent promising therapeutic targets for the symptomatic treatment of multiple CNS pathologies. A series of N-benzyl substituted benzamidines were synthesised and the benzyl ring was further replaced with various polycyclic moieties. Compounds were evaluated for activity at GluN2B containing NMDA receptors where analogues 9, 12, 16 and 18 were the most potent of the series, replacement of the benzyl ring with polycycles resulted in a complete loss of activity.     

Chemoenzymatic synthesis and antileukemic activity of novel C9- and C14-functionalized parthenolide analogs

Parthenolide is a naturally occurring terpene with promising anticancer properties, particularly in the context of acute myeloid leukemia (AML). Optimization of this natural product has been challenged by limited opportunities for the late-stage functionalization of this molecule without affecting the pharmacologically important α-methylene-γ-lactone moiety. Here, we report the further development and application of a chemoenzymatic strategy to afford a series of new analogs of parthenolide functionalized at the aliphatic positions C9 and C14. Several of these compounds were determined to be able to kill leukemia cells and patient-derived primary AML specimens with improved activity compared to parthenolide, exhibiting LC₅₀ values in the low micromolar range. These studies demonstrate that different O–H functionalization chemistries can be applied to elaborate the parthenolide scaffold and that modifications at the C9 or C14 position can effectively enhance the antileukemic properties of this natural product. The C9-functionalized analogs 22a and 25b were identified as the most interesting compounds in terms of antileukemic potency and selectivity toward AML versus healthy blood cells.