Flavonoid Baicalein Research Articles

In Vitro Study of Isoflavones and Isoflavans as Potent Inhibitors of Human 12‐ and 15‐Lipoxygenases

In this study, we have investigated 16 isoflavone and isoflavan derivatives as potential inhibitors of human lipoxygenase (platelet 12-lipoxygenase, reticulocyte 15-lipoxygenase-1, and epithelial 15-lipoxygenase-2). The flavonoid baicalein, a known lipoxygenase inhibitor, was used as positive control. Four compounds, 6,7-dihydroxy-3'-chloroisoflavone (1c), 7-hydroxy-8-methyl-4'-chloroisoflavan (5a), 7,8-dihydroxy-4'-methylisoflavan (5b), and 7,8-dihydroxy-3'-methylisoflavan (5c), were effective inhibitors of 12-lipoxygenases and 15-lipoxygenase-1 with IC50 's <10μm, while 6,7-dihydroxy-4'-nitroisoflavone (1b) was a selective inhibitor of 12-lipoxygenases. Docking studies, antioxidant assays, and kinetic measurements were carried out for the three best inhibitors (1b, 5b, 5c). The results showed that a catechol group in ring A is critical for the antioxidant properties of these compounds, and probably essential for their inhibitory activity. Kinetic assays showed that compounds 1b, 5b, and 5c are competitive inhibitors with Ki values in the range of 0.3-3μm.

In silico Target Fishing for the Potential Targets and Molecular Mechanisms of Baicalein as an Antiparkinsonian Agent: Discovery of the Protective Effects on NMDA Receptor‐Mediated Neurotoxicity

The flavonoid baicalein has been proven effective in animal models of parkinson's disease; however, the potential biological targets and molecular mechanisms underlying the antiparkinsonian action of baicalein have not been fully clarified. In the present study, the potential targets of baicalein were predicted by in silico target fishing approaches including database mining, molecular docking, structure-based pharmacophore searching, and chemical similarity searching. A consensus scoring formula has been developed and validated to objectively rank the targets. The top two ranked targets catechol-O-methyltransferase (COMT) and monoamine oxidase B (MAO-B) have been proposed as targets of baicalein by literatures. The third-ranked one (N-methyl-d-aspartic acid receptor, NMDAR) with relatively low consensus score was further experimentally tested. Although our results suggested that baicalein significantly attenuated NMDA-induced neurotoxicity including cell death, intracellular nitric oxide (NO) and reactive oxygen species (ROS) generation, extracellular NO reduction in human SH-SY5Y neuroblastoma cells, baicalein exhibited no inhibitory effect on [(3) H]MK-801 binding study, indicating that NMDAR might not be the target of baicalein. In conclusion, the results indicate that in silico target fishing is an effective method for drug target discovery, and the protective role of baicalein against NMDA-induced neurotoxicity supports our previous research that baicalein possesses antiparkinsonian activity.

Baicalein Protects Against Retinal Ischemia by Antioxidation, Antiapoptosis, Downregulation of HIF-1α, VEGF, and MMP-9 and Upregulation of HO-1

