Scopoletin: a review of its pharmacology, pharmacokinetics, and toxicity

Scopoletin is a coumarin synthesized by diverse medicinal and edible plants, which plays a vital role as a therapeutic and chemopreventive agent in the treatment of a variety of diseases. In this review, an overview of the pharmacology, pharmacokinetics, and toxicity of scopoletin is provided. In addition, the prospects and outlook for future studies are appraised. Scopoletin is indicated to have antimicrobial, anticancer, anti-inflammation, anti-angiogenesis, anti-oxidation, antidiabetic, antihypertensive, hepatoprotective, and neuroprotective properties and immunomodulatory effects in both in vitro and in vivo experimental trials. In addition, it is an inhibitor of various enzymes, including choline acetyltransferase, acetylcholinesterase, and monoamine oxidase. Pharmacokinetic studies have demonstrated the low bioavailability, rapid absorption, and extensive metabolism of scopoletin. These properties may be associated with its poor solubility in aqueous media. In addition, toxicity research indicates the non-toxicity of scopoletin to most cell types tested to date, suggesting that scopoletin will neither induce treatment-associated mortality nor abnormal performance with the test dose. Considering its favorable pharmacological activities, scopoletin has the potential to act as a drug candidate in the treatment of cancer, liver disease, diabetes, neurodegenerative disease, and mental disorders. In view of its merits and limitations, scopoletin is a suitable lead compound for the development of new, efficient, and low-toxicity derivatives. Additional studies are needed to explore its molecular mechanisms and targets, verify its toxicity, and promote its oral bioavailability.

frutescens, Daucus carota, Cichorium intybus, Citrus limon, and Citrus aurantium, demonstrating its low toxicity as well as its safe application as a synergistic compound together with synthetic or other natural substances, such as vanillin (Carpinella et al., 2005).
The present review concentrates on recent research progress associated with the role of scopoletin in the prevention and/or treatment of illnesses and disorders, stressing the mechanism of its action and discussion of its toxicity and pharmacokinetic characteristics.Accordingly, recent literature concerning the bioactivity and uses of scopoletin as a chemotherapeutic agent was collated from multiple databases.

Pharmacological activities of scopoletin
A considerable body of evidence has proven the benefits of scopoletin in human health (Figure 3).Table 2 summarizes the health-promoting activities of scopoletin and the underlying mechanism of action for various illnesses and disorders.Details concerning the activity of scopoletin against various illnesses and disorders are discussed in the following sections.induce illnesses.Scopoletin shows maximum antifungal activity against Trichophyton mentagrophytes, Aspergillus niger, and Candida albicans (Navarro-García et al., 2011).The minimum inhibitory concentration (MIC) of scopoletin against Candida glabrata and Candida tropicalis is 67.22 and 119 μg/mL, respectively, which initiates an oxidative imbalance and reduces metabolism to achieve its antibacterial effect on these two Candida species (Das et al., 2020).Scopoletin has antifungal properties effective against a multidrug-resistant strain of C. tropicalis.Its mechanism of action is interference in the synthesis of essential fungal cell components, disruption of cell walls and plasma membranes, and impairment of C. tropicalis biofilm growth, formation, and proliferation (Lemos et al., 2020).Recent studies have reported that scopoletin has strong antitubercular activity; the compound isolated from Morinda citrifolia roots exhibits high activity against Mycobacterium tuberculosis with an MIC of 50 μg/mL (Sam-Ang et al., 2023).The MIC of the crude ethanol

Antiviral activity
Individual fractions of scopoletin isolated from Artemisia annua exert strong virucidal and antiviral effects at a minimum concentration of 50 μg/mL in vitro and have been shown to inhibit SARS-CoV-2 infection (Baggieri et al., 2023).

