Phenolic-rich extracts of Eurycoma longifolia and Cylicodiscus gabunensis inhibit enzymes responsible for the development of erectile dysfunction and are antioxidants

Ex-vivo antioxidant, enzyme inhibitory properties and computational analysis unveil the molecular mechanism of cardiac and penile phosphodiesterase-5 inhibition by bacterial strain HOKA1 extract as an aphrodisiac's agent

The study uses in-vitro antioxidant, ex-vivo enzyme kinetics and in-silico approach using standard protocols to understand their inhibitory mechanism better. The study revealed that bacterial strain HOKA1 isolated from Oniru beach, grown in nutrient agar supplemented with sodium chloride (30%NaCl). Moreso, the bacterial strain HOKA1 extract showed better antioxidant capability and greatly reduced the penile and cardiac cGMP with the highest penile and cardiac concentration between 0.013 and 0.183 μM/Min as compared to the sildenafil citrate (0.00-0.203 μM/Min). Moreover, the kinetic parameters (Vmax and Km) effects revealed that bacterial strain HOKA1 extract inhibited PDE-5 activities better than sildenafil citrate. The GC-MS analysis revealed twenty-nine bioactive compounds in the extract, and these compounds could provide comprehensible supporting evidence for the antioxidant and inhibitory potential of the strain HOKA1 extract on PDE-5 activity. Molecular docking study revealed majority of the GC-MS-identified bioactive constituents from the HOKA1 extract showed high binding energy or lower bonding affinities (-6.8 to -3.3 kcal/mol) compared to reference drug sildenafil citrate (-9.6 kcal/mol), except campesterol (-10.0 kcal/mol); also, ergostane (-9.9 kcal/mol). The results of 100 ns simulation (RMSF, RMSD, Rg and H-bond) show extraordinary stability of PDE-5 with campesterol and ergostane, so also complimentary binding energy of MM-PBSA (campesterol -65.92±4.09 kcal/mol; ergostane -57.23±4.70 kcal/mol) indicating their probability of acting promising PDE-5 inhibitors. Therefore, the study revealed that bacterial strain HOKA1 extract showed a better aphrodisiac property, and its bioactive compounds (campesterol and ergostane) should be considered in upcoming rational development and design of more active selective PDE-5 inhibitors, making a treatment for erectile dysfunction.

Role of Nutraceuticals in Treating Erectile Dysfunction via Inhibition of Phosphodiesterase-5 Enzyme: A Mini Review

Erectile Dysfunction (ED) is a prevalent sexual health condition affecting a significant portion of the male population worldwide. The conventional therapeutic approaches for ED often involve the use of pharmaceutical agents targeting the phosphodiesterase-5 (PDE5) enzyme. Currently, treatment with PDE-5 inhibitors is the standard approach for ED, and four PDE-5 inhibitors, namely sildenafil, vardenafil, tadalafil, and avanafil, are in use. However, these pharmaceutical interventions may be associated with adverse effects and limitations. As a result, there has been a growing interest in exploring alternative and complementary treatment options for ED, such as nutraceuticals, which are bioactive compounds derived from natural sources. Nutraceuticals, which include vitamins, minerals, herbs, and other dietary supplements, have gained popularity for their potential health benefits. Certain nutraceuticals have demonstrated the ability to modulate various physiological pathways, including those involved in erectile function. A notable mechanism of action is the inhibition of the PDE5 enzyme, which plays a pivotal role in the regulation of cGMP levels. By inhibiting PDE5, nutraceuticals can promote the accumulation of cGMP, leading to enhanced penile blood flow and improved erectile function. A comprehensive analysis of the literature showcases various nutraceutical agents, including plant-derived compounds like flavonoids, polyphenols, and amino acids which have exhibited PDE5 inhibitory effects. Mechanistic insights into their action involve modulation of NO release, cGMP elevation, and relaxation of penile smooth muscles, all critical factors for achieving and sustaining erections. This review focuses on elucidating the role of nutraceuticals in treating erectile dysfunction through the inhibition of the PDE5 enzyme.

