Fenchone Derivatives as a Novel Class of CB2 Selective Ligands: Design, Synthesis, X-ray Structure and Therapeutic Potential

The progress of small molecules against cannabinoid 2 receptor (CB2R)

The two subtypes of cannabinoid receptors (CBR), namely CB1R and CB2R, belong to the G protein-coupled receptor (GPCR) superfamily and are confirmed as potential therapeutic targets for a variety of diseases such as inflammation, neuropathic pain, and immune-related disorders. Since CB1R is mainly distributed in the central nervous system (CNS), it could produce severe psychiatric adverse reactions and addiction. In contrast, CB2R are predominantly distributed in the peripheral immune system with minimal CNS-related side effects. Therefore, more attention has been devoted to the discovery of CB2R ligands. In view of the favorable profile of CB2R, many high-binding affinity and selectivity CB2R ligands have been developed recently. This paper reviews recent research progress on CB2R ligands, including endogenous CB2R ligands, natural compounds, and novel small molecules, in order to provide a reference for subsequent CB2R ligand development.

Fennel Essential Oil as a Complementary Therapy in the Management of Diabetes

Diabetes is a serious pathology that affects a significant number of people worldwide. Its progression is rapid and leads to serious complications if glycemic control is missing. The micro and macrovascular complications of diabetes produce disabilities over time that affect the daily lives of patients. The major challenge of diabetes therapy is to reach a stable glycemic state and to delay the onset of specific complications. Aromatherapy is considered an alternative or complementary therapy, but in recent years, there has been a tendency to overuse essential oils. The present study was designed to evaluate and compare the effects produced by the topical and oral administration of fennel essential oil to diabetic rats. Eighteen compounds in fennel essential oil were identified by gas chromatography-mass spectrometry (GC-MS) analysis. The major compounds were trans-anethole (64.6%) and fenchone (24.5%). The in vivo study revealed that after a four-week treatment with fennel essential oil, the rats' glycemic levels were significantly reduced (p ≤ 0.05). Furthermore, there were no differences between the two routes of administration. In addition, an ex vivo study underlined the potential effect of this essential oil in the prevention of cataract formation.

Nephroprotective Effect of Fennel (Foeniculum vulgare) Seeds and Their Sprouts on CCl4-Induced Nephrotoxicity and Oxidative Stress in Rats

Functional and nutritional characteristics of seed sprouts and their association with oxidative stress-related disorders have recently become a focus of scientific investigations. The biological activities of fennel seeds (FS) and fennel seed sprouts (FSS) were investigated in vitro and in vivo. The total phenolic content (TPC), total flavonoids (TF), total flavonols (TFF), and antioxidant activity (AOA) of FS and FSS were examined. HPLC and GC-MS analyses for FS and FSS were carried out. Consequently, the nephroprotective and antioxidative stress potential of FS and FSS extracts at 300 and 600 mg kg^-1 on CCl₄-induced nephrotoxicity and oxidative stress in rats was investigated. In this context, kidney relative weight, blood glucose level (BGL), lipid profile, kidney function (T. protein, albumin, globulin, creatinine, urea, and blood urea nitrogen (BUN)), and oxidative stress biomarkers (GSH, CAT, MDA, and SOD) in the rat's blood as well as the histopathological alteration in kidney tissues were examined. Results indicated that the sprouting process of FS significantly improved TPC, TF, TFL, and AOA in vitro. HPLC identified nineteen compounds of phenolic acids and their derivatives in FS. Thirteen phenolic compounds in FS and FSS were identified, the highest of which was vanillic acid. Six flavonoids were also identified with a predominance of kaempferol. GC-MS indicated that the trans-anethole (1-methoxy-4-[(E)-prop-1-enyl]benzene) component was predominant in FS and FSS, significantly increasing after sprouting. In in vivo examination, administering FS and FSS extracts ameliorated the BGL, triglycerides (TG), total cholesterol (CHO), and their derivative levels compared to CCl₄-intoxicated rats. A notable improvement in FS and FSS with 600 mg kg^-1 compared to 300 mg kg^-1 was observed. A dose of 600 mg FSS kg^-1 reduced the TG, CHO, and LDL-C and increased HDL-C levels by 32.04, 24.62, 63.00, and 67.17% compared to G2, respectively. The atherogenic index (AI) was significantly improved with 600 mg kg^-1 of FSS extracts. FS and FSS improved kidney function, reduced malondialdehyde (MDA), and restored the activity of reduced glutathione (GSH), superoxide dismutase (SOD), and catalase (CAT). Both FS and FSS extracts attenuated the histopathological alteration in CCl₄-treated rats. Interestingly, FSS extract presented better efficiency as a nephroprotection agent than FS extract. In conclusion, FSS can potentially restore oxidative stability and improve kidney function after acute CCl₄ kidney injury better than FS. Therefore, FS and FSS extracts might be used for their promising nephroprotective potential and to help prevent diseases related to oxidative stress. Further research on their application in humans is highly recommended.

