Antimicrobial and acetylcholinesterase inhibition activities of an endemic plant from Sahara: Myrtus nivellei Batt. & Trab. (Myrtaceae)

Myrtus nivellei is a medicinal plant used traditionally in Algeria to treat several disorders including skin diseases, diarrhea, fever and diabetes¹. Very little is known about the phytochemistry and biological activities of this plant, which might contain antimicrobial compounds. In addition, its close relative M. communis is well studied and contains inhibitors of acetylcholinesterase (AChE), an enzyme that is currently targeted to treat symptoms of Alzheimer's disease. The aim of this study is to investigate antimicrobial and anti-AChE activities in M. nivellei and to purify new active compounds. A crude methanol/water (80:20) extract of M. nivellei aerial parts (500 g) was fractionated by liquid/liquid partition using three solvents of increasing polarity. From 500 g of dried plant material we obtained 71.4 g, 1.2 g, 21.4 g, 2.1 and 31.4 g of hydro-alcoholic, petroleum ether, CHCl₃, EtOAc and n-BuOH dried extracts, respectively. All extracts were then tested by bioautography for their anti-AChE activity². The bioautography revealed that the crude extract and the the chloroformic fraction contain at least five active compounds with AChE inhibitory activity. The chloroformic extract (19 g) was then further fractionated with an open column chromatography using different solvents in various proportions. 24 sub-fractions were obtained and tested for their inhibitory activity on AChE. Several of them were still active, including the 5 major components but also other molecules. The most active components will be purified and further studied with AChE microplate assays. In addition, the crude hydro-alcoholic extract was tested on Hepatitis C Virus (HCV) and 36 strains of bacteria. Although it showed no antiviral activity, the crude extract was active (at 0.6 mg/mL or less) on 7 strains of bacteria, including Staphylococcus epidermidis and Mycobacterium smegmatis, which can be involved in skin diseases. Further studies are in progress to identify new active compounds.

Keywords: Myrtus nivellei, acetylcholinesterase inhibition, antimicrobial assays, bio-guided fractionation, bioautography.

References:

[1] Bouzabata A, Bazzali O, Cabral C, Gonçalves MJ, Cruz MT, Bighelli A, Cavaleiro C, Casanova J, Salgueiro L, Tomi F. New compounds, chemical composition, antifungal activity and cytotoxicity of the essential oil from Myrtus nivellei Batt. & Trab., an endemic species of Central Sahara. J Ethnopharmacol 2013; 149: 613 – 620.

[2] Yang Z, Zhang X, Duan D, Song Z, Yang M. Modified TLC bioautographic method for screening acetylcholinesterase inhibitors from plant extracts. J Sep Sci 2009; 32: 3257 – 3259.