Retinal ischemia-associated ocular disorders are vision threatening. This study examined whether the flavonoid baicalein is able to protect against retinal ischemia/reperfusion. Using rats, the intraocular pressure was raised to 120 mmHg for 60 min to induce retinal ischemia. In vitro, an ischemic-like insult, namely oxidative stress, was established by incubating dissociated retinal cells with 100 μM ascorbate and 5 μM FeSO4 (iron) for 1 h. The rats or the dissociated cells had been pretreated with baicalein (in vivo: 0.05 or 0.5 nmol; in vitro: 100 μM), vehicle (1% ethanol), or trolox (in vivo: 5 nmol; in vitro: 100 μM or 1 mM). The effects of these treatments on the retina or the retinal cells were evaluated by electrophysiology, immunohistochemistry, terminal deoxynucleotidyl-transferase-mediated dUTP nick end-labeling (TUNEL) staining, Western blotting, or in vitro dichlorofluorescein assay. In addition, real-time-polymerase chain reaction was used to assess the retinal expression of hypoxia-inducible factor-1α (HIF-1α), matrix metalloproteinase-9 (MMP-9), vascular endothelium growth factor (VEGF), and heme oxygenase-1 (HO-1). The retinal changes after ischemia included a decrease in the electroretinogram b-wave amplitude, a loss of choline acetyltransferase immunolabeling amacrine cell bodies/neuronal processes, an increase in vimentin immunoreactivity, which is a marker for Müller cells, an increase in apoptotic cells in the retinal ganglion cell layer linked to a decrease in the Bcl-2 protein, and changes in the mRNA levels of HIF-1α, VEGF, MMP-9, and HO-1. Of clinical importance, the ischemic detrimental effects were concentration dependently and/or significantly (0.05 nmol and/or 0.5 nmol) altered when baicalein was applied 15 min before retinal ischemia. Most of all, 0.5 nmol baicalein significantly reduced the upregulation of MMP-9; in contrast, 5 nmol trolox only had a weak attenuating effect. In dissociated retinal cells subjected to ascorbate/iron, there was an increase in the levels of reactive oxygen species, which had been significantly attenuated by 100 μM baicalein and trolox (100 μM or 1 mM; a stronger antioxidative effect at 1 mM). Baicalein would seem to protect against retinal ischemia via antioxidation, antiapoptosis, upregulation of HO-1, and downregulation of HIF-1α, VEGF, and MMP-9. The antioxidative effect of baicalein would appear to play a minor role in downregulation of MMP-9.

Protective Effects of Flavonoid Baicalein against Menadione-Induced Damage in SK-N-MC Cells

Oxidative damage and redox metal homeostasis loss are two contributing factors in brain aging and widely distributed neurodegenerative diseases. Oxidative species in company with excessive amounts of intracellular free iron result in Fenton-type reaction with subsequent production of highly reactive hydroxyl radicals which initiate peroxidation of biomolecules and further formation of non-degradable toxic pigments called lipofuscin that amasses in long-lived postmitotic cells such as neurons. Dietary flavonoid baicalein can counteract the detrimental consequences through exertion of a multiplicity of protective actions within the brain including direct ROS scavenging activity and iron chelation. In this study, we evaluated the neuroprotective effects of baicalein in menadione (superoxide radical generator)-treated SK-N-MC neuroblastoma cell line. Our results showed that treatment of cells with menadione led to lipofuscin formation due to elevated intracellular iron contents and accumulation of oxidative products such as MDA and PCO. Also, menadione caused apoptotic cell death in SK-N-MC cells. However, pretreatment with baicalein (40 μM) reversed the harmful effects by chelating free iron and preventing biomolecules peroxidations. Moreover, baicalein prevented cell death through modulation of key molecules in apoptotic pathways including suppression of Bax and caspase-9 activities and induction of bcl2 expression. Key structural features such as presence of hydroxyl groups and iron-binding motifs in baicalein make it the appropriate candidate in antioxidant-based therapy in age-related neurodegenerative diseases.

Inhibition of Tumor Cells Proliferation and Migration by the Flavonoid Furin Inhibitor Isolated From Oroxylum indicum

The medicinally active plant Oroxylum indicum (OI) has drawn considerable research interest because of its many observed biological activities. Of particular interest is its antitumorigenic activity. The plant is a rich source of flavonoids and their glycosides. Recently flavonoids have been described as inhibitors of kexin-type proteases of superfamily Proprotein Convertase Subtilisin/ Kexins (PCSKs) which have been implicated in tumor growth and malignancy. These enzymes particularly furin (PCSK3) cleaves inactive precursor growth factors into their mature forms that promote tumor growth. As a result, finding furin-inhibitors became of high interest in cancer research. In this regard, the plant OI with known anticancer activities may provide an important source. The objective of this study is to examine and compare anti-tumorigenic activity of furin inhibitory flavonoid compounds from OI. Studies were conducted to evaluate the effect on CT-26 cell proliferation and migration of 4 flavonoids baicalein, chrysin, oroxylin-A and its glycoside isolated from OI. Data revealed that baicalein exhibited most potent inhibitory effect on proliferation and migration on the analyzed tumor cell line. Baicalein at 10 μM completely blocked the proliferation even after 5 days. The results are consistent with the observed in vitro anti-furin activity of baicalein as measured against a fluorogenic peptide and pro-hVEGF-C as substrates. Mature VEGF-C is a strong indicator and biomarker of tumor progression and therefore the antifurin activity may explain the observed anticancer properties of baicalein. Since baicalein is the major constituent of OI, our data provided scientific rationale for the observed anticancer activity of OI and also offered a new lead molecule for future exploration as potential antitumor agents.

