Baicalin

Baicalin

1. Identity, Chemistry, and Natural Sources

Chemical Identity

Baicalin (chemical formula: C₂₁H₁₈O₁₁) is among the best-studied and most promising plant flavonoids for therapeutic applications, derived primarily from the dried roots of Scutellaria baicalensis (Chinese skullcap), a perennial flowering plant of the Lamiaceae family. Formally, it is classified as a flavone glycoside — specifically, baicalin (7-glucuronic acid 5,6-dihydroxyflavone) is one of the main single active constituents isolated from the dried roots of Scutellaria baicalensis Georgi; its aglycone form is called baicalein. In chemical terms, baicalin is the 7-O-glucuronide conjugate of baicalein. Baicalein (5,6,7-trihydroxyflavone) is a flavone originally isolated from the roots of Scutellaria baicalensis and Scutellaria lateriflora; it is the aglycone of baicalin.

Botanical Sources

Baicalin (BI, approximately 7.98% yield) is found in the roots of the Chinese herb Scutellaria baicalensis Georgi (also known as Huangqin or Ogon), a plant native to several East Asian countries including the Russian Federation. These compounds are also present in other Scutellaria species, including S. lateriflora, S. galericulata, and others. Beyond the genus Scutellaria, baicalein (the aglycone of baicalin) is also obtained from other sources, such as Oroxylum indicum leaves and Thymus vulgaris L. leaves.

The plant Scutellaria baicalensis produces various natural products including amino acids, essential oils, flavonoids, phenylethanoids, and sterols. More than 30 types of flavones can be found in its roots, including baicalin, baicalein, chrysin, oroxylin A, oroxylin A 7-O-glucuronide, wogonin, and wogonoside. More than 40 compounds in total have been isolated from the root, including terpenoids, volatile oils, polysaccharides, beta-sitosterol, and flavonoids such as baicalin.

Common Forms and Preparations

Baicalin is commercially available in several pharmaceutical and nutraceutical forms. Currently marketed preparations of baicalin include capsules and tablets; however, both the flavone and glucuronide moieties can form intramolecular hydrogen bonds that result in poor solubility in water, causing low oral bioavailability. Baicalin capsules (250 mg per capsule, approval no. H20158009) were approved by the state food and drug administration of China in 2005 for the adjuvant therapy of hepatitis, at a dose of 2 capsules 3 times a day. Beyond approved formulations, research has explored emerging novel baicalin preparations including nano/micro-scale baicalin delivery systems, which show better absorption and higher bioavailability in preclinical studies and show promise for future clinical applications. These novel systems include cationic solid lipid nanoparticles, cyclodextrin inclusion complexes, nanocrystalline formulations, and nanoemulsions.

2. Traditional and Historical Use

Traditional Chinese Medicine (TCM)

This medicinal plant, known by the common name Baikal skullcap or Chinese skullcap, is native to China, Korea, Mongolia, and the Russian Far East and Siberia. It is one of the 50 fundamental herbs used in traditional Chinese medicine (TCM), where it bears the name huáng qín (Chinese: 黄芩). The plant was originally documented in Shennong Bencao Jing, the first Chinese Materia Medica, during the Eastern Han Dynasty (25 CE–220 CE), described as a crude drug with bitter taste and cold in nature.

The most authoritative book on traditional Chinese medicine, Bencao Gangmu (Compendium of Materia Medica), first published in 1593, reported that Scutellaria baicalensis had been used in the treatment of diarrhea, dysentery, hypertension, hemorrhaging, insomnia, inflammation, and respiratory infections. Chinese people have used the dried root of this medicinal plant for more than 2,000 years. It is known as Huang-Qin in the traditional Chinese medicine system and is now listed officially in the Chinese Pharmacopoeia.

In TCM theory, the root was historically classified as a "heat-clearing" and "dampness-draining" herb. Traditionally, the plant was used to treat conditions including clearing away heat, purging fire, dampness-warm and summer fever syndromes, polydipsia resulting from high fever, carbuncle, sores and other pyogenic skin infections, upper respiratory infections such as acute tonsillitis, laryngopharyngitis and scarlet fever, viral hepatitis, nephritis, pelvitis, dysentery, hematemesis, and epistaxis. The plant was also traditionally used to prevent miscarriage.