Anticancer activity
The antitumor activity of scopoletin may result from its antiproliferation, anti-migration, pro-apoptotic, anti-invasion, and antiangiogenic inhibition of multiple drug resistance, regulation of the mitogen-activated protein kinase (MAPK) and PI3K/AKT/mTOR pathways, and its effect on cell cycle arrest (Antika et al., 2023).
Scopoletin shows anti-proliferative action on BW5147 murine lymphoma cells and MCF-7 human adenocarcinoma cells (Barreiro Arcos et al., 2006;Manuele et al., 2006;Nasseri et al., 2022).It exerts anticancer effects on human cervical cancer cell lines by inducing apoptosis and cell cycle arrest and inhibiting cell invasion and the phosphoinositide 3-kinase (PI3K)/protein kinase B (AKT) signaling pathway (Tian et al., 2019).It is indicated to play a role in triggering cell cycle arrest and increasing apoptosis in PC3 cells via activation of caspase-3 (Liu et al., 2001).Scopoletin has been reported to activate nuclear factor-kappa B (NF-κB), caspase-3, and PARP cleavage, leading to apoptosis of promyeloleukemic HL-60 cells (Kim et al., 2005).Scopoletin causes human melanoma cell A375 apoptosis through downregulation of cyclin-D1; proliferation of cell nuclear antigen, survivin, and Stat-3;and upregulation of p53 and caspase-3 (Khuda-Bukhsh et al., 2010).Similar outcomes have been observed for cholangiocarcinoma cells and cervical cancer cells with respect to cell cycle arrest (G 0 /G 1) and apoptosis induction, and an increase in cytotoxicity by coadministration of cisplatin and scopoletin is indicated (Asgar et al., 2015).Scopoletin has a significant inhibitory effect on A549 cells, with an IC 50 of approximately 16 μg/mL (Yuan et al., 2021).In human Jurkat leukemia cells and leukemia-induced BALB/ c mice, scopoletin shows anti-leukemia activity associated with cancer cell apoptosis and inhibition of inflammation and angiogenesis and mitigation of bone marrow myeloblast imbalance (Ahmadi et al., 2019).Angiogenesis plays an important role in tumor growth and metastasis (Yamakawa et al., 2018).Beh et al. observed that scopoletin (10,30, and 100 nmol/egg) decreases the number of vascular branch points in a dose-dependent manner in chick embryo chorioallantoic membranes (Beh et al., 2012).Tabana et al. concluded that scopoletin (100 and 200 mg/kg, p.o.) shows anti-tumorigenic and anti-angiogenic activity in a nude mouse xenograft model by inhibiting vascular endothelial growth factor A (VEGFA), fibroblast growth factor 2 (FGF2), and extracellular signal-regulated kinase-1 (ERK-1) (Tabana et al., 2016).Scopoletin inhibits in vitro tube formation, proliferation, and migration in human umbilical vein endothelial cells and functions by obstructing VEGFR2 autophosphorylation and inhibiting ERK1/2, p38 MAPK, and Akt activation (Pan et al., 2009;Pan et al., 2011b;Cai et al., 2013).Scopoletin exposure upregulates cell cycle arrest in cancer cells, including cervical (Tian et al., 2019), cholangiocarcinoma (Prompipak et al., 2021), breast cancer (Yu et al., 2021), hepatoma, and lung cancer cells (Shi et al., 2020).A recent study has reported that matrine and scopoletin are effective ingredients of the Qinghao-Kushen combination combating liver cancer, which reduce the expression of GSK-3β in HepG2 cells and upregulate GSK-3β in HepG2.2.15 cells (Ji et al., 2022).

Anti-inflammatory activity
Administration of scopoletin inhibits mouse ear edema induced by ethyl phenylpropiolate, 12-O-tetradecanoylphorbol-13-acetate, Main biological activities and possible molecular mechanisms of scopoletin.

Anti-dendritic cell activity
Rheumatoid arthritis is an autoimmune disorder characterized by synovial hyperplasia and inflammation as well as resulting in joint destruction and deformity (Sajti et al., 2004).The synovium relies on blood supply for proliferation and formation of a pannus that invades the cartilage and bone, causing osteoclast activation and cartilage and bone destruction (Kimura et al., 2007).Dendritic cells are bone marrow-derived cells that arise from lymphoid-bone marrow hematopoiesis and coordinate innate and adaptive immune responses (Collin and Ginhoux, 2019).Immature dendritic cells are preferentially localized at the lining or sublining layer of the rheumatoid arthritis synovium (Page et al., 2002).Scopoletin (1 and 5 μM) functionally decreases the proliferation of bone marrow immature dendritic cells (Ren et al., 2020).Scopoletin (50 and 100 mg/kg), in part, improves the clinical state of rat adjuvant-induced arthritis through ameliorating synovial inflammation and destruction of cartilage and bone, thus blocking synovial angiogenesis, triggering apoptosis of fibroblast-like synoviocytes, and inhibiting COX-2 (Ying et al., 2009;Pan et al., 2010;Chen et al., 2021;Gao et al., 2011).The anti-rheumatoid arthritis activity of scopoletin (15, 30, and 60 μM) is likely exerted by suppression of IL-6 generation by fibroblast-like synoviocytes of adjuvant arthritis and potential activation of the MAPK/protein kinase C/cAMP response element-binding protein (CREB) (Dou et al., 2013).Furthermore, scopoletin (30, 40, and 50 μM) inhibits fibroblast-like synovial cells and blocks NF-κB signal transduction, thus combating rheumatoid arthritis (Chen et al., 2022).In addition, scopoletin isolated from Bouvardia ternifolia (Cav.)Schltdl.inhibits NF-κB expression, thereby exerting its anti-rheumatoid arthritis action in Freund's complete adjuvant-induced ICR mice (Zapata Lopera et al., 2022).