Anti-Bladder-Tumor Effect of Baicalein fromScutellaria baicalensisGeorgi and Its ApplicationIn Vivo

Some phytochemicals with the characteristics of cytotoxicity and/or antimetastasis have generated intense interest among the anticancer studies. In this study, a natural flavonoid baicalein was evaluated in bladder cancer in vitro and in vivo. Baicalein inhibits 5637 cell proliferation. It arrests cells in G1 phase at 100 μM and in S phase below 75 μM. The protein expression of cyclin B1 and cyclin D1 is reduced by baicalein. Baicalein-induced p-ERK plays a minor role in cyclin B1 reduction. Baicalein-inhibited p65NF-κB results in reduction of cell growth. Baicalein-induced pGSK(ser9) has a little effect in increasing cyclin B1/D1 expression instead. The translation inhibitor cycloheximide blocks baicalein-reduced cyclin B1, suggesting that the reduction is caused by protein synthesis inhibition. On the other hand, neither cycloheximide nor proteasome inhibitor MG132 completely blocks baicalein-reduced cyclin D1, suggesting that baicalein reduces cyclin D1 through protein synthesis inhibition and proteasomal degradation activation. In addition, baicalein also inhibits cell invasion by inhibiting MMP-2 and MMP-9 mRNA expression and activity. In mouse orthotopic bladder tumor model, baicalein slightly reduces tumor size but with some hepatic toxicity. In summary, these results demonstrate the anti-bladder-tumor properties of the natural compound baicalein which shows a slight anti-bladder-tumor effect in vivo.

In vitro antifungal activity of the flavonoid baicalein against Candida species

The aim of the present study was to evaluate the in vitro activity of baicalein, the flavone constituent of Scutellaria baicalensis, and synergism of the combination of baicalein and fluconazole against Candida albicans, Candida tropicalis and Candida parapsilosis. The MIC(50) (lowest concentration at which there was 50 % inhibition of growth) of baicalein alone against six Candida strains ranged from 13 to 104 µg ml(-1). For the three species tested, exposure to baicalein at the MIC(50) concentrations obtained for each strain resulted in a high loss of viability. The fluconazole plus baicalein combination markedly reduced the MICs of both drugs for all three strains analysed. In addition, a synergistic effect between baicalein and fluconazole was observed for C. parapsilosis in terms of MIC(50) (fractional inhibitory concentration index = 0.207). Scanning electron microscopy analysis revealed that yeast cells exposed to baicalein at MIC(50) produced a profusely flocculent extracellular material, resembling a biofilm-like structure. In conclusion, these results showed the antifungal capability of baicalein against Candida species and highlight a promising role of baicalein when used in combination with fluconazole against Candida infections.

Preferential inhibition of hepatocellular carcinoma by the flavonoid Baicalein through blocking MEK-ERK signaling

