Modified Akuamma Alkaloids with Increased Potency at the Mu-opioid Receptor.

Akuammine (1) and pseudoakuammigine (2) are indole alkaloids found in the seeds of the akuamma tree (Picralima nitida). Both alkaloids are weak agonists of the mu opioid receptor (µOR); however, they produce minimal effects in animal models of antinociception. To probe the interactions of 1 and 2 at the opioid receptors, we have prepared a collection of 22 semisynthetic derivatives. Evaluation of this collection at the µOR and kappa opioid receptor (κOR) revealed structural-activity relationship trends and derivatives with improved potency at the µOR. Most notably, the introduction of a phenethyl moiety to the N1 of 2 produces a 70-fold increase in potency and a 7-fold increase in selectivity for the µOR. The in vitro potency of this compound resulted in increased efficacy in the tail-flick and hot-plate assays of antinociception. The improved potency of these derivatives highlights the promise of exploring natural product scaffolds to probe the opioid receptors.

Erratum: Catechin ameliorates depressive symptoms in Sprague Dawley rats subjected to chronic unpredictable mild stress by decreasing oxidative stress.

[This corrects the article DOI: 10.3892/br.2019.1226.].

Assessment of preclinical effect of (+)-catechin hydrate on sexual function: An in silico and in vivo study.

Considering dopamine-enhancing effect of (+)-catechin, the present study was designed to evaluate dopamine-2 (D2) receptor agonistic and phosphodiesterase-5 (PDE5) enzyme inhibitory effects in in silico and effect on male sexual function of Sprague Dawley rats in vivo. (+)-Catechin and standard (sildenafil and bromocriptine) were docked using Autodock Vina 1.1.2 and visualised by UCSF Chimera 1.14. Significant interactions in terms of binding energies were observed for catechin with both proteins. In in vivo study, the rats were dosed orally for 54 days with (+)-catechin hydrate (50 mg/kg), sildenafil citrate (standard, 4 mg/kg) and carboxymethylcellulose (vehicle, 0.25% w/v). The aphrodisiac effects were evaluated on the day 14, 28, 42 and 54 using the behavioural parameters of mounting and intromission. After the study, animals were sacrificed and testes and spermatozoa were assessed for safety profile. Results showed a significant increase in mount and intromission frequencies and a significant reduction in mount and intromission latencies in the catechin group on all tested days when compared to vehicle control. (+)-Catechin was found to be safe on histology of testes, sperm count, sperm motility and sperm morphology parameters. In conclusion, catechin demonstrated an enhancement in sexual behaviour without eliciting toxicity on the male reproductive system in rats.

Catechin ameliorates depressive symptoms in Sprague Dawley rats subjected to chronic unpredictable mild stress by decreasing oxidative stress.

Catechin is an active ingredient of green tea. It is reported to inhibit corticosteroid-induced anxiety and depression-like symptoms. Considering the complex nature of depression, effects of catechin need to be studied in a clinically relevant depression model. The present study was designed to explore the antidepressant effect of catechin in Sprague Dawley rats subjected to chronic unpredictable mild stress (CUMS). Animals were subjected to CUMS and treated with (+)-catechin (50 mg/kg) or escitalopram (10 mg/kg) orally; a CUMS control and a vehicle control that was not exposed to CUMS were also established. Various stressors were applied daily in an unpredictable manner for 8 weeks achieve CUMS. Sucrose preference test were performed after 4 and 8 weeks and forced swim tests (FSTs) were conducted at weeks 4, 6 and 8. At the end of week 8, animals were sacrificed and the brain homogenate was studied for antioxidant parameters. Compared with the vehicle control, animals of the CUMS control group showed a significant decrease in sucrose intake. Catechin and escitalopram treatment significantly improved the sucrose intake compared with the CUMS control. A similar trend was observed in the FSTs, where catechin and escitalopram treatment significantly reduced the immobility time, and antioxidant parameters, including catalase, glutathione and superoxide dismutase levels were recovered in treated animals compared with the CUMS control. Thus, it was concluded that catechin reverses CUMS-induced depression in rats by ameliorating oxidative stress, which may help to develop a novel treatment for major depressive disorder.

