A Comprehensive Overview on Valuable Tropane Alkaloids: Scopolamine, Atropine, and Hyoscyamine

Tropane alkaloids such as scopolamine (C17H21NO4), atropine (C17H23NO3) and hyoscyamine (C17H23NO3) are the most important plant secondary metabolites in the pharmaceutical industry due to anticholinergic activity, competition with muscarinic receptors and also treating different human diseases. Scopolamine, hyoscyamine and atropine are the most important tropane alkaloids used as anticoagulants and spasmolytic drugs in the digestive system and urinary excretion. Tropane alkaloids are natural phytochemical compounds, which are present in different plant families. These compounds are the main secondary metabolites in Solanaceae family plants such as Hyoscyamus niger and Atropa belladonna. The main source of raw material for the production of tropane alkaloids in the world is Duboisia spp. leaves which contain 2-4% alkaloids (more than 60% scopolamine, and 30% hyoscyamine). Common methods of analysis of tropane alkaloids include gas chromatography (GC), high-performance liquid chromatography (HPLC) and capillary electrophoresis (CE), in which liquid chromatography is mostly adopted. Various enzymes involved in the biosynthesis of tropane alkaloids, in which N- Putrescine methyltransferase (PMT), tropinone reductase I and II, and hyoscyamine 6-beta-hydroxylase (H6H) have a key role. To increase the biosynthesis of these important alkaloids, many studies were focused on the manipulation of key genes expressing enzymes in the biosynthesis pathway such as pmt and h6h genes. Although many biotechnological and agronomic studies have been done to increase the biosynthesis efficiency of these metabolites, further investigations are necessary. This paper is intended to provide a comprehensive overview of these tropane alkaloids.