Classical TCM formulae documented in the Discussion of Cold-Induced Disorders (Shang Han Lun) by Zhang Zhong-Jing (Han Dynasty, 220 CE) included formulas containing Scutellaria baicalensis, such as Minor Bupleurum (xiao chai hu tang). Traditional uses of S. baicalensis date back to the Western Zhou Dynasty around 1,000 BC, where it was used to treat liver and lung diseases.

Scutellaria baicalensis has long been a mainstay in Chinese medicine, used for anxiety, depression, neurological conditions, and gastric distress. Scutellaria lateriflora has been used in traditional Native American medicine. The specific preparations used historically included decoctions of the dried root (often harvested in spring or autumn), which were boiled in water and consumed as teas, or incorporated into multi-herb classical formulas.

3. Key Constituents and Chemical Relationships

Baicalin, Baicalein, and Related Flavonoids

Flavones such as baicalin, wogonoside, and their aglycones baicalein and wogonin are the major bioactive compounds extracted from the root of S. baicalensis. These flavones have been reported to have various pharmacological functions, including anti-cancer, hepatoprotection, antibacterial and antiviral, antioxidant, anticonvulsant, and neuroprotective effects.

The relationship between baicalin and baicalein is clinically significant. Orally administered baicalin is easily metabolized to baicalein by β-glucuronidase produced by intestinal microbiota. The produced baicalein is well absorbed from the intestine into the body, and most of the baicalein absorbed is reconverted to baicalin and baicalein 6-O-glucuronide by UDP-glucuronosyltransferase in the small intestine or liver. It has been accepted that baicalein is the major form absorbed in the intestine, not baicalin itself.

4. Pharmacokinetics and Bioavailability

Oral Absorption and First-Pass Metabolism

Due to baicalin's poor solubility in water, its absolute bioavailability after oral administration is only 2.2%. Novel baicalin-loaded nanoemulsion formulations have been developed to improve oral bioavailability. Baicalin displays a distinct pharmacokinetic profile including gastrointestinal hydrolysis, enterohepatic recycling, carrier-mediated transport, and complicated metabolism.

Profound differences in serum profile and pharmacokinetics have been observed between oral baicalein and baicalin. Baicalin demonstrated significantly later time to peak concentration (t_max) and lower peak serum concentration (C_max) of baicalein conjugated metabolites than baicalein, indicating that baicalin is absorbed more slowly and to a lesser extent than baicalein.

After combining with human plasma proteins, baicalin was reported to bind serum albumin quickly and be distributed to various tissues. The metabolites of baicalin have been observed in various tissues (heart, liver, spleen, lung, kidney, and brain), and the main organs for its metabolism were reported to be the liver and kidney.

The in vivo disposition of baicalin is affected by combinations of other herbs, and baicalin can interact with other co-administered drugs due to competition between metabolic enzymes and protein binding. Furthermore, baicalin exhibits altered pharmacokinetic properties under different pathological conditions.

5. Mechanisms of Action

Anti-Inflammatory Pathways

Baicalin has been demonstrated to have anti-inflammatory and immunomodulatory functions, most of which are regulated by inhibiting the activation of nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB) signaling pathway and nucleotide-binding oligomerization domain-like receptor pyrin domain protein 3 (NLRP3) inflammasome, as well as suppressing pro-inflammatory factor expression.

Baicalin exerts a strong anti-inflammatory effect by regulating the TLR4–NF-κB–MAPK signaling pathway; it also reduces oxidative stress by regulating the Nrf2–Keap1 pathway; it can inhibit many kinds of viruses such as influenza virus, respiratory viruses, and hepacivirus; and it can inhibit the growth of tumor cells by blocking the cell cycle or inducing apoptosis.