Baicalein is a purified flavonoid extracted from the roots of Scutellaria baicalensis or Scutellaria radix. Although previous studies have suggested that Baicalein possesses an in vitro anti-hepatocellular carcinoma activity, its in vivo effects and mechanisms of action are still not completely understood. In this study, Baicalein at concentrations of 40-120 µM exhibited significant cytotoxicity to three hepatocellular carcinoma (HCC) cell lines but marginal cytotoxicity to a normal liver cell line in vitro. Compared to a standard chemotherapy drug, 5-fluorouracil (5-FU), Baicalein had greater effect on HCC cells but less toxicity on normal liver cells. Treatment with Baicalein dramatically reduced mitochondrial transmembrane potential, and activated caspase-9 and caspase-3. Blockade of Baicalein-induced apoptosis with a pan-caspase inhibitor partially attenuated Baicalein-induced growth inhibition in HCC. Baicalein treatment significantly inhibited tumor growth of HCC xenografts in mice. Induction of apoptosis was demonstrated in Baicalein-treated xenograft tumors by the terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) assay. Furthermore, Baicalein treatment dramatically decreased the levels of phosphorylation of MEK1, ERK1/2 and Bad in vitro and in vivo. Overexpression of human MEK1 partially blocked Baicalein-induced growth inhibition. Consequently, these findings suggest that Baicalein preferentially inhibits HCC tumor growth through inhibition of MEK-ERK signaling and by inducing intrinsic apoptosis.

Electrochemical sensor for Baicalein using a carbon paste electrode doped with carbon nanotubes

We report on the voltammetric determination of the flavonoid Baicalein by using a carbon paste electrode that was doped with multi-walled carbon nanotubes. The resulting sensor exhibits excellent redox activity towards Baicalein due to the large surface area and good conductivity of the electrode. Cyclic voltammetry at various scan rates was used to investigate the redox properties of Baicalein. At the optimum conditions, the sensor displays a linear current response to Baicalein in the 0.02–10 μM concentration range, with a limit of detection of 4.2 n M. The method was successfully applied to the determination of Baicalein in spiked human blood serum samples and in a Chinese oral liquid.

Abstract 1975: The mitochondrial pathway in baicalein and wogonin-induced apoptosis in human colorectal cancer cells

Abstract Treating colorectal cancer patients commonly involves several conventional modalities, including surgery, radiation, and chemotherapy. The complexity of colorectal cancer, however, requires additional alternatives to improve the therapeutic efficacy of conventional treatment and the quality of life of cancer patients. Medicinal botanicals have recently gained attention as additions to colorectal cancer management. Numerous effective anticancer drugs have been developed from botanicals, and identifying new herbal sources for ideal chemoprevention remains essential to advance the treatment of colorectal cancer. Scutellaria baicalensis extract (SbE) has chemopreventive effects on several cancers. Baicalin, a major constituent of SbE, also may have the negative effect of decreasing the anti-tumor potential of SbE. In this study, we prepared a baicalin knockout fraction (BKF) of SbE and evaluated its antiproliferative activity and mechanism of action. The constituents of BKF, baicalin fraction (BF), and SbE were quantified by HPLC. We then used an MTS assay to determine the effects of BKF, BF, SbE, and the representative flavonoids on the proliferation of human colorectal cancer cells (HCT-116 and HT-29). Cell cycle, cyclin A expression and cell apoptosis were assayed by flow cytometry. Apoptosis-related gene expression was visualized by quantitative real-time polymerase chain reaction (PCR), and mitochondrial membrane potential was estimated after staining with JC-1. HPLC analysis showed that BKF contained baicalein and wogonin; BF contained only baicalin. SbE had little antiproliferative effect on cancer cells, even increasing cancer cell growth at certain concentrations. BF increased cancer cell growth. BKF showed potent antiproliferative effects on cancer cells. BKF arrested cells in the S and G2/M phases, increased expression of cyclin A, and significantly induced cell apoptosis. Multiple genes in the mitochondrial pathway were involved in BKF-induced apoptosis, and subsequent cellular functional analysis validated the pathway. These results suggest that knocking out baicalin from SbE produces a BKF that significantly inhibits the growth of colorectal cancer cells. The active anticancer compounds in SbE are flavonoid aglycons, baicalein and wogonin, and the mitochondrial apoptotic pathway is part of baicalein and wogonin-induced apoptosis. (This work was supported in part by the NIH/NCCAM grants AT004418 and AT005362). Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 1975. doi:1538-7445.AM2012-1975

Curcumin Prevents Aggregation in α-Synuclein by Increasing Reconfiguration Rate

α-Synuclein is a protein that is intrinsically disordered in vitro and prone to aggregation, particularly at high temperatures. In this work, we examined the ability of curcumin, a compound found in turmeric, to prevent aggregation of the protein. We found strong binding of curcumin to α-synuclein in the hydrophobic non-amyloid-β component region and complete inhibition of oligomers or fibrils. We also found that the reconfiguration rate within the unfolded protein was significantly increased at high temperatures. We conclude that α-synuclein is prone to aggregation because its reconfiguration rate is slow enough to expose hydrophobic residues on the same time scale that bimolecular association occurs. Curcumin rescues the protein from aggregation by increasing the reconfiguration rate into a faster regime.

