Exposure Characteristics of the Analogous β-Carboline Alkaloids Harmaline and Harmine Based on the Efflux Transporter of Multidrug Resistance Protein 2

Neurobiological research on N,N-dimethyltryptamine (DMT) and its potentiation by monoamine oxidase (MAO) inhibition: from ayahuasca to synthetic combinations of DMT and MAO inhibitors

The potent hallucinogen N,N-dimethyltryptamine (DMT) has garnered significant interest in recent years due to its profound effects on consciousness and its therapeutic psychopotential. DMT is an integral (but not exclusive) psychoactive alkaloid in the Amazonian plant-based brew ayahuasca, in which admixture of several β-carboline monoamine oxidase A (MAO-A) inhibitors potentiate the activity of oral DMT, while possibly contributing in other respects to the complex psychopharmacology of ayahuasca. Irrespective of the route of administration, DMT alters perception, mood, and cognition, presumably through agonism at serotonin (5-HT) 1A/2A/2C receptors in brain, with additional actions at other receptor types possibly contributing to its overall psychoactive effects. Due to rapid first pass metabolism, DMT is nearly inactive orally, but co-administration with β-carbolines or synthetic MAO-A inhibitors (MAOIs) greatly increase its bioavailability and duration of action. The synergistic effects of DMT and MAOIs in ayahuasca or synthetic formulations may promote neuroplasticity, which presumably underlies their promising therapeutic efficacy in clinical trials for neuropsychiatric disorders, including depression, addiction, and post-traumatic stress disorder. Advances in neuroimaging techniques are elucidating the neural correlates of DMT-induced altered states of consciousness, revealing alterations in brain activity, functional connectivity, and network dynamics. In this comprehensive narrative review, we present a synthesis of current knowledge on the pharmacology and neuroscience of DMT, β-carbolines, and ayahuasca, which should inform future research aiming to harness their full therapeutic potential.

Discovery of a novel chemotype as DYRK1A inhibitors against Alzheimer's disease: Computational modeling and biological evaluation

Dual-specificity tyrosine phosphorylation-regulated kinase 1 A (DYRK1A) plays an essential role in Tau and Aβ pathology closely related to Alzheimer's disease (AD). Accumulative evidence has demonstrated DYRK1A inhibition is able to reduce the pathological features of AD. Nevertheless, there is no approved DYRK1A inhibitor for clinical use as anti-AD therapy. This is somewhat due to the lack of effective and safe chemotypes of DYRK1A inhibitors. To address this issue, we carried out in silico screening, in vitro assays and in vivo efficacy evaluation with the aim to discover a new class of DYRK1A inhibitors for potential treatment of AD. By in silico screening, we selected and purchased 16 potential DYRK1A inhibitors from the Specs chemical library. Among them, compound Q17 (Specs ID: AO-476/40829177) potently inhibited DYRK1A. The hydrogen bonds between compound Q17 and two amino acid residues named GLU239 and LYS188, were uncovered by molecular docking and molecular dynamics simulation. The cell-based assays showed that compound Q17 could protect the SH-SY5Y human neuroblastoma cell line from okadaic acid (OA)-induced injury by targeting DYRK1A. More importantly, compound Q17 significantly improved cognitive dysfunction of 3 × Tg-AD mice, ameliorated pathological changes, and attenuated Tau hyperphosphorylation as well as Aβ deposition. In summary, our computational modeling strategy is effective to identify novel chemotypes of DYRK1A inhibitors with great potential to treat AD, and the identified compound Q17 in this study is worthy of further study.

Anticancer Potential of β-Carboline Alkaloids: An Updated Mechanistic Overview

his comprehensive review is designed to evaluate the anticancer properties of β-carbolines derived from medicinal plants, with the ultimate goal of assessing their suitability and potential in cancer treatment, management, and prevention. An exhaustive literature survey was conducted on a wide array of β-carbolines including, but not limited to, harmaline, harmine, harmicine, harman, harmol, harmalol, pinoline, tetrahydroharmine, tryptoline, cordysinin C, cordysinin D, norharmane, and perlolyrine. Various analytical techniques were employed to identify and screen these compounds, followed by a detailed analysis of their anticancer mechanisms. Natural β-carbolines such as harmaline and harmine have shown promising inhibitory effects on the growth of cancer cells, as evidenced by multiple in vitro and in vivo studies. Synthetically derived β-carbolines also displayed noteworthy anticancer, neuroprotective, and cognitive-enhancing effects. The current body of research emphasizes the potential of β-carbolines as a unique source of bioactive compounds for cancer treatment. The diverse range of β-carbolines derived from medicinal plants can offer valuable insights into the development of new therapeutic strategies for cancer management and prevention.