Botanical drugs for treating erectile dysfunction: clinical evidence

Phosphodiesterase-5 inhibitors (PDE5-i) have been widely used in clinical practice for the treatment of erectile dysfunction (ED). However, due to its suboptimal therapeutic effects and side effects, it is necessary to develop new medicines for ED treatment. Botanical drugs have been widely investigated as potential ED treatment drugs and have shown promising therapeutic effects. This review summarized 34 studies, including five botanical drugs with PDE5 inhibitory activity, seven botanical drugs without PDE5 inhibitory activity, and six mixed botanical drugs. The results of clinical studies regarding the aforementioned botanical drugs and relevant mechanisms are summarized in this study. It is necessary to conduct high-quality clinical trials to verify the dosage, targeted patients and therapeutic effects, and further pharmacology experiments are also needed to identify the active compounds.

A Review on the Pharmacological Importance of PDE5 and Its Inhibition to Manage Biomedical Conditions

Phosphodiesterase type 5 (PDE5) is a cyclic GMP (cGMP) specific protein. It hydrolyzes the phosphodiesterase linkage and catalyzes the conversion of cGMP to 5’ GMP, which controls different physiological activities of the body. PDE5 is associated with biomedical conditions like neurological disorders, pulmonary arterial hypertension, cardiomyopathy, cancer, erectile dysfunction, and lower urinary tract syndrome. Inhibition of PDE5 has now been proven pharmaceutically effective in a variety of therapeutic conditions. Avanafil, tadalafil, sildenafil, and vardenafil are the most commonly used PDE5 inhibitors (PDE5i) today which are often used for the management of erectile dysfunction, lower urinary tract syndromes, malignancy, and pulmonary arterial hypertension. However, these synthetic PDE5i come with a slew of negative effects. Some of the most common side effects include mild headaches, flushing, dyspepsia, altered color vision, back discomfort, priapism, melanoma, hypotension and dizziness, non-arteritic anterior ischemic optic neuropathy (NAION), and hearing loss. In light of the potential negative effects of this class of medications, there is a lot of room for new, selective PDE5 inhibitors to be discovered. We have found 25 plant botanical compounds effectively inhibiting PDE5 which might be useful in treating a variety of disorders with minimal or no adverse effects.

Almond and date fruits enhance antioxidant status and have erectogenic effect: Evidence from in vitro and in vivo studies

This study was designed to investigate the efficacies of almond and date fruits on redox imbalance and enzymes relevant to the pathogenesis of erectile dysfunction. The total polyphenol contents, ferric reducing antioxidant power, and vitamin C content were determined spectrophotometrically. Phenolic and amino acid compositions were quantified using HPLC; meanwhile, the antioxidant activities were determined using DPPH, ABTS, FRAP, and metal chelation. Also, the effect of almond and date extract on advanced glycated end-products (AGEs) formation, arginase, and phosphodiesterase-5 activities was evaluated in vitro. Thereafter, the influence of almond and date supplemented diets on copulatory behaviors in normal rats was assessed, followed by arginase and phosphodiesterase-5 activities determination in vivo. The results revealed that date and almond extracts exerted antioxidant properties, prevented AGEs formation in vitro, and inhibited arginase and phosphodiesterase-5 activities in vitro and in vivo. Besides, almond and date supplemented diets significantly enhance sexual behaviors in normal rats when compared with the control. Among the active compounds identified were gallic acid, ellagic acid, quercetin, and rutin. All the 20 basic amino acids were identified. Given the aforementioned, date and almond could represent a reliable source of functional foods highly rich in compounds with antioxidant activity, and arginase and PDE-5 inhibitory properties. PRACTICAL APPLICATIONS: Fruits are essential part of the human diet that furnish the body with important nutrients. Despite the crucial roles of fruits in human diets, some fruits like almond and date are underutilized among Nigerians. However, we characterized the important compounds present in these fruits and how their presence contributes to the biological activities of the fruits. Finally, we relate the chemical composition and the observed biological activities to the overall health and wellness of the consumers.

Medicinal plants as a potential source of Phosphodiesterase-5 inhibitors: A review

ETHNOPHARMACOLOGICAL RELEVANCE

The prevalence and distress caused by erectile dysfunction (ED) to both male and female partners are increasing at a steady rate. ED has now become the most treated sexual disorder for men among young and old age groups due to varying physical and psychological factors. The treatment with synthetic Phosphodiesterase-5 (PDE5) inhibitors are cost-effective but due to adverse effects such as priapism, loss of vision, heart attack and syncope, the daily life patterns of these patients are distressed and hence the need for alternative medicaments or sources are of utmost important. Therefore, the exploration of medicinal plants as PDE5 inhibitors will be worthwhile in tackling the problems as many plant extracts and fractions have been long used as aphrodisiacs and sexual stimulants which may be found to be active against PDE5 enzyme.

