Abstract
Morroniside belongs to a group of iridoid glycosides and is the primary active component of Cornus officinalis Sieb. et Zucc. This species is a rich source of iridoid glycosides and has been used as a traditional Chinese medicinal herbs for centuries. In this review, we discuss the pharmacokinetics and pharmacodynamics of morroniside. Morroniside is quickly absorbed and metabolized and is widely distributed throughout the body. It also exerts various pharmacological effects. Numerous pharmacological studies have indicated that morroniside plays a role in protecting the nervous system, treating osteoarthritis, inhibiting platelet aggregation, preventing diabetic angiopathies and renal damage, and reducing bone resorption, among others. Future research need to be conducted in support of the development of morroniside as a potential drug.
Morroniside, one of the most important iridoid glycosides, is the main active ingredient extracted from Cornus officinalis Sieb. et Zucc. This species is a rich source of iridoid glycosides and has been used as a traditional Chinese medicinal herbs for centuries. Its chemical structure is shown in Figure 1. 1 An increasing number of reports confirm that morroniside exerts various pharmacological effects. Moreover, the absorption, distribution, metabolism, excretion, and other metabolic properties of morroniside have been systematically studied worldwide (Figure 2). Pharmacokinetic profiles help greatly in elaborating the relationship between the intensity and time course of pharmacology, understanding and confirming the action mechanism, and in vivo toxicological effects of drugs, and investigating potential interactions in drug development and clinical applications.
Chemical structure of morroniside.
Pharmacokinetics and pharmacodynamics of morroniside.
In support of the development of morroniside as a candidate drug, the current review provides a critical evaluation of recent studies regarding the pharmacokinetics and pharmacodynamics of morroniside. Besides the introduction and the conclusions, the article falls into 2 parts, including pharmacokinetics and pharmacodynamics. The included references were searched and identified from English databases (PubMed, SCI, Wiley InterScience, IEEE, etc.) as well as Chinese databases (CNKI, VIP, Wanfang Data, CSCD, etc.) by using the key word “morroniside.”
Pharmacokinetics
Absorption
Several studies have been conducted to determine the concentration of morroniside in biological matrices by high performance liquid chromatography (HPLC) 2 and HPLC/electrospray ionization tandem mass spectrometry (LC–MS/MS). 3,4
Differences in the pharmacokinetic parameters of morroniside likely arise from the different origins of its varieties, such as pure morroniside, 2 -5 crude C. officinalis and its jiuzhipin, 6,7 Rehmannia glutinosa, and C. officinalis Sieb drug pair extract. 8 The main pharmacokinetics parameters of morroniside from various sources are listed in Table 1.
The Main Pharmacokinetics Parameters of Morroniside From Different Sources.
Values are expressed as mean ± SD. T1/2z half-life, C max maximum concentration, T max peak time, AUC area under the curve, MRT mean residence time, CLz/F clearance, Vd apparent volume of distribution.