Flavonoid baicalein modulates H2O2-induced mitogen-activated protein kinases activation and cell death in SK-N-MC cells.

It is believed that ROS-induced oxidative stress triggers numerous signaling pathways which are involved in neurodegenerative diseases, including Alzheimer's disease. To find the effective drugs for neurodegenerative diseases, the deep delve into molecular mechanisms underlie these diseases is necessary. In the current study, we investigated the effects of flavonoid baicalein on H(2)O(2)-induced oxidative stress and cell death in SK-N-MC cells. Our results revealed that the treatment of SK-N-MC cells with H(2)O(2) led to a decrease in cell viability through phosphorylation and activation of extracellular signal-regulated kinases (ERKs) and c-Jun N-terminal kinases (JNKs) pathways followed by increase in Bax/Bcl2 ratio and initiation of caspase-dependent apoptotic pathways. In addition, our results showed that the exposure of SK-N-MC cells to H(2)O(2) ended up in reduction of glutathione (GSH) levels of SK-N-MC cells via JNK/ERK-mediated down-regulation of γ-glutamyl-cysteine synthetase (γ-GCS) expression. Our results demonstrated that flavonoid baicalein protected against H(2)O(2)-induced cell death by inhibition of JNK/ERK pathways activation and other key molecules in apoptotic pathways, including blockage of Bax and caspase-9 activation, induction of Bcl-2 expression and prevention of cell death. Baicalein supported intracellular defense mechanisms through maintaining GSH levels in SK-N-MC cells by the removal of inhibition effects of JNK/ERK pathways from γ-GCS expression. In addition, baicalein attenuated lipid and protein peroxidation and intracellular reactive oxygen species in SK-N-MC cells. In accordance with these observations, baicalein can be a promising candidate in antioxidant therapy and designing of natural-based drug for ROS-induced neurodegenerative disorders.

A Medicinal Herb Scutellaria lateriflora Inhibits PrP Replication in vitro and Delays the Onset of Prion Disease in Mice

Transmissible spongiform encephalopathies (TSE) are characterized by the misfolding of the host encoded prion protein (PrPC) into a pathogenic isoform (PrPSc) which leads to the accumulation of β-sheet-rich fibrils and subsequent loss of neurons and synaptic functions. Although many compounds have been identified which inhibit accumulation or dissolve fibrils and aggregates in vitro there is no therapeutic treatment to stop these progressive neurodegenerative diseases. Here we describe the effects of the traditional medicinal herb Scutellaria lateriflora (S. lateriflora) and its natural compounds, the flavonoids baicalein and baicalin, on the development of prion disease using in vitro and in vivo models. S. lateriflora extract as well as both constituents reduced the PrPres accumulation in scrapie-infected cell cultures and cell-free conversion assays and lead to the destabilization of pre-existing PrPSc fibrils. Moreover, tea prepared from S. lateriflora, prolonged significantly the incubation time of scrapie-infected mice upon oral treatment. Therefore S. lateriflora extracts as well as the individual compounds can be considered as promising candidates for the development of new therapeutic drugs against TSEs and other neurodegenerative diseases like Alzheimer’s and Parkinson’s disease.

