Abstract
The use of herbal medicinal preparations in dementia therapy has been studied based on experience from traditional medicine. A dichloromethane extract of gum ammoniacum, the gum-resin from Dorema ammoniacum D. Don had shown acetylcholinesterase (AChE) inhibitory activity in a previous study. The aim of this study was the isolation and characterization of the active compounds from this resin. The extract was investigated by a respective colorimetric microplate assay and the active zones were identified via TLC bioautography and isolated using several chromatographic techniques. The structures of the active components were characterized by one- and two-dimensional 1H and 13C NMR spectroscopy and mass spectrometry as (2′S,5′S)-2′-ethenyl-5′-(3-hy-droxy-6-methyl-4-oxohept-5-en-2-yl)-7-methoxy-2′-methyl-4H-spiro[chromene-3,1′-cyclopentane]-2,4-dione (1), which is an analogue of doremone A and a new natural compound, and as (2′S,5′R)-2′-ethenyl-5′-[(2R,4R)-4-hydroxy-6-methyl-3-oxohept-5-en-2-yl]-7-methoxy-2′-methyl-4H-spiro[chromene-3,1′-cyclo-pentane]-2,4-dione (2 = doremone A), (4E,8E)-1-(2,4-dihydroxyphenyl)-5,9,13-trimethyltetradeca-4,8,12-trien-1-one (3 = dshamirone), and 4,7-dihydroxy-3-[(2E,6E)-3,7,11-trimethyldodeca-2,6,10-trien-1-yl]-2H-chromen-2-one (4 = am-moresinol). Dshamirone turned out to be the most active compound with an IC50 value for AChE inhibitory activity of 23.5 μM, whereas the other substances showed weak activity. The concentrations of the analytes in the resin were determined by HPLC as 3.1%, 4.6%, 1.9%, and 9.9%, respectively.
Highlights
It is commonly accepted that a cholinergic deficit correlates with the severity of Alzheimer's disease [1]
One therapeutic option is the use of acetylcholinesterase (AChE) inhibitors which block this key enzyme in the breakdown of acetylcholine [2]
A new compound and three known compounds were isolated from gum ammoniacum and their AChE inhibitory activities were determined for the first time
Summary
It is commonly accepted that a cholinergic deficit correlates with the severity of Alzheimer's disease [1]. The gum-resin, commonly known as gum ammoniacum, which is secreted from damaged stems and roots, has been traditionally used as an expectorant, stimulant, and antispasmodic drug in the Unani system of medicine [6]. It is used as an anthelmintic and for gastrointestinal disorders in Iranian traditional medicine (ITM) [7]. A low cytotoxic activity was shown for the essential oil from fruits of D. ammoniacum [9] It is listed in the British Herbal Pharmacopoeia as an antispasmodic and expectorant, and it is used occasionally for chronic bronchitis and persistent coughs [10, 11]
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