Inhibition of Human T Cell Leukemia Virus by the Plant Flavonoid Baicalin (7-Glucuronic Acid, 5,6-Dihydroxyflavone)

Scutellaria baicalensis: a promising natural source of antiviral compounds for the treatment of viral diseases

Viruses, the smallest microorganisms, continue to present an escalating threat to human health, being the leading cause of mortality worldwide. Over the decades, although significant progress has been made in the development of therapies and vaccines against viral diseases, the need for effective antiviral interventions remains urgent. This urgency stems from the lack of effective vaccines, the severe side effects associated with current drugs, and the emergence of drug-resistant viral strains. Natural plants, particularly traditionally-used herbs, are often considered an excellent source of medicinal drugs with potent antiviral efficacy, as well as a substantial safety profile. Scutellaria baicalensis, a traditional Chinese medicine, has garnered considerable attention due to its extensive investigation across diverse therapeutic areas and its demonstrated efficacy in both preclinical and clinical trials. In this review, we mainly focused on the potential antiviral activities of ingredients in Scutellaria baicalensis, shedding light on their underlying mechanisms of action and therapeutic applications in the treatment of viral infections.

Traditional Knowledge to Contemporary Medication in the Treatment of Infectious Disease Dengue: A Review

Dengue has become a worldwide affliction despite incessant efforts to search for a cure for this long-lived disease. Optimistic consequences for dengue vaccine are implausible as the efficiency is tied to previous dengue virus (DENV) exposure and a very high cost is required for large-scale production of vaccine. Medicinal plants are idyllic substitutes to fight DENV infection since they constitute important components of traditional medicine and show antiviral properties, although the mechanism behind the action of bioactive compounds to obstruct viral replication is less explored and yet to be discovered. This review includes the existing traditional knowledge on how DENV infects and multiplies in the host cells, conscripting different medicinal plants that obtained bioactive compounds with anti-dengue properties, and the probable mechanism on how bioactive compounds modulate the host immune system during DENV infection. Moreover, different plant species having such bioactive compounds reported for anti-DENV efficiency should be validated scientifically via different in vitro and in vivo studies.

Endophytic Microbial Diversity: A New Hope for the Production of Novel Anti-tumor and Anti-HIV Agents as Future Therapeutics

Cancer is a collective name for a variety of diseases that can begin in virtually every organ or body tissue as abnormal cells develop uncontrollably and ten million new cancer cases are diagnosed all over the world at present. Whereas HIV is a virus that makes people susceptible to infection and contributes to the condition of acquired immune deficiency syndrome (AIDS). Almost 37 million people are currently diagnosed with HIV and 1 million people die every year, which is the worst-case scenario. Potential medicinal compounds have played a crucial role in the production of certain clinically beneficial novel anti-cancer and anti-HIV agents that are produced from natural sources especially from plants. These include Taxol, Vinblastine, Podophyllotoxin, Betulinic acid, Camptothecin, and Vincristine, etc. In the past decades, bioactive compounds were extracted directly from the plant sources which was more time consuming, led to low yield productivity, high cost, and bad impact on biodiversity. Endophytes, the microorganisms that reside inside the host plant by not causing any kind of harm to them and have potential applications in agriculture, medicine, pollution, and food industries. Therefore, by isolating and characterizing novel endophytes from medicinal plants and extracting their secondary metabolites to produce useful bioactive compounds can be beneficial for well-being and society as a future therapeutics. This approach is not harmful to biodiversity economical, timesaving, low cost, and can lead to the discovery of various industrial and commercially important novel anti-tumor and anti-HIV agents in the future. The Himalayas are home to several medicinal plants and the endophytic microbial biodiversity of the Himalayan region is also not much explored yet. However, the effect of compounds from these endophytes on anticancer and antiviral activity, especially anti-HIV has been largely unexplored. Hence, the present review is designed to the exploration of endophytic microbial diversity that can give rise to the discovery of various novel potential industrially valuable bioactive compounds that can lessen the rate of such type of pandemic diseases in the future by providing low-cost future therapeutics in future.

Baicalin mediated regulation of key signaling pathways in cancer

Baicalin has been widely investigated against different types of malignancies both at the cellular and molecular levels over the past few years. Due to its remarkable anti-proliferative potential in numerous cancer cell lines, it has created immense interest as a potential chemotherapeutic modality compared to other flavonoids. Thus, this review focuses on the recent accomplishments of baicalin and its limitations in cancer prevention and treatment. Further, combination studies and nanoformulations using baicalin to treat cancer along with the metabolism, bioavailability, toxicity, and pharmacokinetics have been discussed. The present review explains biological source, and anti-proliferative potential of baicalin against cancers including breast, colon, hepatic, leukemia, lung, and skin, as well as the relevant mechanism of action to modulate diverse signaling pathways including apoptosis, cell cycle, invasion, and migration, angiogenesis, and autophagy. The anticancer mechanism of baicalin in orthotropic and xenograft mice models have been deliberated. The combination studies of baicalin in novel therapies as chemotherapeutic adjuvants have also been summarized. The low bioavailability, fast metabolism, and poor solubility, and other significant factors that limit the clinical use of baicalin have been examined as a challenge. The improvement in the pharmacokinetics and pharmacodynamics of baicalin with newer approaches and the gaps are highlighted, which could establish baicalin as an effective and safe compound for cancer treatment as well as help to translate its potential from bench to bedside.

