Herbal treatment of Alzheimer's disease
251 OH
O
N
CH3
H3CO
Figure 2. Structure of galanthamine.
which were in compliant with our study. For medical application, galanthamine has been isolated from plant material especially from L. aestivum until that the total chemical synthesis of galanthamine on an industrial scale has been economically achieved [59] and its biosynthetic pathway was fully explained by which 4'-O-methyl-N-norbelladine was the precursor [60]. Crystallographic structure and other conformational properties of the molecule were also reported [61]. Acetylcholinesterase (AChE) inhibitors, which are also called “anticholinesterase drugs”, have been recently approved as a promising treatment approach against AD. Galanthamine has been found to be the longacting and specific inhibitor of AChE enzyme and to potentiate cholinergic nicotinic neurotransmission by allosterically modulating nicotinic acetylcholine receptors which may be of additional value in the treatment of AD [55,6264]. Being one of the newest anticholinesterase drugs emerged in the market, it has been approved as its HBr salt for the first time in Austria (Nivalin®), later licensed as Reminyl® in the USA, some European countries as well as Turkey, and more recently under the name Razadyne®. Undoubtedly, any other drug class, AChE inhibitors may also differ from one another with respect to enormity and duration of effect. According to Giacobini [65], for some AChE inhibitors such as physostigmine, galanthamine, eptastigmine, and metrifonate, the relation between AChE inhibition and cognitive effect seem to be different than other AChE inhibitors including tacrine and donepezil in terms of efficacy and adverse effects. Although the most common side effect observed after galanthamine administration is nausea, it is possible to eliminate nausea by increasing the galanthamine dose slowly [66]. In addition, galanthamine was shown to be safe from the view point of hepatotoxicity [67]. Another advantage of galanthamine