A pilot study of cerebral metabolism and serotonin 5-HT2A receptor occupancy in rats treated with the psychedelic tryptamine DMT in conjunction with the MAO inhibitor harmine

Rationale: The psychedelic effects of the traditional Amazonian botanical decoction known as ayahuasca are often attributed to agonism at brain serotonin 5-HT2A receptors by N,N-dimethyltryptamine (DMT). To reduce first pass metabolism of oral DMT, ayahuasca preparations additionally contain reversible monoamine oxidase A (MAO-A) inhibitors, namely β-carboline alkaloids such as harmine. However, there is lacking biochemical evidence to substantiate this pharmacokinetic potentiation of DMT in brain via systemic MAO-A inhibition. Objectives: We measured the pharmacokinetic profile of harmine and/or DMT in rat brain, and tested for pharmacodynamic effects on brain glucose metabolism and DMT occupancy at brain serotonin 5-HT2A receptors. Methods: We first measured brain concentrations of harmine and DMT after treatment with harmine and/or DMT at low sub-cutaneous doses (1 mg/kg each) or harmine plus DMT at moderate doses (3 mg/kg each). In the same groups of rats, we also measured ex vivo the effects of these treatments on the availability of serotonin 5-HT2A receptors in frontal cortex. Finally, we explored effects of DMT and/or harmine (1 mg/kg each) on brain glucose metabolism with [18F]FDG-PET. Results: Results confirmed that co-administration of harmine inhibited the formation of the DMT metabolite indole-3-acetic acid (3-IAA) in brain, while correspondingly increasing the cerebral availability of DMT. However, we were unable to detect any significant occupancy by DMT at 5-HT2A receptors measured ex vivo, despite brain DMT concentrations as high as 11.3 µM. We did not observe significant effects of low dose DMT and/or harmine on cerebral [18F]FDG-PET uptake. Conclusion: These preliminary results call for further experiments to establish the dose-dependent effects of harmine/DMT on serotonin receptor occupancy and cerebral metabolism.

Mechanism of the Intestinal Absorption of Six Flavonoids from Zizyphi Spinosi Semen Across Caco-2 Cell Monolayer Model

BACKGROUND

Flavonoid compounds are one kind of active ingredients isolated from a traditional Chinese herb Zizyphi spinosae semen (ZSS). Studies have shown that ZSS flavonoids have significant antioxidant effects.

METHODS

In this study, the Caco-2 cell monolayer model was constructed to investigate the intestinal absorption characteristics and mechanism of Isovitexin (IV), Swertisin (ST), Isovitexin-2''-O-β-D-glucopyranoside (IVG), Spinosin (S), 6'''-p-coumaroylspinosin (6-CS) and 6'''-feruloylspinosin (6-FS).

RESULTS

The results of the bidirectional transport assay showed that the six flavonoids have good intestinal absorption in a near-neutral and 37°C environment, and the absorbability in descending order was 6-FS>6- CS>IVG>S>IV>ST. The results of carrier inhibition experiments and transport kinetics indicated that the absorption mechanism of six flavonoids was energy-dependent monocarboxylate transporter (MCT)-mediated active transport. In particular, the para-cellular pathway also participated in the transport of IV, ST, IVG and S. Furthermore, the efflux process of six flavonoids was mediated by P-glycoprotein (P-gp) and multidrug resistance protein (MRP), which may result in a decrease of bioavailability.

CONCLUSION

Our findings provide significant information for revealing the relationship between the intestinal absorption mechanism of flavonoids and its structure as well as laying a basis for the research of flavonoid preparations.

