Solid lipid nanoparticles of lutein with improved dissolution behavior and oral absorption.

The present study aimed to develop solid lipid nanoparticles of lutein (SLN/LT) with improved dissolution behavior and oral absorption. SLN/LT were prepared by a flash nanoprecipitation method using a multi-inlet vortex mixer, and their physicochemical, photochemical, and pharmacokinetic properties were evaluated. The mean particle size of SLN/LT re-dispersed in water was 237 nm, and small spherical particles with no significant aggregation were observed. LT significantly generated singlet oxygen upon exposure to pseudo-sunlight (250 W/m2, 1 h), suggesting its high photoreactivity. The remaining LT in LT solution, crystalline LT, and SLN/LT after irradiation with pseudo-sunlight (250 W/m2, 2 h) were 56.3, 86.7, and 101%, respectively. SLN/LT showed improved dissolution behavior of LT in simulated intestinal fluid, and the dissolved amounts of LT at 2 h were at least 50 times higher than that of crystalline LT. Orally administered SLN/LT (100 mg-LT/kg) exhibited enhanced oral absorption of LT, as evidenced by a relative bioavailability of 3.7 to crystalline LT in rats. SLN/LT may be a promising dosage form for orally available LT supplements, possibly leading to enhanced nutritional functions of LT.

Reactive oxygen species (ROS) assay-based photosafety screening for complex ingredients: Modification of the ROS assay protocol.

A reactive oxygen species (ROS) assay has been widely used for photosafety assessment; however, the phototoxic potential of complex materials, including plant extracts, essential oils, and functional polymers, is unevaluable because of their undefined molecular weights. The present study was undertaken to modify the ROS assay protocol for evaluating phototoxic potentials of those materials with use of their apparent molecular weight (aMw). On preparing sample solutions for the ROS assay, aMw ranging from 150 to 350 was tentatively employed for test substances. The modified ROS assays were applied to 45 phototoxic and 19 non-phototoxic substances, including 44 chemicals and 20 complex materials (plant extracts) for clarification of the predictive performance. Generation of ROS from photo-irradiated samples tended to increase as aMW grew, resulting in the largest number of false-positive predictions at aMW of 350. Some false-negative predictions were also observed when aMW was set at 200 or less. At aMw of 250, all tested phototoxic substances could be correctly identified as photoreactive with no false-negative predictions. Based on these observations, aMw of 250 was found to be suitable for the ROS assay on complex materials, and the sensitivity, specificity, and positive and negative predictivity for the proposed ROS assay were calculated to be 100, 52.6, 83.3, and 100%, respectively. Thus, the proposed approach may be efficacious for predicting phototoxic potentials of complex materials and contribute to the development of new products with a wide photosafety margin.

Strategic application of liposomal system to R-α-lipoic acid for the improvement of nutraceutical properties.

R-α-lipoic acid (RLA) and dihydrolipoic acid (DHLA), a reduced form of RLA, are potent endogenous antioxidants that can reduce oxidative damage. Despite their numerous nutraceutical potentials, clinical applications of RLA are still limited due to its poor solubility and stability problems. This study aimed to develop an RLA-loaded liposome (LIP/RLA) for the improvement of nutraceutical properties. LIP/RLA was developed by a typical solvent injection method. Uniform liposomes of LIP/RLA were observed by transmission electron microscopy, and the mean particle size was calculated to be ∼150 nm from the data of dynamic light scattering. LIP/RLA could prevent the degradation of RLA even under acidic conditions (pH 1.2) possibly due to the encapsulation of RLA into the liposomal structure. In the release test under pH6.8 with lipase, LIP/RLA showed relatively rapid release of RLA, possibly due to the lipolysis of phospholipids by lipase. After the oral administration of LIP/RLA (10 mg-RLA/kg, p.o.) in rats, the systemic exposures of RLA and DHLA increased by 2.8- and 5.8-fold, respectively. In a rat model of acute hepatic injury induced by carbon tetrachloride (CCl4) (0.7 mL-CCl4/kg, p.o.), orally dosed LIP/RLA (3 mg-RLA/kg, p.o.) resulted in 78.7% and 86.4% reductions of plasma alanine aminotransferase, and aspartate aminotransferase, respectively; however, RLA was found to be less effective possibly due to the poor oral absorption. The RLA-loaded liposomal system might be a promising carrier for poorly water-soluble materials with poor stability under acidic conditions, as well as RLA, to improve their oral absorption and nutraceutical properties.