Baicalin inhibits pro-inflammatory cytokine release, MAPK activation, NF-κB pathway activation, and NLRP3 to diminish inflammation. By promoting the expression of interferon regulatory factor (IRF)4 and inhibiting the expression of IRF5, baicalin also lessens inflammation by regulating the transition of M1 to M2 macrophages. Baicalin inhibits NF-κB and p38 phosphorylation as well as mRNA expression, which decreases pro-inflammatory cytokines TNF-α, IL-β, and IL-6 levels.

Antioxidant Mechanisms

The protective effects of baicalin on the nervous system are closely associated with its anti-inflammatory and antioxidant effects. By triggering the Nrf2 pathway and lowering intracellular reactive oxygen species (ROS) levels, these compounds prevent oxidative stress-mediated NF-κB activation. The antioxidant enzyme HO-1 in the Nrf2 pathway also inhibits NF-κB-dependent inflammatory activity.

Antibacterial Mechanisms

Documented mechanisms of antibacterial action include disrupting the Escherichia coli membrane, downregulating quorum-sensing gene expression in Pseudomonas aeruginosa, and inhibiting host inflammatory pathways such as PI3K/Akt/NF-κB. Baicalin can protect the intestinal mucosal barrier by blocking the adhesion of pathogenic Escherichia coli to porcine small intestinal epithelial cells and reducing the inflammatory response in cells. Baicalin can exert inhibitory effects on E. coli by inhibiting the biological activity of ATP synthase of E. coli. This function is important for maintaining the integrity of the intestinal mucosal barrier.

Antiviral Mechanisms

Molecular mechanisms of action of baicalin as an antiviral agent include three categories: the inhibition or stimulation of JAK/STAT, TLR, and NF-κB pathways; up or down modulation of the expression levels of IFN, IL, SOCS1/3, PKR protein, Mx1 protein, and AP-1 protein; and inhibition of cell apoptosis caused by virus infection.

Cardiovascular Mechanisms

Accumulating evidence indicates that baicalin has favorable therapeutic effects on cardiovascular diseases. Previous studies have revealed therapeutic effects of baicalin on atherosclerosis, myocardial ischemia/reperfusion injury, hypertension, and heart failure through anti-inflammatory, antioxidant, and lipid metabolism mechanisms. By controlling programmed cell death and mitigating cellular damage induced by oxidation and inflammation, baicalin successfully reduced endothelial cell apoptosis. In the HUVEC model, baicalin modulates both the ERK1/2 pathway and the NF-κB pathway to reduce endothelial cell apoptosis through both anti-inflammatory and antioxidant mechanisms.

Neuroprotective Mechanisms

Baicalin and baicalein are primary flavonoids derived from the desiccated root of Scutellaria baicalensis that have diverse pharmacological properties and show significant potential for the management of central nervous system disorders. Multiple studies have indicated that these substances effectively reduce the severity of illnesses such as depression, stroke, and degenerative disorders of the central nervous system by exerting antioxidant and anti-inflammatory effects, regulating programmed cell death, and reducing mitochondrial malfunction.

Baicalin has been reported to improve anxiety/depression-like behaviors and promote hippocampal neurogenesis. Baicalin may normalize glucocorticoid receptor (GR) function through SGK1- and FKBP5-mediated GR phosphorylation.

Metabolic and Hepatic Mechanisms

Baicalin was shown to reduce the degree of fatty liver degeneration and obesity in a dose-dependent manner, attributed to baicalin-dependent inhibition of the hepatic calmodulin-dependent protein kinase kinase beta (CaMKKβ)/AMP-activated protein kinase (AMPK)/acetyl-CoA carboxylase (ACC) pathway. Baicalin can effectively improve diabetic nephropathy, mainly by activating the NRF2-mediated antioxidant signaling pathway and inhibiting the MAPK-mediated inflammatory signaling pathway. Baicalin was reported to significantly reduce the expression of pro-inflammatory factors IL-1β, IL-6, and TNF-α through the MAPK pathway.