A Fenchone Derivative Effectively Abrogates Joint Damage Following Post-Traumatic Osteoarthritis in Lewis Rats

BACKGROUND

In a previous report, we have identified the cannabinoid receptor 2 (CB2) agonist HU308 to possess a beneficial effect in preventing age and trauma-induced osteoarthritis (OA) in mice. The effects of HU308 were largely related to the capacity of this compound to induce cartilage anabolism which was dependent on the CREB/SOX9 axis, and exhibited pro-survival and pro-proliferative hallmarks of articular cartilage following treatment. Here, we utilized the novel cannabinoid-fenchone CB2 agonists (1B, 1D), which were previously reported to render anti-inflammatory effects in a zymosan model.

METHODS

Initially, we assessed the selectivity of CB2 using a Gs-protein receptor cAMP potency assay, which was also validated for antagonistic effects dependent on the Gi-protein receptor cAMP pathway. Based on EC50 values, 1D was selected for a zymosan inflammatory pain model. Next, 1D was administered in two doses intra-articularly (IA), in a post-traumatic medial meniscal tear (MMT, Lewis rats) model, and compared to sham, vehicle, and a positive control consisting of fibroblast growth factor 18 (FGF18) administration. The histopathological assessment was carried out according to the Osteoarthritis Research Society International (OARSI) guidelines for rat models following 28 days post-MMT.

RESULTS

The G protein receptor assays confirmed that both 1B and 1D possess CB2 agonistic effects in cell lines and in chondrocytes. Co-administering a CB2 antagonists to 25 mg/kg 1D in a paw inflammatory pain model abolished 1D-related anti-swelling effect and partially abolishing its analgesic effects. Using an MMT model, the high dose (i.e., 24 µg) of 1D administered via IA route, exhibited reduced cartilage damage. Particularly, this dose of 1D exhibited a 30% improvement in cartilage degeneration (zonal/total tibial scores) and lesion depth ratios (44%), comparable to the FGF18 positive control. Synovitis scores remained unaffected and histopathologic evaluation of subchondral bone damage did not suggest that 1D treatment changed the load-bearing ability of the rats. Contrary to the anabolic effect of FGF18, synovial inflammation was observed and was accompanied by increased osteophyte size.

CONCLUSION

The structural histopathological analysis supports a disease-modifying effect of IA-administered 1D compound without any deleterious effects on the joint structure.

Phenolics and Volatile Compounds of Fennel (Foeniculum vulgare) Seeds and Their Sprouts Prevent Oxidative DNA Damage and Ameliorates CCl4-Induced Hepatotoxicity and Oxidative Stress in Rats

Researchers recently focused on studying the nutritional and functional qualities of sprouts generated from seeds. The current study investigated the total phenolic content (TPC), total flavonoids (TF), total flavonols (TFL), antioxidant activity (AOA), specific phenolic acids, and volatile chemicals in fennel seeds (FS) and fennel seed sprouts (FSS). The oxidative DNA damage prevention activity of selected FS and FSS extracts against DNA was examined. Consequently, the antioxidative stress potential of FS and FSS extracts at 300 and 600 mg kg^-1 on CCl₄-induced hepatotoxicity and oxidative stress in rats weas investigated. The liver's functions and oxidative stress biomarkers in rat blood were examined. FSS exhibited rich phytochemical content such as TPC, TF, TFL, and AOA with altered phenolics and volatiles. HPLC identified nineteen compounds of phenolic acids and their derivatives in FS. Thirteen phenolics and six flavonoids were predominantly identified as Vanillic acid and Kaempferol, respectively. GC-MS analysis identified fifty and fifty-one components in FS and FSS, respectively. The predominant component was Benzene, [1-(2-propenyloxy)-3-butenyl] (trans-Anethole) (38.41%), followed by trans-Anethole (Benzene, 1-methoxy-4-(2-propenyl)) (23.65%), Fenchone (11.18%), and 1,7-Octadiene, 2-methyl-6-methylene- Cyclohexene (7.17%). Interestingly, α-Pinene, Fenchone, trans-Anethole (Benzene, 1-methoxy-4-(2-propenyl)), 4-Methoxybenzaldehyde (4-Anisaldehyde), Benzeneacetic acid, α-hydroxy-4-methoxy, and Nonacosane contents were increased. While Dillapiole, 7-Octadecenoic acid, and methyl ester were newly identified and quantified in FSS. The oxidative DNA damage prevention capability of FSS and FS extracts indicated remarkable DNA protection. Administrating FS and FSS extracts at 300 and 600 mg kg^-1 ameliorated AST, ALT, and ALP, as well as GSH, CAT, MDA, and SOD, in a dose-dependent manner. The most efficient treatment of FS or FSS was using a dose of 600 mg Kg^-1, which recorded an improvement rate of 20.77 and 24.17, 20.36 and 24.92, and 37.49 and 37.90% for ALT, AST, and ALP, respectively. While an improvement rate of 40.08 and 37.87%, 37.17 and 46.52%, 114.56 and 154.13%, and 66.05 and 69.69% for GSH, DMA, CAT, and SOD compared to the CCl₄-group, respectively. The observed protection is associated with increased phenolics and volatiles in F. vulgare. Therefore, FS and FSS are recommended as functional foods with bioactive functionality, health-promoting properties, and desired prevention capabilities that may help prevent oxidative stress-related diseases.