Synthesis and Biological Evaluation of Novel Homoisoflavonoids for Retinal Neovascularization

Structure-activity relationship study of novel evodiamine amino acid conjugates with potent anti-colorectal cancer efficacy

Evodiamine has been a promising lead structure with broad-spectrum antitumor activity. Druggability optimization is the most challenging part of evodiamine-based lead-to-candidate campaign. Amino acids as building blocks for conjugates are widely incorporated into approved drug and drug candidates, demonstrating highly attractive druggability. Herein, a series of evodiamine amino acid conjugates were designed and synthesized based on the evodiamine lead compound (±)-8b discovered in our previous work. The structure-activity relationship (SAR) studies culminated in the identification of a promising conjugate (-)-15h featuring a N-Boc-l-glutamine group and a chiral carbon atom (sinister), which exhibited nanomolar antiproliferative activity against LoVo and RKO colorectal cancer cells. Moreover, (-)-15h could inhibit topoisomerases I, arrest the cell cycle in the G2/M phase, and induce apoptosis. Importantly, (-)-15h (tumor growth inhibition rate was 82.53 % in 40 mpk) showed better efficacy and tolerability to that of parent compound (-)-8b (tumor growth inhibition rate was 51.22 % in 40 mpk) in LoVo xenograft model. Further, (-)-15h (tumor growth inhibition rate was 70.09 % in 40 mpk) showed comparable efficacy and better tolerability to that of topotecan (tumor growth inhibition rate was 70.67 % in 0.5 mpk) in HT-29 xenograft model. Collectively, this study further provided a strong scientific basis for amino acid-based structural modifications and a drug lead for anti-colorectal cancer applications.

Exploring the Antiangiogenic and Anti-Inflammatory Potential of Homoisoflavonoids: Target Identification Using Biotin Probes

Chemical proteomics using biotin probes of natural products have significantly advanced our understanding of molecular targets and therapeutic potential. This review highlights recent progress in the application of biotin probes of homoisoflavonoids for identifying binding proteins and elucidating mechanisms of action. Notably, homoisoflavonoids exhibit antiangiogenic, anti-inflammatory, and antidiabetic effects. A combination of biotin probes, pull-down assays, mass spectrometry, and molecular modeling has revealed how natural products and their derivatives interact with several proteins such as ferrochelatase (FECH), soluble epoxide hydrolase (sEH), inosine monophosphate dehydrogenase 2 (IMPDH2), phosphodiesterase 4 (PDE4), and deoxyhypusine hydroxylase (DOHH). These target identification approaches pave the way for new therapeutic avenues, especially in the fields of oncology and ophthalmology. Future research aimed at expanding the repertoire of target identification using biotin probes of homoisoflavonoids promises to further elucidate the complex mechanisms and develop new drug candidates.

A Synthetic Derivative SH 66 of Homoisoflavonoid from Liliaceae Exhibits Anti-Neuroinflammatory Activity against LPS-Induced Microglial Cells

Naturally occurring homoisoflavonoids isolated from some Liliaceae plants have been reported to have diverse biological activities (e.g., antioxidant, anti-inflammatory, and anti-angiogenic effects). The exact mechanism by which homoisoflavonones exert anti-neuroinflammatory effects against activated microglia-induced inflammatory cascades has not been well studied. Here, we aimed to explore the mechanism of homoisoflavonoid SH66 having a potential anti-inflammatory effect in lipopolysaccharide (LPS)-primed BV2 murine microglial cells. Microglia cells were pre-treated with SH66 followed by LPS (100 ng/mL) activation. SH66 treatment attenuated the production of inflammatory mediators, including nitric oxide and proinflammatory cytokines, by down-regulating mitogen-activated protein kinase signaling in LPS-activated microglia. The SH66-mediated inhibition of the nucleotide-binding oligomerization domain-like receptor family pyrin domain containing 3 (NLRP3) inflammasome complex and the respective inflammatory biomarker-like active interleukin (IL)-1β were noted to be one of the key pathways of the anti-inflammatory effect. In addition, SH66 increased the neurite length in the N2a neuronal cell and the level of nerve growth factor in the C6 astrocyte cell. Our results demonstrated the anti-neuroinflammatory effect of SH66 against LPS-activated microglia-mediated inflammatory events by down-regulating the NLRP3 inflammasome complex, with respect to its neuroprotective effect. SH66 could be an interesting candidate for further research and development regarding prophylactics and therapeutics for inflammation-mediated neurological complications.

Challenges and opportunities of developing small-molecule therapies for age-related macular degeneration

Age-related macular degeneration (AMD) is the leading cause of vision loss in senior adults. The disease can be categorized into two types: wet AMD and dry AMD. Wet AMD, also known as exudative or neovascular AMD, is less common but more severe than dry AMD and is responsible for 90% of the visual impairment caused by AMD and affects 20 million people worldwide. Current treatment options mainly involve biologics that inhibit the vascular endothelial growth factor or complement pathways. However, these treatments have limitations such as high cost, injection-related risks, and limited efficacy. Therefore, new therapeutic targets and strategies have been explored to improve the outcomes of patients with AMD. A promising approach is the use of small-molecule drugs that modulate different factors involved in AMD pathogenesis, such as tyrosine kinases and integrins. Small-molecule drugs offer advantages, such as oral administration, low cost, good penetration, and increased specificity for the treatment of wet and dry AMD. This review summarizes the current status and prospects of small-molecule drugs for the treatment of wet AMD. These advances are expected to support the development of effective and targeted treatments for patients with AMD.

Cremastranone-Derived Homoisoflavanes Suppress the Growth of Breast Cancer Cells via Cell Cycle Arrest and Caspase-Independent Cell Death

Breast cancer is the most common cancer and a frequent cause of cancer-related deaths among women wordlwide. As therapeutic strategies for breast cancer have limitations, novel chemotherapeutic reagents and treatment strategies are needed. In this study, we investigated the anti-cancer effect of synthetic homoisoflavane derivatives of cremastranone on breast cancer cells. Homoisoflavane derivatives, SH-17059 and SH-19021, reduced cell proliferation through G2/M cell cycle arrest and induced caspase-independent cell death. These compounds increased heme oxygenase-1 (HO-1) and 5-aminolevulinic acid synthase 1 (ALAS1), suggesting downregulation of heme. They also induced reactive oxygen species (ROS) generation and lipid peroxidation. Furthermore, they reduced expression of glutathione peroxidase 4 (GPX4). Therefore, we suggest that the SH-17059 and SH-19021 induced the caspase-independent cell death through the accumulation of iron from heme degradation, and the ferroptosis might be one of the potential candidates for caspase-independent cell death.