The effect of alcoholic extract from Eucalyptus camaldulensis leaves on HTLV-1 Tax activities

HTLV-1 is a human retrovirus responsible for adult T-cell leukemia (ATL) and certain other clinical disorders. The viral Tax oncoprotein plays a central role in HTLV-1 pathogenicity, mainly due to its capacity of inducing the transcriptional activity of various transcriptional factors like NFқB. Eucalyptus camaldulensis (Ec) is considered as a traditional medicinal plant with valuable therapeutic effects. Here we evaluated the activity of its ethanolic leave extract on different Tax activities by testing its influence on Tax-induced activity of NFқB and HTLV-1 LTR in Jurkat cells. Our results showed that Ec inhibited Tax induced activation of NFқB -, SRF- dependent promoters and HTLV-1 LTR. Ec extract has no effect on the binding of Tax to NFқB while it strongly prevented the degradation of IҝBα induced by Tax probably as a result of preventing the link between Tax and IKKγ. In addition, increasing the cellular level of P-TEFb-cyclinT1 significantly reduced the inhibitory effect of Ec on Tax activities, probably by preventing the interaction between Tax and P-TEFb-cyclin T1. The 40%-MeOH fraction of this extract, which is rich with polyphenols, offered the highest inhibitory effect against Tax activities. Further studies are required for the isolation and identification of active component/s in this extract which may be developed in the future as preventive/curing drugs for HTLV-1 related diseases.

Use of Natural Products in Asthma Treatment

Asthma, a disease classified as a chronic inflammatory disorder induced by airway inflammation, is triggered by a genetic predisposition or antigen sensitization. Drugs currently used as therapies present disadvantages such as high cost and side effects, which compromise the treatment compliance. Alternatively, traditional medicine has reported the use of natural products as alternative or complementary treatment. The aim of this review was to summarize the knowledge reported in the literature about the use of natural products for asthma treatment. The search strategy included scientific studies published between January 2006 and December 2017, using the keywords "asthma," "treatment," and "natural products." The inclusion criteria were as follows: (i) studies that aimed at elucidating the antiasthmatic activity of natural-based compounds or extracts using laboratory experiments (in vitro and/or in vivo); and (ii) studies that suggested the use of natural products in asthma treatment by elucidation of its chemical composition. Studies that (i) did not report experimental data and (ii) manuscripts in languages other than English were excluded. Based on the findings from the literature search, aspects related to asthma physiopathology, epidemiology, and conventional treatment were discussed. Then, several studies reporting the effectiveness of natural products in the asthma treatment were presented, highlighting plants as the main source. Moreover, natural products from animals and microorganisms were also discussed and their high potential in the antiasthmatic therapy was emphasized. This review highlighted the importance of natural products as an alternative and/or complementary treatment source for asthma treatment, since they present reduced side effects and comparable effectiveness as the drugs currently used on treatment protocols.

Baicalin-induced Cytotoxicity and Apoptosis in Multidrug-resistant MC3/5FU Mucoepidermoid Carcinoma Cell Line

Background:

Multidrug Resistance (MDR) is a serious hindrance to cancer chemotherapy and profoundly influences the clinical findings. Many Traditional Chinese Medicines (TCM) have been tested with the aim of developing effective resistance modulators or anticancer drugs to overcome the MDR of human cancers.

Methods:

The anticancer effect of baicalin on multidrug-resistant MC3/5FU (5-fluorouracil) cells was investigated by MTT test and xenografts in nude mice. Cell apoptosis was studied by transmission electron microscopy, Hoechst-33342 staining, DNA fragmentation detection, and flow cytometry. RT-PCR and Rhodamine 123 efflux assay was also used to detect its effect on ABC drug transporter proteins, ABCB1 (P-glycoprotein, P-gp) and ABCC1 (multidrug resistance protein 1, MRP1).

Results:

The results indicate that there was no significant effect of baicalin on ABC transporters expression or efflux function, although it induced potent growth inhibition in MC3/5FU cells. Flow cytometry, Hoechst 33342 staining and transmission electron microscope revealed that baicalin caused MC3/5FU cell death through the induction of apoptosis. It is demonstrated that baicalininduced apoptosis could be mediated by up-regulation of Bax and caspase-3 protein levels and downregulation of Bcl-2 protein levels. In addition, daily intraperitoneal injection of baicalin (100 and 200 mg/kg) for 2 weeks significantly inhibited the growth of MC3/5FU cells xenografts in nude mice.