A study comparing the main pharmacokinetic parameters of rats with doxorubicin-induced chronic kidney disease (CKD) and those of normal rats suggested that the differences could be attributed to changes in metabolic enzyme, P-glycoprotein, and intestinal bacteria in the CKD state. 8 Gang Cao et al discussed the application of the neural network model in predicting the pharmacokinetic parameters of morroniside by establishing a backpropagation (BP) network model. The application of the BP neural network in pharmaceutical research allows the investigation of the pharmacokinetics parameters of traditional Chinese medicine. 5
Distribution
To investigate the tissue distribution of morroniside, a study was conducted to determine the concentration of morroniside in 11 rat tissues—brain, heart, liver, spleen, lung, kidney, stomach, intestine, muscle, fat, and testicle tissues—after oral administration of morroniside (30 mg/kg) by LC–MS/MS. Results indicated that morroniside was rapidly absorbed, distributed, and eliminated in rats; in addition, no long-term accumulation of morroniside was observed in the rat tissues. 9 Xiaona Li also found that no morroniside was present in the brain, which could be attributed to the blood-brain barrier. 2 On the basis of this finding, Shan Xiong examined rats with focal cerebral ischemia-reperfusion injury to determine the distribution of morroniside in the brain. Compared with the normal control group and the sham-operated group, the group with focal cerebral ischemia-reperfusion had a higher concentration of morroniside in the brain. 10
Metabolism
In accordance with ultra-performance liquid crystallography (UPLC) coupled with electrospray time-of-flight mass spectrometry (TOF/MS), Zhao et al found 5 metabolites of morroniside in the plasma, urine, and feces of normal rats. The metabolites were identified as morroniside taurine conjugation, demethylated morronisid, morroniside aglycone, acetylated morroniside aglycone, and morroniside aglycone glucuronide conjugation. 11 Xiaona Li investigated the metabolic pathways and 2 metabolites of morroniside. Morroniside could be degraded to mor-1 and further converted to mor-2. 12 Min Zhao et al not only determined metabolism in rats but also examined the metabolites of morroniside produced by human intestinal bacteria. Analysis of human feces led to the identification of 3 metabolites of morroniside: aglycone (M1), dehydroxylated aglycone (M2), and methylated aglycone (M3). These metabolites vary from the 2 reported morroniside metabolites (mor-1 and mor-2) produced by rat intestinal bacteria. Their findings provide a theoretical principle for the clinical application of morroniside. 13
Excretion
To investigate the urinary pharmacokinetics of morroniside and its metabolites in rats, Xiaona Li collected and detected urine samples of rats at different periods by HPLC. The experimental data showed that the complete excretion time of morroniside and its metabolites in urine continued for 24 hours following oral administration at a dose of 20 mg/kg. 14 Shan Xiong et al compared the excretion of morroniside in rat urine via i.g. and via i.v. The results showed that 21.43‰ (IG) and 100.35% (IV) of the dose administered are excreted as a prototype drug. Their analysis suggested that CYP450 did not participate in the metabolism of morroniside. 15 Minyan Liu et al investigated the excretion kinetics of 10 constituents in rat urine after oral administration of Shensong Yangxin capsules. The mean cumulative urinary excretion percent of morroniside was 11.317% 72 hours after administration. 16
Other Studies
Shan Xiong found morroniside could induce the activity, mRNA and protein expression of CYP 3A in rats after pretreatment of morroniside (10, 30, 90 mg/kg) for 7 days. 17 In addition, the plasma protein binding percentages of morroniside were 40.46% to 48.38%, 24.45% to 34.75%, and 22.60% to 27.11% in rats, beagles, and humans, respectively. 18
Pharmacodynamics
Neuroprotection
Promoting neurogenesis
SH-SY5Y neuroblastoma cells are a type of tumor cells that exhibit low differentiation and high reproduction. They also have similar morphological, physiological, and biochemical functions as those of normal nerve cells. SH-SY5Y neuroblastoma cells have been widely used in the study of pathogenesis and the drug action mechanism underlying nervous system disorders. 19 The axonal length, area of the cell body, and cell count are indicators of cell growth. Huang et al demonstrated that morroniside increased the MTT metabolic rate, axonal length, area of the cell body, and cell count in 10 to 100 μmol/L. These findings suggest that morroniside could increase the survival rate of SH-SY5Y cells. 20 Lentiviral vector modification of human embryonic nervous system cells exhibit potential for the treatment of nervous system disorders; however, the proliferation of neural stem cells is inhibited. Several studies have found that morroniside can reverse the inhibition of proliferation caused by lentivectors. Thus, morroniside can be used to improve the efficiency of gene therapy. 21