Effects of scopoletin on liver diseases
The common clinical liver diseases are mainly viral diseases caused by hepatitis B and C viral infection, drug-induced liver

Acute liver injury
Acute liver injury is the beginning of the progression of many liver diseases leading to liver failure; hence, it is a crucial research focus.Models to simulate acute liver injury mainly include a chemical liver injury model induced by carbon tetrachloride (CCl 4 ), drug-induced liver injury model, drug liver injury model induced by lipopolysaccharide, and alcohol-induced alcoholic liver injury model.

Chronic liver injury 2.4.2.1 Alcoholic fatty liver disease
Lee et al. reported that orally administered scopoletin (0.05%, w/ w) decreased lipid contents in the liver and plasma and the activities of hepatic lipogenic enzymes in alcohol plus 35% kcal high-fat diet (HFD)-induced mice.The potential mechanism for these effects was modulation of AMP-activated protein kinase (AMPK)-sterol regulatory element-binding protein 1C (SREBP-1c) pathwaymediated lipogenesis in HFD-induced mice.The hepatoprotective effect of scopoletin is associated with its stimulation of the antioxidant defense system (Lee et al., 2014).In alcohol-fed rats, scopoletin regulates AMPK and the toll-like receptor 4 (TLR4)/ myeloid differentiation major response gene 88 (MyD88)/NF-κB pathway and alleviates alcoholic hepatic steatosis and inflammation (Lee and Lee, 2015).In addition, Lee et al. reported that scopoletin (0.01 and 0.05 g/L) weakened chronic alcohol-induced insulin resistance and activated the antioxidant defense system through regulation of genes involved in liver glucose and antioxidant metabolism (Lee and Lee, 2015).Scopoletin is among the predominant compounds in the inner shell of chestnut (Castanea crenata) and has protective effects on ethanol-induced oxidative damage in vivo.Its hepatoprotective effects are associated with inhibition of lipid accumulation, peroxidation, and reinforcement of the antioxidant defense system in ethanol-induced mice.Scopoletin (50 μg/mL) increases antioxidant enzyme activities (SOD, catalase, glutathione peroxidase, and glutathione reductase) in alcohol-induced HepG2 cells (Noh et al., 2011).

Non-alcoholic fatty liver disease
In the HFD-induced obesity mice model, scopoletin (0.01% and 0.05% in diet) may mitigate NAFLD and prevent the development of liver fibrosis by regulating lipid metabolism and inflammation.The specific mechanism involves reduction of liver lipid accumulation, improvement in insulin resistance, and reduction in inflammatory factors (TNF-α, IL-6, and IFNγ), chemokine monocyte chemoattractant protein-1 (MCP-1), and leptin levels (Ham et al., 2016).Administration of scopoletin to HFD-fed mice decreases the body weight, liver weight, and serum levels for lipids and liver damage markers (ALT and AST) and regulates the AMPK/SREBP signaling pathway (Park et al., 2017).Scopoletin promotes palmitic acid-induced intracellular accumulation of triglycerides (TGs) and total cholesterol in HepG2 cells (Kim et al., 2017a).Scopoletin (6.25-50 μmol/L) inhibits endoplasmic reticulum stress and reactive oxygen species (ROS) production in primary liver cells of rats and reduces c-Jun N-terminal kinase (JNK) phosphorylation to prevent palmitic acid-and bile acid-induced liver cell death (Wu et al., 2022).
2.5 Effects on the cardiovascular system 2.5.1 Hypotensive activity Ojewole and Adesina, (1983) observed that scopoletin isolated from Tetrapleura tetraptera fruit had non-specific spasmolytic activity on smooth muscles (Ojewole and Adesina, 1983).Subsequently, Oliveira et al. proposed that, with regard to scopoletin derived from the roots of Brunfelsia hopeana, the nonspecific spasmolitic action is exerted through interference with the mobilization of intracellular calcium from norepinephrine (NE)sensitive stores (Oliveira et al., 2001), and the release of sarcoplasmic reticulum Ca 2+ induced by NE is inhibited, resulting in vasodilation of aortic rings (Iizuka et al., 2007).Wigati et al. reported that scopoletin decreases systolic pressure (SBP), diastolic pressure (DBP), and mean arterial blood pressure (MABP) in dexamethasone-induced mice.The mechanism is associated with the activity of an angiotensin-converting enzyme (ACE) inhibitor and the antioxidant activity of scopoletin (Wigati et al., 2017).Recently, scopoletin (0.01, 0.1, 1, 2, and 5 mg/kg, p.o.) has been shown to have antihypertensive effects on chronic and acute hypertensive mice induced by administration of angiotensin II.Scopoletin decreases the pharmacodynamic parameters for SBP and DBP by 75% and 92.8%, respectively (Lagunas-Herrera et al., 2019).Among the complications associated with hypertension, the onset of intracerebral hemorrhage is a devastating stage and is the most disabling type of stroke with the highest mortality rate.Zhang et al. observed that scopoletin improves rat ischemia induced by collagenase injection by reducing the expression of brain edema and other inflammatory mediators, such as TNF-α and IL-1β (Zhang et al., 2021).