Synthesis of proposed structure of ledebourin A

Naturally occurring homoisoflavonoids have attracted significant attention in the field of medicinal chemistry due to their potential health benefits and diverse range of biological properties. Recently, C-prenylated homoisoflavonoids, namely ledebourin A, B, and C, were isolated from the bulbs of Ledebouria floribunda and have exhibited potent antioxidant activity. In this study, we successfully synthesized ledebourin A and its regioisomer, compounds 1 and 9. By comparing the NMR spectra of the synthesized compounds with those of reported ledebourin A, we observed discrepancies. Nonetheless, our synthesis and subsequent findings offer valuable insights into the structural revision and biological activities of these unique prenylated homoisoflavonoids. Both synthesized compounds 1 and 9 exhibited no toxicity towards Hep-G2 cells and displayed the ability to recover glyceraldehyde-induced cell death, suggesting their potential as protective agents against liver damage.

Beyond VEGF: Targeting Inflammation and Other Pathways for Treatment of Retinal Disease

Neovascular eye diseases include conditions such as retinopathy of prematurity, proliferative diabetic retinopathy, and neovascular age-related macular degeneration. Together, they are a major cause of vision loss and blindness worldwide. The current therapeutic mainstay for these diseases is intravitreal injections of biologics targeting vascular endothelial growth factor (VEGF) signaling. Lack of universal response to these anti-VEGF agents coupled with the challenging delivery method underscore a need for new therapeutic targets and agents. In particular, proteins that mediate both inflammatory and proangiogenic signaling are appealing targets for new therapeutic development. Here, we review agents currently in clinical trials and highlight some promising targets in preclinical and early clinical development, focusing on the redox-regulatory transcriptional activator APE1/Ref-1, the bioactive lipid modulator soluble epoxide hydrolase, the transcription factor RUNX1, and others. Small molecules targeting each of these proteins show promise for blocking neovascularization and inflammation. The affected signaling pathways illustrate the potential of new antiangiogenic strategies for posterior ocular disease. SIGNIFICANCE STATEMENT: Discovery and therapeutic targeting of new angiogenesis mediators is necessary to improve treatment of blinding eye diseases like retinopathy of prematurity, diabetic retinopathy, and neovascular age-related macular degeneration. Novel targets undergoing evaluation and drug discovery work include proteins important for both angiogenesis and inflammation signaling, including APE1/Ref-1, soluble epoxide hydrolase, RUNX1, and others.

The Adaptor Protein NumbL Is Involved in the Control of Glucolipotoxicity-Induced Pancreatic Beta Cell Apoptosis

Avoiding the loss of functional beta cell mass is critical for preventing or treating diabetes. Currently, the molecular mechanisms underlying beta cell death are partially understood, and there is a need to identify new targets for developing novel therapeutics to treat diabetes. Previously, our group established that Mig6, an inhibitor of EGF signaling, mediates beta cell death under diabetogenic conditions. The objective here was to clarify the mechanisms linking diabetogenic stimuli to beta cell death by investigating Mig6-interacting proteins. Using co-immunoprecipitation and mass spectrometry, we evaluated the binding partners of Mig6 under both normal glucose (NG) and glucolipotoxic (GLT) conditions in beta cells. We identified that Mig6 interacted dynamically with NumbL, whereas Mig6 associated with NumbL under NG, and this interaction was disrupted under GLT conditions. Further, we demonstrated that the siRNA-mediated suppression of NumbL expression in beta cells prevented apoptosis under GLT conditions by blocking the activation of NF-κB signaling. Using co-immunoprecipitation experiments, we observed that NumbL's interactions with TRAF6, a key component of NFκB signaling, were increased under GLT conditions. The interactions among Mig6, NumbL, and TRAF6 were dynamic and context-dependent. We proposed a model wherein these interactions activated pro-apoptotic NF-κB signaling while blocking pro-survival EGF signaling under diabetogenic conditions, leading to beta cell apoptosis. These findings indicated that NumbL should be further investigated as a candidate anti-diabetic therapeutic target.

PRMT5 is a therapeutic target in choroidal neovascularization

Ocular neovascular diseases including neovascular age-related macular degeneration (nvAMD) are widespread causes of blindness. Patients' non-responsiveness to currently used biologics that target vascular endothelial growth factor (VEGF) poses an unmet need for novel therapies. Here, we identify protein arginine methyltransferase 5 (PRMT5) as a novel therapeutic target for nvAMD. PRMT5 is a well-known epigenetic enzyme. We previously showed that PRMT5 methylates and activates a proangiogenic and proinflammatory transcription factor, the nuclear factor kappa B (NF-κB), which has a master role in tumor progression, notably in pancreatic ductal adenocarcinoma and colorectal cancer. We identified a potent and specific small molecule inhibitor of PRMT5, PR5-LL-CM01, that dampens the methylation and activation of NF-κB. Here for the first time, we assessed the antiangiogenic activity of PR5-LL-CM01 in ocular cells. Immunostaining of human nvAMD sections revealed that PRMT5 is highly expressed in the retinal pigment epithelium (RPE)/choroid where neovascularization occurs, while mouse eyes with laser induced choroidal neovascularization (L-CNV) showed PRMT5 is overexpressed in the retinal ganglion cell layer and in the RPE/choroid. Importantly, inhibition of PRMT5 by PR5-LL-CM01 or shRNA knockdown of PRMT5 in human retinal endothelial cells (HRECs) and induced pluripotent stem cell (iPSC)-derived choroidal endothelial cells (iCEC2) reduced NF-κB activity and the expression of its target genes, such as tumor necrosis factor α (TNF-α) and VEGF-A. In addition to inhibiting angiogenic properties of proliferation and tube formation, PR5-LL-CM01 blocked cell cycle progression at G1/S-phase in a dose-dependent manner in these cells. Thus, we provide the first evidence that inhibition of PRMT5 impedes angiogenesis in ocular endothelial cells, suggesting PRMT5 as a potential therapeutic target to ameliorate ocular neovascularization.

