Phosphodiesterase 5 and Arginase Inhibitory Activities of the Extracts from Some Members of Nelumbonaceae and Nymphaeaceae Families

Advances in the development of phosphodiesterase 5 inhibitors

Phosphodiesterase 5 (PDE5) can hydrolyze cyclic guanosine monophosphate (cGMP), which is critical for maintaining various physiological processes in organisms. Currently, clinically approved indications for PDE5 inhibitors encompass therapeutic agents for erectile dysfunction (ED), symptoms associated with lower urinary tract symptoms (LUTS), and pulmonary artery hypertension (PAH). Despite the fact that the development of selective PDE5 inhibitors has been a significant focus in drug development for some time following the proven success of sildenafil as a PDE5 inhibitor for ED treatment, fewer than ten drugs in this therapeutic class have been marketed in the past 25 years, often accompanied by adverse effects. Therefore, the development of novel, isozyme-selective PDE5 inhibitors is highly warranted. In this review, we systematically summarize the research progress of PDE5 inhibitors over the past 20 years, focusing on the meticulously combing and categorizing the structures of PDE5 inhibitors and natural products exhibiting PDE5 inhibitory activities, along with their therapeutic potentials. We hope that this summary will aid in better understanding of PDE5 inhibitors and provide insights for developing novel therapies targeting PDE5.

Ameliorative Effect of Rauwolfia vomitoria Ethanol Extract on the Erectile Dysfunction Complicated with Coronary Artery Disease: An In-Vivo and Molecular Docking Approach

Erectile dysfunction in men may result as a side effect of the use of serotonin reuptake inhibitors such as paroxetine. Enzymes like phosphodiesterase 5 (PDE-5) and arginase are promising therapeutic targets for managing erectile dysfunction while creatinine kinase-myocardial band (CK-MB) serves as a marker for coronary artery disease. To manage these conditions, it is necessary to seek options in medicinal herbs. Rauwolfia vomitoria (RV) is a plant that has been used as an aphrodisiac but the inhibitory mechanism against these enzymes remain unclear. The study used in-vivo enzymatic biomarkers and molecular docking approach to better understand their inhibitory mechanism. Forty-eight adult male Wistar rats were divided into six groups of eight rats: naive control, paroxetine (PXT, 10 mg/kg), PXT+sildenafil citrate (4 mg/kg), PXT + RVE (12.5, 25 and 50 mg/kg). Exposure to PXT lasted for twenty-one days, and treatment with sildenafil citrate and RVE took place for the next seven days. On day twenty-nine, the rats were sacrificed under anaesthesia and various biochemical assays (PDE-5, Arginase, nitric oxide (NO) were carried out on penile tissue homogenate while CK-MB, lipid profile and testosterone were assayed in the serum of rats. This study also employed gas chromatography -flame ionization detection (GC-FID) to identify the phytoconstituents in RV. From our findings, PXT significantly increased PDE-5, Arginase activities with a concomitant decrease in NO concentration. Rauwolfia vomitoria extract (RVE) decreased the activities of the penile PDE 5 and arginase activities, and increased NO concentrations in dose-dependent ways (12.5, 25, and 50 mg/kg body weight). RVE showed an increase in testosterone and a decrease in CK-MB activities. Moreover, the result of lipid profile revealed the significant reversal of the changes caused by PXT administration, indicating the potential of the extract in ameliorating paroxetine-induced dyslipidemia. All of the phytochemicals found by GC-FID docked against PDE-5 had the lowest binding energies ( - 9.4 to -7.0 kcal/mol) when likened to that of sildenafil citrate ( - 7.4 kcal/mol). The phytochemicals were also docked against arginase which released the lowest binding energy between -10.5 and -9.0 kcal/mol when compared with sildenafil citrate ( - 9.4 kcal/mol). This study is relevant in the design of new treatment option for ED and coronary artery disease.

Vasorelaxant and hypotensive effects of an ethanolic extract of Nymphaea pubescens and its main compound quercetin 3-methyl ether 3'-O-β-xylopyranoside

Aim: Nymphaea plants were traditionally used to treat diseases associated with endothelial dysfunction. The present study investigated the effects of an ethanolic extract of Nymphaea pubescens Willd. (commonly named water lily, WL) and its main compound 1 (quercetin 3-methyl ether 3'-O-β-xylopyranoside) on vascular function in rats. Materials and methods: The vasorelaxant effects of the WL extract and its main compound 1 and their underlying mechanisms of action were evaluated on isolated mesenteric arteries from Wistar rats. Blood pressure and heart rate were measured in anesthetized rats after infusion (i.v) of vehicle, WL extract, and compound 1 (at 0.01, 0.025, 0.05, 0.1, 0.5, and 1 mg/kg). Nifedipine was used as a positive control. Results: Both WL extract and compound 1 induced vasorelaxant effects (with EC50 of 0.08 ± 0.01 mg/mL and 42.8 ± 6.3 µM, respectively) that were reduced by endothelium removal. A significant decrease in these relaxations was observed with L-NAME but not with apamin-charybdotoxin or indomethacin. In the endothelium-denuded condition, WL extract-induced relaxation was enhanced by 4-aminopyridine and glibenclamide, while iberiotoxin and ODQ (1H-[1,2,4]oxadiazolo[4,3-a]quinoxaline-1-one) had no effect. In contrast, compound 1-induced relaxation was not changed by any of these inhibitors. Both WL extract and compound 1 enhanced sodium nitroprusside-induced relaxation and inhibited receptor-operated Ca2+ channels. Only the WL extract was able to reduce PE-induced contraction (p < 0.001). As compared to the vehicle, the infusion of WL extract and compound 1 lowered systolic and diastolic blood pressure. Interestingly, the hypotensive effect of the compound was similar to that of nifedipine. The rebound tachycardia found at the highest dose of nifedipine was not observed with the WL extract or compound 1 (p < 0.05). Conclusion and discussion: Our study demonstrated a vasorelaxant effect of the WL extract and its main compound quercetin 3-methyl ether 3'-O-β-xylopyranoside, relying on the potentiation of the NO-cGMP pathway and calcium inhibitory effects. These vasorelaxant effects were associated with a potent hypotensive effect, providing pharmacological evidence for the traditional use of this plant.

Influence of pallet rich plasma, quercetin and their combination on activity of nitric oxide cycle enzymes in nasal mucosa of patients with atrophic rhinitis

OBJECTIVE

Aim: To study the general activity of NO synthases (gNOS), the activity of inducible and constitutive isoforms of NO synthase, the activity of arginases, and the concentration of nitrites in the nasal mucosa under the conditions of local treatment of chronic atrophic rhinitis (AR) with quercetin and platelet-rich plasma (PRP therapy)..

PATIENTS AND METHODS

Materials and Methods: The study was conducted on 118 patients divided into two groups: control (n=20) and experimental (patients with AR, n=98). Experimental group was divided into 4 subgroups: standard treatment (n=29), PRP therapy (6 injections for 28 day course, n=19), Quercetin (40 mg 3 times a day for 28 days, n=26) and PRP+Quercetin (n=24) groups.

RESULTS

Results: Standard therapy of SaR increases gNOS by 278.38% and arginase activity increases by 222.73%. PRP therapy increases gNOS by 211.43% and arginase by 540.91%. Quercetin elevates gNOS by 108.33% and arginase by 250%. PRP therapy and quercetin increases gNOS by 146.15% and arginase by 536.36%.

CONCLUSION

Conclusions: The use of standard therapy of SaR and addition of PRP therapy, quercetin and their combination effectively restores the production of nitric oxide and the arginase activity in the nasal mucosa.