Synthesis and evaluation of paeonol derivatives as potential multifunctional agents for the treatment of Alzheimer's disease

Key developments and hotspots of exosomes in Alzheimer's disease: a bibliometric study spanning 2003 to 2023

Background

Alzheimer's disease (AD) is a degenerative illness of the central nervous system that is irreversible and is characterized by gradual behavioral impairment and cognitive dysfunction. Researches on exosomes in AD have gradually gained the attention of scholars in recent years. However, the literatures in this research area do not yet have a comprehensive visualization analysis. The aim of this work is to use bibliometrics to identify the knowledge constructs and investigate the research frontiers and hotspots related to exosomes in AD.

Methods

From January 2003 until June 2023, we searched the Web of Science Core Collection for literature on exosomes in AD. We found 585 papers total. The bibliometric study was completed using VOSviewer, the R package "bibliometrix," and CiteSpace. The analysis covered nations, institutions, authors, journals, and keywords.

Results

Following 2019, the articles on exosomes in AD increased significantly year by year. The vast majority of publications came from China and the US. The University of California System, the National Institutes of Health, and the NIH National Institute on Aging in the US were the primary research institutions. Goetzl Edward J. was frequently co-cited, while Kapogiannis Dimitrios was the most prolific author in this discipline with the greatest number of articles. Lee Mijung et al. have been prominent in the last two years in exosomes in AD. The Journal of Alzheimer's Disease was the most widely read publication, and Alzheimers & Dementia had the highest impact factor. The Journal of Biological Chemistry, Proceedings of the National Academy of Sciences of the United States of America, and Journal of Alzheimer's Disease were the three journals with more than 1,000 citations. The primary emphasis of this field was Alzheimer's disease, exosomes, and extracellular vesicles; since 2017, the number of phrases pertaining to the role of exosomes in AD pathogenesis has increased annually. "Identification of preclinical Alzheimer's disease by a profile of pathogenic proteins in neurally derived blood exosomes: a case-control study" was the reference with the greatest citing power, indicating the future steered direction in this field.

Conclusion

Using bibliometrics, we have compiled the research progress and tendencies on exosomes in Alzheimer's disease for the first time. This helps determine the objectives and paths for future study.

Paeonol Derivative, 6'-Methyl Paeonol, Attenuates Aβ-Induced Pathophysiology in Cortical Neurons and in an Alzheimer's Disease Mice Model

Herbs themselves and various herbal medicines are great resources for discovering therapeutic drugs for various diseases, including Alzheimer's disease (AD), one of the common neurodegenerative diseases. Utilizing mouse primary cortical neurons and DiBAC4(3), a voltage-sensitive indicator, we have set up a drug screening system and identified an herbal extraction compound, paeonol, obtained from Paeonia lactiflora; this compound is able to ameliorate the abnormal depolarization induced by Aβ42 oligomers. Our aim was to further find effective paeonol derivatives since paeonol has been previously studied. 6'-Methyl paeonol, one of the six paeonol derivatives surveyed, is able to inhibit the abnormal depolarization induced by Aβ oligomers. Furthermore, 6'-methyl paeonol is able to alleviate the NMDA- and AMPA-induced depolarization. When a molecular mechanism was investigated, 6'-methyl paeonol was found to reverse the Aβ-induced increase in ERK phosphorylation. At the animal level, mice injected with 6'-methyl paeonol showed little change in their basic physical parameters compared to the control mice. 6'-Methyl paeonol was able to ameliorate the impairment of memory and learning behavior in J20 mice, an AD mouse model, as measured by the Morris water maze. Thus, paeonol derivatives could provide a structural foundation for developing and designing an effective compound with promising clinical benefits.

Protective mechanism of Paeonol on central nervous system

Cerebrovascular diseases involve neuronal damage, resulting in degenerative neuropathy and posing a serious threat to human health. The discovery of effective drug components from natural plants and the study of their mechanism are a research idea different from chemical synthetic medicines. Paeonol is the main active component of traditional Chinese medicine Paeonia lactiflora Pall. It widely exists in many medicinal plants and has pharmacological effects such as anti-atherosclerosis, antiplatelet aggregation, anti-oxidation, and anti-inflammatory, which keeps generally used in the treatment of cardiovascular and cerebrovascular diseases. Based on the therapeutic effects of Paeonol for cardiovascular and cerebrovascular diseases, this article reviewed the pharmacological effects of Paeonol in Alzheimer's disease, Parkinson's disease, stroke, epilepsy, diabetes encephalopathy, and other neurological diseases, providing a reference for the research of the mechanism of Paeonol in central nervous system diseases.