Impact of Green Tea Catechin Ingestion on the Pharmacokinetics of Lisinopril in Healthy Volunteers.

Lisinopril, a highly hydrophilic long-acting angiotensin-converting enzyme inhibitor, is frequently prescribed for the treatment of hypertension and congestive heart failure. Green tea consumption may reduce the risk of cardiovascular outcomes and total mortality, whereas green tea or its catechin components has been reported to decrease plasma concentrations of a hydrophilic ß blocker, nadolol, in humans. The aim of this study was to evaluate possible effects of green tea extract (GTE) on the lisinopril pharmacokinetics. In an open-label, randomized, single-center, 2-phase crossover study, 10 healthy subjects ingested 200 mL of an aqueous solution of GTE containing ~ 300 mg of (-)-epigallocatechin gallate, a major catechin component in green tea, or water (control) when receiving 10 mg of lisinopril after overnight fasting. The geometric mean ratio (GTE/control) for maximum plasma concentration and the area under the plasma concentration-time curve of lisinopril were 0.289 (90% confidence interval (CI) 0.226-0.352) and 0.337 (90% CI 0.269-0.405), respectively. In contrast, there were no significant differences in time to reach maximum lisinopril concentration (6 hours in both phases) and renal clearance of lisinopril (57.7 mL/minute in control vs. 56.9 mL/minute in GTE). These results suggest that the extent of intestinal absorption of lisinopril was significantly impaired in the presence of GTE, whereas it had no major effect on the absorption rate and renal excretion of lisinopril. Concomitant use of lisinopril and green tea may decrease oral exposure to lisinopril, and therefore result in reduced therapeutic efficacy.

Photochemically stabilized formulation of dacarbazine with reduced production of algogenic photodegradants.

The present study aimed to develop a photochemically stabilized formulation of dacarbazine [5-(3,3-dimethyl-1-triazeno)imidazole-4-carboxamide; DTIC] for reducing the production of algogenic photodegradant (5-diazoimidazole-4-carboxamide; Diazo-IC). Photochemical properties of DTIC were characterized by UV-visible light spectral analysis, reactive oxygen species (ROS) assay, and photostability testing. A pharmacokinetic study was conducted after intravenous administration of DTIC formulations (1 mg-DTIC/kg) to rats. DTIC exhibited strong absorption in the UVA range, and photoirradiated DTIC exhibited marked ROS generation. Thus, DTIC had high photoreactive potential. After exposure of DTIC (1 mM) to simulated sunlight (250 W/m2) for 3 min, remaining DTIC and yielded Diazo-IC were estimated to be ca. 230 µM and 600 µM, respectively. The addition of radical scavenger (1 mM), including l-ascorbic acid, l-cysteine (Cys), l-histidine, D-mannitol, l-tryptophan, or l-tyrosine, to DTIC (1 mM) could attenuate DTIC photoreactions, and in particular, the addition of Cys to DTIC brought ca. 34% and 86% inhibition of DTIC photodegradation and Diazo-IC photogeneration, respectively. There were no significant differences in the calculated pharmacokinetic parameters of DTIC between DTIC and DTIC with Cys (0.67 mg/kg). From these findings, the supplementary use of Cys would be an effective approach to improve the photostability of DTIC with less production of Diazo-IC.

Role of (-)-epigallocatechin gallate in the pharmacokinetic interaction between nadolol and green tea in healthy volunteers.

