Improvement of ocular blood flow and retinal functions with puerarin analogs

Neuroprotective Effect of Puerarin on Glutamate-Induced Cytotoxicity in Differentiated Y-79 Cells via Inhibition of ROS Generation and Ca(2+) Influx

Glutamate toxicity is estimated to be the key cause of photoreceptor degeneration in the pathogenesis of retinal degenerative diseases. Oxidative stress and Ca(2+) influx induced by glutamate are responsible for the apoptosis process of photoreceptor degeneration. Puerarin, a primary component of Kudzu root, has been widely used in the clinical treatment of retinal degenerative diseases in China for decades; however, the detailed molecular mechanism underlying this effect remains unclear. In this study, the neuroprotective effect of puerarin against glutamate-induced cytotoxicity in the differentiated Y-79 cells was first investigated through cytotoxicity assay. Then the molecular mechanism of this effect regarding anti-oxidative stress and Ca(2+) hemostasis was further explored with indirect immunofluorescence, flow cytometric analysis and western blot analysis. Our study showed that glutamate induced cell viability loss, excessive reactive oxygen species (ROS) generation, calcium overload and up-regulated cell apoptosis in differentiated Y-79 cells, which effect was significantly attenuated with the pre-treatment of puerarin in a dose-dependent manner. Furthermore, our data indicated that the neuroprotective effect of puerarin was potentially mediated through the inhibition of glutamate-induced activation of mitochondrial-dependent signaling pathway and calmodulin-dependent protein kinase II (CaMKII)-dependent apoptosis signal-regulating kinase 1(ASK-1)/c-Jun N-terminal kinase (JNK)/p38 signaling pathway. The present study supports the notion that puerarin may be a promising neuroprotective agent in the prevention of retinal degenerative diseases.

Absorptive interactions of concurrent oral administration of (+)-catechin and puerarin in rats and the underlying mechanisms

AIM

(+)-Catechin and puerarin are polyphenol and flavonoid, respectively, in green tea and foodstuffs. They exhibit potent antioxidant activity and are widely used for treating cardiocerebrovascular diseases. The aim of this work was to investigate the potential interactions between (+)-catechin and puerarin following concurrent oral administration in rats, and their absorption mechanisms in Caco-2 cell monolayers.

METHODS

Pharmacokinetic studies were conducted in male rats received (+)-catechin (140 mg/kg, po) and/or puerarin (200 mg/kg, po). The cell uptake and transport behavior in Caco-2 cell monolayers and the interactions of the two compounds were analyzed.

RESULTS

When (+)-catechin and puerarin were administered concurrently, the AUC0-12 h and Cmax values of puerarin were 2.48-fold and 3.91-fold, respectively, as large as those of puerarin alone; the AUC0-12 h and Cmax values of (+)-catechin were decreased to 57.62% and 77.55%, respectively, compared with those of (+)-catechin alone. In Caco-2 cell monolayers, (+)-catechin (300 and 600 μmol/L) significantly increased the cell uptake and transport of puerarin, whereas puerarin (300 and 600 μmol/L) significantly decreased the cellular uptake and transport of (+)-catechin. Furthermore, both cyclosporine A (P-glycoprotein inhibitor) and MK-571 (MRP-2 inhibitor) significantly increased the cellular uptake and transport of (+)-catechin and puerarin.

CONCLUSION

Concurrent oral administration of (+)-catechin and puerarin significantly increased the absolute oral bioavailability of puerarin, but decreasing that of (+)-catechin. The competitive efflux of (+)-catechin and puerarin by P-glycoprotein and MRP-2 might lead to this interaction during their absorption process in the small intestine.

Measurement of Retinal Blood Flow Using Fluorescently Labeled Red Blood Cells

Blood flow is a useful indicator of the metabolic state of the retina. However, accurate measurement of retinal blood flow is difficult to achieve in practice. Most existing optical techniques used for measuring blood flow require complex assumptions and calculations. We describe here a simple and direct method for calculating absolute blood flow in vessels of all sizes in the rat retina. The method relies on ultrafast confocal line scans to track the passage of fluorescently labeled red blood cells (fRBCs). The accuracy of the blood flow measurements was verified by (1) comparing blood flow calculated independently using either flux or velocity combined with diameter measurements, (2) measuring total retinal blood flow in arterioles and venules, (3) measuring blood flow at vessel branch points, and (4) measuring changes in blood flow in response to hyperoxic and hypercapnic challenge. Confocal line scans oriented parallel and diagonal to vessels were used to compute fRBC velocity and to examine velocity profiles across the width of vessels. We demonstrate that these methods provide accurate measures of absolute blood flow and velocity in retinal vessels of all sizes.

An evidence-based systematic review of kudzu (Pueraria lobata) by the Natural Standard Research Collaboration

An evidence-based systematic review of kudzu (Pueraria lobata) by the Natural Standard Research Collaboration consolidates the safety and efficacy data available in the scientific literature using a validated, reproducible grading rationale. This article includes written and statistical analysis of clinical trials, plus a compilation of expert opinion, folkloric precedent, history, pharmacology, kinetics/dynamics, interactions, adverse effects, toxicology, and dosing.

Physicochemical [corrected] properties of the inclusion complex of puerarin and glucosyl-β-cyclodextrin

Puerarin is a natural isoflavone, found in the Chinese medicinal plant Ge-gen, with many reported health-promoting properties. However, its low water solubility impedes its application in pharmaceutical and functional food products. This study explores the formation of inclusion complex between puerarin and glucosyl-β-cyclodextrin (G-β-CD) to improve the aqueous solubility of puerarin. The complex was prepared by mixing an equal molar mixture of puerarin and G-β-CD for 24 h, followed by freeze-drying. The obtained complex was analyzed by ultraviolet-visible spectroscopy, Fourier transform infrared spectroscopy, scanning electron microscopy, differential scanning calorimetry, X-ray diffractometry, and proton nuclear magnetic resonance spectroscopy. Results showed clearly that the process led to the formation of a supramolecular complex in which the guest molecule, puerarin, was entrapped inside the cavity of the host, G-β-CD. The close association between puerarin and G-β-CD resulted in changes in some of the characteristic spectral, phase-transitional, and morphological properties of puerarin.