Potential Herb-Drug Interactions in the Management of Age-Related Cognitive Dysfunction

Late-life mild cognitive impairment and dementia represent a significant burden on healthcare systems and a unique challenge to medicine due to the currently limited treatment options. Plant phytochemicals have been considered in alternative, or complementary, prevention and treatment strategies. Herbals are consumed as such, or as food supplements, whose consumption has recently increased. However, these products are not exempt from adverse effects and pharmacological interactions, presenting a special risk in aged, polymedicated individuals. Understanding pharmacokinetic and pharmacodynamic interactions is warranted to avoid undesirable adverse drug reactions, which may result in unwanted side-effects or therapeutic failure. The present study reviews the potential interactions between selected bioactive compounds (170) used by seniors for cognitive enhancement and representative drugs of 10 pharmacotherapeutic classes commonly prescribed to the middle-aged adults, often multimorbid and polymedicated, to anticipate and prevent risks arising from their co-administration. A literature review was conducted to identify mutual targets affected (inhibition/induction/substrate), the frequency of which was taken as a measure of potential interaction. Although a limited number of drugs were studied, from this work, interaction with other drugs affecting the same targets may be anticipated and prevented, constituting a valuable tool for healthcare professionals in clinical practice.

Synergistic antidepressant- and anxiolytic-like effects of harmaline along with cinanserin in acute restraint stress-treated mice

RATIONALE

Acute restraint stress (ARS) is an experimental paradigm used for the induction of rodent models of stress-produced neuropsychiatric disorders, such as depression and anxiety. β-carbolines and serotonin (5-HT) systems are involved in the modulation of depression and anxiety behaviors.

OBJECTIVE

This study was designed to examine the effects of intracerebroventricular (i.c.v.) injection of cinanserin (5-HT2 receptor antagonist) on harmaline-induced responses on depression- and anxiety-like behaviors in the ARS mice.

METHODS

For i.c.v. infusion, guide cannula was surgically implanted in the left lateral ventricle of mice. The ARS model was conducted via movement restraint at a period of 4 h. Depression- and anxiety-related behaviors were evaluated by forced swim test (FST) and elevated plus maze (EPM), respectively.

RESULTS

The results displayed that the ARS mice showed depressive- and anxiety-like responses. I.p. administration of different doses of harmaline (0.31, 0.625 and 1.25 mg/kg) or i.c.v. microinjection of cinanserin (1, 2.5, and 5 μg/mouse) blocked depression- and anxiogenic-like behaviors in the ARS mice. Furthermore, co-administration of harmaline (1.25 mg/kg; i.p.) and cinanserin (5 μg/mouse; i.c.v.) prevented the depression- and anxiogenic-like effects in the ARS mice. We found a synergistic antidepressant- and anxiolytic-like effects of harmaline and cinanserin in the ARS mice.

CONCLUSIONS

These results propose an interaction between harmaline and cinanserin to prevent depressive- and anxiogenic-like behaviors in the ARS mice.

Pharmacological effects of harmine and its derivatives: a review

Harmine is isolated from the seeds of the medicinal plant, Peganum harmala L., and has been used for thousands of years in the Middle East and China. Harmine has many pharmacological activities including anti-inflammatory, neuroprotective, antidiabetic, and antitumor activities. Moreover, harmine exhibits insecticidal, antiviral, and antibacterial effects. Harmine derivatives exhibit pharmacological effects similar to those of harmine, but with better antitumor activity and low neurotoxicity. Many studies have been conducted on the pharmacological activities of harmine and harmine derivatives. This article reviews the pharmacological effects and associated mechanisms of harmine. In addition, the structure-activity relationship of harmine derivatives has been summarized.

Toxicokinetics and Toxicodynamics of Ayahuasca Alkaloids N,N-Dimethyltryptamine (DMT), Harmine, Harmaline and Tetrahydroharmine: Clinical and Forensic Impact

Ayahuasca is a hallucinogenic botanical beverage originally used by indigenous Amazonian tribes in religious ceremonies and therapeutic practices. While ethnobotanical surveys still indicate its spiritual and medicinal uses, consumption of ayahuasca has been progressively related with a recreational purpose, particularly in Western societies. The ayahuasca aqueous concoction is typically prepared from the leaves of the N,N-dimethyltryptamine (DMT)-containing Psychotria viridis, and the stem and bark of Banisteriopsis caapi, the plant source of harmala alkaloids. Herein, the toxicokinetics and toxicodynamics of the psychoactive DMT and harmala alkaloids harmine, harmaline and tetrahydroharmine, are comprehensively covered, particularly emphasizing the psychological, physiological, and toxic effects deriving from their concomitant intake. Potential therapeutic utility, particularly in mental and psychiatric disorders, and forensic aspects of DMT and ayahuasca are also reviewed and discussed. Following administration of ayahuasca, DMT is rapidly absorbed and distributed. Harmala alkaloids act as potent inhibitors of monoamine oxidase A (MAO-A), preventing extensive first-pass degradation of DMT into 3-indole-acetic acid (3-IAA), and enabling sufficient amounts of DMT to reach the brain. DMT has affinity for a variety of serotonergic and non-serotonergic receptors, though its psychotropic effects are mainly related with the activation of serotonin receptors type 2A (5-HT_2A). Mildly to rarely severe psychedelic adverse effects are reported for ayahuasca or its alkaloids individually, but abuse does not lead to dependence or tolerance. For a long time, the evidence has pointed to potential psychotherapeutic benefits in the treatment of depression, anxiety, and substance abuse disorders; and although misuse of ayahuasca has been diverting attention away from such clinical potential, research onto its therapeutic effects has now strongly resurged.

