Design, Synthesis, and Biological Evaluation of Novel Tetramethylpyrazine Derivatives as Potential Neuroprotective Agents

Development of Pharmacological Strategies with Therapeutic Potential in Ischemic Stroke

Acute ischemic stroke constitutes a health challenge with great social impact due to its high incidence, with the social dependency that it generates being an important source of inequality. The lack of treatments serving as effective neuroprotective therapies beyond thrombolysis and thrombectomy is presented as a need. With this goal in mind, our research group's collaborative studies into cerebral ischemia and subsequent reperfusion concluded that there is a need to develop compounds with antioxidant and radical scavenger features. In this review, we summarize the path taken toward the identification of lead compounds as potential candidates for the treatment of acute ischemic stroke. Evaluations of the antioxidant capacity, neuroprotection of primary neuronal cultures and in vivo experimental models of cerebral ischemia, including neurological deficit score assessments, are conducted to characterize the biological efficacy of the various neuroprotective compounds developed. Moreover, the initial results in preclinical development, including dose-response studies, the therapeutic window, the long-term neuroprotective effect and in vivo antioxidant evaluation, are reported. The results prompt these compounds for clinical trials and are encouraging regarding new drug developments aimed at a successful therapy for ischemic stroke.

Bone marrow mesenchymal stem cells-derived exosomes mediated delivery of tetramethylpyrazine attenuate cerebral ischemic injury

OBJECTIVES

Tetramethylpyrazine (TEP) can protect the brain from ischemic damage, but it has defects such as short half-life, fast absorption, wide distribution, and rapid elimination, which limits its application. Exosomes (Exos) have the property of loading drugs and transporting signal substances. Here, we elucidated the effect of TEP-loaded bone marrow mesenchymal stem cell (BMSC)-derived Exos (Exo-TEP) on cerebral ischemic injury.

MATERIALS AND METHODS

The Exos were extracted by ultracentrifugation and TEP was loaded into the Exos by electroporation. Oxygen-glucose deprivation (OGD) induced-primary cortical neurons and middle cerebral artery occlusion (MCAO)-induced mouse models were used to determine the effect of Exo-TEP on cerebral ischemic injury in vitro and in vivo.

RESULTS

Exo-TEP exhibited a stable and sustained release pattern compared to free TEP. Exo-TEP treatment was more significant in improving OGD-mediated decrease in cell activity, as well as a elevation in apoptosis and ROS production in cortical neurons. In comparison with Exo and free TEP treatment, Exo-TEP treatment significantly improved pathological changes, shrunk cerebral infarction volume, as well reduced neurological deficit scores and neuronal apoptosis, and oxidative stress.

CONCLUSIONS

Exo-TEP was superior to free TEP in improving cerebral ischemic injury by reducing neuronal apoptosis and oxidative stress.

Application of cinnamic acid in the structural modification of natural products: A review

Natural products can generally exhibit a variety of biological activities, but most show mediocre performance in preliminary activity evaluation. Natural products often require structural modification to obtain promising lead compounds. Cinnamic acid (CA) is readily available and has diverse biological activities and low cytotoxicity. Introducing CA into natural products may improve their performance, enhance biological activity, and reduce toxic side effect. Herein, we aimed to discuss related applications of CA in the structural modification of natural products and provide a theoretical basis for future derivatization and drug development of natural products. Published articles, web databases (PubMed, Science Direct, SCI Finder, and CNKI), and clinical trial websites (https://clinicaltrials.gov/) related to natural products and CA derivatives were included in the discussion. Based on the inclusion criteria, 128 studies were selected and discussed herein. Screening natural products of CA derivatives allowed for classification by their biological activities. The full text is organized according to the biological activities of the derivatives, with the following categories: anti-tumor, neuroprotective, anti-diabetic, anti-microbial, anti-parasitic, anti-oxidative, anti-inflammatory, and other activities. The biological activity of each CA derivative is discussed in detail. Notably, most derivatives exhibited enhanced biological activity and reduced cytotoxicity compared with the lead compound. CA has various advantages and can be widely used in the synthesis of natural product derivatives to enhance the properties of drug candidates or lead compounds.

An Overview of Tetramethylpyrazine (Ligustrazine) and its Derivatives as Potent Anti-Alzheimer’s Disease Agents

Abstract:

Tetramethylpyrazine (TMP), or ligustrazine, is an alkaloid isolated from the Chinese herb Ligusticum wallichii. It is known for its broad-spectrum medicinal properties against several diseases, and various studies have shown that it can modulate diverse biological targets and signaling pathways to produce neuroprotective effects, especially against Alzheimer’s disease (AD). This has attracted significant research attention evaluating TMP as a potent multitarget anti-AD agent. This review compiles the results of studies assessing the neuroprotective mechanisms exerted by TMP as well as its derivatives prepared using a multi-target-directed ligand strategy to explore its multitarget modulating properties. The present review also highlights the work done on the design, synthesis, structure-activity relationships, and mechanisms of some potent TMP derivatives that have shown promising anti-AD activities. These derivatives were designed, synthesized, and evaluated to develop anti-AD molecules with enhanced biological and pharmacokinetic activities compared to TMP. This review article paves the way for the exploration and development of TMP and TMP derivatives as an effective treatment for AD.