Conclusion:

Our results suggest that baicalin possesses considerable cytotoxic activity in multidrug resistance MC3/5FU cells in vitro and in vivo.

A comprehensive review on phytochemistry, pharmacology, and flavonoid biosynthesis of Scutellaria baicalensis

CONTEXT

Scutellaria baicalensis Georgi (Lamiaceae) is a popular medicinal plant. Its roots are used as the famous traditional Chinese medicine Huang-Qin, which is recorded in Chinese Pharmacopoeia, European Pharmacopoeia, and British Pharmacopoeia.

OBJECTIVE

This review comprehensively summarizes research progress in phytochemistry, pharmacology, and flavonoid biosynthesis of S. baicalensis.

METHODS

English and Chinese literature from 1973 to March 2018 was collected from databases including Web of Science, SciFinder, PubMed, Elsevier, Baidu Scholar (Chinese), and CNKI (Chinese). Scutellaria baicalensis, chemical constituents, phytochemistry, biological activities, and biosynthesis were used as the key words.

RESULTS

A total of 126 small molecules (1-126) and 6 polysaccharides have been isolated from S. baicalensis. The small molecules can be classified into four structural types, namely, free flavonoids, flavonoid glycosides, phenylethanoid glycosides, and other small molecules. Extracts of S. baicalensis and its major chemical constituents have been reported to possess anti-viral, anti-tumor, anti-bacterial, antioxidant, anti-inflammatory, hepatoprotective, and neuroprotective activities. Key steps in the biosynthetic pathways of Scutellaria flavonoids have also been summarized.

CONCLUSIONS

This article could be helpful for researchers who are interested in the chemical constituents, bioactivities, biosynthesis, and clinical applications of S. baicalensis.

Therapeutic effect of the natural compounds baicalein and baicalin on autoimmune diseases

A series of natural compounds have been implicated to be useful in regulating the pathogenesis of various autoimmune diseases. The present study demonstrated that the Scutellariae radix compounds baicalein and baicalin may serve as drugs for the treatment of autoimmune diseases, including rheumatoid arthritis and inflammatory bowel disease. Following the administration of baicalein and baicalin in vivo, T cell‑mediated autoimmune diseases in the mouse model were profoundly ameliorated: In the collagen‑induced arthritis model (CIA), the severity of the disease was reduced by baicalein and, consistently, baicalein was demonstrated to suppress T cell proliferation in CIA mice. In the dextran sodium sulfate (DSS)‑induced colitis model, the disease was attenuated by baicalin, and baicalin promoted colon epithelial cell (CEC) proliferation in vitro. The present study further revealed that the mRNA expression of signal transducer and activator of transcription (STAT)3 and STAT4 in the tyrosine‑protein kinase JAK‑STAT signaling pathway in T cells was downregulated by baicalein, contributing to its regulation of T cell proliferation. However, in the DSS model, the STAT4 transcription in CECs, which are the target cells of activated T cells in the gut, was downregulated by baicalin, suggesting that baicalein and baicalin mediated similar STAT expression in different cell types in autoimmune diseases. In conclusion, the similarly structured compounds baicalein and baicalin selectively exhibited therapeutic effects on autoimmune diseases by regulating cell proliferation and STAT gene expression, albeit in different cell types.

Baicalin inhibits PDGF-BB-induced hepatic stellate cell proliferation, apoptosis, invasion, migration and activation via the miR-3595/ACSL4 axis

Hepatic fibrosis is a physiological response to liver injury that includes a range of cell types. The pathogenesis of hepatic fibrosis currently focuses on hepatic stellate cell (HSC) activation into muscle fiber cells and fibroblasts. Baicalin is a flavone glycoside. It is the glucuronide of baicalein, which is extracted from the dried roots of Scutellaria baicalensis Georgi. Previous work focused on the anti-viral, -inflammatory and -tumor properties of baicalin. However, the potential anti-fibrotic effects and mechanisms of baicalin are not known. The present study demonstrated that baicalin influenced the activation, proliferation, apoptosis, invasion and migration of platelet-derived growth factor-BB-induced activated HSC-T6 cells in a dose-dependent manner. To investigate the anti-fibrotic effect of baicalin, a one-color micro (mi)RNA array and reverse transcription-quantitative polymerase chain reaction analyses were used. Results demonstrated that baicalin increased the expression of the miRNA, miR-3595. In addition, the inhibition of miR-3595 substantially reversed the anti-fibrotic effect of baicalin. The present data also suggested that miR-3595 negatively regulates the long-chain-fatty-acid-CoA ligase 4 (ACSL4). Furthermore, ACSL4 acted in a baicalin-dependent manner to exhibit anti-fibrotic effects. Taken together, it was concluded that baicalin induces miR-3595 expression that modulates the expression levels of ACSL4. To the best of our knowledge, the present study is the first to demonstrate that baicalin induces overexpression of human miR-3595, and subsequently decreases the expression of ACSL4, resulting in an anti-fibrotic effect.