Anti-atherosclerotic activity
The relevant literature clearly indicates that lipid accumulation (Cartolano et al., 2018), inflammation (Geovanini and Libby, 2018), and oxidative stress (Förstermann et al., 2017) are the most important risk factors for atherosclerosis.Scopoletin (10 μg/mL) attenuates lipid accumulation and inflammation in the aorta in HFD-induced apolipoprotein E-deficient (ApoE −/− ) mice, which reduces vascular inflammation by AMPK activation to suppress the expression of cell-cycle regulators (cyclin and cyclin-dependent kinase adhesion molecule) in human aortic smooth muscle cells (Park et al., 2017).Subsequently, Garg et al. observed that scopoletin (the main component isolated from Convolvulus pluricaulis extract, 0.4 mg/kg) significantly decreases the levels of atherogenic lipid biomarkers, atherogenic index, and MDA and increases the levels of HDL-C and GSH in tyloxapol-induced hyperlipidemia rats (Garg et al., 2018).In addition, Batra et al. reported that orally administered scopoletin (1, 5, and 10 mg/kg) reduces total cholesterol, low-density lipoprotein (LDL), and TG contents and improves the plasma atherosclerosis index and Castelli risk index in the high-fructose high-fat diet (HFHFD)-induced dyslipidemia model of Wistar rats (Batra et al., 2023a).

Anti-myocardial infarction activity
Recently, in an isoproterenol-induced myocardial infarction rat model, pretreatment with scopoletin (25 and 50 mg/kg) was observed to significantly reduce the heart-to-body weight ratio, cardiac diagnostic markers, MDA content, inflammatory markers, and apoptotic markers (Rong et al., 2023).In addition, Li et al. reported that scopolamine induces endothelial-dependent relaxation mediated through the NO and prostacyclin pathways, thereby alleviating acute myocardial ischemia (Li et al., 2023).

Antidiabetic activity
Diabetes mellitus may be the fastest-growing metabolic disease in the world.Approximately 2.5%-7% of the global population suffers from diabetes, which is a leading cause of illness and death.In diabetes, chronic hyperglycemia results from an interruption of carbohydrate and fat metabolism owing to insufficient insulin secretion, insufficient insulin function, or both (Rauf et al., 2017).
In 3T3-L1 adipocytes and high-glucose-induced HepG2 cells, scopoletin (10, 20, and 50 µM) improves insulin resistance and enhances glucose uptake by activating the PI3K/Akt signaling pathway (Zhang et al., 2010;Jang et al., 2020).Scopoletin (10 and 25 μM) improves insulin sensitivity in methylglyoxalinduced FL83B hepatocytes by activating the PPARγ/Akt pathway and restoring the plasma translocation of GLUT2 (Chang et al., 2015).In addition, improvement in insulin sensitivity in response to scopoletin (1 mg/kg/day, p.o.) can activate the AMPK and the IRS1-PI3K-Akt pathways in pancreatic β cells of high-fructose diet (HFHFD) rats and improves glucose homeostasis in HFHFD-induced diabetes rats (Kalpana et al., 2019;Batra et al., 2023b).Scopoletin (1-5 µM) stimulates insulin secretion by the KATP channel-dependent pathway in INS-1 pancreas β cells (Park et al., 2022).Furthermore, scopoletin (5, 10, 25, and 50 μM) protects INS-1 pancreatic β cells from glycotoxicity induced by high glucose and thus has potential as a drug to protect pancreatic β cells (Park and Han, 2023).Lee and Kim showed that scopoletin has potent inhibitory activity on both advanced glycation end-product (AGE) formation and rat lens aldose reductase (RLAR) in an in vitro bioassay, with an IC 50 of 2.93 ± 0.06 μM and 22.51 ± 2.01 μM, respectively (Lee et al., 2010).The accumulation of AGEs is associated with an increase in the risk of fracture in patients with type 2 diabetes and has a direct adverse effect on bone quality (Yamamoto and Sugimoto, 2016).In vitro studies have revealed that scopoletin (1-20 µM) improves osteoclast formation in diabetes through RANKL and enhances osteoclast formation in diabetes by inducing BMP-2 and Runx2.Oral administration of 10 mg/kg scopoletin promotes the formation of bone trabeculae and collagen fibers in the femoral epiphysis and metaphysis of type 2 diabetes mice (Lee et al., 2021).Aldose reductase (AR) is a crucial ratelimiting enzyme that contributes to cataract induction among patients with diabetes.Scopoletin (10 and 50 mg/kg) mitigates diabetes cataract formation through inhibiting AR activity, polyol accumulation, and GSH generation in galactose-fed rats (Kim et al., 2013).To further explore the specific mechanism by which scopoletin alleviates diabetes retinopathy, Pan et al reported that scopoletin protected retinal ganglion cells from high glucoseinduced damage through ROS-dependent p38 and JNK signaling cascades in a high glucose-induced retinal ganglia cell model (Pan et al., 2022).Diabetes nephropathy is among the most common microvascular complications of type 1 and type 2 diabetes; it is observed in approximately 40% of diabetes patients and is the main cause of chronic kidney disease worldwide (Vučić Lovrenčić et al., 2023).Scopoletin inhibits the proliferation of rat glomerular mesangial cells, reduces extracellular matrix proliferation and cell hypertrophy, reduces extracellular matrix protein accumulation, reduces the expression of the crucial fibrotic factor TGF-β and connective tissue growth factor, inhibits renal fibrosis, and thus improves diabetes glomerulosclerosis (Liang et al., 2021).