Transport properties of puerarin and effect of Radix Angelicae Dahuricae extract on the transport of puerarin in Caco-2 cell model

ETHNOPHARMACOLOGICAL RELEVANCE

Angelicae Dahurica (Hoffm.)Benth.& Hook.f.ex Franch.&Sav combined with Pueraria labota (Willd.)Ohwi has been widely used as herb-pairs in traditional Chinese medicine (TCM) for utilization of antipyretic analgesic and anti-inflammatory drugs, and modern pharmacological studies have shown that application compatibility of the two drugs has the effects of cardiovascular disease treatment. The previous study has proved that Radix Angelicae Dahuricae extract could enhance the intestinal absorption of puerarin in Pueraria. But the underlying compatibility mechanism of the two herbs remains unknown. In this study we tried to further evaluate the improvement of Radix Angelicae Dahuricae extract on the puerarin using the Caco-2 cell model and explore the transport properties of puerarin through the above research to discuss the possible effect mechanism of Radix Angelicae Dahuricae extract on the transport of puerarin and the underlying compatibility mechanism of the two herbs.

AIM OF STUDY

The aim of this work was to study the transport properties of puerarin in Radix Pueraria across Caco-2 cell membrane and to explore how the Radix Angelicae Dahuricae extract affected the transport of puerarin using the well-characterized, human-based intestinal Caco-2 cell model as a platform.

MATERIALS AND METHODS

The bidirectional transport, and the effects of time, drug concentration, pH, P-gp inhibitors (Verapamil, Cyclosporin A), MRP inhibitor (MK-571) and EDTA-Na(2) (tight junction modulator) on the absorption of puerarin were observed. Then the influence of extract of Radix Angelicae Dahuricae on the transport of puerarin was studied. Drug concentration was measured by HPLC and the apparent permeability coefficients (Papp) and apparent permeability ratio (PDR) were calculated.

RESULTS AND CONCLUSIONS

The results showed that the transport (Papp) of puerarin in Caco-2 cell monolayer model had time and concentration dependence, and the transport showed saturation characteristics with the time and concentration of puerarin to a certain degree. The Papp of puerarin transported on Caco-2 cell monolayer model was significantly changed when the specified inhibitors of P-gp were added to the model and the PDR decreased from 1.74 to 0.43. The absorption of puerarin was improved when combined with Radix Angelicae Dahuricae. The intestinal absorption of puerarin is by passive diffusion as the dominating process and active transportation was mediated by P-gp and MRP transporter in Caco-2 cell monolayer model, and Radix Angelicae Dahuricae could enhance the intestinal absorption of puerarin.

The effects of sperminated pullulans on cornea permeability to puerarin and the toxicity

PURPOSE

To investigate the varied effects of sperminated pullulans (SP) with different amino residues on cornea permeability and its local toxicity.

METHODS

Three groups of rabbits were used: control, low-amino residue content SP (SP-L), and high-amino residue content SP (SP-H). The in vitro and in vivo spreading assays were combined with high performance liquid chromatography (HPLC) to measure the concentration of puerarin in the external medium or aqueous humor when 0% SP, 0.2% SP-L, and 0.2% SP-H were included. The toxicity of SP was determined by corneal hydration values, Draize score, aqueous humor protein concentration, corneal endothelial evaluation, as well as light microscopy and electron microscopy.

RESULTS

The application of 0.2% SP-L and 0.2% SP-H to the cornea in vitro increased puerarin apparent permeability coefficient by 1.96-fold (P<0.05) and 2.95-fold (P<0.01), respectively. SP-H showed stronger effect than SP-L (P<0.05). For the in vivo assay, those were 1.81-fold (P<0.05) and 3.71-fold (P<0.01), respectively. With the SP application, the corneal hydration values were <83% and Draize scores were <4, with no apparent changes in histological observations.

CONCLUSION

SP is one potential adjuvant promoting puerarin permeability to the cornea, and the high-content amino residue SP showed stronger effect, without ocular toxicity.

Effects of poly(amidoamine) dendrimers on ocular absorption of puerarin using microdialysis

PURPOSE

The purpose of this study was to investigate the effects of poly(amidoamine) (PAMAM) dendrimers on ocular absorption of puerarin.

METHODS

The samples of rabbits' aqueous humor were collected by in vivo microdialysis. The ocular pharmacokinetic properties of puerarin were measured to evaluate the effects of PAMAM dendrimers on ocular absorption of puerarin.

RESULTS

In the pharmacokinetic studies, the AUC(0∼∞) values of puerarin solution with 0.2% (w/v) PAMAM dendrimers (G3.0, G4.0, G5.0) were greater than those in the control group by 2.3-, 3.5-, and 2.1-folds, respectively. The C(max) values of puerarin solution with 0.2% (w/v) PAMAM dendrimers were 1.5, 2.5, and 1.3 times the values of the control group and the t(1/2) values were significantly longer than that of control group.

CONCLUSIONS

Using PAMAM dendrimers might be a promising strategy to enhance the absorption of puerarin. The generation of PAMAM dendrimers may play a key role in increasing the ocular absorption of puerarin.