Baicalin alleviates oxidative stress damage in trabecular meshwork cells in vitro

Oxidative stress and inflammation play a key role in pathophysiology of glaucoma. Baicalin is known as an anti-oxidative and anti-inflammatory substance, possessing the potential to treat glaucoma. This study was designed to assess the anti-oxidative and anti-inflammatory potentials in culture human trabecular meshwork (hTM) cells. Using hTM cells as the in vitro model, we investigated the effects of baicalin on oxidative stress-induced markers for hTM impairments. We pre-incubated hTM cells with baicalin before hydrogen peroxide stressing or pre- plus co-incubated with baicalin before and during stressing and monitored the cell death, production of intracellular reactive oxygen species (iROS) and inflammatory cytokines, accumulation of carbonylated proteins, and activity of senescence marker. Samples that received pre- plus co-treatment with 10 or 15 μM baicalin showed significantly increased cell survival and decreased iROS production. Further studies demonstrated that pre- plus co-treatment with 15 μM baicalin significantly inhibited proinflammatory factor IL-1α and ELAM-1 production, decreased activities of senescence marker SA-β-gal, and lowered carbonylated protein levels. In contrast, samples that received only pre-treatment did not show any of these protective effects. Baicalin can protect hTM cells against oxidative stress, shedding light on potential treatment for glaucoma.

Ribavirin Inhibits Parrot Bornavirus 4 Replication in Cell Culture

Parrot bornavirus 4 is an etiological agent of proventricular dilatation disease, a fatal neurologic and gastrointestinal disease of psittacines and other birds. We tested the ability of ribavirin, an antiviral nucleoside analog with antiviral activity against a range of RNA and DNA viruses, to inhibit parrot bornavirus 4 replication in duck embryonic fibroblast cells. Two analytical methods that evaluate different products of viral replication, indirect immunocytochemistry for viral specific nucleoprotein and qRT-PCR for viral specific phosphoprotein gene mRNA, were used. Ribavirin at concentrations between 2.5 and 25 μg/mL inhibited parrot bornavirus 4 replication, decreasing viral mRNA and viral protein load, in infected duck embryonic fibroblast cells. The addition of guanosine diminished the antiviral activity of ribavirin suggesting that one possible mechanism of action against parrot bornavirus 4 may likely be through inosine monophosphate dehydrogenase inhibition. This study demonstrates parrot bornavirus 4 susceptibility to ribavirin in cell culture.

Oroxylum indicum (L.) Kurz, an important Asian traditional medicine: from traditional uses to scientific data for its commercial exploitation

ETHNOPHARMACOLOGICAL RELEVANCE

Oroxylum indicum\ (L.) Kurz has been used for centuries as a traditional medicine in Asia in ethnomedicinal systems for the prevention and treatment of several diseases, such as jaundice, arthritic and rheumatic problems, gastric ulcers, tumors, respiratory diseases, diabetes, and diarrhea and dysentery, among others. The present review provides scientific evidence supporting the therapeutic potency of the plant for ethnomedicinal uses and identifies gaps for future research to facilitate commercial exploitation.

METHODS

This review is based on available information on traditional uses and phytochemical, pharmacological, clinical and toxicity data for Oroxylum indicum that was collected from electronic (SciFinder, PubMed, Science Direct, and ACS, among others) and library searches.

KEY FINDING

A variety of traditional medicinal uses of Oroxylum indicum in different Southeast and South Asian countries have been reported in books describing the uses of these plants. Phytochemical investigations of the different parts of the plant resulted in identification of approximately 111 compounds, among which flavonoids, naphthalenoids and cyclohexylethanoids are the predominant groups. The crude extracts and their isolates exhibit a wide spectrum of in vitro and in vivo pharmacological activities involving antimicrobial, anti-inflammatory, anti-arthritic, anticancer, anti-ulcer, hepatoprotective, antidiabetic, antidiarrheal and antioxidant activities. Flavonoids are the major constituents of all parts of the plant. From a toxicity perspective, only aqueous and ethanolic extracts of stem bark, root bark and fruits have been assessed and found to be safe. The major flavonoids of the stem bark, such as baicalein, chrysin and oroxylin A, were reported for the first time as natural flavonoids with potent inhibitory activity against endoprotease enzymes and proprotein convertases, which play a key role in the growth of cancer and in viral and bacterial infections. Flavonoids are the active components of bioactive extracts. Several Ayurvedic medicines have been formulated either singly using this plant or along with other herbs for the treatment of different diseases.