PURPOSE: The aim of the present study is to investigate a possible role of a single dose of (-)-epigallocatechin gallate (EGCG), the major catechin in green tea, for the pharmacokinetic interaction between green tea and nadolol in humans. METHODS: In a randomized three-phase crossover study, 13 healthy volunteers received single doses of 30 mg nadolol orally with water (control), or an aqueous solution of EGCG-concentrated green tea extract (GTE) at low or high dose. Plasma concentrations and urinary excretion of nadolol were determined up to 48 h. In addition, blood pressure and pulse rate were monitored. In vitro transport kinetic experiments were performed using human embryonic kidney 293 cells stably expressing organic anion transporting polypeptide (OATP)1A2 to evaluate the inhibitory effect of EGCG on OATP1A2-mediated substrate transport. RESULTS: Single coadministration of low and high dose GTE significantly reduced the plasma concentrations of nadolol. The geometric mean ratios with 90% CI for area under the plasma concentration-time curves from 0 to infinity of nadolol were 0.72 (0.56-0.87) for the low and 0.60 (0.51-0.69) for the high dose. There were no significant differences in Tmax, elimination half-life, and renal clearance between GTE and water phases. No significant changes were observed for blood pressure and pulse rate between phases. EGCG competitively inhibited OATP1A2-mediated uptake of sulphobromophthalein and nadolol with Ki values of 21.6 and 19.4 µM, respectively. CONCLUSIONS: EGCG is suggested to be a key contributor to the interaction of green tea with nadolol. Moreover, even a single coadministration of green tea may significantly affect nadolol pharmacokinetics.

Lack of pharmacokinetic interaction between fluvastatin and green tea in healthy volunteers.

PURPOSE: The objective of this study is to assess the effects of green tea and its major catechin component, (-)-epigallocatechin gallate (EGCG), on CYP2C9-mediated substrate metabolism in vitro, and the pharmacokinetics of fluvastatin in healthy volunteers. METHODS: The metabolism of diclofenac and fluvastatin in human recombinant CYP2C9 was investigated in the presence of EGCG. In a randomized three-phase crossover study, 11 healthy volunteers ingested a single 20-mg dose of fluvastatin with green tea extract (GTE), containing 150 mg of EGCG, along with water (300 mL), brewed green tea (300 mL), or water (300 mL) after overnight fasting. Plasma concentrations of fluvastatin and EGCG were measured by ultra-performance liquid chromatography with fluorescence detection and a single mass spectrometer. RESULTS: EGCG inhibited diclofenac 4'-hydroxylation and fluvastatin degradation with IC50 of 2.23 and 48.04 µM, respectively. Brewed green tea used in the clinical study also dose-dependently inhibited the metabolism of diclofenac and fluvastatin in vitro. However, no significant effects of GTE and brewed green tea were observed in plasma concentrations of fluvastatin. The geometric mean ratios with 90% CI for area under the plasma concentration-time curve (AUC0-∞) of fluvastatin were 0.993 (0.963-1.024, vs. brewed green tea) and 0.977 (0.935-1.020, vs. GTE). CONCLUSIONS: Although in vitro studies indicated that EGCG and brewed green tea produce significant inhibitory effects on CYP2C9 activity, the concomitant administration of green tea and fluvastatin in healthy volunteers did not influence the pharmacokinetics of fluvastatin.

Protective effects of tranilast on experimental colitis in rats.

The present study aimed to verify the efficacy of tranilast (TL) for treating inflammatory bowel disease (IBD) with the use of an experimental colitis model. The experimental colitis model was prepared by intrarectal instillation of 2,4,6-trinitrobenzenesulfonic acid (TNBS; 40mg/kg) dissolved in water containing 25% ethanol. The pharmacological effects of TL after repeated oral administration were evaluated by biomarker and histological analyses, and the pharmacokinetic behavior of TL was also examined after single oral administration. The intrarectal instillation of TNBS solution caused colitis, as evidenced by ca. 2.2-, 5-, and 3-fold increases in myeloperoxidase (MPO) activity, infiltrated cell numbers, and the thickness of the submucosa in the colon, respectively. However, orally-taken TL (10mg/kg, twice a day for 9days) led to a 92% reduction in the increase of the MPO level by TNBS enema, and cellular infiltration and thickened submucosa in the experimental colitis model tended to also be suppressed by repeated oral administration of TL. The oral bioavailability of TL in TNBS-treated rats was calculated to be as low as ca. 6.5%, and the poor oral absorption of TL may be a limitation of the treatment for IBD. TL could attenuate TNBS-induced colitis on the basis of the obtained results, and the anti-inflammatory effects would have clinical relevance to the therapeutic outcomes of TL in IBD patients. Although further improvement in the oral bioavailability of TL might be required for better pharmacological outcomes, TL would be an efficacious agent for treating IBD.

Ginger Extract-Loaded Solid Dispersion System with Enhanced Oral Absorption and Antihypothermic Action.

