CANESCINE AND PSEUDOYOHIMBINE FROM THE ROOTS OF RAUWOLFIA CANESCENS L.1

Genus Rauvolfia: A review of its ethnopharmacology, phytochemistry, quality control/quality assurance, pharmacological activities and clinical evidence

ETHNOPHARMACOLOGICAL RELEVANCE

The plants are from the genus Rauvolfia Plum. ex L. (Apocynaceae), which is represented by 74 species with many synonyms, and distributed worldwide, especially in the Asian, and African continents. Traditionally, some of them are used for the treatment of various disorders related to the central nervous system (CNS), cardiovascular diseases (CVD), and as an antidote due to the presence of monoterpene indole alkaloids (MIAs) such as ajmaline (144), ajmalicine (164) serpentine (182), yohimbine (190) and reserpine (214).

AIM

The present review provides comprehensive summarization and critical analysis of the traditional to modern applications of Rauvolfia species, and the major focus was to include traditional uses, phytochemistry, quality control, pharmacological properties, as well as clinical evidence that may be useful in the drug discovery process.

MATERIALS AND METHODS

Information related to traditional uses, chemical constituents, separation techniques/analytical methods, and pharmacological properties of the genus Rauvolfia were obtained using electronic databases such as Web of Science, Scopus, SciFinder, PubMed, PubChem, ChemSpider, and Google Scholar between the years 1949-2021. The scientific name of the species and its synonyms were checked with the information of The Plant List.

RESULTS

A total of seventeen Rauvolfia species have been traditionally explored for various therapeutic applications, out of which the roots of R. serpentina and R. vomitoria are used most commonly for the treatment of many diseases. About 287 alkaloids, seven terpenoids, nine flavonoids, and four phenolic acids have been reported in different parts of the forty-three species. Quality control (QC)/quality assurance (QA) of extracts/herbal formulations of Rauvolfia species was analyzed by qualitative and quantitative methods based on the major MIAs such as compounds 144, 164, 182, 190, and 214 using HPTLC, HPLC, and HPLC-MS. The various extracts of different plant parts of thirteen Rauvolfia species are explored for their pharmacological properties such as antimicrobial, antioxidant, antiprotozoal, antitrypanosomal, antipsychotic, cardioprotective, cholinesterase inhibitory, and hepatoprotective. Of which, clinical trials of herbal formulations/extracts of R. serpentina and MIAs have been reported for CVD, CNS, antihypertensive therapy, antidiabetic effects, and psoriasis therapy, while the extracts and phytoconstituents of remaining Rauvolfia species are predominantly significant, owning them to be additional attention for further investigation under clinical trials and QC/QA.

CONCLUSION

The present communication has provided a comprehensive, systematic, and critically analyzed vision into the traditional uses, phytochemistry, and modern therapeutic applications of the genus Rauvolfia are validated by scientific evidence. In addition, different plant parts from this genus, especially raw and finished herbal products of the roots of R. serpentina have been demonstrated for the QC/QA.

Some Observations on the Pharmacology of 10-Methoxydeserpidine

10-Methoxydeserpidine caused a slow sustained fall in the arterial blood pressure of the anaesthetised cat when doses of 2 to 4 mg./kg. were given, an effect seen only when the initial blood pressure was high. Unlike reserpine and deserpidine, 10-methoxydeserpidine did not cause ptosis or loose stools in mice or rats when used at doses of from 10 to 80 mg./kg. and although pentobarbitone sleeping time was not increased, at higher doses of 40 to 80 mg./kg. there was reduction of motor activity, respiratory depression and some animals died. Unlike deserpidine the 10-methoxy derivative had no effect on the pressor responses to compression of the abdominal aorta or stimulation of the splanchnic nerve, but depressed the response to occlusion of the common carotid arteries. The LD50 of 10-methoxydeserpidine was found to be 82 ± 2–6 mg./kg. in mice. Methyl reserpate and reserpic acid showed reserpine-like activity in intact animals and isolated tissues only at very high doses.

A clinical trial of deserpidine and reserpine in the treatment of the chronic schizophrenic

Recent work, such as that of Moore and Martin (1957), has shown that reserpine is of value in the treatment of the chronic schizophrenic patient. Attention has however been drawn to the incidence of side-effects in this form of treatment. These side-effects have limited the application of the drug and have also led to the search for a related substance, of similar clinical effect but without the troublesome toxic effects. This present trial is of a substance, deserpidine (Harmonyl, Abbott Laboratories), which it was thought would fulfil these requirements. The isolation of this alkaloid was first reported in 1955 by Stoll and Hofman, and it has subsequently been identified as 11-desmethoxy-reserpine (Harrisson, 1955) which can be represented thus: