Simple and sensitive liquid chromatography–tandem mass spectrometry assay for simultaneous measurement of five Epimedium prenylflavonoids in rat sera

Development and validation of UPLC-MS/MS method for icariin and its metabolites in mouse urine

An ultra-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) method was utilized to develop a technique for the simultaneous quantification of icariin and its primary metabolites in mouse urine. The levels of icariin, icariside Ⅰ, icariside Ⅱ, baohuoside Ⅱ, wushanicaritin, icaritin, and desmethylicaritin in mouse urine were analyzed subsequent to the oral administration of an icariin suspension. This study aimed to preliminarily investigate the excretion profile of icariin in mice. Using an aqueous solution containing 0.1% formic acid (A) and an acetonitrile solution containing 0.1% formic acid (B) as the mobile phases, icariin and its major metabolites demonstrated satisfactory linearity over the concentration range of 0.25-800 ng·mL-1. The precision and accuracy of intra-day and inter-day measurements were all found to be within 15%. Seventy-two hours after the intragastric administration of icariin suspension to a mouse, the cumulative urinary excretion of icariin, icariside Ⅰ, icariside Ⅱ, baohuoside Ⅱ, wushanicaritin, icaritin, and desmethylicaritin was quantified as 13.48, 18.70, 2,627.51, 2.04, 10.04, 3,420.44, and 735.13 ng, respectively. The UPLC-MS/MS method developed in this research is characterized by its simplicity, sensitivity, and speed, making it well-suited for the concurrent quantification of icariin and its associated metabolites in urine. Additionally, it is appropriate for analyzing urine samples that may contain multiple drugs in future investigations.

Bioactive metabolites reveal the therapeutic consistency of epimedii folium from multi-plant sources for the treatment of kidney-yang deficiency

ETHNOPHARMACOLOGICAL RELEVANCE

Epimedii Folium (Yin-yang-huo in Chinese), a traditional and commonly used herbal medicine (HM), is a representative of multi-plant sources. To date, little is known about the reasons for similar therapeutic effects of this HM from multi-plant sources.

AIM OF THE STUDY

To investigate the underlying reasons for the similar pharmacological effects of Epimedii Folium from two botanical sources (Epimedium koreanum Nakai and Epimedium wushanense T. S. Ying).

MATERIALS AND METHODS

Firstly, the phytochemicals of the extracts of E. koreanum and E. wushanense were systematically analyzed. Meanwhile, their pharmacological effects on kidney-yang deficiency (KYD) syndrome were evaluated in rats induced by hydrocortisone. Subsequently, we proposed a combined effect index (CEI) to assess the effects of two plants on the secretion of testosterone by combing the system exposure of twelve active components in vivo with their regulation activities of testosterone production in vitro. Moreover, the label-free proteomics and Western blot analysis were conducted to evaluate the possible mechanism of Epimedii Folium from two botanical sources.

RESULTS

E. koreanum and E. wushanense exhibited similar pharmacological effects on KYD syndrome with promoting the mating behaviors and testosterone levels of rats, although there is a certain difference in the main components between two plants. The CEI analysis showed that there was no difference (P > 0.05) in the sum of CEIs of two Epimedium, indicating that their similar therapeutic effects are attributed to bioactive metabolites in vivo. Furthermore, Epimedii Folium can regulate testosterone production in rat Leydig cell via reversing expressions of key steroidogenic enzymes, such as steroidogenic acute regulatory protein (StAR) and 3β-hydroxysteroid dehydrogenase (3β-HSD).

CONCLUSION

Our results supply critical evidence for the similar pharmacological effects of two Epimedium species, acting by consistent bioactive components directly exposing in vivo, not chemical compositions presenting in herbs. It provides a reasonable scientific basis for understanding of the HMs originated from multi-plant sources for the same clinical application.