The aim of this study is to enhance the antihypothermic action of ginger extract (GE) employing a solid dispersion (SD) approach. The prepared SD of GE (GE/SD) was characterized in terms of physicochemical and pharmacokinetic properties. The antihypothermic action of GE samples was evaluated in a rat model of hypothermia. GE/SD exhibited improved dissolution behavior of the major active ingredients in GE, 6-gingerol (6G) and 8-gingerol (8G), with levels of dissolution 12- and 31-fold higher than that of GE, respectively. Even after storage under accelerated conditions, limited degradations of 6G and 8G were observed in GE/SD, although 6G and 8G were slightly degraded in GE. After oral administration of GE (300 mg/kg) and GE/SD (100 mg of GE/kg), the relative bioavailabilities of 6G and 8G in GE/SD were 5.0- and 5.8-fold higher than those in GE, respectively. Orally administered GE/SD (30 mg of GE/kg) inhibited ethanol-evoked hypothermia because of improved oral absorption of 6G and 8G. From these observations, the SD approach might be efficacious for enhancing the nutraceutical potentials of GE.

Photochemical Mechanism of Riboflavin-Induced Degradation of Famotidine and a Suggested Pharmaceutical Strategy for Improving Photostability.

The present study aimed to clarify the mechanism of photodegradation of famotidine with riboflavin (FMT/RF), and to develop a photochemically stabilized formulation of FMT/RF. Photochemical properties of RF were characterized by UV-VIS spectral analysis, reactive oxygen species (ROS) assay, and photostability testing. Pharmacokinetic study was conducted in rats after intravenous administration of FMT (1 mg/kg) formulation containing RF (0.01 mg/kg). The UV-VIS spectral pattern of RF partly overlapped with the sunlight spectrum, and ROS generation from photoirradiated RF was remarkable; thus, RF had high photoreactive potential. In the photostability testing, after irradiation (250 W/m(2)), degradation rate for FMT in FMT/RF was ca. 11-fold higher than that in FMT alone. The addition of radical scavengers to FMT/RF led to attenuated photodegradation of FMT/RF; in particular, the addition of L-ascorbic acid (vitamin C; VC) to FMT/RF showed ca. 86% inhibition of the photodegradation of FMT/RF. The pharmacokinetic study on FMT indicated that the addition of VC (1 mg/kg) to FMT/RF had no significant impact on the pharmacokinetic behavior of FMT. These findings suggest that ROS-mediated photochemical reaction would be involved in the photodegradation pathway of FMT/RF, and the complementary use of VC might be an attractive approach to improve the photostability of FMT/RF.

Non-animal photosafety screening for complex cosmetic ingredients with photochemical and photobiochemical assessment tools.

Previously, a non-animal screening approach was proposed for evaluating photosafety of cosmetic ingredients by means of in vitro photochemical and photobiochemical assays; however, complex cosmetic ingredients, such as plant extracts and polymers, could not be evaluated because their molecular weight is often poorly defined and so their molar concentration cannot be calculated. The aim of the present investigation was to establish a photosafety screen for complex cosmetic ingredients by using appropriately modified in vitro photosafety assays. Twenty plant extracts were selected as model materials on the basis of photosafety information, and their phototoxic potentials were assessed by means of ultraviolet (UV)/visible light (VIS) spectral analysis, reactive oxygen species (ROS)/micellar ROS (mROS) assays, and 3T3 neutral red uptake phototoxicity testing (3T3 NRU PT). The maximum UV/VIS absorption value was employed as a judgment factor for evaluating photoexcitability of samples, and the value of 1.0 was adopted as a tentative criterion for photosafety identification. The ROS/mROS assays were conducted at 50 µg/mL, and no false negative prediction was obtained. Furthermore, the ROS/mROS assays at 50 µg/mL had a similar predictive capacity to the ROS/mROS assays in the previous study. A systematic tiered approach for simple and rapid non-animal photosafety evaluation of complex cosmetic ingredients can be constructed using these modified in vitro photochemical assays.

Overview of green tea interaction with cardiovascular drugs.