Effect of scopoletin on neurodegenerative disorders
A neurodegenerative disorder indicates the progressive loss of functions and structures and neuronal cell death arising from different conditions, such as genetic and environmental factors (Gay et al., 2020).Motor neuron degeneration is an important pathological process in many types of nervous system diseases.Motor neuron disease is characterized by chronic progressive degeneration of motor neurons.Many studies have shown that scopoletin has a neuroprotective effect, which is mainly affected via 1) inhibition of monoamine oxidase (MAO) and acetylcholinesterase (AChE), 2) reduction of oxidative damage and chronic inflammation, and 3) protection of the activity of neurotrophic factors.

Anti-Alzheimer's disease activity
Monoamine oxidase can be used to treat neurological disorders as a validated drug target (Carradori and Petzer, 2015).Its main function is to catalyze the oxidative deamination of neurotransmitters and biogenic amines (Edmondson et al., 2004).Yun et al. observed that scopoletin suppresses MAO in a dosedependent manner with an IC 50 value of 19.4 μg/mL (Yun et al., 2001).Furthermore, scopoletin (80 mg/kg, i.p.) is a reversible and selective MAO inhibitor causing an increase in the levels of dopamine and its metabolite (DOPAC) in the mouse brain (Mogana et al., 2013;Basu et al., 2016).
Acetylcholine (ACh) is widely distributed in the brain.The cholinergic system plays a role in crucial physiological processes, such as attention, learning, memory, stress response, wakefulness, and sleep, or sensory information (Ferreira-Vieira et al., 2016).Scopoletin can serve as an inhibitor of AChE, as indicated by the pharmacophore-based virtual screening method.The IC 50 for AChE inhibition is 168.6 µM and 0.27 ± 0.02 mM (Rollinger et al., 2004;Mogana et al., 2013).Scopoletin shows AChE inhibitory activity in the range of 13.92%-34.18%at a concentration of 100 μg/mL (Suchaichit et al., 2018).
Neuronal cell death is an important feature of neurodegenerative disorders.In SH-SY5Y cells subject to hydrogen peroxide (H 2 O 2 ) injury, scopoletin (5 μΜ) attenuates neurodegeneration via restoration of antioxidant enzyme activity, reduction in cell apoptosis, and activation of the SIRT1-ADAM10 signaling pathway, which is implicated in reduction in amyloid β (Aβ) production (Gay et al., 2020).In addition, Aβ is the main component of neuritic plaques in Alzheimer's disease (AD) (Greenberg et al., 2020).Administration of 23 mg/kg scopoletin ameliorates the detrimental impacts of Aβ deposition on memory and learning among 5XFAD transgenic mice under a HFD diet, which is associated with microglia-enhanced phagocytic capacity and weakened microglia M1 phenotype activation (Medrano-Jiménez et al., 2019).Subsequently, Kashyap et al. proposed that scopoletin improves Aβ42-induced neurotoxicity and H 2 O 2induced cytotoxicity in PC12 cells.This effect may mediate inhibition of Aβ42 aggregation, AChE, butyrylcholinesterase, Aβsite precursor protein-cleaving enzyme 1, MAO-B, and oxidative stress (Kashyap et al., 2020).
In conclusion, the imbalance of AChE and MAO, nerve cell death, and Aβ deposition may lead to cognitive and memory impairment.In cholinergically impaired and age-impaired mice models, scopoletin induces a significant increase in presynaptic activity-dependent acetylcholine release, enhances long-term potentiation (LTP) in the hippocampus, and exerts memoryimproving properties (Hornick et al., 2011).The stimulatory role of Convolvulus pluricaulis extracts (500 mg/kg, scopoletin as the active ingredient), which modulate synaptic plasticity in the hippocampal cornu ammonis, enhances LTP and reduces longterm depression, which are the two major synaptic plasticity forms of memory formation (Das R. et al., 2020).