CONCLUSIONS

Pharmacological results have supported some traditional medicinal uses of Oroxylum indicum. Several extracts and their isolates have been reported to exhibit interesting pharmacological properties. These components could be useful as sources of modern medicines following future detailed studies to elucidate their underlying mechanisms, toxicity, synergistic effects and clinical trials. Attention should also be focused on pharmacological studies investigating the traditional uses of the plant, which have not been yet addressed, as well as clinical studies investigating commercial Ayurvedic medicines and other ethnomedicinal preparations in human subjects based on this plant to confirm the safety and quality of the preparations.

Effect of propolis and caffeic acid phenethyl ester (CAPE) on NFκB activation by HTLV-1 Tax

HTLV-1 is the etiological agent of aggressive malignancy of the CD4(+) T-cells, adult T-cell leukemia (ATL), and other severe clinical disorders. The viral Tax protein is a key factor in HTLV-1 pathogenicity. A major part of Tax oncogenic potential is accounted for by its capacity of inducing the transcriptional activity of the NFκB factors, which regulate the expression of numerous cellular genes. Propolis (PE), a natural product produced by honeybees, has been used for a long time in folk medicine. One of PE active components, caffeic acid phenylethyl ester (CAPE), was well characterized and found to be a potent inhibitor of NFκB activation. Therefore, the aim of this study was to pursue the possibility of blocking Tax oncogenic effects by treatment with these natural products. Human T-cell lines were used in this study since these cells are the main targets of HTLV-1 infections. We tried to determine which step of Tax-induced NFκB activation is blocked by these products. Our results showed that both tested products substantially inhibited the activation of NFκB-dependent promoter by Tax. However, only PE could efficiently inhibit also the Tax-induced activation of SRF- and CREB-dependent promoters. Our results showed also that PE and CAPE strongly prevented both Tax binding to IκBα and its induced degradation by Tax. However, both products did not interfere in the nuclear transport of Tax or NFκB proteins.

Correlation between anti-fibrotic effect of baicalin and serum cytokines in rat hepatic fibrosis

AIM: To investigate the correlation between the antifibrotic effect of baicalin and serum cytokine production in rat hepatic fibrosis.

METHODS: Forty male Sprague-Dawley rats were divided randomly into four groups: normal control group, model group, baicalin-treated group, and colchicine-treated group. Except for the normal control group, all rats in the other groups were administered with carbon tetrachloride to induce hepatic fibrosis. At the same time, the last two groups were also treated with baicalin or colchicine. At the end of the 8 wk, all animals were sacrificed. Serum alanine aminotransferase (ALT), aspartate aminotransferase (AST), transforming growth factor (TGF)-β1, tumor necrosis factor (TNF)-α, interleukin (IL)-6 and IL-10 were measured. Liver index, hepatic hydroxyproline content and the degree of liver fibrosis were also evaluated.

RESULTS: The levels of ALT, AST and liver index in the baicalin-treated group were markedly lower than those in the model group (ALT: 143.88 ± 14.55 U/L vs 193.58 ± 24.35 U/L; AST: 263.66 ± 44.23 U/L vs 404.37 ± 68.29 U/L; liver index: 0.033 ± 0.005 vs 0.049 ± 0.009, P < 0.01). Baicalin therapy also significantly attenuated the degree of hepatic fibrosis, collagen area and collagen area percentage in liver tissue (P < 0.01). Furthermore, the levels of serum TGFβ1, TNF-α and IL-6 were strikingly reduced in the baicalin-treated group compared with the model group, while the production of IL-10 was up-regulated: (TGF-β1: 260.21 ± 31.01 pg/mL vs 375.49 ± 57.47 pg/mL; TNF-α: 193.40 ± 15.18 pg/mL vs 260.04 ± 37.70 pg/mL; IL-6: 339.87 ± 72.95 pg/mL vs 606.47 ± 130.73 pg/mL; IL-10: 506.22 ± 112.07 pg/mL vs 316.95 ± 62.74 pg/mL, P < 0.01).

CONCLUSION: Baicalin shows certain therapeutic effects on hepatic fibrosis, probably by immunoregulating the imbalance between profibrotic and antifibrotic cytokines.

New therapeutic aspects of flavones: the anticancer properties of Scutellaria and its main active constituents Wogonin, Baicalein and Baicalin

Traditional Chinese medicines have been recently recognized as a new source of anticancer drugs and new chemotherapy adjuvant to enhance the efficacy of chemotherapy and to ameliorate the side effects of cancer chemotherapies however their healing mechanisms are still largely unknown. Scutellaria baicalensis is one of the most popular and multi-purpose herb used in China traditionally for treatment of inflammation, hypertension, cardiovascular diseases, and bacterial and viral infections. Accumulating evidence demonstrate that Scutellaria also possesses potent anticancer activities. The bioactive components of Scutellaria have been confirmed to be flavones. The major constituents of Scutellaria baicalensis are Wogonin, Baicalein and Baicalin. These phytochemicals are not only cytostatic but also cytotoxic to various human tumor cell lines in vitro and inhibit tumor growth in vivo. Most importantly, they show almost no or minor toxicity to normal epithelial and normal peripheral blood and myeloid cells. The antitumor functions of these flavones are largely due to their abilities to scavenge oxidative radicals, to attenuate NF-kappaB activity, to inhibit several genes important for regulation of the cell cycle, to suppress COX-2 gene expression and to prevent viral infections. The tumor-selectivity of Wogonin has recently been demonstrated to be due to its ability to differentially modulate the oxidation-reduction status of malignant vs. normal lymphocytic cells and to preferentially induce phospholipase C gamma 1, a key enzyme involved in Ca(2+) signaling, through H(2)O(2) signaling in malignant lymphocytes. This review is aimed to summarize the research results obtained since the last 20 years and to highlight the recently discovered molecular mechanisms.