The nerve growth factor (NGF) and brain-derived neurotrophic factor (BDNF) are important bioactive molecules in the nervous system. Both play an important role in the development of the central nervous system while maintaining the normal functions of mature central and peripheral nervous system neurons. Morroniside can also promote the proliferation and differentiation of endogenous neural stem cells in vivo and can play a significant role in promoting the migration of neural stem cells. The results suggest that morroniside can enhance the function of NGF and the expression of BNDF to improve the pathological state of nerve cells and repair damaged neurons. 20,22
The Wnt signaling pathway is a multi-link, multi-site open pathway that can regulate cell proliferation and differentiation during the growth and development of humans and animals, particularly in brain plasticity. Wnt7a is an important ligand in the Wnt signaling pathway, which mediates the Wnt signaling pathway. Wnt7a can regulate the acceleration of cell growth and differentiation, as well as inhibit glial regeneration. In contrast, the adenomatous polyposis coli (APC) gene inhibits the Wnt signaling pathway. It can regulate cell proliferation and differentiation by inhibiting the activation of the Wnt signaling pathway. A study assessed the effect of morroniside on the expression of the Wnt7a gene and APC in rats with focal cerebral ischemia-reperfusion injury. Morroniside was found to promote the expression of Wnt7a and inhibit the expression of APC to activate the Wnt signaling pathway and increase the expression of APC. In addition, the expression of Wnt signaling pathway-related transcription factors, such as neurogenin 2 (Ngn2) and Pax6, promoted the proliferation and differentiation of neural stem cells. 23
Promoting angiogenesis
Angiogenesis is affected by the angiogenic factor–VEGF/VEGFR system. Fibroblast growth factor-2 (FGF-2) is a potential angiogenic factor. Research shows that morroniside can further increase the expression of VEGF and FGF-2 induced by ischemic brain injury to improve the neurovascular microenvironment and promote angiogenesis. 24
Angiogenin-1 (Ang-1) and the hepatocyte growth factor (HGF) are growth factors regulating angiogenesis, which can prevent endothelial cell apoptosis and stimulate its proliferation. The von Willebrand factor (vWF) is synthesized and secreted by vascular endothelial cells and megakaryocytes, which can be used as markers of vascular endothelial cells. A study showed that the expression levels of HGF, vWF, and Ang-1 in the model group were significantly increased 7 d after focal cerebral ischemia-reperfusion. The expression levels of Ang-1 protein (P < 0.05, P < 0.01) and HGF (P < 0.01, P < 0.01) were significantly increased in moderate (90 mg/kg) and large (270 mg/kg) doses of morroniside, respectively, relative to the expression of the model group. The result suggests that the administration of morroniside 24 hours after model establishment can promote angiogenesis. It can also improve the microenvironment of neurovascular units and promote angiogenesis by regulating the expression of the endothelial specific tyrosine kinase receptor (Tie-2). 24,25
CD34+ cells comprise a subset of bone marrow mononuclear cells. They are also the main endogenous source cells of hematopoietic and endothelial cell precursors. It can be used as an important index of angiogenesis. Several studies showed that in the model group, the expression of CD34 protein in the cerebral ischemia–reperfusion increased relative to that of the control group (P < 0.05). This increase suggests that CD34+ cells migrated to the peripheral. Relative to that of the model group, the expression of the CD34 protein increased significantly (P < 0.01) after a large dose of morroniside (270 mg/kg). 26