AIM OF THE STUDY

To provide a review on the different medicinal herbs traditionally used as natural aphrodisiacs, libido or sexual enhancers which are proven for their PDE5 inhibitory effect.

MATERIALS AND METHODS

Ethnobotanical and scientific information was procured, reviewed and compiled from the literature search of electronic databases and search engines.

RESULTS

A total of 97 medicinal plants exhibiting PDE5 inhibitory effect are reviewed in this paper which is supported by preclinical experimental evidence. Among them, 77 plants have been selected according to their traditional and ethnobotanical uses as aphrodisiacs and the rest are screened according to their effectiveness against predisposing factors responsible for ED and sexual dysfunction such as diabetes and hypertension or due to the presence of phytochemicals having structural similarity towards the identified natural PDE5 inhibitors. In addition, sixteen alkaloids, sixty-one phenolics and eight polycyclic aromatic hydrocarbons have been isolated or identified from active extracts or fractions that are exhibiting PDE5 inhibitory activity. Among them, isoflavones and biflavones are the major active constituents responsible for action, where the presence of prenyl group for isoflavones; and the methoxy group at C-5 position of flavones are considered essential for the inhibitory effect. However, the prenylated flavonol glycoside, Icariin and Icariside II isolated from Epimedium brevicornum Maxim (hory goat weed) are the most effective inhibitor, till date from natural sources. Traditional medicines or formulations containing extracts of Ginkgo biloba L., Kaempferia parviflora Wall. ex Baker, Clerodendrum colebrookianum Walp., Eurycoma longifolia Jack and Vitis vinifera L. are also found to be inhibitors of PDE5 enzyme.

CONCLUSION

The review suggests and supports the rational use of traditional medicines that can be further studied for the development of potential PDE5 inhibitors. Many traditional medicines are still used in various regions of Africa, Asia and South America that are poorly characterized and experimented. Despite the availability of a vast majority of traditional formulations as aphrodisiacs or sexual stimulants, there exists a need for systemic evaluation on the efficacy as well as the mechanism of action of the herbal constituents for the identification of novel chemical moieties that can be further developed for maximum efficacy.

Botanical Medicine and Natural Products Used for Erectile Dysfunction

INTRODUCTION

Erectile dysfunction is the persistent or recurrent inability to achieve or maintain an erection sufficient for intercourse. Despite various treatment options, not all patients respond adequately and their usefulness is limited by adverse effects and cost. Botanical medicine and natural products have been and continue to be invaluable and untapped sources of new drugs, including potentially those to treat erectile dysfunction.

OBJECTIVES

To review the current literature on botanical medicine traditionally used as aphrodisiacs and treatment of erectile dysfunction, in particular, scientific and clinical investigations that have been performed, possible active phytoconstituents, and mechanisms of action and to identify gaps in current knowledge to better guide future research efforts.

METHODS

A comprehensive literature search was conducted via PubMed, Scopus, Science Direct, and Web of Science on English publications, using various keywords, for example, "herb", "natural product", combined with "erectile dysfunction", "aphrodisiac", and "sexual performance".

RESULTS

369 relevant articles studying medicinal plants used for erectile dysfunction were analyzed. A total of 718 plants from 145 families and 499 genera were reported to be used traditionally as aphrodisiacs and treatment of erectile dysfunction. Top plants used include Pausinystalia johimbe, Lepidium meyenii, and Panax ginseng. Different plant parts are used, with roots being the most common. Less than half of these plants have been evaluated scientifically, using various research methodologies. Clinical trials conducted were collated. Current scientific investigation shows mixed results about their usefulness in enhancing sexual performance. A limited number of studies have attempted to elucidate the mechanisms of action of these medicinal plants.

CONCLUSION

A comprehensive literature review on botanical medicine and natural products used for treatment of erectile dysfunction was successfully conducted. Although medicinal plants serve as a potential source of lead compounds for erectile dysfunction drugs, further studies are warranted to further evaluate their efficacy and safety. SinVJ-E, Anand GS, Koh H-L. Botanical Medicine and Natural Products Used for Erectile Dysfunction. Sex Med Rev 2020;XX:XXX-XXX.