The PI3K/AKT Pathway-The Potential Key Mechanisms of Traditional Chinese Medicine for Stroke

Stroke is associated with a high disability and fatality rate, and adversely affects the quality of life of patients and their families. Traditional Chinese Medicine (TCM) has been used effectively in the treatment of stroke for more than 2000 years in China and surrounding countries and regions, and over the years, this field has gleaned extensive clinical treatment experience. The Phosphatidylinositol 3 kinase (PI3K)/protein kinase B (AKT) pathway is important for regulation of cell migration, proliferation, differentiation, and apoptosis, and plays a vital role in vascularization and oxidative stress in stroke. Current Western medicine treatment protocols for stroke include mainly pharmacologic or mechanical thrombectomy to restore blood flow. This review collates recent advances in the past 5 years in the TCM treatment of stroke involving the PI3K/AKT pathway. TCM treatment significantly reduces neuronal damage, inhibits cell apoptosis, and delays progression of stroke via various PI3K/AKT-mediated downstream pathways. In the future, TCM can provide new perspectives and directions for exploring the key factors, and effective activators or inhibitors that affect occurrence and progression of stroke, thereby facilitating treatment.

The Roles of Tetramethylpyrazine During Neurodegenerative Disease

With the aging of the world population, neurodegenerative diseases are considered crippling diseases, which seriously affect the quality of life and are an increasing burden on society and the economy. As a major alkaloid in Ligusticum chuanxiong Hort, tetramethylpyrazine (TMP) plays an increasingly significant role during neurodegenerative diseases, including roles as an anti-inflammatory, antioxidative, antiplatelet citatory poisoning, and anti-inflammation. This review focuses on the latest advances in the roles and mechanisms of action of TMP in neurodegenerative diseases to stimulate new concepts and methods for the prevention and treatment of neurodegenerative diseases.

Design, Synthesis, and Biological Evaluation of Novel Tetramethylpyrazine- nitrone Derivatives as Antioxidants

Background:

Thrombolysis and endovascular thrombectomy are the two main therapeutic strategies for ischemic stroke in clinic. However, reperfusion injury causes oxidative stress leading to overproduction of reactive oxygen species, mitochondrial dysfunction and subsequent cell death.

Methods:

We designed and synthesized two tetramethylpyrazine-nitrone derivatives (T-003 and T- 005) and investigated their abilities for scavenging free radicals and protective effects as well as neurite outgrowth promotion in vitro.

Results:

Both of them showed potent radical-scavenging activity and neuroprotective effects against iodoacetic acid-induced cell injury. Furthermore, T-003 and T-005 significantly promoted neurite outgrowth in PC12 cells.

Conclusion:

Our results suggest that compound T-003 and T-005 could be potent antioxidants for the treatment of neurological disease, particularly ischemic stroke.

Recent Advances on Nitrones Design for Stroke Treatment

The recent advances of tetramethylpyrazine nitrones and quinolylnitrones for the treatment of stroke have been reviewed and compared with other agents, showing promising therapeutic applications. As a result of a functional transformation of natural product ligustrazine, (Z)-N-tert-butyl-1-(3,5,6-trimethylpyrazin-2-yl)methanimine oxide (6) is a multitarget small nitrone showing potent thrombolytic activity and free radicals scavenging power, in addition to nontoxicity and blood-brain barrier permeability. Similarly, antioxidant (Z)-N-tert-butyl-1-(2-chloro-6-methoxyquinolin-3-yl)methanimine oxide (17) is a novel agent for cerebral ischemia therapy as it is able to scavenge different types of free radical species, showing strong neuroprotection and reduced infarct size.