Role of Exosomes in the Pathogenesis and Theranostic of Alzheimer's Disease and Parkinson's Disease

Alzheimer's disease (AD) and Parkinson's disease (PD) are the most common neurodegenerative diseases (NDDs) threatening the lives of millions of people worldwide, including especially elderly people. Currently, due to the lack of a timely diagnosis and proper intervention strategy, AD and PD largely remain incurable. Innovative diagnosis and therapy are highly desired. Exosomes are small vesicles that are present in various bodily fluids, which contain proteins, nucleic acids, and active biomolecules, and which play a crucial role especially in intercellular communication. In recent years, the role of exosomes in the pathogenesis, early diagnosis, and treatment of diseases has attracted ascending attention. However, the exact role of exosomes in the pathogenesis and theragnostic of AD and PD has not been fully illustrated. In the present review, we first introduce the biogenesis, components, uptake, and function of exosomes. Then we elaborate on the involvement of exosomes in the pathogenesis of AD and PD. Moreover, the application of exosomes in the diagnosis and therapeutics of AD and PD is also summarized and discussed. Additionally, exosomes serving as drug carriers to deliver medications to the central nervous system are specifically addressed. The potential role of exosomes in AD and PD is explored, discussing their applications in diagnosis and treatment, as well as their current limitations. Given the limitation in the application of exosomes, we also propose future perspectives for better utilizing exosomes in NDDs. Hopefully, it would pave ways for expanding the biological applications of exosomes in fundamental research as well as theranostics of NDDs.

Synthesis of 4-substituted benzyl-2-triazole-linked-tryptamine-paeonol derivatives and evaluation of their selective inhibitions against butyrylcholinesterase and monoamine oxidase-B

Cholinesterase (ChE) and monoamine oxidase (MAO) inhibitors are being used and developed to treat Alzheimer's disease (AD), a major type of dementia patients. Fifteen 4-substituted benzyl-2-triazole-linked-tryptamine-paeonol derivatives were synthesized and evaluated for their inhibitory activities against acetylcholinesterase (AChE), butyrylcholinesterase (BChE), monoamine oxidase-A (MAO-A), and B (MAO-B). Compound 896 was the most potent BChE inhibitor (IC₅₀ = 0.13 μM) with the selectivity index (SI) value of >769.23 for BChE over AChE. Compound 897 was the most potent selective MAO-B inhibitor (IC₅₀ = 0.73 μM; SI = 20.45 for MAO-B over MAO-A). The meta-CF₃ substituent of 896 increased BChE inhibitory activity and the para-CF₃ substituent of 897 increased MAO-B inhibitory activity. Compound 896 was a reversible noncompetitive BChE inhibitor (K_i = 0.171 μM) and 897 was a reversible competitive MAO-B inhibitor (K_i = 0.237 μM). Compound 896 had a lower binding energy (-13.75 kcal/mol) to BChE than 897 (-11.29 kcal/mol), and 897 had a lower binding energy to MAO-B (-11.31 kcal/mol) than that to MAO-A (-6.72 kcal/mol). Little cytotoxicity was observed for 896 and 897 to normal cells (MDCK) and human neuroblastoma cells (SH-SY5Y). This study suggested that 896 and 897 are therapeutic candidates for various neurodegenerative disorders such as AD.

Paeonol regulates NLRP3 inflammasomes and pyroptosis to alleviate spinal cord injury of rat

Background

Spinal cord injury (SCI) is a life-threatening traumatic disorder. Paeonol has been confirmed to be involved in a variety of diseases. The purpose of this study is to investigate the role of paeonol on SCI progression.

