Neuropharmacological evaluation of selected Jordanian traditional herbal medicines

Abstract

Numerous medicinal plants have been described in traditional medicine for treatment of dementias, including Alzheimer’s disease (AD). In this study, some of these plants were evaluated in three different types of pharmacological bioassays related to AD pathology to explore the possible mechanisms underpinning their traditional use. Six selected plants were extracted with ethanol and screened in vitro for acetylcholinesterase (AChE) and cycloxygenase-1 (COX-1) enzyme inhibitory activities; in addition, a range of anti-oxidant activities were evaluated. Of the tested plant extracts, Aloysia citrodora and Peganum harmala root and seeds showed inhibitory effect on AChE (IC50 68, 100 and 93 μg/ml,) respectively).. Moreover, A. citrodora appeared to interact reversibly with the enzyme, while P. harmala appeared to show irreversible inhibition. Asphodelus microcarpus, Inula viscosa and A. citrodora displayed COX-1 enzyme inhibitory activity (IC50 34.9, 3.4 and 3.2 μg/ml respectively). DPPH radical scavenging activity was demonstrated by all tested plants. Two extracts in particular (Arbutus andrachne and A. microcarpus) exhibited potent nitric oxide (NO) scavenging activity (IC50 4.5 and 5.0 ug/ml respectively). Four extracts A. citriodora, P. harmala (Root) and (seed) and A. microcarpus exhibited strong metal chelating ability (IC50 4.5, 6.2, 6.5 and 6.7 μg/ml,) respectively). The modest reversible interaction of A. citrodora with AChE, COX-1inhibitory and antioxidant activity, and strong metal chelating ability make this plant a promising candidate for future development in the treatment of AD, either as a whole extract or as individual bioactive constituents. A. andrachne and A. microcarpus extracts should be further evaluated since they exhibited promising NO scavenging activities. Key words: Anti-acetylcholinesterase, anti-inflammatory, anti-oxidant, metal chelating ability, Jordanian medicinal plants, Alzheimer’s disease.