Determination of puerarin in rabbit aqueous humor by liquid chromatography tandem mass spectrometry using microdialysis sampling after topical administration of puerarin PAMAM dendrimer complex

To study pharmacokinetic properties of puerarin poly(amido amine) (PAMAM) dendrimer complex, a sensitive liquid chromatography tandem mass spectrometry method (LC-MS/MS) was developed and validated to determine puerarin in rabbit aqueous humor using microdialysis sampling. Astilbin was used as the internal standard. The linear range for puerarin was from 2 to 1000ng/mL (r=0.9986) based on 20μL of aqueous humor. The coefficients of variations for intra-day and inter-day precisions were less than 10.0%, and the relative error of accuracy was within ±6.3%. The mean extraction recovery of puerarin varied from 80.4% to 85.5%. Microdialysis provides a complete concentration versus time profile. A significant difference was observed in main pharmacokinetic parameters of C(max), AUC and t(1/2) between puerarin solution and puerarin PAMAM dendrimer complex. Complex formation resulted in an obvious increase in bioavailability of puerarin after topical administration to rabbit according to the above LC-MS/MS assay method.

Kudzu root: traditional uses and potential medicinal benefits in diabetes and cardiovascular diseases

Kudzu root (Gegen in Chinese) is the dried root of Pueraria lobata (Willd.) Ohwi, a semi-woody, perennial and leguminous vine native to South East Asia. It is often used interchangeably in traditional Chinese medicine with thomson kudzu root (Fengen in Chinese), the dried root of P. thomsonii, although the Chinese Pharmacopoeia has separated them into two monographs since the 2005 edition. For more than 2000 years, kudzu root has been used as a herbal medicine for the treatment of fever, acute dysentery, diarrhoea, diabetes and cardiovascular diseases. Both English and Chinese literatures on the traditional applications, phytochemistry, pharmacological activities, toxicology, quality control and potential interactions with conventional drugs of both species have been included in the present review. Over seventy phytochemicals have been identified in kudzu root, with isoflavonoids and triterpenoids as the major constituents. Isoflavonoids, in particular puerarin, have been used in most of the pharmacological studies. Animal and cellular studies have provided support for the traditional uses of kudzu root on cardiovascular, cerebrovascular and endocrine systems, including diabetes and its complications. Further studies to define the active phytochemical compositions, quality standards and clinical efficacy are warranted. Strong interdisciplinary collaboration to bridge the gap between traditional medicine and modern biomedical medicine is therefore needed for the development of kudzu root as an effective medicine for the management of diabetes and cardiovascular diseases.

Potential of the bioflavonoids in the prevention/treatment of ocular disorders

OBJECTIVES

Flavonoids are a common group of plant polyphenols that give colour and flavour to fruits and vegetables. In recent years, flavonoids have gained importance in the pharmaceutical field through their beneficial effects on human health and are widely available as nutritional supplements. Several pharmacological actions of the bioflavonoids may be useful in the prevention or treatment of ocular diseases responsible for vision loss such as diabetic retinopathy, macular degeneration and cataract. This review aims to summarize the potential therapeutic applications of various bioflavonoids in different ocular diseases and also discusses delivery of these agents to the ocular tissues.

KEY FINDINGS

It is apparent that the flavonoids are capable of acting on various mechanisms or aetiological factors responsible for the development of different sight threatening ocular diseases. From a drug delivery perspective, ocular bioavailability depends on the physicochemical and biopharmaceutical characteristics of the selected flavonoids and very importantly the route of administration.

SUMMARY

The potential therapeutic applications of various bioflavonoids in ocular diseases is reviewed and the delivery of these agents to the ocular tissues is discussed. Whereas oral administration of bioflavonoids may demonstrate some pharmacological activity in the outer sections of the posterior ocular segment, protection of the retinal ganglionic cells in vivo may be limited by this delivery route. Systemic or local administration of these agents may yield much higher and effective concentrations of the parent bioflavonoids in the ocular tissues and at much lower doses.

Puerarin suppresses AGEs-induced inflammation in mouse mesangial cells: a possible pathway through the induction of heme oxygenase-1 expression

Puerarin is a natural product isolated from Puerarin lobata and has various pharmacological effects, including anti-hyperglycemic and anti-allergic properties. In the present study, we investigated the effect of puerarin against advanced glycation end products (AGEs)-induced inflammation in mouse mesangial cells. Puerarin acts by inducing the expression of heme oxygenase-1 (HO-1) in a dose- and time-dependent manner. Puerarin was able to enhance phosphorylation of protein kinase C (PKC) delta, but not PKC alpha/beta II, in a time-dependent manner. Induction of HO-1 expression by puerarin was suppressed by GF109203X, a general inhibitor of PKC, and by rottlerin, a specific inhibitor of PKC delta. However, induction was not suppressed by Gö6976, a selective inhibitor for PKC alpha/beta II. Additionally, the knockdown of endogenous PKC delta by small interfering RNA (siRNA) resulted in the inhibition of HO-1 expression and Akt phosphorylation. Puerarin increased antioxidant response element (ARE)-Luciferase activity in a dose- and time-dependent manner in transfected mouse mesangial cells. Mutation of the ARE sequence abolished puerarin-induced HO-1 expression. Furthermore, puerarin treatments resulted in a marked increase in NF-E2 related factor-2 (Nrf-2) translocation, leading to up-regulation of HO-1 expression. However, transfection of Nrf-2 specific siRNA abolished HO-1 expression. Pretreatment with puerarin inhibited the expressions of COX-2, MMP-2 and MMP-9. But, these effects were reversed by ZnPP, an inhibitor of HO-1. Taken together, our results demonstrate that puerarin-induced expression of HO-1 is mediated by the PKC delta-Nrf-2-HO-1 pathway and inhibits N-carboxymethyllysine (CML)-induced inflammation in mouse mesangial cells.