Methods

Sprague Dawley (SD) rat was used for the establishment of SCI model to explore the anti-inflammation, anti-oxidation, and neuroprotective effects of paeonol (60 mg/kg) on SCI in vivo. For in vitro study, mouse primary microglial cells (BV-2) were induced by lipopolysaccharide (LPS)/adenosine triphosphate (ATP) treatment. The effect of paeonol on the polarization of LPS/ATP-induced BV-2 cells was determined by detection the expression inducible nitric oxide synthase (iNOS), tumour necrosis factor alpha (TNF-α), arginase-1 (Arg-1), and interleukin (IL)-10 using qRT-PCR. ELISA was used to assess the levels of IL-1β, IL-18, TNF-α, malondialdehyde (MDA), and glutathione (GSH). Western blotting was conducted to determine the levels of NLRP3 inflammasomes and TLR4/MyD88/NF-κB (p65) pathway proteins.

Results

Paeonol promoted the recovery of locomotion function and spinal cord structure, and decreased spinal cord water content in rats following SCI. Meanwhile, paeonol reduced the levels of apoptosis-associated speck-like protein (ASC), NLRP3, active caspase 1 and N-gasdermin D (N-GSDMD), repressed the contents of IL-1β, IL-18, TNF-α and MDA, and elevated GSH level. In vitro, paeonol exerted similarly inhibiting effects on pyroptosis and inflammation. Meanwhile, paeonol promoted BV-2 cells M2 polarization. In addition, paeonol also inactivated the expression of TLR4/MyD88/NF-κB (p65) pathway.

Conclusion

Paeonol may regulate NLRP3 inflammasomes and pyroptosis to alleviate SCI, pointing out the potential for treating SCI in clinic.

Biological Activities of Paeonol in Cardiovascular Diseases: A Review

Paeonol is a naturally existing bioactive compound found in the root bark of Paeonia suffruticosa and it is traditionally used in Chinese medicine for the prevention and management of cardiovascular diseases. To date, a great deal of studies has been reported on the pharmacological effects of paeonol and its mechanisms of action in various diseases and conditions. In this review, the underlying mechanism of action of paeonol in cardiovascular disease has been elucidated. Recent studies have revealed that paeonol treatment improved endothelium injury, demoted inflammation, ameliorated oxidative stress, suppressed vascular smooth muscle cell proliferation, and repressed platelet activation. Paeonol has been reported to effectively protect the cardiovascular system either employed alone or in combination with other traditional medicines, thus, signifying it could be a hypothetically alternative or complementary atherosclerosis treatment. This review summarizes the biological and pharmacological activities of paeonol in the treatment of cardiovascular diseases and its associated underlying mechanisms for a better insight for future clinical practices.

Genus Paeonia: A comprehensive review on traditional uses, phytochemistry, pharmacological activities, clinical application, and toxicology

ETHNOPHARMACOLOGICAL RELEVANCE

Paeonia, which comprises approximately 52 shrubs or herbaceous perennials around the world, is the only genus of the Paeoniaceae and is pervasively distributed in Asia, southern Europe, and North America. Many species of the genus Paeonia have been used for centuries in ethnomedical medical systems.

AIM OF THE REVIEW

The present study aims to summarize the traditional uses, clinical applications, and toxicology of the genus Paeonia, to critically evaluate the state-of-the-art phytochemical and pharmacological studies of this genus published between 2011 and 2020, and to suggest directions for further in-depth research on Paeonia medicinal resources.

MATERIALS AND METHODS

Popular and widely used databases such as PubMed, Scopus, Science Direct, and Google Scholar were searched using the various search strings; from these searches, a number of citations related to the traditional uses, phytochemistry, biological activities, clinical application, and toxicology of the genus Paeonia were retrieved.

RESULTS

The use of 21 species, 2 subspecies, and 7 varieties of the genus Paeonia as traditional herbal remedies has been reported, and many ethnomedicinal uses, such as the treatment of hematemesis, blood stasis, dysmenorrhea, amenorrhea, epilepsy, spasms, and gastritis, have been recorded. The roots and root bark are the most frequently reported parts of the plants used in medicinal applications. In phytochemical investigations, 451 compounds have been isolated from Paeonia plants to date, which contains monoterpenoid glucosides, flavonoids, tannins, stilbenes, triterpenoids and steroids, and phenols. Studies of their pharmacological activities have revealed the antioxidant, anti-inflammatory, antitumour, antibacterial, antiviral, cardiovascular protective, and neuroprotective properties of the genus Paeonia. In particular, some bioactive extracts and compounds (total glucosides of peony (TGP), paeonol, and paeoniflorin) have been used as therapeutic drugs or tested in clinical trials. In addition to the "incompatibility" of the combined use of "shaoyao" and Veratrum nigrum L. roots in traditional Chinese medicine theory, Paeonia was considered to have no obvious toxicity based on the available toxicological tests.