β-Carbolines in Experiments on Laboratory Animals

Some studies have ascribed a protective effect against neurodegenerative diseases to the β-carbolines harman (H) and norharman (NH), which occur mostly in coffee and coffee substitutes. We determined the concentrations of β-carbolines and undesirable compounds (such as acrylamide) in roasted coffee substitute ingredients and found that chicory coffee was optimal. Two in vivo experiments were conducted with seventeen-month-old male Sprague Dawley rats fed a diet with the addition of pure carboline standards in the first stage, and chicory in the second. We observed an increase in the level of H and NH in blood plasma, as well as higher activity of animals in the battery behavioral test, particularly in the second stage. The results of in vitro studies-particularly the level of the expression in brain tissue of genes associated with aging processes and neurodegenerative diseases-clearly show the benefits of a diet rich in β-carbolines.

Molecular hybrid design, synthesis, in vitro and in vivo anticancer evaluation, and mechanism of action of N-acylhydrazone linked, heterobivalent β-carbolines

A series of N-acylhydrazone-linked, heterobivalent β-carboline derivatives was designed and synthesized from l-tryptophan in a nine-step reaction sequence. The effort resulted in the heterobivalent β-carbolines 10a-t in good yields. The target compounds were characterized by ¹H NMR, ¹³C NMR and high-resolution mass spectrometry (HRMS). The in vitro cytotoxic activity of the synthesized compounds was evaluated against normal EA.HY926 cells and five cancer cell lines: LLC (Lewis lung carcinoma), BGC-823 (gastric carcinoma), CT-26 (murine colon carcinoma), Bel-7402 (liver carcinoma), and MCF-7 (breast carcinoma). Compound 10e, with an IC₅₀ value of 2.41 μM against EA.HY926 cells, was the most potent inhibitor. It showed cytotoxicity against all five cancer cell lines of different origin - murine and human, with IC₅₀ values ranging from 4.2 ± 0.7 to 18.5 ± 3.1 μM. A study of structure-activity relationships indicated that the influence on cytotoxic activities of the substituent in the R₉'-position followed the tendency, 2,3,4,5,6-perfluorophenylmethyl > 4-fluorobenzyl > 3-phenylpropyl group. The antitumor efficacies of the selected compounds were also evaluated in mice. Compound 10e exhibited potent antitumor activity, with tumor inhibition of more than 40% for Sarcoma 180 and 36.7% for Lewis lung cancer. Furthermore, the pharmacological mechanisms showed that compound 10e has a certain impairment in the motility of LLC cells, which suggests the anti-metastatic potential. And compound 10e inhibited angiogenesis in chicken chorioallantoic membrane assay, and the anti-angiogenetic potency was more potent than the reference drug combretastatin A4-phosphate (CA4P) at a concentration 50 μM.

Transepithelial transport mechanisms of 7,8-dihydroxyflavone, a small molecular TrkB receptor agonist, in human intestinal Caco-2 cells