Evaluation of the aphrodisiac potential of a chemically characterized aqueous extract of Tamarindus indica pulp.

ETHNOPHARMACOLOGICAL RELEVANCE: Tamarindus indica is an ingredient in the traditional aphrodisiac formulations in Africa and India. It is also a widely used food ingredient in other tropical countries. AIM OF THE STUDY: The present study was aimed to evaluate the aphrodisiac potential and reproductive safety profile of aqueous extract of Tamarindus indica in male Wistar rats. MATERIALS AND METHODS: The aqueous extract was prepared by maceration of pulp followed by reduction of volume in rotavapor under heat followed by freeze drying. The prepared extract was characterized for contents of total phenol, flavonoid, and saponin. It was also subjected to phytoconstituent analysis using GCMS. Further, the extract was evaluated for acute toxicity study. The aphrodisiac and reproductive toxicity potential were evaluated in animals after grouping them in four with six animals each namely, normal control, standard (Sildenafil citrate, 4mg/kg p.o.) and extract of Tamarindus indica treated groups at two dose levels, 125 and 250mg/kg p.o. The study was conducted for 54 days with daily once dosing of extract and standard. Equal number of females was grouped without treatment for evaluation of parameters of sexual desire (mount frequency and intromission frequency) and parameters of sexual arousal (mount latency and intromission latency). These parameters were evaluated on day 14, 28, 42 and 54. Animals were sacrificed on day 54, testes were removed and studied for histopathological changes. RESULTS: The extract showed 6.6mg gallic acid equivalent/g of total phenol, 2.3mg catechin equivalent/g of flavonoid and 11.6% saponin. Forty chemical constituents were identified by GCMS analysis. In acute toxicity study, the extract was found to be safe till 2000mg/kg p.o. Efficacy study showed significant (p<0.05) improvement in parameters of sexual desire (mount frequency and intromission frequency) and parameters of sexual arousal on all observed days except mount frequency for 125mg/kg on 42nd day and intromission frequency for both doses of tamarind compared to normal control. Improvements in these parameters were comparable to the standard drug. Histopathology study and sperm count suggested an increase in sperm production without any sign of toxicity in testis. Sperm motility significantly (p<0.05) increased in the treatment groups that received extract at 250mg/kg compared to normal control. CONCLUSION: Aqueous extract of Tamarindus indica possessed aphrodisiac activity together with spermatogenic potential.

Evaluation of antidepressant activity of methanolic extract of Saraca asoca bark in a chronic unpredictable mild stress model.

It is well established that chronic exposure to stressful events plays an important role in the etiology of depression. Saraca asoca (Roxb.), De. wild, or Saraca indica, belonging to family Fabaceae, is endogenous to India. The flowers, seeds, bark, and leaves of the plant have been used widely in Ayurveda medicine. The bark extract of S. asoca has shown chemoprotection, myeloprotection, and antioxidant potential. Owing to the above-mentioned properties of the plant, the present study sought to evaluate the effect of a methanolic extract of S. asoca bark in rats exposed to chronic unpredictable mild stress (CUMS) daily for 8 weeks using a forced-swim test, an open-field test, and a sucrose-preference test. The effect of the extract on endogenous antioxidant levels in the brain was also assessed using catalase activity, superoxide dismutase activity, reduced glutathione levels, and malondialdehyde levels in the brain. Male Sprague-Dawley rats received 100 mg/kg (oral) of the extract daily 1 h before daily stress exposure for 8 weeks. The extract showed a significant reduction in the immobility time in the forced-swim test, increased the total number of line crossing, rearing, and grooming in the open-field test, and increased the sucrose consumption as well as the levels of endogenous antioxidants significantly in comparison with the CUMS control group. Therefore, S. asoca might be a useful agent for the treatment or alleviation of symptoms associated with depression possibly by reducing CUMS-induced oxidative stress and reactive oxygen species in the brain.