Erratum: Neural protection by naturopathic compounds-an example of tetramethylpyrazine from retina to brain

Given the advantages of being stable in the ambient environment, being permeable to the blood-brain and/or blood-eye barriers and being convenient for administration, naturopathic compounds have growingly become promising therapeutic candidates for neural protection. Extracted from one of the most common Chinese herbal medicines, tetramethylpyrazine (TMP), also designated as ligustrazine, has been suggested to be neuroprotective in the central nervous system as well as the peripheral nerve network. Although the detailed molecular mechanisms of its efficacy for neural protection are understood limitedly, accumulating evidence suggests that antioxidative stress, antagonism for calcium, and suppression of pro-inflammatory factors contribute significantly to its neuroprotection. In animal studies, systemic administration of TMP (subcutaneous injection, 50 mg/kg) significantly blocked neuronal degeneration in hippocampus as well as the other vulnerable regions in brains of Sprague-Dawley rats following kainate-induced prolonged seizures. Results from us and others also demonstrated potent neuroprotective efficacy of TMP for retinal cells and robust benefits for brain in Alzheimer's disease or other brain injury. These results suggest a promising prospect for TMP to be used as a treatment of specific neurodegenerative diseases. Given the assessment of the distribution, metabolism, excretion, and toxicity information that is already available on most neuroprotective naturopathic compounds such as TMP, preclinical data to justify bringing such therapeutic compounds to clinical trials in humans is feasible.[This corrects the article on p. in vol. .].

Neural protection by naturopathic compounds-an example of tetramethylpyrazine from retina to brain

Given the advantages of being stable in the ambient environment, being permeable to the blood–brain and/or blood–eye barriers and being convenient for administration, naturopathic compounds have growingly become promising therapeutic candidates for neural protection. Extracted from one of the most common Chinese herbal medicines, tetramethylpyrazine (TMP), also designated as ligustrazine, has been suggested to be neuroprotective in the central nervous system as well as the peripheral nerve network. Although the detailed molecular mechanisms of its efficacy for neural protection are understood limitedly, accumulating evidence suggests that antioxidative stress, antagonism for calcium, and suppression of pro-inflammatory factors contribute significantly to its neuroprotection. In animal studies, systemic administration of TMP (subcutaneous injection, 50 mg/kg) significantly blocked neuronal degeneration in hippocampus as well as the other vulnerable regions in brains of Sprague–Dawley rats following kainate-induced prolonged seizures. Results from us and others also demonstrated potent neuroprotective efficacy of TMP for retinal cells and robust benefits for brain in Alzheimer’s disease or other brain injury. These results suggest a promising prospect for TMP to be used as a treatment of specific neurodegenerative diseases. Given the assessment of the distribution, metabolism, excretion, and toxicity information that is already available on most neuroprotective naturopathic compounds such as TMP, it would not take much preclinical data to justify bringing such therapeutic compounds to clinical trials in humans.

The study on the entrapment efficiency and in vitro release of puerarin submicron emulsion

The entrapment efficiency (EE) and release in vitro are very important physicochemical characteristics of puerarin submicron emulsion (SME). In this paper, the performance of ultrafiltration (UF), ultracentrifugation (UC), and microdialysis (MD) for determining the EE of SME were evaluated, respectively. The release study in vitro of puerarin from SME was studied by using MD and pressure UF technology. The EE of SME was 86.5%, 72.8%, and 55.8% as determined by MD, UF, and UC, respectively. MD was not suitable for EE measurements of puerarin submicron oil droplet, which could only determine the total EE of submicron oil droplet and liposomes micelles, but it could be applied to determine the amount of free drug in SMEs. Although UC was the fastest and simplest to use, its results were the least reliable. UF was still the relatively accurate method for EE determination of puerarin SME. The release of puerarin SME could be evaluated by using MD and pressure UF, but MD seemed to be more suitable for the release study of puerarin emulsion. The drug release from puerarin SME at three drug concentrations was initially rapid, but reached a plateau value within 30 min. Drug release of puerarin from the SME occurred via burst release.

Protective effect of puerarin on diabetic retinopathy in rats

Puerarin is a major active ingredient extracted from the traditional Chinese medicine Ge-gen. The purpose of this study is to investigate the protective effect of puerarin on diabetic retinopathy (DR) and its mechanisms in rats. Seventy-two male Wistar rats were selected and divided at random into three main groups: control group, streptozotocin (STZ) group and puerarin + STZ group. Retinal histopathological observation and electron microscopic examination were performed; retinal vascular endothelial growth factor (VEGF) and hypoxia inducible factor 1 (HIF-1alpha) gene expressions were examined by Reverse transcription-polymerase chain reaction (RT-PCR) analysis. Results showed that the DR induced by STZ was significantly reduced by the treatment of puerarin as judged by the reduction of morphological changes of inner nuclear layer and outer nuclear layer at any time-point. Puerarin regulates expressions of VEGF and HIF-1alpha stimulated by STZ. It was concluded that puerarin exerts significant protective effects against DR in rats, likely regulating angiogenesis factors expressions, and thus may be an effective and promising medicine for treatment of DR.