Synthesis and Structure Revision of Naturally Occurring Homoisoflavane (+)-Dracaeconolide B

Dracaeconolide B (1), a naturally occurring homoisoflavane, was isolated from the red resin of Dracaena cochinchinensis. Efforts have been made to elucidate the exact structure of compound 1 since it was confirmed that dracaeconolide B did not contain a 7-hydroxy-5,8-dimethoxy moiety. The structure of dracaeconolide B was revised by synthesis of three homoisoflavanes containing a 5,6,7-trioxygenated moiety each and analysis by NMR spectroscopy. The revised structure of dracaeconolide B was proposed as 3-(4-hydroxybenzyl)-7-hydroxy-5,6-dimethoxychromane. Noyori's Ru-catalyzed asymmetric transfer hydrogenation was used to synthesize (+)-dracaeconolide B. The absolute configuration of the compound was revised to S based on the results obtained by the electronic circular dichroism calculation. We examined the antiangiogenic activity of (S)- and (R)-dracaeconolide B and of synthetic 5,6,7- and 5,7,8-trioxygenated homoisoflavanes. The results can potentially help in the synthesis of related natural products and support drug discovery to treat neovascular eye diseases.

Synthetic Homoisoflavane Derivatives of Cremastranone Suppress Growth of Colorectal Cancer Cells through Cell Cycle Arrest and Induction of Apoptosis

Colorectal cancer is diagnosed as the third most prevalent cancer; thus, effective therapeutic agents are urgently required. In this study, we synthesized six homoisoflavane derivatives of cremastranone and investigated their cytotoxic effects on the human colorectal cancer cell lines HCT116 and LoVo. We further examined the related mechanisms of action using two of the potent compounds, SH-19027 and SHA-035. They substantially reduced the cell viability and proliferation in a dose-dependent manner. Treatment with SH-19027 and SHA-035 induced cell cycle arrest at the G2/M phase and increased expression of p21 both of which are implicated in cell cycle control. In addition, the apoptotic cell population and apoptosis-associated marker expression were accordingly increased. These results suggest that the synthesized cremastranone derivatives have anticancer effects through the suppression of cell proliferation and induction of apoptosis. Therefore, the synthesized cremastranone derivatives could be applied as novel therapeutic agents against colorectal cancer.

Redox-neutral and metal-free synthesis of 3-(arylmethyl)chroman-4-ones via visible-light-driven alkene acylarylation

A metal- and aldehyde-free visible-light-driven photoredox-neutral alkene acylarylation with readily available cyanoarenes is described. A variety of 3-(arylmethyl)chroman-4-ones (i.e., homoisoflavonoids) and analogs are efficiently synthesized with good functional group tolerance. This mild protocol relies on a phosphoranyl radical-mediated acyl radical-initiated cyclization and selective radical-radical coupling sequence, and is also further highlighted by subsequent derivatization to chromone and 2H-chromene as well as its application in the three-component alkene acylarylation.

Total Synthesis and Antibacterial Evaluation of Empetroxepins A and B and related analogs

Empetroxepins A and B, which are 10,11-dihydrodibenz[b,f]oxepins produced by the Black Crowberry (Empetrum nigrum), displayed weak anti-tubercular activity upon isolation, but have not been explored for antibiotic activity despite their molecular similarity to other phenolic antibacterial natural products. Herein we detail the first total synthesis of Empetroxepins A and B via a selective demethylation strategy and antibacterial structure activity relationship (SAR) study of the natural products and related analogs. Empetroxepin A was found to be weakly active against susceptible strains of Staphylococcus aureus (SA) and Bacillus subtilis (BS) with MICs = 256 μg/mL against both, whereas Empetroxepin B was found to be weakly active against only BS (MIC = 256 μg/mL). Neither natural product was active against Escherichia coli (EC). Antibiotic activity was improved through derivatization of the 10,11-dihydrodibenz[b,f]oxepin core with the best compound of the SAR series, 9-chloro-10,11-dihydrodibenzo[b,f]oxepine-2,3,4-triol, having MICs of 8 μg/mL, 16 μg/mL, and 256 μg/mL against SA, BS, and EC respectively.

Asymmetric hydrogenation and transfer hydrogenation in the enantioselective synthesis of flavonoids

In this review, we explore the applications of Asymmetric Hydrogenation (AH) and Asymmetric Transfer Hydrogenation (ATH) in the total synthesis of natural flavonoids and their analogues, highlighting the limitations and opportunities in the field.

Inhibition of APE1/Ref-1 for Neovascular Eye Diseases: From Biology to Therapy

Proliferative diabetic retinopathy (PDR), neovascular age-related macular degeneration (nvAMD), retinopathy of prematurity (ROP) and other eye diseases are characterized by retinal and/or choroidal neovascularization, ultimately causing vision loss in millions of people worldwide. nvAMD and PDR are associated with aging and the number of those affected is expected to increase as the global median age and life expectancy continue to rise. With this increase in prevalence, the development of novel, orally bioavailable therapies for neovascular eye diseases that target multiple pathways is critical, since current anti-vascular endothelial growth factor (VEGF) treatments, delivered by intravitreal injection, are accompanied with tachyphylaxis, a high treatment burden and risk of complications. One potential target is apurinic/apyrimidinic endonuclease 1/reduction-oxidation factor 1 (APE1/Ref-1). The multifunctional protein APE1/Ref-1 may be targeted via inhibitors of its redox-regulating transcription factor activation activity to modulate angiogenesis, inflammation, oxidative stress response and cell cycle in neovascular eye disease; these inhibitors also have neuroprotective effects in other tissues. An APE1/Ref-1 small molecule inhibitor is already in clinical trials for cancer, PDR and diabetic macular edema. Efforts to develop further inhibitors are underway. APE1/Ref-1 is a novel candidate for therapeutically targeting neovascular eye diseases and alleviating the burden associated with anti-VEGF intravitreal injections.