HPLC phenolic fingerprinting, antioxidant and anti-phosphodiesterase-5 properties of Rauwolfia vomitoria extract

Background In Nigerian traditional medicine, Rauwolfia vomitoria has been reported to be useful in the management of various human diseases, but there is no relevant information to substantiate its involvement in managing diseases arising from vascular dysfunction and oxidative stress. However, this study sought to investigate the antioxidant property of R. vomitoria and its effect on phophodiesterase-5 activity in vitro. Methods The antioxidant property was assessed through ferric-reducing antioxidant power (FRAP), copper chelation, and ABTS radical-scavenging activity. In addition, the effect of R. vomitoria on phosphodiesterase-5 (PDE-5) activity was assessed in vitro. Furthermore, analysis of phenolic compounds present in R. vomitoria was carried out using high-performance liquid chromatography (HPLC). Results The findings in this study revealed that R. vomitoria inhibited PDE-5 in a dose-dependent manner (IC50 = 252.42 μg/mL). Furthermore, the antioxidant activity of R. vomitoria was established through FRAP (19.68 mg AAE/g), ABTS radical-scavenging ability (74.25 mmol TEAC/g), and Cu2+-chelating ability (IC50 = 0.13 mg/mL). Conclusions The antioxidant property of R. vomitoria and its inhibitory effect on PDE-5 could be useful in the management of diseases arising from vascular dysfunction and oxidative stress.

Discovery, synthesis and antibacterial evaluation of phenolic compounds from Cylicodiscus gabunensis

BACKGROUND

Cylicodiscus gabunensis Harms (Family Leguminosae) (CG) is an African medicinal plant used as a treatment of various ailments including malaria, liver diseases, and gastrointestinal disturbances. Its extracts showed potent in vitro antibacterial activity. However, the antibacterial components are unknown.

METHODS

In this study, the stem bark of the CG plant was extracted and its antibacterial property against a panel of Gram-negative and Gram-positive bacterial strains assessed using the disk diffusion assay method. Bioassay-guided fractionation of the bioactive extracts was employed to identify bioactive constituents using both gas and liquid chromatography mass spectrometry. Chemical synthesis was used to make the analogues of gallic acid. Microplate dilution assays and scanning electron microscopy (SEM) were used to evaluate the antibacterial properties and mechanism of action of the active fractions and pure compounds.

RESULTS

The most bioactive sub-fractions derived from CG comprised of ethyl gallate, gallic acid and polyphenols. Five alkyl/alkenyl gallates were synthesized. A preliminary structure-activity relationship of gallic acid derivatives was obtained using the synthetic analogues and a series of commercially available phenolic compounds. Increasing the length of alkyl chains generally increases the potency of the alkyl gallates. Introducing a double bond with restricted conformations of the C-5 side chain has little effect on the antibacterial property. SEM analysis of the effect of alkyl gallates on Staphylococcus aureus indicates that they appear to interrupt S. aureus bacterial cell wall integrity.

CONCLUSIONS

The results of this research rationalise the ethnobotanical use of C. gabunensis and suggest that gallate derivatives may serve as promising antibacterial agents for the treatment of infectious diseases.

Modulatory effect of some citrus (Citrus limon, Citrus reticulata, Citrus maxima) peels on monoamine oxidase, phosphodiesterase-5 and angiotensin-1 converting enzyme activities in rat heart homogenate

Background

Citrus peels have been reported useful in folk medicine for the management of cardiovascular diseases, but there is dearth of information on the possible mechanisms for their therapeutic action. The aim of this study was to investigate the effect of methanolic extracts from some citrus [lime (Citrus limon), tangerine (Citrus reticulata), shaddock (Citrus maxima)] peels on some enzymes relevant to the management of cardiovascular diseases [monoamine oxidase (MAO), phosphodiesterase-5 (PDE-5) and angiotensin-1-converting enzyme (ACE)].

Methods

Effect of methanolic extracts of lime, tangerine and shaddock peels on MAO, PDE-5 and ACE were carried out using standard methods. In addition, the ability of the extracts to prevent oxidative damage in rat heart homogenates was also investigated. Finally, the total polyphenol content of extracts was determined.

Results

The results revealed that methanolic extracts of lime, tangerine and shaddock peels inhibited MAO, PDE-5, ACE and pro-oxidants induced lipid peroxidation in rat heart homogenate in a concentration-dependent manner.

Conclusions

Findings in this study revealed citrus peel methanolic extracts as natural inhibitor of enzymes (MAO, PDE-5 and ACE) implicated in cardiovascular diseases. Therefore, citrus peels could help in the management of cardiovascular diseases possibly through inhibition of these enzymes.