Matrix metalloproteinases (MMPs) comprise the most important class of proteases decomposing the extracellular matrix. They also play an important role in physiological and pathological processes. MMP-2 and MMP-9 are important members of the MMP family. As the most important extracellular matrix-degrading enzymes, they are most closely related to blood-brain barrier damage. Tissue inhibitor of metalloproteinase (TIMP), a natural inhibitor of MMPs, binds with MMPs to reduce the activity of MMPs in vivo. The results reveal that morroniside can effectively reduce MMP-induced damage to the blood-brain barrier by increasing TIMP expression and decreasing MMP expression after cerebral ischemia-reperfusion, which is favorable for the rehabilitation of stroke. 20,27
Inhibiting neural cell apoptosis
Apoptosis involves the activation, regulation, and expression of a series of genes. The classical apoptotic pathways include the death receptor pathway and the mitochondrial pathway. The former induces apoptosis by activating caspase-3, binding death ligands to corresponding death receptors on the cell surface. The latter is mitochondria induced by an apoptotic stimulator, which releases cytochrome-C (Cyt-C) into the cytoplasm. Cyt-C binds with dATP and the apoptotic protease activator to form a complex. This complex activates caspase-9 and caspase-3 after caspase-9 cutting induces apoptosis. The Bcl-2 family can regulate the permeability of the mitochondrial membrane, downregulate Bcl-2 or overexpress Bax in the Bcl-2 family, increase the permeability of the mitochondrial membrane, and induce apoptosis. Morroniside is found to inhibit the gene expression of caspase-3 and caspase-9 as well as the activation of caspase-3 protease, reduce the expression and activation of caspase-3 in brain tissue after cerebral ischemia–reperfusion, and inhibit the downregulation of Bcl-2, thereby inhibiting neuronal apoptosis. By measuring the content of Cyt-C, morroniside was found to significantly reduce the release of Cyt-C and inhibit the oxidative damage of nerve cells to suppress nerve cell apoptosis. 28 -30
Antioxidant
Morroniside can play a neuroprotective role by reducing the contents of reactive oxygen species (ROS) and nitric oxide, inhibiting the decrease in glutathione (GSH) and lipid peroxidation in the cortex, and enhancing the total antioxidant capacity of the rat cortex. It also significantly inhibits the increase in malondialdehyde and reduces the potential of the cell membrane to considerably to influence neuroprotective effects. 22,31,32,33
Reducing calcium overload
Ca2+ is one of the important signal transduction messengers in brain neurons. Ca2+ overload can change the permeability of the cell membrane, lead to mitochondrial dysfunction, promote the release of Cyt-C, and activate phospholipase. Studies have shown that morroniside can play a neuroprotective role by inhibiting the increase in intracellular free Ca2+ concentration and reducing the release of lactate dehydrogenase. 31
Treating Osteoarthritis
One study investigated the influence of morroniside on cultured human osteoarthritis (OA) chondrocytes and a rat experimental model of OA. The results indicated that morroniside strengthened the proliferating cell nuclear antigen expression and cytoactive. Moreover, in human OA chondrocytes, morroniside at varying doses activates different kinases and drives different pathways. 34 Morroniside exerts a promotional effect on proliferation in primary and subculture rat mesenchymal stem cells (RMSCs). The specific mechanism of morroniside promoting RMSC proliferation has yet to be clarified, but the process may occur by secreted factors, cell-to-cell interactions, and/or interactions between cellular adhesion molecules and extracellular matrices. 35 Manyu Li et al also found that morroniside isolated from Liuwei Dihuang pills may directly promote the differentiation and inhibit the apoptosis of MC3T3-E1 cells. The anti-osteoporotic mechanisms in MC3T3-E1 cells are likely to improve the activity of alkaline phosphatase, increase the contents of collagen type I and osteocalcin, downregulate the mRNA expression of caspase-3 and capase-9, and upregulated the mRNA expression of bcl-2. 36
Hypoglycemic Effects