6. Scientific Evidence by Area of Use

6.1 Anti-Inflammatory and Inflammatory Diseases

The anti-inflammatory evidence for baicalin is extensive at the preclinical level. Baicalin is one of the most abundant flavonoids found in the dried roots of Scutellaria baicalensis Georgi, and it has demonstrated anti-inflammatory, antiviral, antitumor, antibacterial, anticonvulsant, antioxidant, hepatoprotective, and neuroprotective effects; however, its low hydrophilicity and lipophilicity limit its bioavailability and pharmacological functions. Robust evidence supports the anti-inflammatory effect of baicalin in LPS-induced inflammation in macrophages, where it decreases the expression of pro-inflammatory proteins and genes. Similarly, in various animal models of inflammatory diseases, baicalin shows protective effects by modulating the Th17/Treg paradigm, reducing pro-inflammatory cytokine levels, and increasing Treg cell and related cytokine levels.

Evidence strength: The overwhelming majority of anti-inflammatory evidence derives from in vitro cell-culture and animal studies. Controlled clinical trials in humans specifically testing baicalin for inflammatory diseases are limited.

6.2 Antiviral Activity

Baicalin is one of the bioactive flavonoid glycosides isolated from the dried root of Scutellaria baicalensis Georgi with antiviral properties. In recent years, its antiviral activity has been widely investigated to explore molecular mechanisms of action. Literature searches have suggested that baicalin can serve as a potential candidate for the development of a novel broad-spectrum antiviral drug.

With rising interest in the antiviral effect of baicalin, numerous studies have been carried out focusing on its clinical applications. Baicalin could be combined with other medicines to treat viral diseases such as chronic hepatitis B and A H1N1 influenza. Possible underlying molecular mechanisms involve improving immunity in patients via regulation of T-lymphocyte subset levels and up-regulation of CD3+, CD4+, and CD4+/CD8+ levels in patients infected with A H1N1 influenza.

For hepatitis B specifically, a study reported that baicalin reduces the level of alanine aminotransferase (ALT), aspartate transaminase (AST), and total bilirubin (TBil), and HBV-DNA was reduced, along with reduction of hepatic fibrosis in chronic hepatitis B patients. Additionally, baicalin enhances the therapeutic efficiency of interferon α-1b against chronic hepatitis B, and treatment with a combination of the two compounds can more effectively improve liver function, alleviate liver fibrosis (p < 0.01), and decrease the incidence of adverse reactions (p < 0.05) compared to treatment with interferon α-1b alone.

Regarding SARS-CoV-2, several studies have suggested that flavonoids of Scutellaria baicalensis (including baicalin, baicalein, and scutellarin) can inhibit the replication of the SARS-CoV-2 virus. However, this evidence remains at the in vitro and computational modeling level; no randomized clinical trials confirming antiviral clinical benefit in COVID-19 were identified in the reviewed literature.

Evidence strength: Antiviral evidence is mixed. There is preliminary clinical evidence for use in hepatitis B (primarily from Chinese clinical studies involving combination therapy), and in vitro and animal evidence for influenza, HIV, HCV, HSV, and SARS-CoV-2. Large, well-controlled human trials are lacking.

6.3 Liver Disease

Several studies showed that baicalin protects against several types of liver diseases including viral hepatitis, fatty liver disease, xenobiotic-induced liver injury, cholestatic liver injury, and hepatocellular carcinoma, with a variety of pharmacological mechanisms. Baicalin possesses anti-obese, anti-viral, and anti-dyslipidemia effects, playing a critical role in improving liver function after injury or alleviating liver diseases.

For non-alcoholic fatty liver disease (NAFLD), an oxidative stress study in NAFLD revealed that baicalin at concentrations ranging from 0.01 nM to 100 μM did not exhibit any cytotoxic effects on HepG2 cells at 24 h and 48 h, as determined by the CCK-8 assay. Because baicalin has multiple anti-fatty liver effects, it is considered a potential drug for the treatment of fatty liver disease. Baicalin enhances lipid metabolism and inhibits hepatic de novo lipogenesis by inhibiting the CaMKKβ/AMPK/ACC pathway.

Since baicalin is mainly metabolized in the liver, co-administration with other herbs or drugs may affect its in vivo properties, ultimately affecting its effects. Therefore, the therapeutic dosage of baicalin should be carefully explored not only because of these factors but also due to its low bioavailability, and techniques to enhance its absorption or liver targeting should be developed.