7,8-Dihydroxyflavone (7,8-DHF), as a high-affinity TrkB receptor agonist, has been extensively explored in many human disorders involving brain-derived neurotrophic factor (BDNF) such as Alzheimer's disease, Parkinson's disease, depression, and obesity. However, to date, the transepithelial transport mechanisms of 7,8-DHF in the intestines remain unclear. The aim of our work was to quantify and to characterize in vitro transport of naturally occurring 7,8-DHF distinguished by its physicochemical and pharmacological properties. We discussed the transport mechanisms of 7,8-DHF using the Caco-2 cell model to determine the bi-directional permeability with different environmental factors (time, concentration, pH, metabolic inhibitors etc.). The influx and efflux characteristics of 7,8-DHF were also clarified. 7,8-DHF was poorly transported across Caco-2 cell monolayers by mainly passive diffusion via a transcellular pathway and not a paracellular pathway. The transport of 7,8-DHF was time and concentration-dependent in both the apical (AP) to basolateral (BL) side and the reverse direction. Interestingly, decreasing the pH from 7.4 to 6.0 markedly enhanced 7,8-DHF transport. It is noteworthy that 7,8-DHF transport was strongly inhibited by metabolic inhibitors and was highly dependent on temperature. The efflux ratio (ER) values at different concentrations were all above 1.5, indicating the existence of the efflux transporter. We found that breast cancer resistance protein (BCRP) was not involved in 7,8-DHF secretion and that the transport mechanism of 7,8-DHF was passive transport with an active efflux mediated by P-glycoprotein (P-gp) and multidrug resistance associated proteins (MRPs), particularly MRP 2. Moreover, the use of various influx transporter inhibitors in Caco-2 cells showed that organic cation transporters (OCTs) and organic anion-transporting polypeptides (OATPs) participated in 7,8-DHF transport. Taken together, the elucidated transport characteristics of 7,8-DHF provide useful information for designing novel and efficient delivery systems and avoiding food-food or food-drug interactions.

Subchronic toxicity and concomitant toxicokinetics of long-term oral administration of total alkaloid extracts from seeds of Peganum harmala Linn: A 28-day study in rats

ETHNOPHARMACOLOGICAL RELEVANCE

The seeds of Peganum harmala Linn, in which the most abundant active compounds are harmaline and harmine, have been widely used as a traditional medicine in various countries to treat a broad spectrum of diseases including asthma, cough, depression, Parkinson's and Alzheimer's diseases. However, few studies on long-term or subchronic toxicity of seeds of P. harmala were reported after overdose.

AIM OF THE STUDY

To investigate the subchronic toxicity and concomitant toxicokinetics of total alkaloid extracts from seeds of P. harmala (TAEP) after oral administration for four weeks in rats.

MATERIALS AND METHODS

The subchronic toxicity and concomitant toxicokinetics of TAEP were evaluated after 28-day oral administration in rats at daily dose levels of 15, 45, and 150 mg/kg. The signs of toxicity and mortality were monitored and recorded daily. The body weight and average food consumption were measured weekly. The analyses of hematology, biochemistry, urine, relative organ weights and histopathology were conducted at the termination of treatment and recovery phase. For concomitant toxicokinetics study, the plasma toxicokinetic parameters, tissue distribution, and excretion of predominant ingredients harmaline and harmine in TAEP and metabolites harmalol and harmol were tested.

RESULTS

Following initial repeated exposure to high-dose (150 mg/kg/day) of TAEP excitotoxic reaction, such as tremor, was observed, but tolerated on the fourth day after multiple dosing. The significant alterations in blood glucose and lipid metabolism in liver were observed, but recovered after four weeks of drug withdrawal. The no-observed-adverse-effect level (NOAEL) of TAEP was considered to be 45 mg/kg/day under the present study conditions. There were no significant gender differences in most indexes of subchronic toxicity throughout the experimental period with the exception of food consumption and body weight. In concomitant toxicokinetics study, the alterations of dynamic characteristic for harmaline, harmine and metabolite harmol after multiple oral administration at three doses had been observed. Harmaline, harmine and metabolites harmalol and harmol were widely distributed in organs and there was no accumulation in the tissues examined. The reduction of harmaline and metabolite harmalol in brain after multiple dosing at dose of 150 mg/kg might be closely related to the tremor tolerance. The main excretory pathway for metabolites harmalol and harmol was urinary excretion via kidney.

CONCLUSIONS

The results revealed that TAEP at doses of 15 and 45 mg/kg/day in rats might be safe. Excitotoxic reaction such as tremor occurred initially at dose of 150 mg/kg/day, however, the toxicity was tolerant and reversible. In addition, harmaline and harmine in TAEP had a quick absorption into blood and metabolized to harmalol and harmol, and there was no drug accumulation in the detected tissues. Further studies should be investigated to clarify the mechanisms of tremor tolerance and neurotoxicity of TAEP.