An Efficient Regioselective Synthesis of 8-Formylhomoisoflavonoids with Neuroprotective Activity by Enhancing Autophagy

6-Formylisoophiopogonone B (7a) and 8-formylophiopogonone B (7b), two natural products isolated from Ophiopogon japonicus, represent a subgroup of rare 6/8-formyl/methyl-homoisoflavonoid skeletons. Herein we report an efficient method for the synthesis of these formyl/methyl-homoisoflavonoids. The synthesized compounds were evaluated for their neuroprotective effects on the MPP⁺-induced SH-SY5Y cell injury model and showed marked activity. Exploration of the neuroprotective mechanisms of compound 7b led to an increased expression of autophagy marker LC3-II and down-regulation of autophagy substrate p62/SQSTM1. Molecular docking studies showed that 7b may prevent the inhibition of the classic PI3K-AKT-mTOR signaling pathway by interfering with the human HSP90AA1.

Ferrochelatase regulates retinal neovascularization

Ferrochelatase (FECH) is the terminal enzyme in heme biosynthesis. We previously showed that FECH is required for endothelial cell growth in vitro and choroidal neovascularization in vivo. But FECH has not been explored in retinal neovascularization, which underlies diseases like proliferative diabetic retinopathy and retinopathy of prematurity. Here, we investigated the inhibition of FECH using genetic and chemical approaches in the oxygen-induced retinopathy (OIR) mouse model. In OIR mice, FECH expression is upregulated and co-localized with neovascular tufts. Partial loss-of-function Fechm1Pas  mutant mice showed reduced retinal neovascularization and endothelial cell proliferation in OIR. An intravitreal injection of the FECH inhibitor N-methyl protoporphyrin had similar effects. Griseofulvin is an antifungal drug that inhibits FECH as an off-target effect. Strikingly, intravitreal griseofulvin decreased both pathological tuft formation and areas of vasoobliteration compared to vehicle, suggesting potential as a FECH-targeting therapy. Ocular toxicity studies revealed that intravitreal injection of griseofulvin in adult mice does not disrupt retinal vasculature, function, or morphology. In sum, mutation and chemical inhibition of Fech reduces retinal neovascularization and promotes physiological angiogenesis, suggesting a dual effect on vascular repair upon FECH inhibition, without ocular toxicity. These findings suggest that FECH inhibitors could be repurposed to treat retinal neovascularization.

Pharmacological Potential of Small Molecules for Treating Corneal Neovascularization

Under healthy conditions, the cornea is an avascular structure which allows for transparency and optimal visual acuity. Its avascular nature is maintained by a balance of proangiogenic and antiangiogenic factors. An imbalance of these factors can result in abnormal blood vessel proliferation into the cornea. This corneal neovascularization (CoNV) can stem from a variety of insults including hypoxia and ocular surface inflammation caused by trauma, infection, chemical burns, and immunological diseases. CoNV threatens corneal transparency, resulting in permanent vision loss. Mainstay treatments of CoNV have partial efficacy and associated side effects, revealing the need for novel treatments. Numerous natural products and synthetic small molecules have shown potential in preclinical studies in vivo as antiangiogenic therapies for CoNV. Such small molecules include synthetic inhibitors of the vascular endothelial growth factor (VEGF) receptor and other tyrosine kinases, plus repurposed antimicrobials, as well as natural source-derived flavonoid and non-flavonoid phytochemicals, immunosuppressants, vitamins, and histone deacetylase inhibitors. They induce antiangiogenic and anti-inflammatory effects through inhibition of VEGF, NF-κB, and other growth factor receptor pathways. Here, we review the potential of small molecules, both synthetics and natural products, targeting these and other molecular mechanisms, as antiangiogenic agents in the treatment of CoNV.

Ocular Disease Therapeutics: Design and Delivery of Drugs for Diseases of the Eye

The ocular drug discovery field has evidenced significant advancement in the past decade. The FDA approvals of Rhopressa, Vyzulta, and Roclatan for glaucoma, Brolucizumab for wet age-related macular degeneration (wet AMD), Luxturna for retinitis pigmentosa, Dextenza (0.4 mg dexamethasone intracanalicular insert) for ocular inflammation, ReSure sealant to seal corneal incisions, and Lifitegrast for dry eye represent some of the major developments in the field of ocular therapeutics. A literature survey also indicates that gene therapy, stem cell therapy, and target discovery through genomic research represent significant promise as potential strategies to achieve tissue repair or regeneration and to attain therapeutic benefits in ocular diseases. Overall, the emergence of new technologies coupled with first-in-class entries in ophthalmology are highly anticipated to restructure and boost the future trends in the field of ophthalmic drug discovery. This perspective focuses on various aspects of ocular drug discovery and the recent advances therein. Recent medicinal chemistry campaigns along with a brief overview of the structure-activity relationships of the diverse chemical classes and developments in ocular drug delivery (ODD) are presented.

Total Synthesis of Naturally Occurring 5,7,8-Trioxygenated Homoisoflavonoids

Homoisoflavonoids are in the subclass of the larger family of flavonoids but have one more alkyl carbon than flavonoids. Among them, 5,7,8-trioxygenated homoisoflavonoids have not been extensively studied for synthesis and biological evaluation. Our current objective is to synthesize 2 5,7,8-trioxygenated chroman-4-ones and 12 5,7,8-trioxygenated homoisoflavonoids that have been isolated from the plants Bellevalia eigii, Drimiopsis maculata, Ledebouria graminifolia, Eucomis autumnalis, Eucomis punctata, Eucomis pallidiflora, Chionodoxa luciliae, Muscari comosum, and Dracaena cochinchinensis. For this purpose, 1,3,4,5-tetramethoxybenzene and 4'-benzyloxy-2',3'-dimethoxy-6'-hydroxyacetophenone were used as starting materials. Asymmetric transfer hydrogenation using Noyori's Ru catalyst provided 5,7,8-trioxygenated-3-benzylchroman-4-ones with R-configuration in high yield and enantiomeric excess. By selective deprotection of homoisoflavonoids using BCl3, the total synthesis of natural products including 10 first syntheses and three asymmetric syntheses has been completed, and three isomers of the reported dracaeconolide B could be provided. Our research on 5,7,8-trioxygenated homoisoflavonoids would be useful for the synthesis of related natural products and pharmacological applications.