CONCLUSION

A large number of phytochemical and pharmacological reports have indicated that Paeonia is an important medicinal herb resource, and some of its traditional uses including the treatment of inflammation and cardiovascular diseases and its use as a neuroprotective agent, have been partially confirmed through modern pharmacological studies. Monoterpenoid glucosides are the main active constituents. Although many compounds have been isolated from Paeonia plants, the biological activities of only a few of these compounds (paeoniflorin, paeonol, and TGP) have been extensively investigated. Some paeoniflorin structural analogues and resveratrol oligomers have been preliminarily studied. With the exception of several species (P. suffruticosa, P. ostii, P. lactiflora, and P. emodi) that are commonly used in folk medicine, many medicinal species within the genus do not receive adequate attention. Conducting phytochemical and pharmacological experiments on these species can provide new clues that may lead to the discovery of medicinal resources. It is necessary to identify the effective phytoconstituents of crude extracts of Paeonia that displayed pharmacological activities by bioactivity-guided isolation. In addition, comprehensive plant quality control, and toxicology and pharmacokinetic studies are needed in the future studies.

Paeonol Derivatives and Pharmacological Activities: A Review of Recent Progress

Paeonol, 2-hydroxy-4-methoxy acetophenone, is one of the main active ingredients of traditional Chinese medicine such as Cynanchum paniculatum, Paeonia suffruticosa Andr and Paeonia lactiflora Pall. Modern medical research has shown that paeonol has a wide range of pharmacological activities. In recent years, a large number of studies have been carried out on the structure modification of paeonol and the mechanism of action of paeonol derivatives has been studied. Some paeonol derivatives exhibit good pharmacological activities in terms of antibacterial, anti-inflammatory, antipyretic analgesic, antioxidant and other pharmacological effects. Herein, the research progress on paeonol derivatives and their pharmacological activities were systematically reviewed.

A novel organic cation transporter involved in paeonol transport across the inner blood-retinal barrier and changes in uptake in high glucose conditions

Paeonol exerts various pharmacological effects owing to its antiangiogenic, antioxidant, and antidiabetic activities. We aimed to investigate the transport mechanism of paeonol across the inner blood-retinal barrier both in vitro and in vivo. The carotid artery single injection method was used to investigate the retina uptake index of paeonol. The retina uptake index (RUI) value of [³H]paeonol was dependent on both concentration and pH. This value decreased significantly in the presence of imperatorin, tramadol, and pyrilamine when compared to the control. However, para-aminohippuric acid, choline, and taurine had no effect on the RUI value. Conditionally immortalized rat retina capillary endothelial cells (TR-iBRB cell lines) were used as an in vitro model of the inner blood-retinal barrier (iBRB). The uptake of [³H]paeonol by the TR-iBRB cell lines was found to be time-, concentration-, and pH-dependent. However, the uptake was unaffected by the absence of sodium or by membrane potential disruption. Moreover, in vitro structural analog studies revealed that [³H]paeonol uptake was inhibited in the presence of organic cationic compounds including imperatorin, clonidine and tramadol. This is consistent with the results obtained in vivo. In addition, transfections with OCTN1, 2 or plasma membrane monoamine transporter (PMAT) small interfering RNA did not affect paeonol uptake in TR-iBRB cell lines. Upon pre-incubation of these cell lines with high glucose (HG) media, [³H]paeonol uptake decreased and mRNA expression levels of angiogenetic factors, such as hypoxia inducible factor-1 (HIF-1) and vascular endothelial growth factor (VEGF) increased. However, after the pretreatment of unlabeled paeonol in HG conditions, the mRNA levels of VEGF and HIF-1 were comparatively reduced, and the [³H]paeonol uptake rate was restored. After being exposed to inflammatory conditions induced by glutamate, TNF-α, and LPS, paeonol and propranolol pretreatment significantly increased the uptake of both [³H]paeonol and [³H]propranolol in TR-iBRB cell lines compared to their respective controls. Our results demonstrate that the transport of paeonol to the retina across the iBRB may involve the proton-coupled organic cation antiporter system, and the uptake of paeonol is changed by HG conditions.