Research shows that by regulating the secretion of endothelial cells, inhibiting oxidative stress, and releasing inflammatory factors and anti-cell adhesion to protect vascular endothelial cells, morroniside can achieve the goal of diabetes treatment. 37 Studies in Japan indicate that morroniside is an important bioactive constituent used in Chinese medicine to exert hypoglycemic effects. Morroniside exerts lowering effects on oxidative stress, elevated triglyceride, and advanced glycation end product (AGE) formation in the kidneys of db/db mice, which are mediated via modulation by nuclear factor-kappa B expression and renal sterol regulatory element binding proteins. 38 Similarly, morroniside improves the conditions of diabetic hepatic complications by regulating apoptosis, inflammation, and oxidative stress. 39,40 By measuring renal and serum biochemical factors as well as protein expression related to lipid homeostasis and inflammation, the db/db mice administered orally with morroniside may inhibit inflammation and abnormal lipid metabolism owing to ROS in the kidneys in type-2 diabetes. 41,42 Two studies have been reported on the effect of morroniside on diabetic nephropathy (DN). By establishing an in vitro model for simulating DN damage, the effect of morroniside and the protective mechanism in regulating the receptor for advanced glycation end products signaling pathway or inhibiting hyperglycemia and oxidative stress in DN. 43,44 In China, morroniside was found to considerably weaken high glucose-induced cardiomyocyte apoptosis and protect myocardial cell injury. 45 It also contributed to the prevention of diabetic angiopathies. 46 In another study, the synergistic effect of morroniside and ursolic acid was observed, suggesting that both could ameliorate diabetes-associated damage and complications. 47 As one of the original constituents migrating to blood, morroniside facilitates the increase in rat preadipocytes and inhibits the accumulation of fat during differentiation, as determined after oral administration of the Liuwei Dihuang pill in rats. 48
Decreasing the Side Effects of Anticancer Medicines
Experimental data show that morroniside reverses the apoptotic effect of H2O2 on human embryonic lung fibroblast (HELF) cell growth. Thus, morroniside protects cell proliferation and normal cell morphology, as well as downregulates retinoblastoma protein in HELF cells. The results confirm that morroniside can be used to reduce the adverse reactions of anticancer medicines in normal cells. 49
Inhibiting Platelet Aggregation
Previous studies suggested that morroniside could inhibit platelet aggregation induced by adenosine diphosphate (ADP), arachidonic acid, and platelet activating factor in rabbits. 50 Further studies demonstrated that morroniside could inhibit the increase in platelet Ca2+ 51 and decrease cycloxygenase 52 and thromboxane B2. 53 These actions comprise the mechanism underlying morroniside inhibition of platelet aggregation induced by ADP in rabbits.
Others
A study conducted by Japanese researchers indicated that 7-O-cinnamoylmorroniside, the morroniside cinnamic acid conjugate, is prepared and evaluated on E-selectin mediated cell-cell adhesion as an important part of inflammatory processes. This finding shows that the morroniside cinnamic acid conjugate inhibits TNF-α-induced E-selectin expression. 54 As an orthosteric agonist of spinal glucagon-like peptide-1 receptors, morroniside can produce desensitization in a neuropathic pain model. 55 Hongmin Yu et al reported that morroniside could reduce melanin synthesis in a co-culture system by inhibiting tyrosinase activity. 56 Zhou et al first revealed that morroniside could significantly enhance the proliferation and migration of the outer root sheath cell in vitro. Morroniside regulates the growth and development of hair follicles partly by activating the canonical Wnt/β-catenin signaling pathway. The results indicate that morroniside can potentially treat hair loss. 57
Conclusions
Recent studies have proved that morroniside plays a vital role in human health. Owing to its valuable biological functions and health benefits, morroniside exhibits considerable potential as an active ingredient for treatment or adjuvant treatment of cerebral apoplexy, thrombus, diabetes, cancer, OA, and inflammation. More ideal dosage forms of morroniside should be designed to improve the pharmacokinetic characteristics of the compound. Further research need to be conducted to investigate the activity of morronisides in human subjects.
Footnotes
Declaration of Conflicting Interests
The author(s) declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.
Funding
The author(s) disclosed receipt of the following financial support for the research, authorship, and/or publication of this article: The project was financially supported by National Major Scientific and Technical Special Projects for Innovative Drug of China (Grant no. 2012ZX09301003–001–007); Ten-thousand Talents Program of Zhejiang Province (ZJWR0102035); the Innovation Project of Shandong Academy of Medical Sciences and the Science and Technology Research Program of Shandong Academy of Medical Sciences (Grant no. 2016–41).