Bufadienolides and anti-angiogenic homoisoflavonoids from Rhodocodon cryptopodus, Rhodocodon rotundus and Rhodocodon cyathiformis

BACKGROUND

Homoisoflavonoids have been shown to have potent anti-proliferative activities in endothelial cells over other cell types and have demonstrated a strong antiangiogenic potential in vitro and in vivo in animal models of ocular neovascularization. Three species of Rhodocodon (Scilloideaea subfamily of the Asparagaceae family), endemic to Madagascar, R. cryptopodus, R. rotundus and R. cyathiformis, were investigated.

PURPOSE

To isolate and test homoisoflavonoids for their antiangiogenic activity against human retinal microvascular endothelial cells (HRECs), as well as specificity against other ocular cell lines.

METHODS

Plant material was extracted at room temperature with EtOH. Compounds were isolated using flash column chromatography and were identified using NMR and CD spectroscopy and HRESIMS. Compounds were tested for antiproliferative effects on primary human microvascular retinal endothelial cells (HRECs), ARPE19 retinal pigment epithelial cells, 92-1 uveal melanoma cells, and Y79 retinoblastoma cells. HRECs exposed to compounds were also tested for migration and tube formation ability.

RESULTS

Two homoisoflavonoids, 3S-5,7-dihydroxy-(3'-hydroxy-4'-methoxybenzyl)-4-chromanone (1) and 3S-5,7-dihydroxy-(4'-hydroxy-3'-methoxybenzyl)-4-chromanone (2), were isolated along with four bufadienolides. Compound 1 was found to be non-specifically antiproliferative, with GI50 values ranging from 0.21-0.85 μM across the four cell types, while compound 2 showed at least 100-fold specificity for HRECs over the other tested cell lines. Compound 1, with a 3S configuration, was 700 times more potent that the corresponding 3R enantiomer recently isolated from a Massonia species.

CONCLUSION

Select homoisoflavonoids have promise as antiangiogenic agents that are not generally cytotoxic.

Brønsted Acid Catalyzed Tandem Defunctionalization of Biorenewable Ferulic acid and Derivates into Bio-Catechol

An efficient conversion of biorenewable ferulic acid into bio-catechol has been developed. The transformation comprises two consecutive defunctionalizations of the substrate, that is, C-O (demethylation) and C-C (de-2-carboxyvinylation) bond cleavage, occurring in one step. The process only requires heating of ferulic acid with HCl (or H₂ SO₄ ) as catalyst in pressurized hot water (250 °C, 50 bar N₂ ). The versatility is shown on a variety of other (biorenewable) substrates yielding up to 84 % di- (catechol, resorcinol, hydroquinone) and trihydroxybenzenes (pyrogallol, hydroxyquinol), in most cases just requiring simple extraction as work-up.

Synthesis and Neuroprotective Biological Evaluation of Quinazolinone Derivatives via Scaffold Hopping

Objective:

To develop efficient method for the synthesis of quinazolinone derivatives bearing different functional groups on ring A and ring B and evaluation as neuroprotective agents.

Methods:

Synthetic route to quinazolinone derivatives was furnished by condensation/cyclocondensation/ reduction sequence of the activated N-acylbenzotriazoles. The structures of the targets compounds have been deduced upon their spectral data (1HNMR, 13CNMR and Mass spectroscopy). The neuroprotective activities of the synthesized compounds are also evaluated.

Results:

Preliminary screening on a MPP+ induced SH-SY5Y cell injury model of the synthesized compounds resulted in four compounds (6q, 6r, 6u, and 8e) showed promising neural cell protection activities. The action mechanisms of these compounds on neuroprotection were then analyzed by docking and reverse docking modeling.

Conclusion:

A series of quinazolinone derivatives, including different substitution types on rings A and B were designed and synthesized via scaffold hopping. With the help of neuroprotective biological evaluation, several efficient therapeutic neuroprotective agents were found for further evaluation as drug candidate against neurodegenerative disorder.

Pd-Catalyzed sequential hydroarylation and olefination reactions of 3-allylchromones

In this paper, a novel approach to regioselective α- or γ-hydroarylation of 3-allylchromones with electron-rich arenes has been presented. Results of this study indicated that the regioselectivity was dependent on the substituent at the γ-position of the allyl group. Hydrogen or alkyl substitution favored α-hydroarylation, whereas aryl substitution favored γ-hydroarylation. This methodology provides an efficient means to achieve the α- or γ-selective hydroarylation of 3-allylchromones. Application of α-hydroarylation to perform Pd-catalyzed one-pot sequential α-hydroarylation and π-chelation-assisted olefination has also been reported.

Prospective Application of Activity-Based Proteomic Profiling in Vision Research-Potential Unique Insights into Ocular Protease Biology and Pathology

Activity-based proteomic profiling (ABPP) is a powerful tool to specifically target and measure the activity of a family of enzymes with the same function and reactivity, which provides a significant advantage over conventional proteomic strategies that simply provide abundance information. A number of inherited and age-related eye diseases are caused by polymorphisms/mutations or abnormal expression of proteases including serine proteases, cysteine proteases, and matrix metalloproteinases, amongst others. However, neither conventional genomic, transcriptomic, nor traditional proteomic profiling directly interrogate protease activities. Thus, leveraging ABPP to probe the activity of these enzyme classes as they relate to normal function and pathophysiology of the eye represents a unique potential opportunity for disease interrogation and possibly intervention.

Enantioselective Synthesis of Homoisoflavanones by Asymmetric Transfer Hydrogenation and Their Biological Evaluation for Antiangiogenic Activity

Neovascular eye diseases are a major cause of blindness. Excessive angiogenesis is a feature of several conditions, including wet age-related macular degeneration, proliferative diabetic retinopathy, and retinopathy of prematurity. Development of novel antiangiogenic small molecules for the treatment of neovascular eye disease is essential to provide new therapeutic leads for these diseases. We have previously reported the therapeutic potential of anti-angiogenic homoisoflavanone derivatives with efficacy in retinal and choroidal neovascularization models, although these are racemic compounds due to the C3-stereogenic center in the molecules. This work presents asymmetric synthesis and structural determination of anti-angiogenic homoisoflavanones and pharmacological characterization of the stereoisomers. We describe an enantioselective synthesis of homoisoflavanones by virtue of ruthenium-catalyzed asymmetric transfer hydrogenation accompanying dynamic kinetic resolution, providing a basis for the further development of these compounds into novel experimental therapeutics for neovascular eye diseases.