Simplified Procedure for General Synthesis of Monosubstituted Piperazines-From a Batch Reaction Vessel to a Flow (Microwave) Reactor

We reported a novel simplified synthetic procedure for the preparation of monosubstituted piperazine derivatives which can now be easily prepared in a one-pot-one-step way from a protonated piperazine with no need of introduction of a protecting group. Reactions, proceeding either at room or higher temperatures in common solvents, involve heterogeneous catalysis by metal ions supported on commercial polymeric resins. A general synthetic scheme was successfully applied to afford a wide range of monosubstituted piperazines. Furthermore, we picked up a set of piperazine derivatives and studied the possibilities of microwave acceleration of given synthetic reactions to make them even more efficient. Our research proceeded from a simple batch technique to the construction of a flow microwave reactor prototype and resulted in promising findings which are summarized and discussed in the article.

Chemistry, pharmacokinetics, pharmacology and recent novel drug delivery systems of paeonol

Paeonol is a bioactive phenol present in Dioscorea japonica, Paeonia suffruticosa and Paeonia lactiflora. It is reported for various pharmacological activities.

AIM

To review chemistry, pharmacokinetics, pharmacological activities as well as various formulations of paeonol.

MATERIALS AND METHODS

A literature search was done using different search terms for paeonol by using different scientific databases like PubMed, Scopus and ProQuest. Scientific papers published during the period 1969 to 2019 were comprehensively reviewed.

KEY FINDINGS

Researchers have synthesized methoxy, ethoxy, piperazine, chromonylthiazolidine, phenol-phenylsulfonyl, alkyl ether, aminothiazole, tryptamine hybrids and paeononlsilatie derivatives to enhance the stability of paeonol. These derivatives were synthesized and evaluated for in vitro series of biological activities like anti-inflammatory, tyrosinase inhibitory, neuroprotective, anticancer and antiviral activity. Regardless of valuable therapeutic potential, the clinical use of paeonol is restricted due to poor water solubility, low oral bioavailability, low stability and high volatility at room temperature. To enhance the bioavailability of paeonol various formulations are prepared and evaluated for its activity. Paeonol formulations can be categorized as conventional-tablets, topical gel and hydrogel; polymeric delivery system-microparticles, microsponges, dendrimers, nanocapsules, polymeric nanoparticles, nanospheres; lipid-based delivery systems-microemulsion, self-micro-emulsifying drug delivery, liposome, transethosomes, ethosomes, niosomes, proniosomes, lipid-based nanoparticles and nanoemulsion of paeonol.

SIGNIFICANCE

Paeonol has a potential to be developed as a techno-commercial product with respect to its multi-faceted pharmacological properties. Even though in vitro and in vivo studies have been reported the important activities of paeonol, its commercial utilization requires extensive safety and efficacy data.

Neuroprotective effect of biosynthesised gold nanoparticles synthesised from root extract of Paeonia moutan against Parkinson disease - In vitro &In vivo model

Parkinson disease is one of the most common neurological movement disorders affecting geriatric population. Biosynthesized gold nanoparticles are the ideal alternatives spotlighted by many researchers to treat various diseases. In the present study we synthesized gold nanoparticles using the root extract of Paeonia mountan, woody trees which are used in traditional Chinese medicine to be prescribed for diverse diseases. The synthesis of gold nanoparticles was confirmed with UV-Vis spectroscopic analysis and characterized using FTIR, HR-TEM, EDAX and XRD analysis. The cytotoxicity property of synthesized gold nanoparticles was assessed using MTT assay in the murine microglial BV2 cells. The neuroprotective effect of synthesized gold nanoparticles in inflammatory agent lipopolysaccharides triggered murine microglial BV2 cells was evaluated using nitric oxide, prostaglandin E2 and inflammatory cytokines assays such as IL-6&IL-1β. Further to confirm in vivo effect of synthesized nanoparticles, the nanoparticles were treated to Parkinson induced C57BL/6 mice. Behavioral, biochemical and molecular analysis were performed to estimate the potency of synthesized gold nanoparticles against the Parkinson induction in mice model. Our characterization results prove the gold nanoparticles synthesized using Paeonia mountan fulfills the requirement of ideal nanodrug and it potentially inhibited the inflammation in in vitro murine microglial BV2. The results of in vivo experiments authentically confirm gold nanoparticles synthesized using Paeonia mountan alleviates the neuroinflammation and improves the motor coordination in Parkinson induced mice.