Polyurethane End-Capped by Tetramethylpyrazine-Nitrone for Promoting Endothelialization Under Oxidative Stress

Thrombus and restenosis are two main factors that cause the failure of vascular implants. Constructing a functional and confluent layer of endothelial cells (ECs) is considered an ideal method to prevent these problems. However, oxidative stress induced by the disease and implantation can damage ECs and hinder the endothelialization of implants. Thus, developing biomaterials that can protect ECs adhesion and proliferation from oxidative stress is urgently needed for the rapid endothelialization of vascular implants. In this work, a novel polyurethane (PU-TBN) is synthesized by employing tetramethylpyrazine-nitrone (TBN) as end-group to endow polymers with dual functions of antioxidant activity and promoting endothelialization. Common PU without TBN is also prepared to be control. Compared to PU, PU-TBN significantly promotes human umbilical vein endothelial cells (HUVECs) adhesion and proliferation, where cells spread well and a confluent endothelial layer is formed. PU-TBN also shows obvious free radical scavenging activity, and thus effectively attenuates oxidative stress to protect HUVECs from oxidative apoptosis. Moreover, PU-TBN exhibits enhanced antiplatelets effect, excellent biocompatibility, and similar mechanical properties to PU. These characteristics can endow PU-TBN with great potential to be used as vascular implants or coatings of other materials for rapid endothelialization under complex oxidative stress environment.

Hydrogen as a complementary therapy against ischemic stroke: A review of the evidence

Ischemic stroke is one of the most common sources of mortality in the world. Researchers have been trying to find a complementary therapy to treat ischemic stroke in order to improve its prognosis and expand the therapeutic window for reperfusion treatment. For this reason, many experimental and clinical trials studying the effects of hydrogen against ischemic stroke have been published. Hydrogen gas has been found to eliminate hydroxyl free radical and peroxynitrite anions as well as producing therapeutic effect in patients with ischemic stroke. Many studies have been published illustrating its anti-oxidative, anti-inflammatory and anti-apoptotic effects. The purpose of this article is to review the literature concerning treatment of cerebral I/R injury or ischemic stroke with hydrogen therapy. Specifically, we will examine the appropriate laboratory methods, mechanisms of hydrogen therapy, and outcomes of relevant clinical trials. We conclude this review with a discussion on future investigations of hydrogen therapy to treat ischemic stroke.

A Novel Tetramethylpyrazine Derivative Protects Against Glutamate-Induced Cytotoxicity Through PGC1α/Nrf2 and PI3K/Akt Signaling Pathways

Glutamate-induced excitotoxicity is one of the main causes of neuronal cell death in stroke. Compound 22a has been previously reported as a promising neuroprotective compound derived from tetramethylpyrazine, which is a widely used active ingredient of traditional Chinese medicine Chuanxiong (Ligusticum wallichii Franchat). Compound 22a can protect neurons from oxidative stress-induced PC12 cell death and alleviates the infarct areas and brain edema in a rat permanent middle cerebral artery occlusion model. In the current work, we further investigated the neuroprotective effects and underlying mechanisms of compound 22a against glutamate-induced excitotoxicity in primary culture of rat cerebellar granule neurons (CGNs). We found that pretreatment with compound 22a prevented glutamate-induced neuronal damage by maintaining mitochondrial membrane potential and attenuating cellular apoptosis. Compound 22a could also enhance peroxisome proliferator-activated receptor gamma coactivator 1-alpha (PGC1α) transcriptional activity and induce nuclear accumulation of Nrf2 in PC12 cells. Accordingly, pretreatment with compound 22a reversed the glutamate-induced down-regulation of expression of the proteins PGC1α, transcriptional factor NF-E2-related factor 2 (Nrf2), and hemooxygenase 1 (HO-1). In addition, compound 22a increased the phosphorylation of phosphoinositide 3-kinase (p-PI3K), phosphorylated protein kinase B (p-Akt), and glycogen synthase kinase 3β (p-GSK3β). Meanwhile, the small interfering RNA-mediated silencing of PGC1α expression and selective inhibitors targeting PI3K/Akt (LY294002 and Akt-iv) could significantly attenuate the neuroprotective effect of compound 22a. Taken together, compound 22a protected against glutamate-induced CGN injury possibly in part through regulation of PGC1α/Nrf2 and PI3K/Akt pathways.

Synthesis and biological evaluation of new tetramethylpyrazine-based chalcone derivatives as potential anti-Alzheimer agents

In the current study, a series of new ligustrazine-based chalcones was synthesized. For insertion of tetramethylpyrazine (TMP, also designated as ligustrazine) in chemical backbone of chalcone, a new ligustrazine-based aldehyde was prepared. New ketones were synthesized for inclusion of quinazolin-4-yl amino and pyrazin-2-yl amino moieties. The newly synthesized compounds were screened for acetylcholinesterase, butyrylcholinesterase, and monoamine oxidases (MAO) inhibitory activities and also for in vitro cytotoxicity on PC12 cells. The effect of these compounds against amyloid β-induced cytotoxicity and aggregation was also investigated. The synthesized compounds effectively inhibited the related enzymes and also exhibited neuroprotective effects. Most of the compounds displayed better inhibitory potencies against Aβ aggregation than reference compounds. Some compounds such as 11e and 16b showed very potent effects on multiple targets exhibiting behavior as multifunctional anti-Alzheimer agents.