Sensitive to the massive diffusion of purported metabolic and cardiovascular positive effects of green tea and catechincontaining extracts, many consumers of cardiovascular drugs assume these products as a "natural" and presumably innocuous adjunctive way to increase their overall health. However, green tea may interfere with the oral bioavailability or activity of cardiovascular drugs by various mechanisms, potentially leading to reduced drug efficacy or increased drug toxicity. Available data about interactions between green tea and cardiovascular drugs in humans, updated in this review, are limited so far to warfarin, simvastatin and nadolol, and suggest that the average effects are mild to modest. Nevertheless, in cases of unexpected drug response or intolerance, it is warranted to consider a possible green tea-drug interaction, especially in people who assume large volumes of green tea and/or catechin-enriched products with the conviction that "more-is-better".

Green tea extract affects the cytochrome P450 3A activity and pharmacokinetics of simvastatin in rats.

Effects of green tea extract (GTE) on the activity of cytochrome P450 (CYP) enzymes and pharmacokinetics of simvastatin (SIM) were investigated in rats. Inhibitory effects of GTE on CYP3A activity were investigated in rat hepatic microsomes (RHM) using midazolam (MDZ) 1'-hydroxylation as a probe reaction. SD female rats received a single oral dose of GTE (400 mg/kg) or troleandomycin (TAO, a CYP3A selective inhibitor, 500 mg/kg), followed 30 min later by SIM (20 mg/kg). Plasma concentrations of SIM and its active metabolite, simvastatin acid, were determined up to 6 h after the SIM administration using LC/MS/MS. In RHM, GTE inhibited MDZ 1'-hydroxylation with IC50 and K(i)(app) values of 12.5 and 18.8 µg/mL, respectively, in a noncompetitive manner. Area under plasma concentration-time curves for SIM in the GTE and TAO groups were increased by 3.4- and 10.2-fold, respectively, compared with the control. The maximum concentrations of SIM were higher in the GTE (3.3-fold) and TAO (9.5-fold) groups. GTE alters the pharmacokinetics of SIM, probably by inhibiting intestinal CYP3A.

Effects of green tea catechins on cytochrome P450 2B6, 2C8, 2C19, 2D6 and 3A activities in human liver and intestinal microsomes.

The effects of green tea catechins on the main drug-metabolizing enzymatic system, cytochrome P450 (CYP), have not been fully elucidated. The objective of the present study was to evaluate the effects of green tea extract (GTE, total catechins 86.5%, w/w) and (-)-epigallocatechin-3-gallate (EGCG) on the activities of CYP2B6, CYP2C8, CYP2C19, CYP2D6 and CYP3A in vitro, using pooled human liver and intestinal microsomes. Bupropion hydroxylation, amodiaquine N-deethylation, (S)-mephenytoin 4'-hydroxylation, dextromethorphan O-demethylation and midazolam 1'-hydroxylation were assessed in the presence or absence of various concentrations of GTE and EGCG to test their effects on CYP2B6, CYP2C8, CYP2C19, CYP2D6 and CYP3A activities, respectively. Each metabolite was quantified using UPLC/ESI-MS, and the inhibition kinetics of GTE and EGCG on CYP enzymes was analyzed. In human liver microsomes, IC50 values of GTE were 5.9, 4.5, 48.7, 25.1 and 13.8 µg/mL, for CYP2B6, CYP2C8, CYP2C19, CYP2D6 and CYP3A, respectively. ECGC also inhibited these CYP isoforms with properties similar to those of GTE, and produced competitive inhibitions against CYP2B6 and CYP2C8, and noncompetitive inhibition against CYP3A. In human intestinal microsomes, IC50 values of GTE and EGCG for CYP3A were 18.4 µg/mL and 31.1 µM, respectively. EGCG moderately inhibited CYP3A activity in a noncompetitive manner. These results suggest that green tea catechins cause clinically relevant interactions with substrates for CYP2B6 and CYP2C8 in addition to CYP3A.

Development of rapid and simultaneous quantitative method for green tea catechins on the bioanalytical study using UPLC/ESI-MS.