Anti-Parkinsonism disease activity
Although the pathogenesis of Parkinson's disease (PD) is not entirely resolved, it has been reported that excessive production of ROS, mitochondrial dysfunction, neuroinflammation, and environmental toxins can promote the loss of dopaminergic neurons in PD (Ryan et al., 2015).Rotenone-induced Sprague-Dawley (SD) rats and SH-SY5Y cell models have shown that scopoletin inhibits cell apoptosis and oxidative stress by activating DJ-1-Nrf2-antioxidant response element (ARE) signaling (Narasimhan et al., 2019).In the same model, scopoletin attenuates rotenone-induced apoptosis of dopaminergic neurons in SD rats.The mechanism involves inhibition of the mitochondrial pathway of internal apoptosis, regulated by the Bcl2 family (Kishore Kumar et al., 2017).In addition, scopoletin (2.5 mM) is an antioxidant, reducing mitochondrial dysfunction and oxidative stress caused by an increase in ROS concentrations so as to restore motor ability and enhance the mitochondrial and cellular health of dopaminergic neurons in a Drosophila fly model of PD (Pradhan et al., 2020).

Anti-Huntington's activity
In a 3-nitropropionic acid-induced model of Huntington's disease, administration of 20 mg/kg scopoletin attenuates motor deficits and oxidative damage in rats where it improves behavioral parameters (locomotor, rotarod, and narrow beam walking activity) and biochemical parameters (MDA, SOD, GSH, and nitrite) (Kaur et al., 2016).

Anti-mental disorder
Worldwide, the prevalence of mental illness is approximately 25%.The mental illness mentioned in this paper refers to the medical concept of mental pain defined in the DSM-5 diagnostic criteria traditionally used for research.However, due to its long-term effects, mental illness is also considered a disability (Littlewood, 2001;Sayce and Boardman, 2008).

Anti-anxiety activity
Biebersteinia multifida root extract (45 mg/kg, i.p., including scopoletin) exhibits an anxiolytic effect that shows the same antianxiety effect as that of diazepam but lasts longer for 90 min (Monsef-Esfahani et al., 2013).In the Freund's adjuvant-induced chronic inflammation anxiety mouse model, scopoletin (50 mg/kg, i.p.) exerts an anxiolytic effect through ameliorating anxiety-like behaviors, for which the mechanism is associated with suppression of the NF-κB/MAPK signaling pathways involving antiinflammatory activities and regulation of the excitatory/inhibitory receptor balance (Luo et al., 2020).

Anti-schizophrenia activity
Scopoletin at a specific dose of 0.1 mg/kg can alleviate the positive symptoms of schizophrenia.Scopoletin exerts anticlimbing and anti-stereotypy effects on apomorphine-induced cage climbing and methamphetamine-induced stereotypy behaviors, respectively, in mice (Pandy and Vijeepallam, 2017).

Miscellaneous properties 2.10.1 Anti-gout-lowering uric acid activity
Ding et al. showed that scopoletin (100 and 200 mg/kg, i.p.) causes a significant reduction in uric acid activity associated with potassium oxonate by decreasing the serum uric acid level and enhancing urine urate (Ding et al., 2005), although the mechanism is not clear.Scopoletin (200 mg/kg, p.o.) remarkably lowers the serum uric acid level of a yeast extract in potassium oxonate-induced mice; the therapeutic mechanisms are associated with inhibition of the activity of hepatic xanthine oxidase and promotion of uric acid excretion (Zeng et al., 2017).

Anti-vitiligo activity
Vitiligo is a skin disease.The death or loss-of-function of skin melanocytes leads to partial discoloration of the skin (Pichler et al., 2006).Ahn et al. reported that scopoletin increases melanin synthesis in B16F10 cells by activating cAMP-responsive CREB phosphorylation and microphthalmia-associated transcription factor (MITF), resulting in an increase in the expression of tyrosinase (Ahn et al., 2014).In addition, scopoletin (40 μg/mL) stimulates melanin synthesis through activation of the cAMP/PKA/ p38 MAPK pathway in B16 melanoma cells (Kim et al., 2017b).Furthermore, scopoletin (10, 20, and 25 μΜ) enhances melanogenesis responses in zebrafish and B16F10 cells, which is associated with increases in melanin content and expression of tyrosinase-related protein 1 and MITF (Heriniaina et al., 2018).

Anti-spinal cord injury activity
In a rat model of spinal cord injury, scopoletin (100 mg/kg, i.p.) improves locomotion 325 recovery and motor neuronal loss through stimulation of autophagy by triggering the AMPK/mammalian 326 target of the rapamycin (mTOR) signaling pathway (Zhou et al., 2020).