Protective effects of puerarin on carbon tetrachloride-induced hepatotoxicity

Puerarin, the main isoflavone glycoside found in the root of Pueraria lobata, has been used for various medicinal purposes in traditional Chinese medicine for thousands of years. The purpose of this study was to investigate the protective effects of puerarin against hepatotoxicity induced by carbon tetrachloride (CCl4) and the mechanism of its hepatoprotective effect. In mice, pretreatment with puerarin prior to the administration of CCl4 significantly prevented the increased serum enzymatic activity of alanine aspartate aminotransferase and hepatic malondialdehyde formation in a dose-dependent manner. In addition, pretreatment with puerarin significantly prevented both the depletion of reduced glutathione (GSH) content and the decrease in glutathione S-transferase (GST) activity in the liver of CCl4-intoxicated mice. Hepatic GSH levels and GST activity were increased by treatment with puerarin alone. CCl4-induced hepatotoxicity was also prevented, as indicated by liver histopathology. The effects of puerarin on cytochrome P450 (CYP) 2E1, the major isozyme involved in CCl4 bioactivation, were also investigated. Treatment of the mice with puerarin resulted in a significant decrease in the CYP2E1-dependent aniline hydroxylation in a dose-dependent manner. Consistent with these observations, the CYP2E1 protein levels were also lowered. Puerarin exhibited anti-oxidant effects on FeCl2-ascorbate induced lipid peroxidation in mouse liver homogenates, and on superoxide radical scavenging activity. These results suggest that the protective effects of puerarin against the CCl4-induced hepatotoxicity possibly involve mechanisms related to its ability to block CYP-mediated CCl4 bioactivation, induction of GST activity and free radical scavenging effects.

Binding of puerarin to human serum albumin: a spectroscopic analysis and molecular docking

Puerarin is a widely used compound in Chinese traditional medicine and exhibits many pharmacological activities. Binding of puerarin to human serum albumin (HSA) was investigated by ultraviolet absorbance, fluorescence, circular dichroism and molecular docking. Puerarin caused a static quenching of intrinsic fluorescence of HSA, the quenching data was analyzed by Stern-Volmer equation. There was one primary puerarin binding site on HSA with a binding constant of 4.12 x 10(4) M(-1) at 298 K. Thermodynamic analysis by Van Hoff equation found enthalpy change (DeltaH(0)) and entropy change (DeltaS(0)) were -28.01 kJ/mol and -5.63 J/mol K respectively, which indicated the hydrogen bond and Van der Waas interaction were the predominant forces in the binding process. Competitive experiments showed a displacement of warfarin by puerarin, which revealed that the binding site was located at the drug site I. Puerarin was about 2.22 nm far from the tryptophan according to the observed fluorescence resonance energy transfer between HSA and puerarin. Molecular docking suggested the hydrophobic residues such as tyrosine (Tyr) 150, Tyr 148, Tyr 149 and polar residues such as lysine (Lys) 199, Lys 195, arginine 257 and histidine 242 played an important role in the binding reaction.

Potential involvement of calcium and nitric oxide in protective effects of puerarin on oxygen-glucose deprivation in cultured hippocampal neurons

The aim of this study was to clarify the mechanisms underlying neuroprotection of puerarin (Pur) against cerebral hypoxia-ischemia. Primary hippocampal cultures were prepared from 2-day-old Sprague-Dawley rats. After 8 days in vitro, the cultures subjected to 3h oxygen/glucose deprivation (OGD). Flow cytometric analysis of annexin-V and propidium iodide (PI) labeling cells found that apoptosis and necrosis were significantly reduced in the cultured hippocampal neurons by addition of Pur during 3h OGD and for the following 24h. Pur (40 and 100 microM) also attenuated glutamate (Glu) induced neuronal damage, suppressing apoptosis and necrosis induced by Glu of 0.5mM. Furthermore, the changes in intracellular Ca(2+) and generation of nitric oxide (NO) were measured by confocal laser scanning microscopy with Fluo-3, a Ca(2+) probe, and diaminofluorescein diacetate (DAF DA), a NO probe, respectively. In agreement with the results from flow cytometric analysis, Pur (40 and 100 microM) markedly slowed down OGD-induced Ca(2+) influx and lowered the intracellular Ca(2+) peak. Meanwhile, NO synthesis induced by OGD was significantly inhibited by Pur. Our findings suggest that Pur can ameliorate hippocampal neuronal death induced by OGD in vitro. The protective effects of Pur are associated with inhibiting the action of glutaminergic transmitter, intracellular Ca(2+) elevation and neuronal NO synthesis.

Development of a poloxamer analogs/carbopol-based in situ gelling and mucoadhesive ophthalmic delivery system for puerarin

Conventional ophthalmic solutions often eliminate rapidly after administration and cannot provide and maintain an adequate concentration of the drug in the precorneal area. To solve these problems, we developed a thermosensitive in situ gelling and mucoadhesive ophthalmic drug delivery system containing puerarin based on poloxamer analogs (21% (w/v) poloxamer 407/5% (w/v) poloxamer 188) and carbopol (0.1% (w/v) or 0.2% (w/v) carbopol 1342P NF). The combined solutions would convert to firm gels under physiological condition and attach to the ocular mucosal surface for a relative long time. The incorporation of carbopol 1342P NF not only did not affect the pseudoplastic behavior with hysteresis of the poloxamer analogs solution and led to a higher shear stress at each shear rate, but also enhanced the mucoadhesive force significantly. In vitro release studies demonstrated diffusion-controlled release of puerarin from the combined solutions over a period of 8h. In vivo evaluation (the elimination of puerarin in tear and intraocular pressure-lowering effect) indicated the combined solutions had better ability to retain drug than poloxamer analogs or carbopol alone. It appears that ocular bioavailability can be increased more readily by using the in situ gelling and mucoadhesive vehicle.