Anticonvulsant and Neuroprotective Effects of Paeonol in Epileptic Rats

Paeonol is the main active compound in the root bark extract of the peony tree, and it has antioxidative and anti-inflammatory effects. Recent studies have reported the neuroprotective effects of paeonol including its capacity in improving impaired memory. However, the effect of paeonol on epilepsy is yet to be demystified. We aimed to investigate the therapeutic effect of paeonol in epilepsy and its relationship with oxidative stress damage and neuronal loss in the rat brain to reveal the underlying mechanisms of epileptic seizures. A rat model for chronic epilepsy was established, and the seizure scores of the rats in different groups were recorded. The seizure duration and the seizure onset latency were used to evaluate the anticonvulsant effects of paeonol. Terminal deoxynucleotidyl transferase dUTP nick end-labeling staining, Nissl staining and H/E staining were used to evaluate the effects of paeonol on neuronal loss and apoptosis in epileptic rats. The colorimetric assessment of malondialdehyde (MDA) content, superoxide dismutase (SOD) activity, catalase activity and total antioxidant capacity of paeonol were used in assessing paeonol's effect on oxidative stress in epileptic rats. Evaluation of Caspase-3 mRNA and protein expression levels were determined using western blot and quantitative real-time (RT-q)PCR. In this study, we found that paeonol reduced the seizure scores of epileptic rats and attenuated the duration and onset latency of seizures. Paeonol can also increase the activities of total antioxidant capacity, SOD and catalase activity and reduce MDA content as well. This suggests that paeonol can improve the level of oxidative stress in rats. More significantly, paeonol can improve neuronal loss and apoptosis in epileptic rats. These results indicate that paeonol has anticonvulsant and neuroprotective effects in epileptic rats. This effect may be caused by reducing oxidative stress.

Involvement of a Novel Organic Cation Transporter in Paeonol Transport Across the Blood-Brain Barrier

Paeonol has neuroprotective function, which could be useful for improving central nervous system disorder. The purpose of this study was to characterize the functional mechanism involved in brain transport of paeonol through blood-brain barrier (BBB). Brain transport of paeonol was characterized by internal carotid artery perfusion (ICAP), carotid artery single injection technique (brain uptake index, BUI) and intravenous (IV) injection technique in vivo. The transport mechanism of paeonol was examined using conditionally immortalized rat brain capillary endothelial cell line (TR-BBB) as an in vitro model of BBB. Brain volume of distribution (V_D) of [³H]paeonol in rat brain was about 6-fold higher than that of [¹⁴C]sucrose, the vascular space marker of BBB. The uptake of [3H]paeonol was concentration-dependent. Brain volume of distribution of paeonol and BUI as in vivo and inhibition of analog as in vitro studies presented significant reduction effect in the presence of unlabeled lipophilic compounds such as paeonol, imperatorin, diphenhydramine, pyrilamine, tramadol and ALC during the uptake of [³H]paeonol. In addition, the uptake significantly decreased and increased at the acidic and alkaline pH in both extracellular and intracellular study, respectively. In the presence of metabolic inhibitor, the uptake reduced significantly but not affected by sodium free or membrane potential disruption. Similarly, paeonol uptake was not affected on OCTN2 or rPMAT siRNA transfection BBB cells. Interestingly. Paeonol is actively transported from the blood to brain across the BBB by a carrier mediated transporter system.