Evidence strength: Preclinical (cell and animal) evidence for hepatoprotective activity is substantial. The hepatitis B combination-therapy data represent the strongest clinical signal, though these studies are largely from Chinese clinical settings and may not be large randomized controlled trials by Western standards.

6.4 Antibacterial Activity

Baicalin exhibits remarkable antibacterial activity in vitro and has demonstrated therapeutic efficacy against gastrointestinal infections, meningitis, pulmonary diseases, and sepsis, among other infectious disorders, in animal models. These findings encompass activity against both gram-positive and gram-negative organisms, with documented effects on E. coli, Pseudomonas aeruginosa, and other pathogens.

Evidence strength: Predominantly in vitro and animal evidence. No large controlled clinical trials in humans for antibacterial indications were identified in the reviewed literature.

6.5 Cardiovascular Disease

Baicalin can play a therapeutic role in cardiovascular diseases through antioxidant biological function. Baicalin has been reported to ameliorate acute myocardial infarction in rats induced by isoproterenol by inhibiting nitric oxide synthase, oxidative stress, and inflammation. In recent years, new ideas related to baicalin in ferroptosis, coagulation, and fibrinolytic systems have been proposed, and new progress has been made in understanding the mechanism by which baicalin protects cardiomyocytes. However, many relevant underlying mechanisms remain unexplained, and much experimental data is lacking. Therefore, further research is needed to determine these mechanisms.

Evidence strength: Largely preclinical (in vitro and animal). No identified clinical trials specifically investigating baicalin as a cardiovascular therapeutic were found in the literature reviewed.

6.6 Neurological and Neuropsychiatric Conditions

Baicalin is a flavone glycoside derived from flowering plants belonging to the Scutellaria genus. Previous studies have reported baicalin's anti-inflammatory and neuroprotective properties in rodent models, indicating its potential in neuropsychiatric disorders where alterations in numerous processes are observed. However, the extent of baicalin's therapeutic effects remains undetermined in a human cell model.

Research into baicalin's mitochondrial effects may be highly relevant to human conditions with impaired energy production and changes in inflammation and neurogenesis, such as in bipolar depression and schizophrenia. Further investigation of the utility of baicalin as a treatment for diverse neuropsychiatric illnesses characterized by mitochondrial dysfunction is warranted.

Despite a vast number of preclinical studies on baicalin and baicalein, very few clinical trials have evaluated the efficacy and safety of these phytochemicals in neurological conditions. Evidence for Parkinson's disease, Alzheimer's disease, depression, anxiety, and stroke is almost entirely derived from rodent models.

Evidence strength: Weak for human neurological applications. Preclinical (animal model) evidence is promising, but the translation to humans is unconfirmed, and robust clinical trials are lacking.

6.7 Metabolic Syndrome, Obesity, and Diabetes

An in vivo study showed that intraperitoneal injection of baicalin (50 mg/kg) in obese mice (C57BL/6J) not only resulted in body weight loss and improvement of insulin resistance (HOMA-IR) but also reduced glucose intolerance and hyperglycemia. In this study, baicalin was also shown not to be toxic to the liver of mice.

Evidence strength: Preliminary, based on animal experiments. Clinical studies in humans examining baicalin for obesity or type 2 diabetes were not identified in the reviewed literature.

6.8 Lung Diseases

The flavonoids baicalin and baicalein were discovered in the root of Scutellaria baicalensis Georgi and are primarily used in traditional Chinese medicine, herbal supplements, and healthcare. Accumulated investigations have demonstrated therapeutic benefits of baicalin in treating various lung diseases due to its antioxidant, anti-inflammatory, immunomodulatory, antiapoptotic, anticancer, and antiviral effects. The anti-inflammatory effect in the lung was probably caused by inhibition of NF-κB activation, upregulation of histone deacetylase 2 (HDAC2) activity, and modulation of the HDAC2/NF-κB/plasminogen activator inhibitor 1 (PAI-1) signaling pathways.