Preparation and evaluation of a Carbopol/HPMC-based in situ gelling ophthalmic system for puerarin

The purpose of this study was to develop a pH-triggered in situ gelling vehicle for ophthalmic delivery of puerarin. The effect of hydroxypropyl-beta-cyclodextrin (HP-beta-CD) on the aqueous solubility and in vitro corneal permeation of puerarin was also investigated. The puerarin solubility increased linearly and proportionally to the HP-beta-CD concentrations and 5% (w/v) HP-beta-CD enhanced its ocular permeability significantly. Carbopol 980NF was used as the gelling agent in combination with HPMC (Methocel E4M) which acted as a viscosity-enhancing agent. The optimum concentrations of Carbopol 980NF and HPMC E4M for the in situ gel-forming delivery systems were 0.1% (w/v) and 0.4% (w/v), respectively. When these two vehicles were combined, an in situ gel that had the appropriate gel strength and gelling capacity under physiological condition could be obtained. This combined solution could flow freely under non- physiological condition and showed the character of pseudoplastic fluid under both conditions. Both in vitro release studies and in vivo pharmacokinetics studies indicated that the combined polymer systems performed better in retaining puerarin than puerarin eye drops did. These results demonstrate that the Carbopol 980NF/HPMC E4M can be a viable alternative to conventional puerarin eye drops to enhance ocular bioavailability and patient compliance.

Puerarin protects rat pancreatic islets from damage by hydrogen peroxide

The protective effect of puerarin, an isoflavone purified from Chinese herb radix of Pueraria lobata, on hydrogen peroxide (H(2)O(2))-induced rat pancreatic islets damage was investigated. Exposure of islets to 500 microM H(2)O(2) could cause a significant viability loss and an increase in apoptotic rate. Pretreatment of islets with puerarin for 48 h resulted in a reduction in viability loss and apoptotic rate. 100 microM puerarin significantly inhibited the apoptosis of islets induced by H(2)O(2). In addition, preincubation with puerarin could restore the H(2)O(2)-induced decrease in basal and glucose-stimulated insulin secretion in pancreatic islets. Puerarin was also found to inhibit the free radicals production induced by H(2)O(2) and to increase catalase and superoxide dismutase (SOD) activities in the isolated pancreatic islets. These results suggest that puerarin can protect islets against oxidative stress probably due to stimulating the activities of the antioxidant enzymes. Puerarin may be effective in preventing islet cells from the toxic action of reactive oxygen species in diabetes.

Optimization and Physicochemical Characterization of Thermosensitive Poloxamer Gel Containing Puerarin for Ophthalmic Use

The purpose of this study was to systematically optimize an ophthalmic thermosensitive poloxamer analogs gel containing puerarin that was a free flowing liquid below the room temperature and could shift to a gel with an eligible gel strength and bioadhesive force in physiological condition (dilution by the simulated tear fluid and at 35.0 degrees C). A two-factor, five-level central composite design (CCD) was employed to the optimization procedure. The effect of formulation variables (the w/v concentration of poloxamer 407 (X1) and poloxamer 188 (X2)) on a number of response variables (the gelation temperature before (Y1) and after (Y2) the simulated tear fluid diluted, the difference between them (Y3)) was systemically investigated. A second order polynomial equation was fitted to the data. The resulting equation and response surface plots were used to predict the responses in the optimal region. Finally, 21.0% (w/v) poloxamer 407 and 5.0% (w/v) poloxamer188 were chosen as the optimal poloxamer gel matrix. The influence of the other ingredients on the physicochemical properties of the formulation was also investigated. Hydroxypropyl-beta-cyclodextrin (HPCD) enhanced the gelation temperature and reduced the gel strength and the bioadhesive force, while puerarin and benzalkonium chloride (BC) had a comparatively smaller influence. All the isotonicity agents studied had the gelation temperatures lowered, and the gel strengths and the bioadhesive forces enhanced. But only sodium chloride appears to be a promising isotonicity agent for the poloxamer gel containing puerarin, HPCD and BC.

Puerarin Induces Angiogenesis in Myocardium of Rat with Myocardial Infarction

Puerarin is a major effective ingredient extracted from the traditional Chinese medicine ge-gen (radix puerariae, RP). Recently, puerarin has been used to treat patients with coronary artery diseases (CAD). However, the mechanisms of puerarin on coronary artery diseases are still not very clear. In this study, we investigated the role of puerarin on angiogenesis in the non-ischemic and ischemic myocardium. We found that puerarin (120, 60 mg/kg, i.p.) could reduce infarct area in the heart of rat with myocardial infarction (MI). Puerarin (120 mg/kg) induced angiogenesis in the non-ischemic and ischemic myocardium, which was one of the mechanisms of curing coronary artery diseases. The gene expression or activation of vascular endothelial growth factor (VEGF), hypoxia-inducible factor 1alpha (HIF-1alpha) and endothelial nitric oxide synthase (eNOS) that correlated with angiogenesis were also induced by puerarin. From these results, we suggested that puerarin may induce therapeutic angiogenesis in myocardium of rat with MI. The mechanism may be that puerarin can induce VEGF and eNOS expression.

Protection by puerarin against MPP+-induced neurotoxicity in PC12 cells mediated by inhibiting mitochondrial dysfunction and caspase-3-like activation

Puerarin, a main isoflavone glycoside distributed in Pueraria lobata (Willd.) Ohwi, showed inhibitory activity on H2O2-induced PC12 cells damage in our previous work. However, there is insufficient evidence in protective mechanism of puerarin, especially that relating to the mitochondrial function. In this study, when cells were pretreated with puerarin prior to 0.4 mM MPP+, protective roles were accompanied by a reduction of cell viability loss, morphological changes of apoptosis and apoptotic rate. To explore the protective mechanism of puerarin in MPP+-induced PC12 cells, mitochondrial function and caspase-3-like activity were measured. The results indicated that puerarin inhibited the release of mitochondrial cytochrome c to cytosol and the loss of mitochondrial membrane potentials. In addition, puerarin also reduced MPP+-induced caspase-3-like activation. Taken together, the above results suggest that pretreatment of PC12 cells with puerarin could block MPP+-mediated apoptosis by mitochondria-dependent caspase cascade.