Paeonol: pharmacological effects and mechanisms of action

Paeonia suffruticosa possesses various medicinal benefits and has been used extensively in traditional oriental medicine for thousands of years. Paeonol is the main component isolated from the root bark of Paeonia suffruticosa. The pharmacological effects of Paeonia suffruticosa are mostly attributed to paeonol. Paeonol injection has been successfully applied in China for nearly 50 years for inflammation/pain-related indications. Currently, the dosage forms of paeonol approved by China Food and Drug Administration include tablet, injection, and external preparations such as ointment and adhesive plaster. So far, the clinical applications of paeonol are mainly focusing on the anti-inflammatory activity. Studies of other pharmacological activities of paeonol are developing rapidly, and which may play an important role in the future. Besides, substantial mechanisms of pharmacological action of paeonol have been clarified in recent years. In this review, we summarize the pharmacological effects anti-inflammatory, neuroprotective, anti-tumor, anti-cardiovascular diseases and associated mechanisms of action of paeonol up to date.

Paeonol suppresses solar ultraviolet-induced skin inflammation by targeting T-LAK cell-originated protein kinase

Excessive exposure to solar UV (SUV) is related with numerous human skin disorders, such as skin inflammation, photoaging and carcinogenesis. T-LAK cell- originated protein kinase (TOPK), an upstream of p38 mitogen-activated protein kinase (p38) and c-Jun N-terminal kinases (JNKs), plays an important role in SUV -induced skin inflammation, and targeting TOPK has already been a strategy to prevent skin inflammation. In this study, we found that the expression of TOPK, phosphorylation of p38 or JNKs was increased in human solar dermatitis tissues. The level of phosphorylation of p38 or JNKs increased in a dose and time dependent manner in HaCat cells or JB6 Cl41 cells after SUV treatment. Paeonol is an active component isolated from traditional Chinese herbal medicines, and MTS (3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2H-tetrazdium) assay showed that it has no toxicity to cells. Microscale thermophoresis (MST) assay showed that paeonol can bind TOPK ex vivo. In vitro kinase assay showed paeonol can inhibit TOPK activity. Ex vivo studies further showed paeonol suppressed SUV-induced phosphorylation level of p38, JNKs, MSK1 and histone H2AX by inhibiting TOPK activity in a time and dose dependent manner. Paeonol inhibited the secretion of IL-6 and TNF-α in HaCat and JB6 cells ex vivo. In vivo studies demonstrated that paeonol inhibited SUV-induced increase of TOPK, the phosphorylation of p38, JNKs and H2AX, and the secretion of IL-6 and TNF-α in Babl/c mouse. In summary, our data indicated a protective role of paeonol against SUV-induced inflammation by targeting TOPK, and paeonol could be a promising agent for the treatment of SUV-induced skin inflammation.

Protective effects of paeonol on subacute/chronic brain injury during cerebral ischemia in rats

Ischemic stroke is a highly complex pathological process that is divided into acute, subacute and chronic phases. Paeonol is a biologically active natural product with a variety of pharmacological effects, including those on neuronal activity. However, the effects of paeonol on subacute/chronic ischemic stroke have remained to be elucidated. The present study was designed to investigate the effects of paeonol against subacute and chronic cerebral ischemic injury and to explore the possible underlying mechanisms. Male adult Sprague Dawley rats were randomly divided into a sham group (treated with saline), a model group [subjected to middle cerebral artery occlusion (MCAO) and treated with saline] and a paeonol-treated group (MCAO + paeonol at 25 mg/kg). Behavioral impairment, infarct volume and ischemic/contralateral hemispheric ratios were assessed at 72 h and at 28 days after MCAO, respectively. Immunofluorescence was employed to determine the neuronal damage and glial responses after MCAO. Compared with the model group, paeonol treatment significantly attenuated behavioral impairment, ischemic infarct volume and moderate cerebral edema in the ischemic brain at 72 h, as well as brain atrophy at 28 days after reperfusion. Furthermore, paeonol treatment ameliorated neuronal damage in the ischemic core and boundary zone regions at 72 h after reperfusion and in the boundary zone at 28 days after reperfusion. In addition, paeonol treatment reduced the proliferation of astrocytes in the boundary zone, and inhibited microglial activation in the ischemic core and boundary zone regions at 72 h and 28 days after reperfusion. These results demonstrated the protective effects of paeonol against subacute/chronic cerebral ischemia, and the mechanism of action may include subacute/chronic microglial activation and astrocyte proliferation.