Mouse Pharmacokinetics and in Vitro Metabolism of (±)-Cremastranone

The objective of this study was to characterize pharmacokinetics and metabolism of (±)-cremastranone (CMT) in mouse. Plasma concentrations of CMT following a single oral dose (10 mg/kg) were all below quantitation limit throughout 24-h time course, indicating poor oral bioavailability. Its plasma levels declined rapidly, with a half-life (t_1/2) of 1.5 ± 0.3 min following a single intravenous dose (5 mg/kg). They were below the quantitation limit after 15 min post-dosing. CMT showed a high plasma clearance (CL_p) of 7.73 ± 3.09 L/h/kg. Consistently, CMT was metabolized rapidly, with a t_1/2 < 1 min when it was incubated with liver or intestine S9 fractions of mouse and human in the presence of cofactors for CYP450, uridine 5'-diphosphate (UDP)-glucuronosyltransferase (UGT), and sulfotransferase (ST). Further studies showed that CMT was metabolized by CYP450, UGT, and ST in vitro in liver S9 fractions of mouse and human, with UGT being the major enzyme responsible for its rapid metabolism. CMT was metabolized by UGT and ST in intestine S9 fractions of mouse and human. Mono-demethylated (M1), mono-glucuronide (M2), and mono-sulfate (M3 and M4) metabolites were tentatively identified in vitro. In conclusion, the pharmacokinetics of CMT is suboptimal as a systemic agent, especially as an oral therapy, due to its extensive metabolism. This report provides possible structural modifications to design CMT derivatives with better pharmacokinetic properties.

The Antiangiogenic Activity of Naturally Occurring and Synthetic Homoisoflavonoids from the Hyacinthaceae ( sensu APGII)

Excessive blood vessel formation in the eye is implicated in wet age-related macular degeneration, proliferative diabetic retinopathy, neovascular glaucoma, and retinopathy of prematurity, which are major causes of blindness. Small molecule antiangiogenic drugs are strongly needed to supplement existing biologics. Homoisoflavonoids have been previously shown to have potent antiproliferative activities in endothelial cells over other cell types. Moreover, they demonstrated a strong antiangiogenic potential in vitro and in vivo in animal models of ocular neovascularization. Here, we tested the antiangiogenic activity of a group of naturally occurring homoisoflavonoids isolated from the family Hyacinthaceae and related synthetic compounds, chosen for synthesis based on structure-activity relationship observations. Several compounds showed interesting antiproliferative and antiangiogenic activities in vitro on retinal microvascular endothelial cells, a disease-relevant cell type, with the synthetic chromane, 46, showing the best activity (GI50 of 2.3 × 10-4 μM).

Naturally Occurring Homoisoflavonoids: Phytochemistry, Biological Activities, and Synthesis (Part II)

This review documents all the new homoisoflavonoids (HIFs) that have been reported since 2007, whose total number has grown from 159 in 2007 to 295 at the present time. This review contains their structures, biological sources, plant parts they are obtained from, and, if reported, their optical rotations and melting points. The same classification is followed as an earlier review to ease reference to both reviews. This review takes note of the recent revision of plant families that were known to contain HIFs that have now been merged into one big family, Asparagaceae. Homoisoflavonoids also occur in Fabaceae and others. Two taxa, Ophiopogoan japonicus (Asparagaceae) and Caesalpinia sappan (Fabaceae), have been the source of many HIFs. These are briefly summarized. The biological properties of HIFs are also reviewed under the topics such as antioxidant, anti-inflammatory, antimicrobial, antidiabetic, and cytotoxic. The review also surveys the total synthesis of natural HIFs. All new compounds are classified and tabulated following the same style as the previous review.

Dedicated to Professor Andrew Paul Krapcho on the occasion of his 87th Birthday.

Nutraceuticals for the Treatment of Diabetic Retinopathy

Diabetic retinopathy (DR) is one of the most common complications of diabetes mellitus and is characterized by degeneration of retinal neurons and neoangiogenesis, causing a severe threat to vision. Nowadays, the principal treatment options for DR are laser photocoagulation, vitreoretinal surgery, or intravitreal injection of drugs targeting vascular endothelial growth factor. However, these treatments only act at advanced stages of DR, have short term efficacy, and cause side effects. Treatment with nutraceuticals (foods providing medical or health benefits) at early stages of DR may represent a reasonable alternative to act upstream of the disease, preventing its progression. In particular, in vitro and in vivo studies have revealed that a variety of nutraceuticals have significant antioxidant and anti-inflammatory properties that may inhibit the early diabetes-driven molecular mechanisms that induce DR, reducing both the neural and vascular damage typical of DR. Although most studies are limited to animal models and there is the problem of low bioavailability for many nutraceuticals, the use of these compounds may represent a natural alternative method to standard DR treatments.

Small molecule target identification using photo-affinity chromatography

Identification of the protein targets of bioactive small molecules is a routine challenge in chemical biology and phenotype-based drug discovery. Recent years have seen an explosion of approaches to meeting this challenge, but the traditional method of affinity pulldowns remains a practical choice in many contexts. This technique can be used as long as an affinity probe can be synthesized, usually with a crosslinking moiety to enable photo-affinity pulldowns. It can be applied to varied tissue types and can be performed with minimal specialized equipment. Here, we provide our protocol for photo-affinity pulldown experiments, with notes on making this method generally applicable to varied target identification challenges.