Difference of growth-inhibitory effect of Scutellaria baicalensis-producing flavonoid wogonin among human cancer cells and normal diploid cell

Methanol extract from cultured Scutellaria baicalensis cells inhibited the proliferation of human monocytic leukemia cell line THP-1 and human osteogenic sarcoma cell line HOS. The inhibitory effects of baicalin, baicalein and wogonin, the three major flavonoids contained in the extract, were studied. It should be noted that wogonin did not show the inhibitory effect on human fetal lung normal diploid cell line TIG-1, as compared to the inhibition observed in cancer cells. Physiological analyses in THP-1 cells showed that wogonin induced cell cycle arrest at G(2)/M phase and apoptosis. This is the first report discovering a cancer-specific apoptosis-inducing activity of wogonin.

Efflux of baicalin, a flavone glucuronide of Scutellariae Radix, on Caco-2 cells through multidrug resistance-associated protein 2

Baicalin and its aglycone, baicalein, being are strong antioxidants and have various pharmacological actions. Baicalein has shown a unique metabolic fate in rat intestine, being excreted into the intestinal lumen from mucosal (epithelial) cells following glucuronidation of baicalein absorbed after oral administration. The purpose of this study was to examine the absorption and excretion of baicalin and baicalein in a Caco-2 cell monolayer model to evaluate the disposition of baicalin and baicalein in the human intestine. When baicalein at 5 microM was loaded on the apical side of the Caco-2 cell monolayer, baicalein was not transferred to the basolateral side, but more baicalin was excreted onto the apical side than was being absorbed onto the basolateral side. The amount of baicalin recovered on both sides accounted for more than 90% of the baicalein absorbed from the apical surface. This was supported by the fact that Caco-2 cell microsomes showed UDP-glucuronate glucuronosyltransferase activity towards baicalein to form baicalin. On the other hand, when baicalein was loaded at higher concentrations, baicalin excretion became saturated, and then baicalein was transferred to the basolateral side. Furthermore, baicalin efflux was not inhibited by MDR1/P-glycoprotein substrates such as ciclosporin and vinblastine, but significantly inhibited by multidrug resistance-associated protein 2 (MRP2, ABCC2) substrates such as probenecid and genistein. MRP2 was also detected in Caco-2 cells by Western blotting using specific antibodies. In addition, baicalin, but not baicalein, enhanced dose-dependently the vanadate-sensitive ATPase activity of human MRP2. These results indicated that, in Caco-2 cells, any baicalein absorbed after loading at low concentrations of baicalein was not transferred to the basolateral side, but was first transformed into baicalin in the cells and excreted through the action of MRP2, mainly to the apical side.

Baicalin-induced apoptosis is mediated by Bcl-2-dependent, but not p53-dependent, pathway in human leukemia cell lines

Acute lymphoblastic leukemia (ALL), especially T-acute lymphoblastic leukemia (T-ALL), is a common childhood malignant neoplastic disorder. Chemotherapy agents, particularly those that can induce apoptosis, are the major intervening strategy in the treatment of ALL. In this study, we investigated in T-ALL cell line, CCRF-CEM, the in vitro cytotoxic effect and the mechanism of action of baicalin, a compound extracted from Scutellaria baicalensis Georgi and S. rivularis Benth (Labiateae). Results demonstrated that baicalin displayed a remarkable cytotoxic effect in CCRF-CEM, with an IC(50) value of 10.6 microg/ml. It triggered apoptotic effect by fragmentizing cellular DNA and arrested the cell cycle at G(0)/G(1) phase. Baicalin (37.5 microg/ml) had not effected the expression of p53 and Fas protein. It was shown to decline the expression of Bcl-2 (22.0 pg/ml), which consequently caused the loss (52.7%) of transmembrane potential (Delta Psi m) in the mitochondria after 72 hours of treatment. Baicalin (37.5 microg/ml) also elevated the amount of cytosolic cytochrome c (19.2 microg/ml), which finally triggered the activation of caspase-3 (50.1 pmol/min). In conclusion, baicalin was found to induce apoptosis in T-ALL cell lines through multiple pathways. This finding encourages further investigation of baicalin in its role as a potential candidate for chemotherapeutic agents in T-ALL.