Ethyl Acetate Extract Components of Bushen-Yizhi Formula Provides Neuroprotection against Scopolamine-induced Cognitive Impairment

Alzheimer's disease (AD) is a multifactorial neurodegenerative disorder and there is no effective cure for this devastating disease to date. Bushen Yizhi Formula (BSYZ-F), a Chinese herbal compound, has proved to be effective for AD. In this study, we further investigate the effective part of BSYZ-F, ethyl acetate extract components of BSYZ-F (BSYZ-E), protects scopolamine (SCOP)-induced cognitive impairment, which shows a similar effect to BSYZ-F. We also find that BSYZ-E could protect against SCOP-induced cholinergic system dysfunction. In neuron function level, BSYZ-E remarkably elevates protein levels of nerve growth factor (NGF) and brain-derived neurotrophic factor (BDNF). BSYZ-E also significantly mitigates SCOP-induced apoptosis, oxidative stress and nitrosative stress. Conclusively, BSYZ-E, the effective part of BSYZ-F, can provide neuroprotection against SCOP-induced cognitive impairment through a multifunctional strategy. These findings suggest that BSYZ-E might be developed as a therapeutic drug for AD by targeting multiple pathways of the pathogenesis.

Optimization of paeonol-loaded poly(butyl-2-cyanoacrylate) nanocapsules by central composite design with response surface methodology together with the antibacterial properties

With the aim to enhance dissolution rate and bioavailability of paeonol, paeonol-loaded poly(butyl-2-cyanoacrylate) nanocapsules (Pae@PNCs) were prepared by interfacial spontaneous polymerization for the first time. Herein, a rotatable central composite design (RCCD) with three-factor five-level was applied to evaluate the optimization experiments. To the maximum percentage encapsulation efficiency (EE%) and minimum particle size (nm) of the Pae@PNCs, a quadratic polynomial model was generated to predict and evaluate the independent variables with respect to the dependent variables. RSM model goodness fitting were confirmed by the ANOVA Table (P<0.05) through variance analysis, which predicted values of EE (%) and particle size (R² and adjusted R² were close to 1, respectively) in good agreement with experimental values. By solving the regression equation and analyzing the response surface, three-dimensional model graphs and plots, the optimal result for the preparation of Pae@PNCs were found to be: pH (2.34), Poloxamer F-68 (0.80% m/v) and ethyl acetate/α-BCA ratio (16.67 v/v) for the highest EE% (73.58±2.76%) and the smallest particle size (42.06±1.20nm). The release profiles and antibacterial activity in vitro from the optimal Pae@PNCs were performed. The results indicated that it has slow and well-controlled release, and has strong antibacterial activity in vitro than paeonol. This understanding can help to predict the conditions of optimization of poly(butyl-2-cyanoacrylate) nanoparticles formation and to improve paeonol bioavailability and pharmacological properties.

Synthesis and Evaluation of Aminothiazole-Paeonol Derivatives as Potential Anticancer Agents

In this study, novel aminothiazole-paeonol derivatives were synthesized and characterized using ¹H-NMR, ¹³C-NMR, IR, mass spectroscopy, and high performance liquid chromatography. All the new synthesized compounds were evaluated according to their anticancer effect on seven cancer cell lines. The experimental results indicated that these compounds possess high anticancer potential regarding human gastric adenocarcinoma (AGS cells) and human colorectal adenocarcinoma (HT-29 cells). Among these compounds, N-[4-(2-hydroxy-4-methoxyphenyl)thiazol-2-yl]-4-methoxybenzenesulfonamide (13c) had the most potent inhibitory activity, with IC₅₀ values of 4.0 µM to AGS, 4.4 µM to HT-29 cells and 5.8 µM to HeLa cells. The 4-fluoro-N-[4-(2-hydroxy-4-methoxyphenyl)thiazol-2-yl]benzenesulfonamide (13d) was the second potent compound, showing IC₅₀ values of 7.2, 11.2 and 13.8 µM to AGS , HT-29 and HeLa cells, respectively. These compounds are superior to 5-fluorouracil (5-FU) for relatively higher potency against AGS and HT-29 human cancer cell lines along with lower cytotoxicity to fibroblasts. Novel aminothiazole-paeonol derivatives in this work might be a series of promising lead compounds to develop anticancer agents for treating gastrointestinal adenocarcinoma.