Abstract 9215: Flavonoids Baicalein Mitigates Post-Resuscitation Myocardial Dysfunction and Improves Survival via PI3K-Akt-eNOS Pathway

Background: Post-resuscitation myocardial dysfunction is a model of global ischemia-reperfusion (IR) injury that is associated with poor prognosis. Flavonoids baicalein has been shown to reduce myocardial IR injury. We therefore investigated the role of baicalein in mitigating post-resuscitation myocardial dysfunction and the potential protective mechanisms. Methods: Using an established rat model of asphyxia cardiac arrest and CPR, we administered baicalein (20 mg/kg) 2 h before cardiac arrest and compared the left ventricular (LV) function with those of standard CPR control. The arterial blood was sampled for measurement of reactive oxygen species (ROS) using chemiluminescence method. The LV systolic and diastolic functions were assessed by dP/dt max and -dP/dt max. Two hours after return of spontaneous circulation (ROSC), the heart was harvested for measurement of malondialdehyde (MDA), phosphorylation of Akt and endothelial nitric oxide synthase (eNOS). In a subgroup with minimal invasive procedures, the survival and neurological outcomes were monitored up to 3 days. Results: In standard CPR group, the systemic ROS generation and myocardial MDA were increased in the post-resuscitation phase. The dP/dt max and -dP/dt max were significantly compromised. Treatment of baicalein reduced systemic ROS and myocardial MDA (both P &lt;0.001), and improved post-CPR dP/dt max and -dP/dt max ( P &lt;0.05 and 0.01, respectively). The survival and neurological outcomes were also ameliorated (Logrank P &lt; 0.001 and P &lt; 0.01, respectively). In terms of the protective mechanism, the phosphorylated Akt (p-Akt) and eNOS (p-eNOS) of the heart 2 h post-CPR were both increased in baicalein group. If NOS inhibitor N ω -nitro-L-arginine methyl ester (10 mg/kg) was cotreated with baicalein, the improved dP/dt max and -dP/dt max were diminished. The survival and neurological outcomes also became worse. If phosphoinositide 3 kinase (PI3K) inhibitor wortmannin (15 μ g/kg) was cotreated, the increased p-Akt and p-eNOS were reversed. The improvements in LV function and survival/neurological outcomes were also abrogated. Conclusion: Baicalein improves post-resuscitation myocardial dysfunction and prognosis through antioxidant protection and PI3K-Akt-eNOS signaling.

Abstract 17393: Early Reperfusion Phase as the Critical Therapeutic Window for Flavonoids Baicalein's Cardioprotection via Oxidant Scavenging and Nitric Oxide Signaling

Background: Baicalein is a natural flavonoid with antioxidant activities protecting against ischemia-reperfusion (IR) injury. Previous studies suggest that oxidative burst occurs early after reperfusion that leads to accelerated cell death thereafter. We therefore investigated the timing of baicalein treatment in relation to its oxidant modulating effects and IR protection in order to sort out the critical therapeutic window. Methods: Using an established cardiomyocyte model of IR, we administered baicalein (100 μ M) at 0, 15, 30, 60 and 120 min after reperfusion and compared the cell viability, reactive oxygen species (ROS) and nitric oxide (NO) profiles with those of IR control. The cell viability was assessed by propidium iodide. The intracellular ROS were monitored by 2’,7’-dichlorofluorescin diacetate (DCFH-DA), while NO was assessed by 4’,5’-diaminofluorescin diacetate (DAF-2 DA). Results: Baicalein administered at 0 min of reperfusion significantly reduced cell death (35.5 ± 2.6% vs. 57.4 ± 1.9% in IR control, P &lt; 0.001). Delay of baicalein for 15 or 30 min led to time-dependent decrease of cytoprotection (cell death 40.6 ± 1.7% and 44.5 ± 3.0%, P &lt; 0.001 and 0.05 vs. IR control). If baicalein was delayed for 60 or 120 min, the protective effect was lost. In IR control, a transient but significant ROS burst was seen within 15 min of reperfusion. Baicalein treated at 0 min significantly decreased the ROS burst ( P &lt; 0.01). If treatment was delayed for 15 min, the ROS burst became unaffected at all. In terms of NO, baicalein treatment at 0 min resulted in a significant increase of NO in the later phase (&gt; 30 min) of reperfusion. Cotreatment of baicalein with NO synthase (NOS) inhibitor L-NAME (200 μ M) not only decreased NO at reperfusion but abrogated the protective effect. If baicalein was delayed for 15 min, not only the NO increase was delayed, the level of NO was also lower. These suggest that NOS activation in the early phase of reperfusion is critical for NO signaling and protection. Conclusion: Baicalein protects cardiomyocytes from IR injury via oxidant scavenging and NOS-mediated NO signaling. The critical therapeutic window is within the first 15 to 30 min of reperfusion, during which reperfusion ROS burst can be timely scavenged and NOS effectively activated.