Role of Intestinal First-Pass Metabolism of Baicalein in its Absorption Process

PURPOSE

The aim of the present study was to investigate the role of intestinal first-pass metabolism of baicalein (B) in its absorption process.

METHODS

The intestinal absorption of B was characterized using Caco-2 cell monolayer model and rat in situ single-pass intestinal perfusion model. In addition, preliminary metabolic kinetics of B was evaluated in both rat and human intestinal S9 fractions.

RESULTS

B was well absorbed and extensively metabolized to baicalin (BG), baicalein-7-O-beta-glucuronide, in rat intestinal perfusion model, whereas less extent of metabolism was observed in the Caco-2 cell monolayer model. Moreover, BG generated in the intestinal epithelium during the absorption of B also rapidly transported to both the apical side (the apical chamber of Caco-2 model and the perfusate of the intestinal perfusion model) as well as the basolateral side of the small intestine (the basal chamber of Caco-2 model and the mesenteric vein of the intestinal perfusion model). From the preliminary metabolic studies, it was found that a higher loading dose of B resulted in a less extent of metabolism in intestine. In addition, the extent of metabolism of B was similar in jejunum and ileum when 50 microM of B was perfused through different sections of rat small intestine.

CONCLUSION

The first-pass metabolism of B in small intestine may play an important role in its low oral bioavailability.

Baicalein and baicalin are potent inhibitors of angiogenesis: Inhibition of endothelial cell proliferation, migration and differentiation

In recent studies, we have shown that baicalein and baicalin, 2 major flavonoids of Scutellaria baicalensis Georgi, exhibit anticancer activity against several cancers in vitro. In our present study, we assessed their potential as anti-angiogenic agents in vivo employing chicken chorioallantoic membrane (CAM) assay and in vitro human umbilical vein endothelial cells (HUVECs) culture. When CAMs were treated with either baicalein or baicalin for 48 hr, the angiogenic response induced by basic fibroblast growth factor (bFGF) was markedly reduced in a dose-dependent manner. Further characterization showed that both flavonoids exhibited dual antiproliferative (at low dose) and apoptogenic (at high dose) effects on HUVECs. In biochemical analysis, treatment of HUVECs with baicalein and baicalin for 24 hr resulted in a dose-dependent decrease in the matrix metalloproteinase (MMP)-2 activity. Moreover, the migration of endothelial cells and the differentiation of endothelial cells into branching networks of tubular structures in vitro were also inhibited by these 2 flavonoids in a dose-dependent manner. Baicalein is more potent than baicalin in anti-angiogenesis in vivo as well as in vitro. Taken together, the results of our study provide evidence that baicalein and baicalin possess an anti-angiogenesis potential that is a previously unrecognized biologic activity.

Baicalin induces apoptosis via mitochondrial pathway as prooxidant

Baicalin is a flavonoid and a major component of a herbal medicine, Sho-saiko-to, which is commonly used for treatment of chronic hepatitis in Japan and China. Flavonoids including baicalin have been reported to not only function as anti-oxidants but also cause cytotoxic effect. We investigated the mechanism of baicalin-induced cytotoxicity in leukemia-derived T cell line, Jurkat cells. When cells were cultured with 50-200 microg/ml baicalin for 6h, caspase-3 was activated and then cells fell into apoptosis. Induction of apoptosis by baicalin was accompanied with the marginal generation of intracellular reactive oxygen species (ROS), the increase of the cytosolic fractions of cytochrome c, and the disruption of mitochondrial transmembrane potential (DeltaPsi(m)) prior to the activation of caspase-3. The pre-culture with 5 mM of buthionine sulfoximine (BSO), an inhibitor of glutathione (GSH) synthesis, facilitated baicalin-induced disruption of DeltaPsi(m) and induction of apoptosis. The pre-culture with N-benzyloxycarbonyl-valyl-alanyl-aspartyl fluoromethylketone (Z-VAD-fmk), a pan-caspase inhibitor, partially suppressed the induction of apoptosis. On the other hand, baicalin showed little toxic effect on peripheral blood mononuclear cells (PBMCs) from healthy volunteers. These results indicate that baicalin acts as a prooxidant and induces caspase-3 activation and apoptosis via mitochondrial pathway.

Anti-HIV activity of medicinal herbs: usage and potential development

The acquired immunodeficiency syndrome (AIDS) is a result of human immunodeficiency virus (HIV) infection which subsequently leads to significant suppression of immune functions. AIDS is a significant threat to the health of mankind, and the search for effective therapies to treat AIDS is of paramount importance. Several chemical anti-HIV agents have been developed. However, besides the high cost, there are adverse effects and limitations associated with using chemotherapy for the treatment of HIV infection. Thus, herbal medicines have frequently been used as an alternative medical therapy by HIV positive individuals and AIDS patients. The aim of this review is to summarize research findings for herbal medicines, which are endowed with the ability to inhibit HIV. In this article, we will emphasize a Chinese herbal medicine, Scutellaria baicalensis Georgi and its identified components (i.e., baicalein and baicalin), which have been shown to inhibit infectivity and replication of HIV. Potential development of anti-AIDS compounds using molecular modeling methods will also be discussed.