Evidence strength: Predominantly preclinical. A 2023 review (Frontiers in Pharmacology) searched both PubMed and ClinicalTrials.gov and found limited human clinical data despite extensive mechanistic and animal data.

6.9 Anticancer Properties

Baicalin has been reported effective in exerting several pharmacological activities including anticancer effects. The pharmacological properties of baicalin are attributed to its ability to scavenge reactive oxygen species (ROS) and interact with several signaling molecules related to apoptosis, autophagy, cell cycle, cytoprotection, inflammation, and mitochondrial dynamics.

Baicalin and baicalein have been studied for their therapeutic potential and mechanism of action in the regulation of tumor microenvironmental immune cells, endothelial cells, fibroblasts, and extracellular matrix, leading to inhibition of tumor angiogenesis, progression, and metastasis. Discussion also covers biotransformation pathways, related therapeutic challenges, and future research directions to improve bioavailability and clinical anticancer applications. Recent advances warrant continued study of these compounds as natural approaches for cancer interception and therapy.

Evidence strength: Largely in vitro and animal. No established clinical trial data confirming anticancer efficacy for baicalin as a standalone therapeutic in human cancer were identified. Research is ongoing and active at the preclinical stage.

7. Dosage Forms and Reported Dosages

The following dosages are presented as reported in the cited scientific literature and do not represent recommendations.

• Approved hepatitis adjuvant therapy (China): Baicalin capsules 250 mg per capsule (approval no. H20158009), dosed as 2 capsules 3 times a day.
• Baicalein chewable tablets (multiple-ascending-dose clinical study): Dosing regimens tested were 200, 400, and 800 mg once daily on days 1 and 10, and twice daily on days 3–9.
• Safety finding from same study: In the dose range of 200–800 mg, multiple-dose oral baicalein administration was safe and well tolerated, and no serious accumulation of baicalein was observed.
• Drug-interaction study (healthy volunteers): 16 healthy volunteers received 500 mg baicalin in a pharmacokinetic interaction study with cyclosporine A.
• Animal metabolic study: Intraperitoneal injection of baicalin at 50 mg/kg was used in obese C57BL/6J mice to investigate hepatic insulin resistance and gluconeogenic activity.
• Human urinary pharmacokinetic study: 10 healthy male subjects took 5.2 g baicalin commercial powder orally; the total cumulative excretion rate of baicalein glucuronide and sulfate in urine at 48 h accounted for 2.9% and 4.3% of the administered dose, respectively.
• Acute/subacute mouse toxicity study (OECD 423/407): Acute toxicity was assessed at 4,000 mg/kg; subacute toxicity evaluated escalating doses from 1,000 to 4,000 mg/kg.

8. Body Systems and Health Areas Associated with Baicalin

The literature review showed that baicalin and baicalein have a wide range of therapeutic activities in vitro and in vivo. These activities can be generally divided into nine main categories including neurological and neurodegenerative problems, metabolic syndrome, hepatic diseases, cardiovascular problems, infectious diseases, and others. A structured summary of the body systems studied follows:

• Gastrointestinal system: Scutellaria baicalensis has been used for anxiety, depression, neurological conditions, and gastric distress. Baicalin has documented effects on intestinal mucosal integrity and gastrointestinal infection.
• Hepatic system: Studies show that baicalin protects against viral hepatitis, fatty liver disease, xenobiotic-induced liver injury, cholestatic liver injury, and hepatocellular carcinoma.
• Cardiovascular system: Therapeutic effects of baicalin on atherosclerosis, myocardial ischemia/reperfusion injury, hypertension, and heart failure through anti-inflammatory, antioxidant, and lipid metabolism mechanisms have been identified in preclinical studies.
• Central nervous system: Baicalin has significant potential for the management of central nervous system disorders including depression, stroke, and neurodegenerative disorders through antioxidant and anti-inflammatory effects, regulation of programmed cell death, and reduction of mitochondrial malfunction.
• Pulmonary system: Accumulated investigations have demonstrated therapeutic benefits of baicalin in treating various lung diseases due to its antioxidant, anti-inflammatory, immunomodulatory, antiapoptotic, anticancer, and antiviral effects.
• Immune system: Baicalin modulates multiple immune pathways, including macrophage polarization and T-lymphocyte subsets, with demonstrated immunomodulatory activity across preclinical models.
• Metabolic and endocrine system: Baicalin possesses potential therapeutic effects on metabolic disorders. Animal evidence supports a role in obesity, insulin resistance, and dyslipidemia.
• Renal system: Studies have shown that baicalin can effectively improve diabetic nephropathy, mainly by activating the NRF2-mediated antioxidant signaling pathway and inhibiting the MAPK-mediated inflammatory signaling pathway.

