Activities of extract and constituents of Banisteriopsis caapi relevant to parkinsonism

Introduction

Schwarz and colleagues situate their study in the context of both traditional and more recent therapeutic interest in Banisteriopsis caapi, a principal botanical component of the ayahuasca brew. Earlier work has shown that B. caapi contains beta-carboline alkaloids such as harmine and harmaline that inhibit monoamine oxidases (MAOs), enzymes that would otherwise degrade monoamine neurotransmitters and compounds such as N,N-dimethyltryptamine. Historical, and more recent, anecdotal and small clinical reports have suggested symptomatic benefit from B. caapi extracts in patients with Parkinson's disease (PD), a disorder characterised by striatal dopamine deficiency for which current treatments such as L-DOPA can produce long-term complications including dyskinesia and motor fluctuations. This study therefore set out to examine in vitro activities of an aqueous stem extract of B. caapi and two of its major constituents, harmine and harmaline, that are relevant to Parkinsonism. Specifically, the investigators tested MAO-A and MAO-B inhibitory activity in rat liver homogenates and assessed the ability of the extract and the alkaloids to stimulate release of [3H]dopamine from rat striatal slices, with the aim of determining whether these pharmacological properties could provide a biochemical basis for the reported clinical effects.