[Treatment of Parkinson disease]

Beauty of the beast: anticholinergic tropane alkaloids in therapeutics

Tropane alkaloids (TAs) are among the most valued chemical compounds known since pre-historic times. Poisonous plants from Solanaceae family (Hyoscyamus niger, Datura, Atropa belladonna, Scopolia lurida, Mandragora officinarum, Duboisia) and Erythroxylaceae (Erythroxylum coca) are rich sources of tropane alkaloids. These compounds possess the anticholinergic properties as they could block the neurotransmitter acetylcholine action in the central and peripheral nervous system by binding at either muscarinic and/or nicotinic receptors. Hence, they are of great clinical importance and are used as antiemetics, anesthetics, antispasmodics, bronchodilator and mydriatics. They also serve as the lead compounds to generate more effective drugs. Due to the important pharmacological action they are listed in the WHO list of essential medicines and are available in market with FDA approval. However, being anticholinergic in action, TA medication are under the suspicion of causing dementia and cognitive decline like other medications with anticholinergic action, interestingly which is incorrect. There are published reviews on chemistry, biosynthesis, pharmacology, safety concerns, biotechnological aspects of TAs but the detailed information on anticholinergic mechanism of action, clinical pharmacology, FDA approval and anticholinergic burden is lacking. Hence the present review tries to fill this lacuna by critically summarizing and discussing the above mentioned aspects.

Tropane Alkaloids: Chemistry, Pharmacology, Biosynthesis and Production

Tropane alkaloids (TA) are valuable secondary plant metabolites which are mostly found in high concentrations in the Solanaceae and Erythroxylaceae families. The TAs, which are characterized by their unique bicyclic tropane ring system, can be divided into three major groups: hyoscyamine and scopolamine, cocaine and calystegines. Although all TAs have the same basic structure, they differ immensely in their biological, chemical and pharmacological properties. Scopolamine, also known as hyoscine, has the largest legitimate market as a pharmacological agent due to its treatment of nausea, vomiting, motion sickness, as well as smooth muscle spasms while cocaine is the 2nd most frequently consumed illicit drug globally. This review provides a comprehensive overview of TAs, highlighting their structural diversity, use in pharmaceutical therapy from both historical and modern perspectives, natural biosynthesis in planta and emerging production possibilities using tissue culture and microbial biosynthesis of these compounds.

[No Parkinsonian syndrome following acute paraquat poisoning]

Paraquat structurally resembles N-methyl-4-phenyltetrahydropyridine (MPTP) and its metabolite 1-methyl-4-phenylpyridine (MPP+). MPTP and MPP+ are neurotoxic chemicals, which induce in exposed humans and in animal-models a Parkinson's disease. A high correlation between the incidence of Parkinson's disease and herbicide use in Canada led to the assumption that paraquat could give rise to parkinsonism. We have therefore carried out a follow-up study with patients having had dermal contact with paraquat or having swallowed paraquat accidentally or in a suicidal attempt. 7 patients took part in the study. Three of them had dermal contact. One had ingested paraquat by accident and three were survivors from suicidal paraquat intake. It was possible to exclude parkinsonism in all patients. One patient exhibited tardive dykinesia most likely due to a long term therapy with neuroleptic drugs.