Synthesis and biological evaluation of unique stereodimers of sinomenine analogues as potential inhibitors of NO production

Bioactivities and Mechanisms of Action of Sinomenine and Its Derivatives: A Comprehensive Review

Sinomenine, an isoquinoline alkaloid extracted from the roots and stems of Sinomenium acutum, has been extensively studied for its derivatives as bioactive agents. This review concentrates on the research advancements in the biological activities and action mechanisms of sinomenine-related compounds until November 2023. The findings indicate a broad spectrum of pharmacological effects, including antitumor, anti-inflammation, neuroprotection, and immunosuppressive properties. These compounds are notably effective against breast, lung, liver, and prostate cancers, exhibiting IC50 values of approximately 121.4 nM against PC-3 and DU-145 cells, primarily through the PI3K/Akt/mTOR, NF-κB, MAPK, and JAK/STAT signaling pathways. Additionally, they manifest anti-inflammatory and analgesic effects predominantly via the NF-κB, MAPK, and Nrf2 signaling pathways. Utilized in treating rheumatic arthritis, these alkaloids also play a significant role in cardiovascular and cerebrovascular protection, as well as organ protection through the NF-κB, Nrf2, MAPK, and PI3K/Akt/mTOR signaling pathways. This review concludes with perspectives and insights on this topic, highlighting the potential of sinomenine-related compounds in clinical applications and the development of medications derived from natural products.

Chemistry and biology of ent-morphinan alkaloids

Morphinan alkaloids have attracted constant attention since the isolation of morphine by Sertürner in 1805. However, a group of 45 compounds possessing a complete ent-morphinan backbone can also be found in the literature. These compounds are related to the morphinandienone subgroup and display a substitution pattern which is different from the morphinans. In particular, these alkaloids could be substituted at position C-2 and C-8 either by a hydroxy function or a methoxy moiety. Four groups of ent-morphinan alkaloids can be proposed, the salutaridine, pallidine, cephasugine and erromangine series. Interestingly, the botanical distribution of the ent-morphinans is more widespread than for the morphinans and includes the Annonaceae, Berberidaceae, Euphorbiaceae, Fumariaceae, Hernandiaceae, Lauraceae, Menispermaceae, Monimiaceae, Papaveraceae, and Ranunculaceae families. To date, their exact mode of production remains elusive and their interplay with the biosynthetic pathway of other classes of benzyltetrahydroisoquinoline alkaloids, in particular aporphines, should be confirmed. Exploration of the biological and therapeutic potential of these compounds is limited to some areas, namely central nervous system (CNS), inflammation, cancer, malaria and viruses. Further studies should be conducted to identify the cellular/molecular targets in view of promoting these compounds as new scaffolds in medicinal chemistry.

Avanafil as a Novel Therapeutic Agent Against LPS-Induced Acute Lung Injury via Increasing CGMP to Downregulate the TLR4-NF-κB-NLRP3 Inflammasome Signaling Pathway

AIM

We demonstrate the effect of PDE5 inhibitors in cases of acute lung injury via the relationship between cGMP/NO and the TLR4-NF-κB-NLRP3 pathway.

MATERIALS AND METHODS

This study was performed with 30 male Wistar albino rats. Lipopolysaccharide (LPS) was administered intratracheally to the rats and acute lung injury (ALI) was induced. Twelve hours after LPS administration, avanafil, prepared at suitable doses according to the body weights of the animals, was administered by oral gavage. Lung tissue samples of all groups were examined histopathologically and by immunochemical staining (IL-1β, iNOS, TLR4, and NF-κB). The iNOS, NLRP3, and IL-1B mRNA expression levels in the lung tissues were measured by RT-PCR. The left upper lobes of the rat lungs were dried at 70 °C for 48 h and lung water content was calculated.

RESULT

Statistically significant increases in iNOS, NLRP3, and IL-1β mRNA expressions were observed in the rats with ALI compared to the healthy controls (p < 0.0001). Those increased expressions were reduced at both doses of avanafil (p < 0.0001). This reduction was found to be greater at 20 mg/kg (p < 0.0001). IL-1β, iNOS, TLR4, and NF-κB immunopositivity was moderate/severe in the ALI group and mild in the group with ALI + avanafil at 20 mg/kg (p < 0.05). When the wet/dry lung ratios were calculated, a statistically significant increase was seen in the ALI group compared to the healthy rats (p < 0.05). That increase was decreased with both avanafil doses (p < 0.05).

CONCLUSION

We suggest that avanafil may prevent the progression of ALI and be effective in its treatment. We hope that this study will be supported by future clinical studies to yield a new indication for avanafil.

Compounds with NO Inhibitory Effect from the Rattan Stems of Sinomenium acutum, a Kind of Chinese Folk Medicine for Treating Rheumatoid Arthritis

Three new alkaloids (1-3), one new diphenyl ether (4) and fifteen known alkaloids (5-19) were isolated from the rattan stems of Sinomenium acutum. Comprehensive analyses of HR-ESI-MS, 1D (¹ H and ¹³ C), 2D-NMR (¹ H-¹ H COSY, HSQC, HMBC, NOESY), circular dichroism (CD), UV and IR revealed the structures and absolute configurations of these new compounds. The structures of other compounds were determined by comparison of their ¹ H and ¹³ C-NMR data with previous literature reports. By measuring the amount of NO produced, the anti-inflammatory properties of the isolated compounds were studied. The results showed that compounds 4 and 5 had strong NO inhibitory activity.

New cassane- and norcassane-type diterpenoids from the seed kernels of Caesalpinia sinensis and their anti-inflammatory activity in vitro

The first investigation of phytochemistry on the seed kernels of Caesalpinia sinensis led to the isolation and characterization of six new compounds including three tricyclic-type cassane diterpenoids (1--3) and three norcassane-type diterpenoids (4-6), together with three know compounds (7-9). Compounds 1-9 represented the first discovery of cassane-type diterpenoids from C. sinensis. Their structures were elucidated by a combination of spectroscopic analysis, single-crystal X-ray diffraction experiment and ECD calculation. The characters for compounds 4 and 5 possessing the 15,16-degradative cassane skeleton were observed, which was extremely rare structural type in the genus Caesalpinia. The anti-inflammatory activities of all isolates were evaluated via examining their inhibitory effects against NO production in LPS-simulated RAW 264.7 cells. The results demonstrated that compound 1 exhibited the most significantly inhibitory efficacy with inhibition rate 67.3% at 10 μM. The iNOS enzyme activity assay further revealed that compound 1 showed potent NO inhibitory effect by reducing the enzymatic activity of iNOS.

Design and synthesis of new disubstituted benzoxazolone derivatives that act as iNOS inhibitors with potent anti-inflammatory activity against LPS-induced acute lung injury (ALI)

Acute lung injury (ALI) is a pulmonary disease that acts as a severe acute inflammatory response with no specific drugs. iNOS, a catalyst of the excessive production of NO, has been demonstrated to participate in the inflammatory process, and targeting iNOS may be a promising therapeutic pathway to alleviate ALI. In our research, eighteen new disubstituted benzoxazolone derivatives were synthesized, characterized, and evaluated for activity against NO production in an LPS-induced RAW264.7 cell. The results showed that these compounds could obviously inhibit the over-generation of NO and disubstitution at the 4, N-position of the benzoxazolone ring, presenting better potency than substitution only at the 4-position. Among the analogues generated, compounds 2c, 2d, and 3d showed NO inhibitory activity with IC₅₀ values of 16.43, 14.72, and 13.44 µM and iNOS inhibitory activity with IC₅₀ values of 4.605, 3.342, and 9.733 µM, respectively. Meanwhile, compounds 2c, 2d, and 3d could also inhibit the release of IL-6, IL-1β in vitro and suppress xylene-induced ear edema in vivo to realize anti-inflammatory activity. Furthermore, compound 2d could significantly protect the LPS-induced ALI, presenting as decreased inflammatory cytokines and obvious pathological changes. Immunohistochemistry and molecular modeling demonstrated that compound 2d significantly inhibited the expression of iNOS in vivo and interacted with iNOS through two hydrogen bindings with the MET368 and ILE195 residues of the iNOS protein. These results demonstrated that compound 2d could be a promising lead structure for iNOS inhibitors, with anti-inflammatory activity to treat LPS-induced acute lung injury.

The present and future synthetic strategies of structural modifications of sinomenine

This review summarizes the modifications of sinomenine, a hot compound derived from herbal plants, which possesses diverse biological activities and low cytotoxicity.

Design and synthesis of sinomenine isoxazole derivatives via 1,3-dipolar cycloaddition reaction

A novel structure of sinomenine isoxazole derivatives is synthesised from sinomenine hydrochloride and aromatic aldehydes and requires six steps. 19 target compounds have been obtained in good yields. The sinomenine hydrochloride transforms to 4-alkynyl sinomenine, which is a key intermediate product to synthesise the target sinomenine isoxazole compounds, after a neutralisation reaction with ammonia and substitution reaction with 3-chloropropyne. Another key intermediate product is 1,3-dipole, which can be obtained from aromatic aldehyde. After treatment with hydroxylamine hydrochloride and then sodium carbonate solution, aromatic aldehyde is converted to aldehyde oxime, which reacts with N-chlorosuccinimide (NCS) to afford aryl hydroximino chloride. 1,3-Dipole is eventually formed in situ while triethylamine (TEA) in DMF is added dropwise. Then 4-alkynyl sinomenine is added to provide the sinomenine isoxazole derivative via 1,3-dipolar cycloaddition reaction as the key step. All the target compounds are characterised by melting point, ¹H NMR, ¹³C NMR, HRMS and FT-IR spectroscopy.

Synthesis of C-ring hydrogenated sinomenine cinnamate derivatives via Heck reactions

The synthesis of C-ring hydrogenated sinomenine derivatives is accomplished from sinomenine by treatment with Zn-Hg/HCl, halogenation with NIS, and Heck reactions with various acrylates. A total of nine novel sinomenine cinnamate derivatives are obtained in 84%–93% yields. The structures of all the derivatives are characterized by 1H NMR, 13C NMR, and MS spectroscopy.