Flow injection-chemiluminescence determination of puerarin in pharmaceutical preparations

Strong chemiluminescence was observed when cerium(IV) reacted with rhodamine 6G in sulfuric acid medium in the presence of puerarin. This phenomenon has been utilized to design a sensitive and selective flow injection-chemiluminescence method for the determination of puerarin. Under the optimum conditions, the proposed procedure has a linear range between 1.3 x 10(-9) and 8.0 x 10(-7)g/mL, with a detection limit of 8.4 x 10(-10)g/mL puerarin and a relative standard deviation of 1.86% (n = 11) at 5.0 x 10(-8)g/mL puerarin. The method was successfully applied to the determination of puerarin in pharmaceutical preparations. The mechanism of this chemiluminescence reaction has been proposed.

In vitro enzymatic modification of puerarin to puerarin glycosides by maltogenic amylase

Puerarin (daidzein 8-C-glucoside), the most abundant isoflavone in Puerariae radix, is prescribed to treat coronary heart disease, cardiac infarction, problems in ocular blood flow, sudden deafness, and alcoholism. However, puerarin cannot be given by injection due to its low solubility in water. To increase its solubility, puerarin was transglycosylated using various enzymes. Bacillus stearothermophilus maltogenic amylase (BSMA) was the most effective transferase used compared with Thermotoga maritima maltosyl transferase (TMMT), Thermus scotoductus 4-alpha-glucanotransferase (TS4alphaGTase), and Bacillus sp. I-5 cyclodextrin glucanotransferase (BSCGTase). TMMT and TS4alphaGTase lacked acceptor specificity for puerarin, which lacks an O-glucoside linkage between D-glucose and 7-OH-daidzein. The yield exceeded 70% when reacting 1% puerarin (acceptor), 3.0% soluble starch (donor), and 5U/100 microL BSMA at 55 degrees C for 45 min. The two major transfer products of the BSMA reaction were purified using C(18) and GPC chromatography. Their structures were identified as alpha-d-glucosyl-(1-->6)-puerarin and alpha-D-maltosyl-(1-->6)-puerarin using ESI+ TOF MS-MS and 13C NMR spectroscopy. The solubility of the transfer products was 14 and 168 times higher than that of puerarin, respectively.

Effects of some natural flavonoids on retinal function recovery after ischemic insult in the rat

PURPOSE

There are six natural flavonoids studied recently and their effects on ocular blood flow measured with colored microsphere technique. It was found that three out of six compounds showed strong positive effects in increasing the ocular blood flow. In this study, we tried to find out whether these results can be translated on their effects to improve retinal function recovery after ischemic insult.

METHODS

Electroretinography was used to measure the b-wave recovery as an indication of retinal function recovery.

RESULTS

Naringenin, hesperetin, and rutin were found to produce marked positive effects on b-wave recovery, whereas naringin, hesperidin, and quercetin showed poor recovery of b-wave after ischemic insult of the retina.

CONCLUSION

It was found that the compounds that showed strong increase of ocular blood flow also showed marked increase of retinal function recovery, whereas those that showed poor increase of ocular blood flow also showed poor effects on the retinal function recovery.

Structure-activity relationship (SAR) between some natural flavonoids and ocular blood flow in the rabbit

PURPOSE

Flavonoids with two to five hydroxy groups, with or without sugar, and/or methoxy groups were studied on their effects to affect ocular blood flow.

METHODS

Colored microsphere technique was used to determine the ocular blood flow in rabbit eyes.

RESULTS

Flavonoids with three free hydroxy (OH) groups seemed to produce the optimal effects in increasing ocular blood flow (naringenin and hesperitin, Pfalts and Bauer, Waterbury, CT). Whether the OH groups are below three (naringenin, hesperitin, Pfalts and Bauer, Waterbury, CT) or above four (Quercetin, Pfalts and Bauer, Waterbury, CT), they produced no effects on the ocular blood flow. When OH groups are four (rutin, Aldrich, Milwaukee, WI), it produced mixed effects on ocular blood flow. The attachment of rutinose and/or methoxy group in the structure did not affect the ocular blood flow one way or the other.

CONCLUSION

The ocular blood flow is increased significantly by the number of OH group in the molecule, with three the best to increase the ocular blood flow.

Establishment ofin vitro test system for the evaluation of the estrogenic activities of natural products

In order to evaluate estrogenic compounds in natural products, an in vitro detection system was established. For this system, the human breast cancer cell line MCF7 was stably transfected using an estrogen responsive chloramphenicol acetyltransferase (CAT) reporter plasmid yielding MCF7/pDsCAT-ERE119-Ad2MLP cells. To test the estrogenic responsiveness of this in vitro assay system, MCF7/pDsCAT-ERE119-Ad2MLP cells were treated with various concentrations of 17beta-estradiol. Treatments of 10(-8) to 10(-12) M 17beta-estradiol revealed significant concentration dependent estrogenic activities compared with ethanol. We used in vitro assay system to detect estrogenic effects in Puerariae radix and Ginseng radix Rubra extracts. Treatment of 500 and 50 microg/ml of Puerariae radix extracts increased the transcriptional activity approximately 4- and 1.5-fold, respectively, compared with the ethanol treatment. Treatment of 500, 50, and 5 microg/ml of Ginseng radix Rubra extracts increased the transcriptional activity approximately 3.2-, 2.7-, and 1.4-fold, respectively, compared with the ethanol treatment. These observations suggest that Puerariae radix and Ginseng radix Rubra extracts have effective estrogenic actions and that they could be developed as estrogenic supplements.

Effects of Dihydrogenation of Flavones and Number of Hydroxy Groups in the Molecules on Ocular Blood Flow in Rabbits and Retinal Function Recovery in Rats

PURPOSE

It has been found that the number of hydroxy groups in the molecule of flavones and flavanones affect the ocular blood flow significantly. However, the effects of dihydrogenation of flavones into flavanones on ocular blood flow and retinal function recovery have not been studied and required investigation.

