Narcissus nivalis: A New Source of Galanthamine1

Amaryllidaceae alkaloids from the bulbs of Crinum latifolium L. and their cholinesterase inhibitory activities

Eleven previously undescribed Amaryllidaceae alkaloids, crinalatifolines A-K (1-11), and two first naturally occurring alkaloids, dihydroambelline (12) and N-demethyldihydrogalanthamine (13), were isolated from the bulbs of Crinum latifolium L. Additionally, thirty-seven known alkaloids and one alkaloid artifact were also isolated from this plant species. Their structures and absolute configurations were elucidated using extensive spectroscopic techniques, including IR, NMR, MS, and ECD. Evaluations of the cholinesterase inhibitory activities of most of these compounds were conducted. Among the tested compounds, ungeremine exhibited the highest potency against acetylcholinesterase and butyrylcholinesterase, with the IC50 values of 0.10 and 1.21 μM, respectively. These values were 9.4- and 2.4-fold more potent than the reference drug galanthamine.

Crinamine from Crinum asiaticum var. japonicum inhibits hypoxia inducible factor-1 activity but not activity of hypoxia inducible factor-2

In a search for natural product inhibitors of hypoxia inducible factor-1 (HIF-1) function, crinamine (1), a crinane type alkaloid, showed potent dose dependent inhibition (IC50 = 2.7 microM) of HIF-1alpha in a cell-based reporter gene assay. Crinamine (1) was isolated from the aerial parts of Crinum asiaticum var. japonicum together with lycorine (2), norgalanthamine (3) and epinorgalanthamine (4). The other components (2-4) showed no significant inhibition of HIF-1alpha induced transcriptional activity.

Chemical and biological aspects of Narcissus alkaloids

This chapter discusses the chemical and biological aspects of Narcissus alkaloids. Numerous alkaloids have been isolated from Narcissus speciesasaresult of the continuing search for novel alkaloids with pharmacological activity in the Amaryllidaceae family. The alkaloids isolated from this genus, classified in relation to the different skeleton types. The different Narcissus wild species and intersectional hybrids, grouped into subgenera and sections, with their corresponding alkaloids, arranged according to their ring system are listed. The biosynthetic pathways of Narcissus alkaloids includes: (1) enzymatic preparation of the precursors, (2) primary cyclization mechanisms, (3) enzymatic preparation of intermediates, (4) secondary cyclization, diversification, and restructuring. The chapter discusses proton nuclear magnetic resonance (1H NMR), carbon nuclear magnetic resonance (13C NMR), and mass spectrometry (MS) for Narcissus alkaloids. A list of the different Narcissus alkaloids, their spectroscopic properties, and literature with the most recent spectroscopic data is given. Several Narcissus extracts shows the following activities: antiviral, prophage induction, antibacterial, antifungal, antimalarial, insecticidal, cytotoxic, antitumor, antimitotic, antiplatelet, hypotensive, emetic, acetylcholine esterase inhibitory, antifertility, antinociceptive, chronotropic, pheromone, plant growth inhibitor, and allelopathic.

Clinical Pharmacokinetics of Galantamine

Galantamine is the most recently approved cholinergic drug for the treatment of Alzheimer's disease, the most common type of dementia. Vascular dementia and Alzheimer's disease with cerebrovascular disease are also common in older patients. Dementia affects cognition, causes losses in ability to perform activities of daily living and often results in the emergence of psychiatric and abnormal behavioural symptoms. Dementia also results in an ever-increasing burden and a decreased quality of life for caregivers. Treatments for dementia, particularly Alzheimer's disease, have focused on improving function in the cholinergic system. Vascular dementia and diffuse Lewy body dementia are also associated with significant defects in cholinergic function. Galantamine works by inhibiting acetylcholinesterase and by allosterically modulating nicotinic receptors. In clinical trials, galantamine has shown benefits in the domains of cognition, function in activities of daily living, and behaviour. Galantamine is about 90% bioavailable and displays linear pharmacokinetics. It has a relatively large volume of distribution and low protein binding. Metabolism is primarily through the cytochrome P450 system, specifically the CYP2D6 and CYP3A4 isoenzymes. Population pharmacokinetic modelling with galantamine has shown that the variables affecting clearance are age, sex, and bodyweight. Model simulations demonstrate the importance of a slower dose-escalation schedule in patients with moderate hepatic impairment. In several large trials, galantamine has been shown to be well tolerated, with most adverse events being mild-to-moderate and gastrointestinal in nature. Based on the literature and clinical trial experience, galantamine appears to be an excellent treatment option for patients with Alzheimer's disease, vascular dementia or Alzheimer's disease with cerebrovascular disease.