A rapid and quantitative analytical method for the simultaneous determination of green tea catechins using ultra-performance liquid chromatography/electrospray ionization-mass spectrometry was developed. Total analytical run time was 3.5 min for the detection of (-)-epicatechin (EC), (-)-epicatechin-3-O-gallate (ECG), (-)-epigallocatechin (EGC), (-)-epigallocatechin-3-O-gallate (EGCG) and myricetin as the internal standard (IS) in rat plasma. The calibration curves were linear over the range of 10-5000 ng/mL for all the catechins. The inter- and intra-day precision (relative standard deviation) and accuracy (percentage deviation) of the method were both lower than 10%. The average extraction recoveries in plasma ranged from 68.5 to 86.5%, and the lower limits of quantification of EC, EGC, ECG and EGCG were 10 ng/mL with a signal-to-noise ratio of >10. The assay developed was successfully applied to a pharmacokinetic study of catechins following intravenous and intragastric administrations of green tea extract in rats. Plasma concentrations of four catechins were detected up to 5-24 h after administration, and the pharmacokinetic parameters of catechins were in agreement with previous studies. From these findings, taken together with the high productivity and precision, the developed method could be a reliable and reproducible tool for the evaluation of pharmacokinetic properties of catechins.

Novel solid self-emulsifying drug delivery system of coenzyme Q10 with improved photochemical and pharmacokinetic behaviors.

The present study was undertaken to develop a solid self-emulsifying drug delivery system of coenzyme Q(10) (CoQ(10)/s-SEDDS) with high photostability and oral bioavailability. The CoQ(10)/s-SEDDS was prepared by spray-drying an emulsion preconcentrate containing CoQ(10), medium-chain triglyceride, sucrose ester of fatty acid, and hydroxypropyl cellulose, and its physicochemical, photochemical, and pharmacokinetic properties were evaluated. The CoQ(10)/s-SEDDS powder with a diameter of ca. 15 µm was obtained by spray-drying, in which the CoQ(10) was mostly amorphized. The CoQ(10)/s-SEDDS exhibited immediate self-emulsification when introduced to aqueous media under gentle agitation, forming uniform fine droplets with a mean diameter of ca. 280 nm. There was marked generation of reactive oxygen species, in particular superoxide, from CoQ(10) exposed to simulated sunlight (250W/m(2)), suggesting potent photoreactivity. Nano-emulsified solution of CoQ(10) under light exposure underwent photodegradation with 22-fold higher degradation kinetics than crystalline CoQ(10), although the CoQ(10)/s-SEDDS was less photoreactive. After the oral administration of CoQ(10)/s-SEDDS (100 mg-CoQ(10)/kg) in rats, enhanced exposure of CoQ(10) was observed with increases in both C(max) and AUC of ca. 5-fold in comparison with those of orally administered crystalline CoQ(10). From the improved physicochemical and pharmacokinetic data, the s-SEDDS approach upon spray-drying might be a suitable dosage option for enhancing nutraceutical and pharmaceutical values of CoQ(10).

In vitro and in vivo characterization of new formulations of St. John's Wort extract with improved pharmacokinetics and anti-nociceptive effect.

The main purpose of the present study was to develop a novel formulation of St. John's Wort (SJW) extract with the aim of improving its pharmacokinetics and anti-nociceptive effect. Several formulations of SJW were prepared, including cyclodextrin inclusion (SJW-CD), solid dispersion (SJW-SD), dry-emulsion (SJW-DE), and nano-emulsion (SJW-NE). Physicochemical properties of SJW formulations were characterized with a focus on the morphology, dissolution behavior, colloidal properties, and dispersion stability in water. Although all the SJW formulations and SJW extract itself exhibited fine dissolution behavior in water, SJW extract and most formulations tended to cream, aggregate, or flocculate after dispersion in distilled water. In contrast, there were no significant changes in appearance and particle size of the SJW-NE for at least a few weeks, suggesting that SJW-NE was the most stable form as a carrier of SJW in the present study. After oral administration of the SJW-NE formulation (5.2 mg hyperforin/kg) in mice, higher hyperforin exposure in plasma (1188 ± 41 nM·h) and the brain (52.9 ± 1.6 pmol/g tissue·h) was observed with 2.8- and 1.3-fold increases of the area under the concentration curve from 0 to 6 hours (AUC(0-6)) compared to those of the SJW extract (417 ± 41 nM·h in plasma and 41.6 ± 1.5 pmol/g tissue·h in the brain). In the formalin test for scoring properties of the first and second phases of the pain response in mice, single oral administration of SJW-NE significantly reduced the nociceptive response compared with SJW extract. From these findings, the NE approach might be efficacious in improving the oral bioavailability and anti-nociceptive effect of SJW extract.

