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A series of Lycopodium alkaloids, namely lycosquarosine A (1), acetylaposerratinine (2), huperzine A (3), huperzine B (4), 8α-hydrophlemariurine B (5) and huperzinine (6), has been isolated from Vietnamese Huperzia squarrosa. Among them, lycosquarosine A (1) is the new metabolite of the natural source. Lycosquarosine A completely inhibited AChE activity in a dose dependent manner with an IC50 value of 54.3 μg/mL, while acetylaposerratinine (2) showed stronger inhibitory activity than 1 with an IC50 value of 15.2 μg/mL. This result indicates that these alkaloids may be a potent source of AChE inhibitors. This is the first report on the alkaloid constituents of H. squarrosa from Vietnam and the potential cholinesterase inhibitory activity of these compounds might suggest new sources of anti-Alzheimer disease agents.
Keywords: Huperzia squarrosa; Lycopodiaceae; lycosquarosine A; acetylcholinesterase; Lycopodium alkaloids.
1. INTRODUCTION
Alzheimer’s disease (AD) is a neurodegenerative disease and the most frequent and predominant cause of dementia among the elderly, provoking progressive cognitive decline, psychobehavioral disturbances, memory loss, presence of senile plaques, neurofibrillary tangles and a decrease in cholinergic transmission [1,2]. The majority of AD cases are sporadic, whereas 5% are early onset familial AD [3,4]. Neuropathological evidence has demonstrated that cholinergic functions decline in the basal forebrain and cortex in senile dementia of the Alzheimer type [5]. Accordingly, the enhancement of cholinergic neurotransmission has been considered as one potential therapeutic approach against AD. Although the pathogenesis of AD is complicated and involves numerous pathways, two major hypotheses are currently under consideration regarding the molecular mechanism: The cholinergic hypothesis and the amyloid cascade hypothesis. Thus, the focus herein is upon selective cholinesterase (ChE) inhibitors in order to alleviate cholinergic deficits and improve neurotransmission. Pursuant to this, both could be established as viable therapeutic targets for AD [5– 7]. Several AD histopathologic criteria are commonly used [8-10]. One treatment strategy to enhance the cholinergic function is the use of acetylcholinesterase (AChE, EC 3.1.1.7) inhibitors to increase the amount of acetylcholine, which is present in the synapses between cholinergic neurons [11]. AChE inhibitors such as donepezil, rivastigmine and galantamine, which are the most extensively studied AChE inhibitors, have been shown to significantly improve cognitive function in AD [12,13].
Club moss (Lycopodiaceae) species are well-known to be a rich source of Lycopodium alkaloids possessing a complex heterocyclic ring system and wide ranging biological properties that have
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A series of Lycopodium alkaloids, namely lycosquarosine A (1), acetylaposerratinine (2), huperzine A (3), huperzine B (4), 8α-hydrophlemariurine B (5) and huperzinine (6), has been isolated from Vietnamese Huperzia squarrosa. Among them, lycosquarosine A (1) is the new metabolite of the natural source. Lycosquarosine A completely inhibited AChE activity in a dose dependent manner with an IC50 value of 54.3 μg/mL, while acetylaposerratinine (2) showed stronger inhibitory activity than 1 with an IC50 value of 15.2 μg/mL. This result indicates that these alkaloids may be a potent source of AChE inhibitors. This is the first report on the alkaloid constituents of H. squarrosa from Vietnam and the potential cholinesterase inhibitory activity of these compounds might suggest new sources of anti-Alzheimer disease agents.
Keywords: Huperzia squarrosa; Lycopodiaceae; lycosquarosine A; acetylcholinesterase; Lycopodium alkaloids.
1. INTRODUCTION
Alzheimer’s disease (AD) is a neurodegenerative disease and the most frequent and predominant cause of dementia among the elderly, provoking progressive cognitive decline, psychobehavioral disturbances, memory loss, presence of senile plaques, neurofibrillary tangles and a decrease in cholinergic transmission [1,2]. The majority of AD cases are sporadic, whereas 5% are early onset familial AD [3,4]. Neuropathological evidence has demonstrated that cholinergic functions decline in the basal forebrain and cortex in senile dementia of the Alzheimer type [5]. Accordingly, the enhancement of cholinergic neurotransmission has been considered as one potential therapeutic approach against AD. Although the pathogenesis of AD is complicated and involves numerous pathways, two major hypotheses are currently under consideration regarding the molecular mechanism: The cholinergic hypothesis and the amyloid cascade hypothesis. Thus, the focus herein is upon selective cholinesterase (ChE) inhibitors in order to alleviate cholinergic deficits and improve neurotransmission. Pursuant to this, both could be established as viable therapeutic targets for AD [5– 7]. Several AD histopathologic criteria are commonly used [8-10]. One treatment strategy to enhance the cholinergic function is the use of acetylcholinesterase (AChE, EC 3.1.1.7) inhibitors to increase the amount of acetylcholine, which is present in the synapses between cholinergic neurons [11]. AChE inhibitors such as donepezil, rivastigmine and galantamine, which are the most extensively studied AChE inhibitors, have been shown to significantly improve cognitive function in AD [12,13].
Club moss (Lycopodiaceae) species are well-known to be a rich source of Lycopodium alkaloids possessing a complex heterocyclic ring system and wide ranging biological properties that have
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