Antiinflammatory constituents from Heterotheca inuloides

Three new compounds, cadalen-15-oic acid (1), 3,7-dihydroxy-3(4H)-isocadalen-4-one (2), and dicadalenol (3), were isolated from the aerial parts of Heterotheca inuloides (Mexican arnica), together with the known compounds 7-hydroxycadalene (4), 7-hydroxy-4alphaH-3,4-dihydrocadalene (5), 1alpha-hydroxy-1(4H)-isocadalen-4-one (6), 1alpha-hydroxy-4alphaH-1,2,3,4-tetrahydrocadalen-15-oic acid (7), 7-(3,3-dimethylallyloxy)coumarin, caryolan-1,9beta-diol, and quercetin. The structures of the new compounds were elucidated by spectroscopic methods. The antiinflammatory activities of the extracts and the isolated compounds were evaluated by determining the inhibition of TPA-induced mouse ear edema. The natural products 3, caryolan-1,9beta-diol, and quercetin were the most active substances tested and displayed dose-dependent activities.

Galantamine: a review of its use in Alzheimer's disease

Currently, acetylcholinesterase (AChE) inhibitors are the most promising class of drugs for the treatment of Alzheimer's disease (AD). Galantamine is a reversible, competitive, tertiary alkaloid AChE inhibitor. The drug is selective for AChE rather than butyrylcholinesterase. In addition to inhibition of AChE galantamine interacts allosterically with nicotinic acetylcholine receptors to potentiate the action of agonists at these receptors. Recipients of galantamine 16 or 24 mg/day achieved significant improvements in cognitive and global symptoms relative to placebo recipients in large (n = 285 to 978 patients with mild to moderate AD) well-designed trials of 3 to 6 months' duration. Galantamine also improved activities of daily living in these patients and significantly reduced the requirement for caregiver assistance with activities of daily living. Moreover, galantamine recipients achieved significantly better outcomes on behavioural symptoms than placebo recipients. In a long term study (12 months), galantamine 24 mg/day slowed the progression of symptoms of the disease and maintained cognitive function and activities of daily living in patients with mild to moderate AD. Galantamine was generally well tolerated with the majority of adverse events being mild to moderate in intensity and transient. Predictably, adverse events were cholinergic in nature and generally related to the gastrointestinal system. These effects were reduced in patients receiving the recommended dose escalation regimen. Galantamine had no clinically relevant effects on vital signs, haematological or biochemical laboratory parameters and, importantly, there were no reports of hepatotoxicity. The incidence of serious adverse events was similar between galantamine (8 to 32 mg/day) and placebo groups (6 to 16% of patients across all treatment groups).

CONCLUSIONS

Galantamine is an effective well tolerated symptomatic treatment for AD which improves cognition, function and activities of daily living in the short term (up to 6 months) in patients with mild to moderate AD. In addition, it delays the development of behavioural disturbances and psychiatric symptoms, and reduces caregiver burden (as measured by caregiver time). In the long term (up to 1 year), galantamine maintains cognition and activities of daily living. Adverse events associated with galantamine are mainly cholinergic, usually mild to moderate in intensity and transient. Galantamine has been evaluated in several large well-designed studies and, given the relative lack of established treatment options, it may be considered as one of the first-line pharmacological treatments in patients with mild to moderate AD.

The pharmacology of galanthamine and its analogues

Galanthamine is an alkaloid found in the bulbs of snowdrops and several Amaryllidaceae plants. At submicromolar concentrations, it inhibits acetylcholinesterase activity, but it is much less potent against butyrylcholinesterase activity. Galanthamine has been used in anaesthetics to reverse neuromuscular paralysis by tubocurarine-like muscle relaxants, but it is a tertiary amine that gets into the brain to cause central effects. Galanthamine is being studied as a possible therapeutic agent in Alzheimer's disease because of its central cholinergic effects. Positive effects have been demonstrated in several learning and memory tests in animals.