A selective HPLC-MS/MS method for quantification of SND-117 in rat plasma and its application to a pharmacokinetic study

Rheumatoid arthritis (RA), a chronic systemic inflammatory disorder affects many adults. Sinomenine, a natural product, has been clinically available for the treatment of RA in China. SND-117, a sinomenine derivative with much more potent activity, might serve as a candidate for anti-arthritis. The aim of the present study was to develop a sensitive and rapid high performance liquid chromatography tandem mass spectrometry (HPLC-MS/MS) method for quantification of SND-117 in rat plasma and to understand its absolute bioavailability. The HPLC-MS/MS method was developed and fully validated for determination of SND-117 in rat plasma, and the pharmacokinetic differences were investigated after different administration routes. The pharmacokinetics parameters were calculated by non-compartment model with DAS 3.0 software. After the oral or intravenous administration of different doses of SND-117, the time to peak is 1.5h, half-life time is 8-10h. The absolute oral bioavailability of SND-117 in rats was 9.60%. The results showed that SND-117 in rats was quickly absorbed, slowly eliminate, and the kinetics were linear. This method was suitable for pharmacokinetic studies of SNA-117 in rats.

Access to a Structurally Complex Compound Collection via Ring Distortion of the Alkaloid Sinomenine

Many compound collections used in high-throughput screening are composed of members whose structural complexity is considerably lower than that of natural products. We previously reported a strategy for the synthesis of complex and diverse small molecules from natural products using ring-distortion reactions, called complexity-to-diversity (CtD), and herein, CtD is applied in the synthesis of 16 diverse scaffolds and 65 total compounds from the alkaloid natural product sinomenine. Chemoinformatic analysis shows that these compounds possess complex ring systems and marked three-dimensionality.

Microfluidics assisted synthesis and bioevaluation of sinomenine derivatives as antiinflammatory agents

Sinomenine (1) is currently used for the treatment of rheumatoid arthritis (RA) in China and there is still room for the improvement of its efficacy. In present study, capillary based microfluidic system was effectively applied for the syntheses of two novel series of sinomenine derivatives. The Heck reactions in microreactor gave much higher conversions compared to the batch ones. The two-step synthesis of the isoxazoline in microreactor greatly shortened the reaction time without any isolation of intermediates. The inhibitory activity of synthesized compounds on the TNF-α-induced nuclear factor kappa B (NF-κB) activation was evaluated in vitro. Among the compounds, 3c and 3g showed the potent inhibitory activity. Furthermore, 3g exhibited the antiinflammatory effect in vivo.

Ultrasound-promoted synthesis and immunosuppressive activity of novel quinazoline derivatives

An environmentally friendly and mild Bischler cyclization was developed to access quinazolines with diverse substitution. Based on this method, a library of 53 quinazoline derivatives was prepared and tested in vitro for cytotoxicity and inhibition on T-cell and B-cell proliferation. Compounds 6b, 7b, 17b, 33, and 35 showed higher inhibitory activity on both T-cell and B-cell proliferations, with IC(50) values of 6.16, 6.30, 5.43, 2.54, and 9.80 μM on T-cell, respectively. All the tested compounds showed no obvious cytotoxicity at 10 μM concentration. The preliminary structure-activity relationship was concluded revealing that 4-position is the key modification site for potent quinazoline immunosuppressive agent.

Synthesis and biological evaluation of novel sinomenine derivatives as anti-inflammatory agents

Sinomenine (1) is clinically available for the treatment of rheumatoid arthritis (RA), however, its efficacy is quite weak. In the present study, a library of novel sinomenine-based homodimers and monomers through variable-length linkers were designed and synthesized, and their bioactivities were evaluated using RAW264.7 cells and mice. Among the compounds, 2f and 3b possessed much more potent inhibitory effects on the production of nitric oxide (NO), interleukin-6 (IL-6) and tumor necrosis factor-α (TNF-α) than 1. Preliminary mechanism investigation revealed that 3b inhibited nuclear factor-κB (NF-κB) signaling pathway specifically, 2f suppressed both NF-κB and mitogen-activated protein kinase (MAPK) cascades. Moreover, 3b and 2f significantly alleviated the lipopolysaccharide (LPS)-induced mortality. These two compounds might serve as valuable candidates for anti-inflammatory drug discovery.

Oxadiazole derivatives containing 1,4-benzodioxan as potential immunosuppressive agents against RAW264.7 cells

A series of oxadiazole derivatives containing 1,4-benzodioxan (4a-4s) have been first synthesized for their potential immunosuppressive activity. Among the compounds, compound 4i showed the most potent biological activity against RAW264.7 cells (inhibition=37.66±2.34% for NO overproduction and IC(50)=0.05μM for iNOS). Docking simulation was performed to position compound 4i into the iNOS structure active site to determine the probable binding model. RT-PCR experiment results demonstrated that some of these compounds possessed good immunosuppressive activity against iNOS, especially for compound 4i. Therefore, compound 4i with potent inhibitory activity may be a potential agent.