9. Safety Considerations and Drug Interactions

Acute and Subacute Toxicity

Acute exposure in mice showed no mortality, with an LD50 greater than 4,000 mg/kg, and no lasting physiological effects, with only transient gastrointestinal symptoms in one subject. Baicalin showed high acute safety with an LD50 over 4,000 mg/kg in mice, and a subacute no-observed-adverse-effect level (NOAEL) of 2,000 mg/kg, indicating its potential as a neuroprotective agent.

Subacute administration caused temporary gastrointestinal issues and occasional compulsive behaviors, all resolving within 24 h. Behavioral assessments indicated intact neurocognitive function and emotional stability. Hematological profiles revealed sex-specific responses, with males showing higher lymphocyte percentages and females demonstrating renal changes. Biochemical analyses indicated liver metabolic changes, including alkaline phosphatase suppression and reduced triglycerides, along with mild nephrotoxic signs. Histopathological evaluations confirmed non-necrotic liver stress and unchanged hippocampal structure.

Researchers emphasize that "natural" does not equate to "harmless," and rigorous safety pharmacology must accompany efficacy studies. Due to interspecies metabolic disparities, findings from mouse models require validation in higher-order animal models.

Cytochrome P450 Interactions

It has been demonstrated that Radix Scutellariae and its extracts, including baicalin, influence the pharmacokinetics of co-administered cyclosporine. Previous studies have found that baicalin enhanced levels of liver microsomal CYP and selectively induced CYP1A1, 2B1, and 2C11 in mice. Oral treatment with baicalin resulted in a significant decrease in acetaminophen-induced CYP2E1 activity together with its inhibition of CYP2E1 expression. Recent studies found that baicalin could significantly induce CYP2B6-catalyzed bupropion hydroxylation and had no effect on gene expression of CYP3A4 and MDR1.

The effect of baicalin on different kinds of cytochrome P450 has not been completely understood, and the direct relationship between baicalin and specific CYP enzymes has not been investigated sufficiently. This incomplete characterization represents an important gap in safety knowledge, particularly for patients taking multiple medications.

Interactions with Cyclosporine A

Three studies have investigated the interaction between baicalin and cyclosporin, obtaining different results: no interaction if both were injected intravenously, decreased absorption (Cmax, AUC0–t, and AUC0–∞) with oral administration of high-dose baicalin, and increased absorption (Cmax and AUC0–540) with oral administration of low-dose baicalin. Most studies have linked the mechanism to dual regulation of the CYP3A subfamily and P-glycoprotein.

A controlled human pharmacokinetic study investigated this interaction directly. In a two-period study, 16 healthy volunteers received a single 200 mg oral cyclosporine A dose alone (reference period) or in combination with 500 mg baicalin (test period). The authors concluded that a single dose of baicalin produced no clinically significant effect on cyclosporine A pharmacokinetics in this design; however, a study using multiple doses of baicalin demonstrated decreased oral bioavailability of ciclosporin, which may be attributable to the induction of P-gp. Overall, more studies are warranted, especially clinical trials, to determine the clear interaction of baicalin associated with P-gp.

Antibiotic Interactions and Pharmacokinetic Implications

Antibiotics may decrease the absorption of baicalin by reducing the hydrolysis process in the gastrointestinal tract without affecting the absorption process of baicalein itself. This occurs because gut bacteria that produce β-glucuronidase — required to convert baicalin to its absorbable aglycone form — can be depleted by antibiotic use, potentially altering the pharmacological activity of co-administered baicalin.