Baicalein inhibits the migration and invasive properties of human hepatoma cells

Flavonoids have been demonstrated to exert health benefits in humans. We investigated whether the flavonoid baicalein would inhibit the adhesion, migration, invasion, and growth of human hepatoma cell lines, and we also investigated its mechanism of action. The separate effects of baicalein and baicalin on the viability of HA22T/VGH and SK-Hep1 cells were investigated for 24 h. To evaluate their invasive properties, cells were incubated on matrigel-coated transwell membranes in the presence or absence of baicalein. We examined the effect of baicalein on the adhesion of cells, on the activation of matrix metalloproteinases (MMPs), protein kinase C (PKC), and p38 mitogen-activated protein kinase (MAPK), and on tumor growth in vivo. We observed that baicalein suppresses hepatoma cell growth by 55%, baicalein-treated cells showed lower levels of migration than untreated cells, and cell invasion was significantly reduced to 28%. Incubation of hepatoma cells with baicalein also significantly inhibited cell adhesion to matrigel, collagen I, and gelatin-coated substrate. Baicalein also decreased the gelatinolytic activities of the matrix metalloproteinases MMP-2, MMP-9, and uPA, decreased p50 and p65 nuclear translocation, and decreased phosphorylated I-kappa-B (IKB)-β. In addition, baicalein reduced the phosphorylation levels of PKCα and p38 proteins, which regulate invasion in poorly differentiated hepatoma cells. Finally, when SK-Hep1 cells were grown as xenografts in nude mice, intraperitoneal (i.p.) injection of baicalein induced a significant dose-dependent decrease in tumor growth. These results demonstrate the anticancer properties of baicalein, which include the inhibition of adhesion, invasion, migration, and proliferation of human hepatoma cells in vivo.

Inhibitory Activity of Flavonoids against Class I Phosphatidylinositol 3-Kinase Isoforms

Class I PI3 Kinase (PI3K) phosphorylates phosphatidylinositol 4,5-bisphophate (PIP2) to generate the second messenger phosphatidylinositol 3,4,5-trisphosphate (PIP3) and therefore plays an important role in fundamental cellular responses such as proliferation. There are four isoforms of class I PI3K which are known to have different functions and relate to various diseases such as cancer and inflammation. Flavonoids are abundant in fruits, vegetables and plant-derived beverages such as tea. So far, various pharmacological effects of flavonoids have been reported. We previously reported that the flavonoid baicalein exhibits potent PI3K-inhibitory activity. Recently we examined the inhibitory activity of eighteen flavonoids against PI3Kα by using an in vitro homogenous time resolved fluorescence (HTRF) kinase assay, and deduced their structure-activity relationships by comparing the activities of the analogues. Our result suggests that the number of hydroxyl groups in the A and B rings might promote the activity, while loss of C2-C3 double bond might reduce the activity. Furthermore, the activity against 4 class I PI3K isoforms of some selected flavonoids was investigated, and the results indicate that the flavonoids seem to exhibit more potent activity on PI3Kα and δ isoforms compared with that on PI3Kβ and γ isoforms.

Baicalein alleviates diabetic peripheral neuropathy through inhibition of oxidative–nitrosative stress and p38 MAPK activation