METHODS

The colored microsphere technique and electroretinography method were used for the study of ocular blood flow and retinal function, respectively.

RESULTS

Maximum effects on ocular blood flow were obtained when there were 3 hydroxy groups in the molecule of flavones and flavanones. Dihydrogenation of flavones to flavanones increased the ocular blood flow further. The same is true for retinal function recovery after ischemic insult.

CONCLUSION

These results indicate that hydrogenation is an excellent way to convert natural flavones into more potent compounds of flavanones.

Structural Requirements of Flavonoids for Increment of Ocular Blood Flow in the Rabbit and Retinal Function Recovery in Rat Eyes

PURPOSE

We have recently reported that the effect of a flavonoid on ocular blood flow depends upon the number of hydroxy (OH) groups in its backbone structure. To elucidate the structural features on the number and type of functional groups present in the flavonoid molecule plus the number of OH groups, flavonoids with four to five OH groups, with or without methoxy groups, were studied on their effects to affect the ocular blood flow and the retinal function recovery.

METHODS

A colored microsphere technique was used to determine the ocular blood flow in albino rabbit eyes and electroretinography was used to measure the retinal function recovery.

RESULTS

Flavonols with four free OH groups produced no effects on the ocular blood flow (fisetin, kaempferol), whereas flavanone and flavones with four free OH groups and without the C2-C3 double bond produced the rapid increment on ocular blood flow (dihydrofisetin and luteolin, respectively). Similarly, flavonols with five free OH groups produced no effects on the ocular blood flow (morin, quercetin). Yet, flavanone with five free OH groups and without the C2-C3 double bond produced the rapid increment on ocular blood flow (dihydroquercetin). Flavanols with five free OH groups and without the C2-C3 double bond and the carbonyl group produced no effects on the ocular blood flow (catechin). Flavonols with four free OH groups and a methoxy group on the 7 position produced no effects on the ocular blood flow (Rhamnetin). Flavonols with four free OH groups and a methoxy group at the 5 (5-methylquercetin) or 3' position (isorhamnetin) produced positive effects on the ocular blood flow also. Flavonol with five methoxy groups but no OH group produced positive effects on the ocular blood flow (pentamethylquercetin). Flavonols with an excessive number of OH groups, having both a catechol-like structure in the C ring and a catechol at the B ring, produced no effect on the ocular blood flow (rhamnetin, quercetin). Parallel results were obtained on retinal function recovery after ischemic insult.

CONCLUSION

The presence of OH groups at certain positions and the double bond at C2-C3 in the flavonoid molecules, which produces lipophilic action, can affect the increment on ocular blood flow and retinal function recovery. O-methylation can increase ocular blood flow and retinal function recovery as well.

RP-HPLC determination of puerarin in Chinese traditional medicinal preparations containing pueraria

Puerarin in a Gegen(Pueraria)-based Chinese traditional medicinal preparations, Ganmao Qingre Granules, from four different pharmaceutical manufacturers and in two different dosage forms, were determined using RP-HPLC with methanol-5 mmol l(-1) KH(2)PO(4) (pH = 4.0) (V:V = 27:73) as mobile phase and UV detection at 248 nm. Ultrasonication and reflux were compared as pretreatment procedures for the sample. Linear range over 0.2-200 microg ml(-1) of puerarin was obtained, and the limit of detection was 0.1 microg ml(-1). Recovery was within 99.7-103%.

Effects of N-nitropyrazoles on ocular blood flow of rabbits and retinal function recovery of rat eyes after ischemic insults

Twelve compounds of N-nitropyrazoles were studied for their effects on ocular blood flow in rabbits and retinal function recovery in rat eyes after ischemic insults. Of the twelve N-nitropyrazoles examined, nine increased choroidal blood flow while five increased retinal blood flow significantly. On the other hand, all twelve compounds increased blood flow in iris and ciliary muscle without exception. As for retinal function recovery after ischemic insult in rat eyes, eight out of the twelve compounds showed more significant facilitation than the control. The structure activity relationship of the N-nitropyrazoles to increase ocular blood flow and to facilitate retinal function recovery after ischemic insults were discussed.

Complementary and alternative medicine for glaucoma

Given the recent interest in complementary and alternative medicine (CAM), some patients may seek such treatments to supplement their traditional glaucoma management. The prevalence of CAM use for glaucoma is approximately 5%. We reviewed the literature to determine the potential benefit of various alternative treatments. Aside from a temporary osmotic effect from high dose intravenous ascorbic acid, there is no evidence that megavitamin supplementation has a beneficial effect on glaucoma. During exercise, autoregulation in healthy eyes seems to maintain a consistent blood flow rate to the optic nerve despite fluctuations in intraocular pressure (IOP). In a glaucomatous eye, the very modest IOP-lowering that follows exercise may be offset by the initial elevation in IOP that occurs when one first initiates exercise. At this time, there is no evidence to encourage or discourage the use of special diets, acupuncture, relaxation techniques, or therapeutic touch specifically for the treatment of glaucoma. Very little research has been done on the majority of herbal remedies with regard to their treatment of glaucoma. Marijuana can cause a profound lowering of IOP, but the high nonresponse rate, short half life, and significant toxicity are strong indicators that it is not an appropriate therapeutic agent. Ginkgo biloba and some other Chinese herbal remedies do not affect IOP, but may improve blood flow to the optic nerve and, as such, may have a beneficial effect on glaucoma. These agents have recognized toxicities. Although there are some well-designed studies of alternative treatments, many of the recommendations for using alternative treatments are currently unsupported by the data provided.