Soluble Epoxide Hydrolase Inhibition for Ocular Diseases: Vision for the Future

Ocular diseases cause visual impairment and blindness, imposing a devastating impact on quality of life and a substantial societal economic burden. Many such diseases lack universally effective pharmacotherapies. Therefore, understanding the mediators involved in their pathophysiology is necessary for the development of therapeutic strategies. To this end, the hydrolase activity of soluble epoxide hydrolase (sEH) has been explored in the context of several eye diseases, due to its implications in vascular diseases through metabolism of bioactive epoxygenated fatty acids. In this mini-review, we discuss the mounting evidence associating sEH with ocular diseases and its therapeutic value as a target. Substantial data link sEH with the retinal and choroidal neovascularization underlying diseases such as wet age-related macular degeneration, retinopathy of prematurity, and proliferative diabetic retinopathy, although some conflicting results pose challenges for the synthesis of a common mechanism. sEH also shows therapeutic relevance in non-proliferative diabetic retinopathy and diabetic keratopathy, and sEH inhibition has been tested in a uveitis model. Various approaches have been implemented to assess sEH function in the eye, including expression analyses, genetic manipulation, pharmacological targeting of sEH, and modulation of certain lipid metabolites that are upstream and downstream of sEH. On balance, sEH inhibition shows considerable promise for treating multiple eye diseases. The possibility of local delivery of inhibitors makes the eye an appealing target for future sEH drug development initiatives.

Small molecules inhibit ex vivo tumor growth in bone

Bone is a common site of metastasis for breast, prostate, lung, kidney and other cancers. Bone metastases are incurable, and substantially reduce patient quality of life. To date, there exists no small-molecule therapeutic agent that can reduce tumor burden in bone. This is partly attributed to the lack of suitable in vitro assays that are good models of tumor growth in bone. Here, we take advantage of a novel ex vivo model of bone colonization to report a series of pyrrolopyrazolone small molecules that inhibit cancer cell invasion and ex vivo tumor growth in bone at single-digit micromolar concentration. We find that the compounds modulated the expression levels of genes associated with bone-forming osteoblasts, bone-destroying osteoclasts, cancer cell viability and metastasis. Our compounds provide chemical tools to uncover novel targets and pathways associated with bone metastasis, as well as for the development of compounds to prevent and reverse bone tumor growth in vivo.

Sappanone A prevents hypoxia-induced injury in PC-12 cells by down-regulation of miR-15a

OBJECTIVE

We aimed to explore the effect of Sappanone A on neurologic damage induced by hypoxia.

METHODS

PC-12 cells were pre-treated with Sappanone A and were simulated by hypoxia. miRNA transfection was performed to overexpress or suppress the expression of miR-15a in PC-12 cells. Cell viability, apoptosis, migration, and expression levels of miR-15a were tested to evaluate the in vitro impact of Sappanone A on hypoxia-injured PC-12 cells.

RESULTS

Hypoxia exposure induced a significant damage in PC-12 cells, as evidenced by the repressed cell growth, the induced apoptosis and the impaired migrating capacity. Sappanone A pretreatment protected PC-12 cells against hypoxia-mediated cell damage. More interestingly, Sappanone A treatment down-regulated miR-15a, and the neuroprotective effects of Sappanone A were attenuated by miR-15a overexpression while were accelerated by miR-15a suppression. Finally, Sappanone A significantly activated Wnt/β-catenin and PI3K/AKT signaling pathways. And the activation of these two signaling induced by Sappanone A were repressed by miR-15a overexpression and were enhanced by miR-15a suppression.

CONCLUSION

Sappanone A exerted protective activity in PC-12 cells which were stimulated by hypoxia. One of the possible mechanisms of the neuroprotective effect is that: Sappanone A down-regulated the expression of miR-15a, and thus activated Wnt/β-catenin and PI3K/AKT signaling pathways.

Novel Hypoxia-Inducible Factor 1α (HIF-1α) Inhibitors for Angiogenesis-Related Ocular Diseases: Discovery of a Novel Scaffold via Ring-Truncation Strategy

Ocular diseases featuring pathologic neovascularization are the leading cause of blindness, and anti-VEGF agents have been conventionally used to treat these diseases. Recently, regulating factors upstream of VEGF, such as HIF-1α, have emerged as a desirable therapeutic approach because the use of anti-VEGF agents is currently being reconsidered due to the VEGF action as a trophic factor. Here, we report a novel scaffold discovered through the complete structure-activity relationship of ring-truncated deguelin analogs in HIF-1α inhibition. Interestingly, analog 6i possessing a 2-fluorobenzene moiety instead of a dimethoxybenzene moiety exhibited excellent HIF-1α inhibitory activity, with an IC₅₀ value of 100 nM. In particular, the further ring-truncated analog 34f, which showed enhanced HIF-1α inhibitory activity compared to analog 2 previously reported by us, inhibited in vitro angiogenesis and effectively suppressed hypoxia-mediated retinal neovascularization. Importantly, the heteroatom-substituted benzene ring as a key structural feature of analog 34f was identified as a novel scaffold for HIF-1α inhibitors that can be used in lieu of a chromene ring.

Antiangiogenic Activity and Cytotoxicity of Triterpenoids and Homoisoflavonoids from Massonia pustulata and Massonia bifolia

The Hyacinthaceae family (sensu APGII), with approximately 900 species in around 70 genera, plays a significant role in traditional medicine in Africa as well as across Europe and the Middle and Far East. The dichloromethane extract of the bulbs of Massonia pustulata (Hyacinthaceae sensu APGII) yielded two known homoisoflavonoids, (R)-5-hydroxy-3-(4-hydroxybenzyl)-7-methoxy-4-chromanone 1: and 5-hydroxy-3-(4-hydroxybenzyl)-7-methoxy-4-chromone 2: and four spirocyclic nortriterpenoids, eucosterol 3: , 28-hydroxyeucosterol 4: and two previously unreported triterpenoid derivatives, (17S,23S)-17α,23-epoxy-3β,22β,29-trihydroxylanost-8-en-27,23-olide 5: , and (17S, 23S)-17α,23-epoxy-28,29-dihydroxylanost-8-en-3-on-27,23-olide 6: . Compounds 1, 2, 3: , and 5: were assessed for cytotoxicity against CaCo-2 cells using a neutral red uptake assay. Compounds 1, 2: , and 5: reduced cell viability by 70% at concentrations of 30, 100, and 100 µM, respectively. Massonia bifolia yielded three known homoisoflavonoids, (R)-(4'-hydroxy)-5-hydroxy-7-methoxy-4-chromanone 1: , (R)-(4'-hydroxy)-5,7-dihydroxy-4-chromanone 7: and (R)-(3'-hydroxy-4'-methoxy)-5,7-dihydroxy-4-chromanone 9: , two previously unreported homoisoflavonoids, (E)-3-benzylidene-(3',4'-dihydroxy)-5-hydroxy-7-methoxy-4-chromanone 8: and (R)-(3',4'-dihydroxy)-5-hydroxy-7-methoxy-4-chromanone 10,: and a spirocyclic nortriterpenoid, 15-deoxoeucosterol 11: . Compounds 1, 1AC, 7, 8, 9,: and 10: were screened for antiangiogenic activity against human retinal microvascular endothelial cells. Some compounds showed dose-dependent antiproliferative activity and blocked endothelial tube formation, suggestive of antiangiogenic activity.