Facilitating the digestion activity
Sun et al. preliminarily confirmed that scopoletin isolated from Cynachum auriculatum has an anti-functional dyspepsia effect (Sun et al., 2024).Scopoletin remarkably prevents acid reflux esophagitis production, with a similar efficiency to that of standard anti-secretory agents (ranitidine and lansoprazole) through its anti-inflammatory and anti-secretory attributes, such as its pro-kinetic activity, which can accelerate gastric emptying and intestinal transit (Mahattanadul et al., 2011).The potential mechanism is partially ascribed to the active component stimulating the 5-HT 4 receptor (Nima et al., 2012).

Inducing the expression of latent HIV
Reversing the incubation period of HIV-1 can promote the killing of infected cells, which is crucial for treatment strategies.In HIV-1 latently infected Jurkat T cell lines, scopoletin (2.0 mM) can significantly influence the incubation period of HIV-1 without cytotoxicity in a dose-dependent manner (Zhu et al., 2023).

Inducing metabolomic profile disturbances
Yao et al. evaluated the metabolic effects of scopoletin in zebrafish embryos using non-targeted metabolomics methods.Exposure to scopoletin (2.1, 6.2, and 18.5 μg/mL) resulted in significant metabolic disorders, mainly involving phosphonate and phosphinate metabolism, vitamin B6 metabolism, histidine metabolism, sphingolipid metabolism, and folate biosynthesis (Yao et al., 2022).compound, or novel chemical entity upon its administration to the body (Fan and de Lannoy, 2014).Pharmacokinetics research provides compound-/drug-specific data to determine doses and dosing routes for individual patients, minimize toxicity, and offer a cornerstone for illnesses (Visser, 2018).

Absorption, metabolism, and elimination
Absorption, metabolism, and elimination transformations of scopoletin are widely used for monitoring its possible effects on different lifestyle-related disorders.
Coumarin is quickly absorbed from the human gastrointestinal tract and is thoroughly metabolized by the liver, and only 2%-6% of the coumarin enters the systemic circulation intact (Ritschel et al., 1977;Ritschel et al., 1979).Scopoletin is a coumarin analog, and its rapid absorption, metabolism, and excretion from the human body may explain the poor bioavailability (Zeng et al., 2015).One study has shown that scopoletin is eliminated by first-order kinetics after intraperitoneal injection of Ding Gong Teng in mice.It showed the characteristics of a two-compartment open model: rapid absorption, rapid distribution, rapid action, and slow elimination.After intramuscular injection of Ding Gong Teng (scopoletin content: 2030 mg/L) in rabbits, the absorption showed double peaks: the first peak appeared at 8.08 min, and the concentration of scopoletin was 145.45 μg/L; the second peak appeared at 2.45 h, and the scopoletin concentration was 48.66 μg/L (Min et al., 2000).The pharmacokinetic study of Ding Gong Teng injection in rabbits showed that scopoletin was eliminated quickly, the elimination rate constant was 0.56 h, the half-life was 1.81 h, and the concentration at 4 h after administration was 5.32 μg/L.An additional study reported that scopoletin was well-absorbed in a human colon adenocarcinoma cell line model, indicating that it is well-absorbed in the gut lumen (Galkin et al., 2009).The aforementioned results suggest that scopoletin undergoes extensive metabolism in the body.Wang et al. determined that hepatic injury does not significantly influence the pharmacokinetics of scopoletin (Wang et al., 2018).The reason for this may be that cytochrome P450 enzymes had underwent partial change in the process of liver injury.It is also possible that scopoletin is not a P-glycoprotein substrate (Nabekura et al., 2015;Yang et al., 2015), which would explain the decrease in the bioavailability of scopoletin.The bioavailability of scopoletin is low (approximately 6.0%) (Zeng et al., 2017), which may be associated with its low water solubility and instability in physiological media.It may also reflect limited solubility, poor absorption and metabolism, or decomposition in the gastrointestinal tract (Issell et al., 2008).
Nevertheless, after oral administration of a Hedyotis diffusa extract (4.837 g/kg equivalent to 30.45 mg/kg of scopoletin), scopoletin was rapidly absorbed into the circulatory system in rats, and the half-life and average retention time were more than 10 h (Chen et al., 2018), indicating that the clearance rate of scopoletin in the plasma was slow.

Distribution
Following oral administration of 6 g/kg of Angelicae Pubescentis Radix extract to rats at the lower limit of quantification levels (2.16 ng/mL), scopoletin could not be determined in the rat plasma.Analysis of its tissue distribution showed that scopoletin was extensively distributed in multiple tissues, particularly the heart, liver, and kidneys, reflecting its pharmacological roles (Chang et al., 2013).
The pharmacokinetic deficiencies and outlook for scopoletin can be briefly summarized as follows: 1) the optimal method to investigate the pharmacokinetics of scopoletin requires clarification; 2) there are distinct differences in pharmacokinetic parameters between mice of different genders, and additional studies should be conducted to explore the underlying mechanism of gender differences; 3) the pharmacokinetic parameters of scopoletin have only been studied in mice/rat and rabbit models.