General Safety Profile in Humans

Both single-dose and multi-dose ascending placebo-controlled studies show that baicalein tablets are safe and well tolerated. The medication safety evaluation of baicalein chewable tablets reveals that multiple oral doses of baicalein are safe and well tolerated, with no serious accumulation in the dose range of 200–800 mg.

For natural products like baicalin, which are often perceived as inherently safe, rigorous safety assessments are imperative to define therapeutic windows and mitigate off-target organ damage. The existing safety data in humans are derived from short-term pharmacokinetic studies in healthy volunteers; long-term safety data in patient populations with chronic disease are not yet adequately characterized in the reviewed literature.

References

• Meng X, et al. "Baicalin: Natural Sources, Extraction Techniques, and Therapeutic Applications Against Bacterial Infections." Molecules, 2025. PMC12429897.
• Zhao Q, Chen XY, Martin C. "Scutellaria baicalensis, the golden herb from the garden of Chinese medicinal plants." Science Bulletin, 2016. PMC5031759.
• The Pharmacological Efficacy of Baicalin in Inflammatory Diseases. PMC10253382.
• Pharmacological effects of baicalin in lung diseases. PMC10164968.
• Neuroprotective effects of baicalin and baicalein on the central nervous system and the underlying mechanisms. PMC11699331.
• Research progress on pharmacological effects and new dosage forms of baicalin. PMC9677381.
• Pharmacological mechanisms by which baicalin ameliorates cardiovascular disease. PMC11341428.
• Recent Advances in the Therapeutic Effects and Molecular Mechanisms of Baicalin. PMC12190052.
• Antiviral Properties of Baicalin: a Concise Review. PMC8493948.
• Pharmacological properties of baicalin on liver diseases: a narrative review. PMC8460515.
• Potential therapeutic effects of baicalin and baicalein. PMC11210699.
• Integrated neurobehavioral and organ-specific safety profiling of baicalin: acute/subacute toxicity studies. PMC12408625.
• A Single Dose of Baicalin Has No Clinically Significant Effect on the Pharmacokinetics of Cyclosporine A in Healthy Chinese Volunteers. PMC6528491.
• Concentration-Dependent Inhibitory Effect of Baicalin on the Plasma Protein Binding and Metabolism of Chlorzoxazone, a CYP2E1 Probe Substrate. PMC3534641.
• Inhibitory Effects of Baicalin on the Expression and Activity of CYP3A Induce the Pharmacokinetic Changes of Midazolam in Rats. PMC3655607.
• Safety, tolerability, and pharmacokinetics of oral baicalein tablets in healthy Chinese subjects: A multiple-ascending-dose study. PMC8504836.
• Recent insights into the biological functions of baicalin. PMC9489896.
• Comparison of metabolic pharmacokinetics of baicalin and baicalein in rats. PubMed 12631413.
• Nanoemulsion improves the oral bioavailability of baicalin in rats: in vitro and in vivo evaluation. PubMed 24124365.
• Multiple-Ascending-Dose Pharmacokinetics and Safety Evaluation of Baicalein Chewable Tablets in Healthy Chinese Volunteers. PubMed 27352310.
• Baicalin promotes hippocampal neurogenesis via SGK1- and FKBP5-mediated glucocorticoid receptor phosphorylation in a neuroendocrine mouse model of anxiety/depression. PubMed 27502757.
• The potential of baicalin to enhance neuroprotection and mitochondrial function in a human neuronal cell model. PubMed 38503930.
• Role of Intestinal Microbiota in Baicalin-Induced Drug Interaction and Its Pharmacokinetics. Molecules, 2016.
• Drug-herb interactions between Scutellaria baicalensis and pharmaceutical drugs. Biomedicine & Pharmacotherapy, 2021.
• Sarup P, Malik J, Pahuja S. A comprehensive insight into baicalein and baicalin: neuroprotective perspectives in Alzheimer's disease. Exploration of Neuroprotective Therapy, 2025.
• An overview of anti-SARS-CoV-2 and anti-inflammatory potential of baicalein and its metabolite baicalin. European Journal of Medicinal Chemistry, 2023.