Convolamine, a tropane alkaloid extracted from Convolvulus plauricalis, is a potent sigma-1 receptor-positive modulator with cognitive and neuroprotective properties

BACKGROUND AND AIM

By using an in vivo phenotypic screening assay in zebrafish, we identified Convolamine, a tropane alkaloid from Convulvus plauricalis, as a positive modulator of the sigma-1 receptor (S1R). The wfs1abKO zebrafish larva, a model of Wolfram syndrome, exhibits an increased visual-motor response due to a mutation in Wolframin, a protein involved in endoplasmic reticulum-mitochondria communication. We previously reported that ligand activating S1R, restored the cellular and behavioral deficits in patient fibroblasts and zebrafish and mouse models.

EXPERIMENTAL PROCEDURES

We screened a library of 108 repurposing and natural compounds on zebrafish motor response.

KEY RESULTS

One hit, the tropane alkaloid Convolamine, restored normal mobility in wfs1abKO larvae without affecting wfs1abWT controls. They did not bind to the S1R agonist/antagonist binding site nor dissociated S1R from BiP, an S1R activity assay in vitro, but behaved as a positive modulator by shifting the IC50 value of the reference agonist PRE-084 to lower values. Convolamine restored learning in Wfs1∆Exon8 , Dizocilpine-treated, and Aβ25-35 -treated mice. These effects were observed at low ~1 mg/kg doses, not shared by Convolvine, the desmethyl metabolite, and blocked by an S1R antagonist.

CONCLUSION AND IMPLICATIONS

Convolamine therefore acts as an S1R positive modulator and this pharmacological action is relevant to the traditional use of Shankhpushpi in memory and cognitive protection.

Neuroprotective Herbs for the Management of Alzheimer's Disease

Background—Alzheimer’s disease (AD) is a multifactorial, progressive, neurodegenerative disease that is characterized by memory loss, personality changes, and a decline in cognitive function. While the exact cause of AD is still unclear, recent studies point to lifestyle, diet, environmental, and genetic factors as contributors to disease progression. The pharmaceutical approaches developed to date do not alter disease progression. More than two hundred promising drug candidates have failed clinical trials in the past decade, suggesting that the disease and its causes may be highly complex. Medicinal plants and herbal remedies are now gaining more interest as complementary and alternative interventions and are a valuable source for developing drug candidates for AD. Indeed, several scientific studies have described the use of various medicinal plants and their principal phytochemicals for the treatment of AD. This article reviews a subset of herbs for their anti-inflammatory, antioxidant, and cognitive-enhancing effects. Methods—This article systematically reviews recent studies that have investigated the role of neuroprotective herbs and their bioactive compounds for dementia associated with Alzheimer’s disease and pre-Alzheimer’s disease. PubMed Central, Scopus, and Google Scholar databases of articles were collected, and abstracts were reviewed for relevance to the subject matter. Conclusions—Medicinal plants have great potential as part of an overall program in the prevention and treatment of cognitive decline associated with AD. It is hoped that these medicinal plants can be used in drug discovery programs for identifying safe and efficacious small molecules for AD.

Effect of Shankhpushpi on Alcohol Addiction in Mice

Alcohol addiction is a worldwide problem. It has mainly two components: dependence and withdrawal. Characteristic properties of most anti-addictive compounds include anti-anxiety, anticonvulsant, antidepressant, and nootropic actions. Shankhpushpi (Convolvulus pluricaulis. Convolvulaceae), known ethnopharmacologically as brain tonic, possess all the properties mentioned above. Here, we screen shankhpushpi for possible anti-addictive potential. Effect of shankhpushpi churna was measured on ethanol withdrawal anxiety using elevated plus maze. The role of shankhpushpi on chronic ethanol consumption (21 days) was measured using two bottle choice protocol of voluntary drinking. We also measured the effect of the above herb on cortico-hippocampal GABA levels. Shankhpushpi was found to reduce alcohol withdrawal anxiety in a dose-dependent manner. The herb also decreased ethanol intake and increased water intake significantly (P < 0.001) after 4 days of administration. Both these effects were blocked (P < 0.001) by GABAA antagonist suggesting the role of GABAA receptor. Chronic administration of shankhpushpi also significantly (P < 0.01) increased cortico-hippocampal GABA levels in mice. Shankhpushpi reduced both alcohol dependence and withdrawal in a GABAA-dependent manner, thus showing anti-addictive potential.

Dermal wound healing potency of single alkaloid (betaine) versus standardized crude alkaloid enriched-ointment of Evolvulus alsinoides

CONTEXT

Evolvulus alsinoides Linn. (Convolvulaceae), well known as shankhpushpi in Ayurvedic text, is traditionally used for several healing purposes.

OBJECTIVE

A comparative evaluation of dermal wound healing potential of acidic and basic alkaloid enriched-ointment (AAO and BAO) of aerial parts of E. alsinoides versus pure alkaloid, betaine (BEO), was undertaken.

MATERIAL AND METHODS

The effect of topical application (50 mg/animal/day) of AAO-1%, AAO-2%, BAO-1%, BAO-2%, BEO-0.5% and BEO-1% was assessed through excision (14 days) and incision (10 days) models on rats. The percentage wound contraction, total protein content, and breaking strengths were determined followed by histopathological studies.

RESULTS AND DISCUSSION

The total alkaloid in acidic and basic alkaloid enriched fractions was found to be 0.1114 and 0.1134 μg/mL, respectively. Thus, 0.1528, 0.3056, 0.1380 and 0.2459 μg of total alkaloid were estimated to be present in AAO-1%, AAO-2%, BAO-1% and BAO-2%, respectively. AAO and BAO promoted wound healing activity significantly in both the models. Higher rate of wound contraction (p < 0.001) with significant increase in protein content in the treatment groups (from 2.32 to 2.55) demonstrated stimulation of cellular proliferation and epithelization, which was further supported by histopathological reports. High skin breaking strength (mean value 393 in control was increased to the range of 535-572 in treated groups) proved a significant (p < 0.001) wound healing potential of E. alsinoides. Early dermal and epidermal regeneration in drug-treated groups also confirmed the positive effect.

CONCLUSION

Observation of higher healing power of alkaloid enriched-ointment compared with single alkaloid ointment corroborated the synergy mechanism.

Attenuating effect of bioactive coumarins from Convolvulus pluricaulis on scopolamine-induced amnesia in mice

Convolvulus pluricaulis Chois. (Convolvulaceae) has been used in Ayurveda as Medhya Rasyana (nervine tonic) to treat various mental disorders. This study was designed to isolate the bioactive compound(s) of this plant and to evaluate their effect against scopolamine-induced amnesia. Column chromatography of the chloroform and ethyl-acetate fractions led to the isolation of three coumarins identified as scopoletin, ayapanin and scopolin. All the three compounds at 2.5, 5, 10 and 15 mg/kg, p.o. were evaluated for memory-enhancing activity against scopolamine-induced amnesia using elevated plus maze and step down paradigms. Effect on acetylcholinesterase activity in mice brain was also evaluated. Scopoletin and scopolin, in both the paradigms, significantly and dose dependently attenuated the scopolamine-induced amnesic effect. Furthermore, these compounds at 10 and 15 mg/kg exhibited activity comparable to that of standard drug, donepezil. The compounds also exhibited significant acetylcholinesterase inhibitory activity.