Potential Pharmacokinetic Drug⁻Drug Interaction Between Harmine, a Cholinesterase Inhibitor, and Memantine, a Non-Competitive N-Methyl-d-Aspartate Receptor Antagonist

Harmine (HAR) is a beta-carboline alkaloid widely distributed in nature. It exhibits psychopharmacological effects of improving learning and memory. However, excessive dose of HAR can cause central tremor toxicity, which may be related to the glutamate system. Memantine (MEM) is a non-competitive N-methyl-d-aspartate receptor antagonist. It can be used for the treatment of Alzheimer's disease and also can block the neurotoxicity caused by glutamate. Therefore, combination of HAR and MEM would be meaningful and the pharmacokinetics investigation of HAR and MEM in combination is necessary. A ultra-performance liquid chromatography tandem mass spectrometry (UPLC-MS/MS) method was established and validated for the simultaneous quantitative determination of MEM, HAR and harmol (HOL), a main metabolite of HAR, in rat plasma after oral administration of HAR and MEM in combination (5.0 mg/kg of MEM combined with 20.0, 40.0, 80.0 mg/kg of HAR). The contents of HAR and HOL were determined after oral administration of HAR (20.0, 40.0 and 80.0 mg/kg), and the content of MEM was determined after oral administration of MEM (5.0 mg/kg). Blood samples were collected from each rat at 0 (pre-dose), 0.08, 0.17, 0.25, 0.33, 0.50, 0.75, 1.0, 2.0, 4.0, 8.0, 12.0 and 24.0 h after administration. The maximum peak concentration (Cmax) of MEM was obviously decreased, and the area under the plasma concentration versus time curve from zero to time t (AUC(0-t)) and mean residence time (MRT) were significantly increased after combination with HAR. The Cmax and AUC(0-t) of HAR and its metabolite HOL were increased after combination with MEM. These findings suggested that co-administration of HAR and MEM could extend their residence time in rats, and then might increase the efficacy for treatment of Alzheimer's disease. Therefore, this study will provide a basis for the rational combined application of HAR and MEM.

Analogous β-Carboline Alkaloids Harmaline and Harmine Ameliorate Scopolamine-Induced Cognition Dysfunction by Attenuating Acetylcholinesterase Activity, Oxidative Stress, and Inflammation in Mice

The analogous β-carboline alkaloids, harmaline (HAL) and harmine (HAR), possess a variety of biological properties, including acetylcholinesterase (AChE) inhibitory activity, antioxidant, anti-inflammatory, and many others, and have great potential for treating Alzheimer’s disease (AD). However, studies have showed that the two compounds have similar structures and in vitro AChE inhibitory activities but with significant difference in bioavailability. The objective of this study was to comparatively investigate the effects of HAL and HAR in memory deficits of scopolamine-induced mice. In the present study, mice were pretreated with HAL (2, 5, and 10 mg/kg), HAR (10, 20, and 30 mg/kg) and donepezil (5 mg/kg) by intragastrically for 7 days, and were daily intraperitoneal injected with scopolamine (1 mg/kg) to induce memory deficits and then subjected to behavioral evaluation by Morris water maze. To further elucidate the underlying mechanisms of HAL and HAR in improving learning and memory, the levels of various biochemical factors and protein expressions related to cholinergic function, oxidative stress, and inflammation were examined. The results showed that HAL and HAR could effectively ameliorate memory deficits in scopolamine-induced mice. Both of them exhibited an enhancement in cholinergic function by inhibiting AChE and inducing choline acetyltransferase (ChAT) activities, and antioxidant defense via increasing the antioxidant enzymes activities of superoxide dismutase and glutathione peroxidase, and reducing maleic diadehyde production, and anti-inflammatory effects through suppressing myeloperoxidase, tumor necrosis factor α, and nitric oxide as well as modulation of critical neurotransmitters such as acetylcholine (ACh), choline (Ch), L-tryptophan (L-Trp), 5-hydroxytryptamine (5-HT), γ-aminobutyric acid (γ-GABA), and L-glutamic acid (L-Glu). Furthermore, the regulations of HAL on cholinergic function, inflammation, and neurotransmitters were more striking than those of HAR, and HAL manifested a comparable antioxidant capacity to HAR. Remarkably, the effective dosage of HAL (2 mg/kg) was far lower than that of HAR (20 mg/kg), which probably due to the evidently differences in the bioavailability and metabolic stability of the two analogs. Taken together, all these results revealed that HAL may be a promising candidate compound with better anti-amnesic effects and pharmacokinetic characteristics for the treatments of AD and related diseases.