With the consideration of the multifactorial etiology of diabetic peripheral neuropathy, an ideal drug or drug combination should target at least several key pathogenetic mechanisms. The flavonoid baicalein (5,6,7-trihydroxyflavone) has been reported to counteract sorbitol accumulation, activation of 12/15-lipoxygenase, oxidative–nitrosative stress, inflammation, and impaired signaling in models of chronic disease. This study evaluated baicalein on diabetic peripheral neuropathy. Control and streptozotocin-diabetic C57Bl6/J mice were maintained with or without baicalein treatment (30mgkg−1d−1, i.p., for 4weeks after 12weeks without treatment). Neuropathy was evaluated by sciatic motor and hind-limb digital sensory nerve conduction velocities, thermal algesia (Hargreaves test), tactile response threshold (flexible von Frey filament test), and intraepidermal nerve fiber density (fluorescent immunohistochemistry with confocal microscopy). Sciatic nerve and spinal cord 12/15-lipoxygenase and total and phosphorylated p38 mitogen-activated protein kinase expression and nitrated protein levels were evaluated by Western blot analysis, 12(S)hydroxyeicosatetraenoic acid concentration (a measure of 12/15-lipoxygenase activity) by ELISA, and glucose and sorbitol pathway intermediate concentrations by enzymatic spectrofluorometric assays. Baicalein did not affect diabetic hyperglycemia, and alleviated nerve conduction deficit and small sensory nerve fiber dysfunction, but not intraepidermal nerve fiber loss. It counteracted diabetes-associated p38 mitogen-activated protein kinase phosphorylation, oxidative–nitrosative stress, and 12/15-lipoxygenase overexpression and activation, but not glucose or sorbitol pathway intermediate accumulation. In conclusion, baicalein targets several mechanisms implicated in diabetic peripheral neuropathy. The findings provide rationale for studying hydroxyflavones with an improved pharmacological profile as potential treatments for diabetic neuropathy and other diabetic complications.

Involvement of GABAergic non-benzodiazepine sites in the anxiolytic-like and sedative effects of the flavonoid baicalein in mice

Baicalein (BA), one of the main flavonoids obtained from the Chinese medicinal herb Scutellaria baicalensis, usually exerts several pharmacological effects. In the central nervous system (CNS), BA exerts a protective effect on neurons against several neuronal insults among other effects, but it is not clear if this effect is due to its metabolite, baicalin. The purpose of the present study was to assess the anxiolytic-like and related properties of BA following its central administration (i.c.v.) in mice. BA (0.02, 0.2 pmol) exerted an anxiolytic-like effect at low doses, increasing the time spent in open arms and the head-dipping whereas reducing the stretched-attend postures in the elevated plus-maze. BA also increased the duration of ether-induced sleep without affecting the pentylenetetrazol (PTZ)-induced convulsions. In addition, pretreatment with flumazenil (FMZ), PTZ, dehydroepiandrosterone sulfate (DHEAS), and dl-p-chlorophenilalanine ethyl ester (PCPA) were conducted in order to investigate its mechanism of action. PTZ and DHEAS, but not FMZ or PCPA, antagonized the BA's anxiolytic-like effect. Taken together our results showed that BA, when directly injected into the CNS, promotes anxiolytic-like and sedative effects, pharmacological activities dependent on GABAergic non-benzodiazepine sites but not on the 5-HT system.

A novel anti-fibrotic agent, baicalein, for the treatment of myocardial fibrosis in spontaneously hypertensive rats

Myocardial interstitial fibrosis causes left ventricular stiffness and diastolic dysfunction. Despite its clinical significance, treatment options are limited. The flavonoid baicalein, extracted from roots of a Chinese medicinal plant, Scutellaria baicalensis Georgi was shown to inhibit liver fibrosis. This study sought to investigate whether chronic treatment with baicalein could attenuate myocardial fibrosis in spontaneously hypertensive rats (SHR). SHR were treated daily with baicalein while the control group received vehicle. At the end of study, SHR control group developed significant myocardial fibrosis that was attenuated by baicalein treatment for 4 and 12 weeks. Rats treated with baicalein were protected against an increase in heart to body weight ratio, plasma level of brain natriuretic peptides, intraventricular septum thickness, myocardial collagen volume of left ventricle (all P < 0.05, respectively). The antifibrotic effects of baicalein were further illustrated by the suppressed expression of left ventricle pro-collagens I and III accompanied by the decreased expression of 12-lipoxygenase, and by reduced expression and activity of matrix metallopeptidase 9 and extracellular signal-regulated kinases. The present results show for the first time that baicalein can inhibit cardiac fibrosis in hypertensive rats.