Antitumor effects of Scutellariae radix and its components baicalein, baicalin, and wogonin on bladder cancer cell lines

OBJECTIVES

To investigate the antitumor effects of Scutellariae radix and its components baicalein, baicalin, and wogonin on human bladder cancer cell lines (KU-1 and EJ-1) and a murine bladder cancer cell line (MBT-2).

METHODS

Bladder cancer cells were incubated with various concentrations of the agents. Antiproliferative activity against the bladder cancer cell lines was examined by 3-(4,5-dimethylthiazol-2-yl)-2,5-diplenyl tetrazolium bromide assay. In an in vivo experiment, the mice were subcutaneously injected with MBT-2 cells, and Scutellariae radix was orally administered at a dose of 2 or 10 mg per mouse one time daily for 10 days from day 11 to day 20.

RESULTS

All the drugs inhibited cell proliferation in a dose-dependent manner, but baicalin exhibited the greatest antiproliferative activity. The concentration of baicalin necessary to obtain 50% inhibition was 3.4 microg/mL for KU-1, 4.4 microg/mL for EJ-1, and 0.93 microg/mL for MBT-2. For KU-1 and MBT-2, the percentage of cell survival significantly decreased (P <0.05) at a baicalin concentration of 1 microg/mL. In an in vivo experiment, antitumor effects of Scutellariae radix on C3H/HeN mice implanted with MBT-2 were investigated. All the control mice showed a progressive increase in tumor volume, reaching 2.81 +/- 0.18 cm(3) on day 20 and 5.36 +/- 0.44 cm(3) on day 25. However, when Scutellariae radix was orally administered at a dose of 10 mg per mouse one time daily for 10 days from day 11 to day 20, the tumor volume was 1.99 +/- 0.19 cm(3) on day 20 and 3.86 +/- 0.26 cm(3) on day 25, a significant inhibition of tumor growth (P <0.05). Conclusions. These results suggest that Chinese herbal medicines may become an attractive and promising treatment for bladder cancer.

Baicalin, an inhibitor of HIV-1 production in vitro

The flavonoid baicalin markedly inhibits replication of human immunodeficiency virus type 1 (HIV-1) in a concentration-dependent manner in normal peripheral blood mononuclear cells (PBMC) stimulated with phytohemagglutinin (PHA) in vitro. The effect was more pronounced when the cells were pretreated with baicalin. Furthermore, baicalin inhibits HIV-1 replication in PHA-stimulated PBMC from asymptomatic HIV-1-seropositive carriers. The 50% inhibitory concentration for HIV-1 replication was approximately 0.5 microg/ml. At the concentration of 2 microg/ml of baicalin, copy numbers of HIV-1 proviral DNA were approximately 50 times less than in untreated controls. In a cell-free infection system, baicalin inhibited the activity of HIV-1 reverse transcriptase (RT), but not the activity of human DNA polymerases alpha and gamma (DNA polymerase beta was slightly inhibited), suggesting that the anti-HIV-1 effect of baicalin may at least partly be due to inhibition of HIV-1 RT.

Inhibition of tomato bushy stunt virus infection using a quercetagetin flavonoid isolated from Centaurea rupestris L

Flower and leaf extracts of Centaurea rupestris L. and also the flavonoid quercetagetin 3'-methylether isolated from these extracts revealed a strong antiviral activity when inoculated simultaneously with tomato bushy stunt virus in two Nicotiana species. Almost complete reduction of local lesion number resulted from these inoculations in N. glutinosa. A similar effect was observed in inoculated leaves of N. megalosiphon causing the absence of systemic infection in 40% of treated plants. The antiphytoviral activity was not a consequence of induced resistance, inhibition of virus multiplication, suppression of symptom development or direct virus inactivation. Results presented in this paper suggest that the flavonoid may interfere with the initiation of virus infection.

Anti-human immunodeficiency virus (anti-HIV) natural products with special emphasis on HIV reverse transcriptase inhibitors

This review article aims at summarizing research findings concerning natural products which are endowed with the ability to inhibit human immunodeficiency virus (HIV). An emphasis is placed on HIV reverse transcriptase inhibitors because the bulk of the literature is focused on these compounds. It was found that a spectacular diversity of chemical structures encompassing proteins, terpenoids, coumarins, xanthones, alkaloids, flavonoids, polyphenols, and polysaccharides, which are elaborated by plant species as phylogenetically remote as the algae, gymnosperms and angiosperms, were capable of rendering the retroviral enzyme less active. The literature pertaining to natural products with HIV protease and integrase inhibitory activities is less voluminous.