Toxicology of scopoletin
No strict boundary is proposed to portray or differentiate favorable or detrimental chemicals.The degree of harmfulness and safety seems to depend on the chemical dose.Therefore, this concept has become the hub of modern toxicology, meaning that dose determines toxicity (Hayes and Dixon, 2017).

Toxicity
As indicated by the acute toxicity test, scopoletin failed to generate treatment-associated mortality and abnormal performance at the limit test dose (2000 mg/kg, p.o.) for 14 days in SD rats (Tabana et al., 2016).This research shows the safety of scopoletin at the dose level, and, therefore, the LD 50 value of scopoletin for oral toxicity is > 2000 mg/kg.Jamuna et al. observed rats for 14 days after administration of oral doses of 10, 50, and 100 mg/kg scopoletin and detected no obvious acute toxicity signs, no net gain or loss of body weight, or gross behavioral variation (Jamuna et al., 2015).In vivo experiments have administered a dose of 50-200 mg/kg (i.p.) scopoletin to SD rats and ICR mice (Ding et al., 2005;Pan et al., 2010;Yao et al., 2012).Table 3 summarizes the reported dosages of scopoletin for different animals.Thus, previous research has defined scopoletin as a relatively safe natural product, but there is a lack of long-term toxicity studies on animals.Strict experiments in vivo should be conducted for improved estimation of the side effects of scopoletin to ensure its safe use.

Cytotoxicity
Scopoletin cytotoxicity has been assessed in numerous cell types in previous in vitro research, such as cancer cells, normal cells, immune cells, and nerve cells, illustrating that scopoletin is a relatively safe natural product.Table 4 summarizes the reported dosages of scopoletin for different cell lines.

Conclusion and future research prospects
In summary, this review summarizes the multiple physiological effects of scopoletin, confirming its significant positive effects on different illnesses, as stated previously.Consequently, many therapeutic intervention measures should be proposed in accordance with the potential mechanisms of the active agent and its derivatives.Moreover, as a natural compound, scopoletin provides a safer alternative for pharmaceutical applications targeting hepatic, neural, and cancer illnesses.Considering the therapeutic activities and the weak oral bioavailability of scopoletin, a large number of its derivatives and pharmaceutical dosages can be designed.Shi et al. considered isoxazole-based hybrids of scopoletin as an efficient chemical modification that improved the anticancer activity of scopoletin (Shi et al., 2017).The 2-fluorobenzylpyridinium derivative is the most potent tested compound, with an IC 50 value of 0.215 ± 0.015 μM, which is significantly ameliorated compared with that of scopoletin (Khunnawutmanotham et al., 2016).Multiple substituted 8,8-dimethyl-8H-pyrano [2,3-f] chromen-2-ones (chromeno-coumarin hybrids) have been synthesized based on scopoletin as vasorelaxing agents.Compared with the parent molecule scopoletin, the sensitivity of these derivatives to experimental tissues was increased by 29.40-70.89times (Singh et al., 2020).In addition, Soluplusbased scopoletin micelles (Sco-Ms) have been produced using a simple thin-film hydration technique, and the oral bioavailability of Sco-Ms was enhanced by 438% compared with that of free scopoletin.Oral delivery of Sco-Ms showed distinctly higher hypouricemic efficiency in hyperuricemic mice compared with that of scopoletin (Zeng et al., 2020).Polymeric nanoparticle encapsulation of scopoletin induced massive apoptosis in the human melanoma cell line A375 (Bhattacharyya et al., 2011).
The poor solubility of scopoletin limits the oral absorption and bioavailability of the compound.Therefore, methods to improve the bioavailability of scopoletin, reduce its toxicity, develop a suitable method for administration, and improve its clinical efficacy should be the focus of future research.In addition, scopoletin is a constituent in many edible plants and food products and thus could be developed as a health food and functional food.Further research on human subjects should be conducted to guarantee its safety, and decomposition products in the human body should be assessed to ensure its safe application in treatments.Similarly, further efforts should be made to verify the effects of food supplements, explore their diverse effects on humans and elucidate the mechanisms of action.Frontiers in Pharmacology frontiersin.org24 Gao et al. 10.3389/fphar.2024.1268464

FGF2Fibroblast growth factor 2 FoxO
Family of mammalian forkhead box OFtsZFilamentous temperature sensitive protein Z

TABLE 1
Main plant sources of scopoletin and their bioactivities.

TABLE 1 (
Continued) Main plant sources of scopoletin and their bioactivities.

TABLE 2
Treatment perspectives of scopoletin.

TABLE 3
Dose range of scopoletin examined in animal models.

TABLE 4
Cytotoxic effects of scopoletin in different cell lines.

TABLE 4 (
Continued) Cytotoxic effects of scopoletin in different cell lines.