Ferrochelatase is a therapeutic target for ocular neovascularization

Ocular neovascularization underlies major blinding eye diseases such as “wet” age‐related macular degeneration (AMD). Despite the successes of treatments targeting the vascular endothelial growth factor (VEGF) pathway, resistant and refractory patient populations necessitate discovery of new therapeutic targets. Using a forward chemical genetic approach, we identified the heme synthesis enzyme ferrochelatase (FECH) as necessary for angiogenesis in vitro and in vivo. FECH is overexpressed in wet AMD eyes and murine choroidal neovascularization; siRNA knockdown of Fech or partial loss of enzymatic function in the Fech^m1Pas mouse model reduces choroidal neovascularization. FECH depletion modulates endothelial nitric oxide synthase function and VEGF receptor 2 levels. FECH is inhibited by the oral antifungal drug griseofulvin, and this compound ameliorates choroidal neovascularization in mice when delivered intravitreally or orally. Thus, FECH inhibition could be used therapeutically to block ocular neovascularization.

Chemical Proteomics Reveals Soluble Epoxide Hydrolase as a Therapeutic Target for Ocular Neovascularization

The standard-of-care therapeutics for the treatment of ocular neovascular diseases like wet age-related macular degeneration (AMD) are biologics targeting vascular endothelial growth factor signaling. There are currently no FDA approved small molecules for treating these blinding eye diseases. Therefore, therapeutic agents with novel mechanisms are critical to complement or combine with existing approaches. Here, we identified soluble epoxide hydrolase (sEH), a key enzyme for epoxy fatty acid metabolism, as a target of an antiangiogenic homoisoflavonoid, SH-11037. SH-11037 inhibits sEH in vitro and in vivo and docks to the substrate binding cleft in the sEH hydrolase domain. sEH levels and activity are up-regulated in the eyes of a choroidal neovascularization (CNV) mouse model. sEH is overexpressed in human wet AMD eyes, suggesting that sEH is relevant to neovascularization. Known sEH inhibitors delivered intraocularly suppressed CNV. Thus, by dissecting a bioactive compound's mechanism, we identified a new chemotype for sEH inhibition and characterized sEH as a target for blocking the CNV that underlies wet AMD.

Synthesis of 3-(2-Olefinbenzyl)-4H-chromen-4-one through Cyclobenzylation and Catalytic C-H Bond Functionalization Using Palladium(II)

An efficient strategy for synthesizing 3-(2-olefinbenzyl)-4H-chromen-4-one in two steps was developed. The first step is a cyclobenzylation reaction between (E)-3-(dimethylamino)-1-(2-hydroxyphenyl)prop-2-en-1-one and benzyl bromide to produce homoisoflavonoid. The second step involves intermolecular Pd-catalyzed π-chelating-assisted C-H bond olefination. Using the C-2/C-3 double bond of chromone, palladium-catalyzed aryl C-H bond activation can be functionalized to generate ortho-olefination derivatives in moderate to high yields.

Homoisoflavonoids as potential antiangiogenic agents for retinal neovascularization

A number of people worldwide have been suffering from ocular neovascularization that may be treated by a variety of drugs but these may possess adverse effects. Therefore, small antiangiogenic molecules with higher potency and lower toxic effects are intended. However, homoisoflavonoids of natural origin show the potential antiangiogenic effect in ocular neovascularization. These homoisoflavonoids are judged quantitatively in terms of statistical validation through multi-chemometric modeling approaches for the betterment and refinement of their structures required for higher antiangiogenic activity targeted to ocular neovascularization. These approaches may be utilized to design better antiangiogenic homoisoflavonoids.

A Critical Analysis of the Available In Vitro and Ex Vivo Methods to Study Retinal Angiogenesis

Angiogenesis is a biological process with a central role in retinal diseases. The choice of the ideal method to study angiogenesis, particularly in the retina, remains a problem. Angiogenesis can be assessed through in vitro and in vivo studies. In spite of inherent limitations, in vitro studies are faster, easier to perform and quantify, and typically less expensive and allow the study of isolated angiogenesis steps. We performed a systematic review of PubMed searching for original articles that applied in vitro or ex vivo angiogenic retinal assays until May 2017, presenting the available assays and discussing their applicability, advantages, and disadvantages. Most of the studies evaluated migration, proliferation, and tube formation of endothelial cells in response to inhibitory or stimulatory compounds. Other aspects of angiogenesis were studied by assessing cell permeability, adhesion, or apoptosis, as well as by implementing organotypic models of the retina. Emphasis is placed on how the methods are applied and how they can contribute to retinal angiogenesis comprehension. We also discuss how to choose the best cell culture to implement these methods. When applied together, in vitro and ex vivo studies constitute a powerful tool to improve retinal angiogenesis knowledge. This review provides support for researchers to better select the most suitable protocols in this field.

Chromone as a Privileged Scaffold in Drug Discovery: Recent Advances

The use of privileged structures in drug discovery has proven to be an effective strategy, allowing the generation of innovative hits/leads and successful optimization processes. Chromone is recognized as a privileged structure and a useful template for the design of novel compounds with potential pharmacological interest, particularly in the field of neurodegenerative, inflammatory, and infectious diseases as well as diabetes and cancer. This perspective provides the reader with an update of an earlier article entitled "Chromone: A Valid Scaffold in Medicinal Chemistry" ( Chem. Rev. 2014 , 114 , 4960 - 4992 ) and is mainly focused on chromones of biological interest, including those isolated from natural sources. Moreover, as drug repurposing is becoming an attractive drug discovery approach, recent repurposing studies of chromone-based drugs are also reported.