In vitro photochemical and phototoxicological characterization of major constituents in St. John's Wort (Hypericum perforatum) extracts.

Extracts from St. John's Wort (SJW: Hypericum perforatum) have been used for the treatment of mild-to-moderate depression. In spite of the high therapeutic potential, orally administered SJW sometimes causes phototoxic skin responses. As such, the present study aimed to clarify the phototoxic mechanisms and to identify the major phototoxins of SJW extract. Photobiochemical properties of SJW extract and 19 known constituents were characterized with focus on generation of reactive oxygen species (ROS), lipid peroxidation, and DNA photocleavage, which are indicative of photosensitive, photoirritant, and photogenotoxic potentials, respectively. ROS assay revealed the photoreactivity of SJW extract and some SJW ingredients as evidenced by type I and/or II photochemical reactions under light exposure. Not all the ROS-generating constituents caused photosensitized peroxidation of linoleic acid and photodynamic cleavage of plasmid DNA, and only hypericin, pseudohypericin, and hyperforin exhibited in vitro photoirritant potential. Concomitant UV exposure of quercitrin, an SJW component with potent UV/Vis absorption, with hyperforin resulted in significant attenuation of photodynamic generation of singlet oxygen from hyperforin, but not with hypericin. In conclusion, our results suggested that hypericin, pseudohypericin, and hyperforin might be responsible for the in vitro phototoxic effects of SJW extract.

Isolation and pharmacological characterization of fatty acids from saw palmetto extract.

Saw palmetto extract (SPE) has been widely used for the treatment of lower urinary-tract symptoms secondary to benign prostatic hyperplasia. The mechanisms of pharmacological effects of SPE include the inhibition of 5alpha-reductase, anti-androgenic effects, anti-proliferative effects, and anti-inflammatory effects. Previously, we showed that SPE bound actively to alpha(1)-adrenergic, muscarinic and 1,4-dihydropyridine calcium channel (1,4-DHP) receptors in the prostate and bladder of rats, whereas its active constituents have not been fully clarified. The present investigation is aimed to identify the main active components contained in hexane and diethyl ether extracts of SPE with the use of column chromatography and preparative HPLC. Based on the binding activity with alpha(1)-adrenergic, muscarinic, and 1,4-DHP receptors, both isolated oleic and lauric acids were deduced to be active components. Authentic samples of oleic and lauric acids also exhibited similar binding activities to these receptors as the fatty acids isolated from SPE, consistent with our findings. In addition, oleic and lauric acids inhibited 5alpha-reductase, possibly leading to therapeutic effects against benign prostatic hyperplasia and related lower urinary-tract symptoms.

Pharmacological effects of saw palmetto extract in the lower urinary tract.

Saw palmetto extract (SPE), an extract from the ripe berries of the American dwarf palm, has been widely used as a therapeutic remedy for urinary dysfunction due to benign prostatic hyperplasia (BPH) in Europe. Numerous mechanisms of action have been proposed for SPE, including the inhibition of 5alpha-reductase. Today, alpha(1)-adrenoceptor antagonists and muscarinic cholinoceptor antagonists are commonly used in the treatment of men with voiding symptoms secondary to BPH. The improvement of voiding symptoms in patients taking SPE may arise from its binding to pharmacologically relevant receptors in the lower urinary tract, such as alpha(1)-adrenoceptors, muscarinic cholinoceptors, 1,4-dihyropyridine receptors and vanilloid receptors. Furthermore, oral administration of SPE has been shown to attenuate the up-regulation of alpha(1)-adrenoceptors in the rat prostate induced by testosterone. Thus, SPE at clinically relevant doses may exert a direct effect on the pharmacological receptors in the lower urinary tract, thereby improving urinary dysfunction in patients with BPH and an overactive bladder. SPE does not have interactions with co-administered drugs or serious adverse events in blood biochemical parameters, suggestive of its relative safety, even with long-term intake. Clinical trials (placebo-controlled and active-controlled trials) of SPE conducted in men with BPH were also reviewed. This review should contribute to the understanding of the pharmacological effects of SPE in the treatment of patients with BPH and associated lower urinary tract symptoms (LUTS).