Sub-chronic toxicity of an aqueous extract of Epimedium sagittatum (Sieb. Et Zucc.) Maxim. in rats

Epimedium sagittatum (Sieb. et Zucc.) Maxim., a traditional medicinal plant in Asia, is widely used in clinical settings but its safety in vivo is unclear. This study investigated the sub-chronic toxicity of E. sagittatum aqueous extract to rats with a 13-week daily intragastric administration of 7.5, 15, or 30 g/kg. Nine constituents of the aqueous extract were identified by ultra-performance liquid chromatography (UPLC). Organ weights, organ coefficients, serum biochemistry parameters, histopathology, and metabolomic analysis were performed. In female rats, treatment increased the liver, thymus, and adrenal gland coefficients (p < 0.05). Liver, pancreas, and adrenal gland injury were observed. The levels of six metabolites were altered by the treatment (p < 0.05). In male rats, treatment altered liver, heart, and thymus coefficients (p < 0.05) and liver, adrenal gland, and heart injury were observed. The levels of 11 metabolites were altered (p < 0.05). The no-observed-adverse-effect level was not determined but would be below 7.5 g/kg in rats treated for 13 weeks. In female rats, E. sagittatum may injure the liver and pancreas and dysregulate the biosynthesis of phenylalanine, tyrosine, tryptophan, valine, leucine, and isoleucine and the metabolism of phenylalanine. In male rats, the extract may injure the liver and adrenal gland and dysregulate the biosynthesis of valine, leucine, and isoleucine and the metabolism of pyruvate.

Antiosteoporosis Effects, Pharmacokinetics, and Drug Delivery Systems of Icaritin: Advances and Prospects

Osteoporosis is a systemic skeletal disorder affecting over 200 million people worldwide and contributes dramatically to global healthcare costs. Available anti-osteoporotic drug treatments including hormone replacement therapy, anabolic agents, and bisphosphonates often cause adverse events which limit their long-term use. Therefore, the application of natural products has been proposed as an alternative therapy strategy. Icaritin (ICT) is not only an enzyme-hydrolyzed product of icariin but also an intestinal metabolite of eight major flavonoids of the traditional Chinese medicinal plant Epimedium with extensive pharmacological activities, such as strengthening the kidney and reinforcing the bone. ICT displays several therapeutic effects, including osteoporosis prevention, neuroprotection, antitumor, cardiovascular protection, anti-inflammation, and immune-protective effect. ICT inhibits bone resorption activity of osteoclasts and stimulates osteogenic differentiation and maturation of bone marrow stromal progenitor cells and osteoblasts. As for the mechanisms of effect, ICT regulates relative activities of two transcription factors Runx2 and PPARγ, determines the differentiation of MSCs into osteoblasts, increases mRNA expression of OPG, and inhibits mRNA expression of RANKL. Poor water solubility, high lipophilicity, and unfavorable pharmacokinetic properties of ICT restrict its anti-osteoporotic effects, and novel drug delivery systems are explored to overcome intrinsic limitations of ICT. The paper focuses on osteogenic effects and mechanisms, pharmacokinetics and delivery systems of ICT, and highlights bone-targeting strategies to concentrate ICT on the ideal specific site of bone. ICT is a promising potential novel therapeutic agent for osteoporosis.

Long term therapeutic effects of icariin‐loaded PLGA microspheres in an experimental model of optic nerve ischemia via modulation of CEBP ‐β/ G‐CSF /noncanonical NF‐ κ B axis

An ischemic insult at optic nerve (ON) is followed by detrimental neuroinflammation that results in progressive and long‐lasting retinal ganglion cell (RGC) death and vision loss. Icariin was reported to be a safe and effective natural anti‐inflammatory drug. Herein, we evaluated the long‐term therapeutic effects of a single intravitreal injection of poly(lactide‐co‐glycolide) PLGA–icariin in a rat model of anterior ischemic optic neuropathy (rAION). Treatment with PLGA microspheres of icariin preserved the visual function and RGC density for 1 month in the rAION model. In addition, ON edema and macrophage infiltration were inhibited by treating PLGA microspheres of icariin. We found that the binding complex of icariin and CCAAT enhancer binding protein beta (CEBP‐β) significantly induced endogenous granulocyte colony‐stimulating factor (G‐CSF) expression to activate noncanonical nuclear factor kappa B (NF‐κB) signaling pathway by promoting an alternative phosphorylation reaction of IKK‐β. Activation of noncanonical NF‐κB signaling pathway promoted the M2 microglia/macrophage polarization and AKT1 activation, which prevented neuroinflammation and RGC apoptosis after ON infarct. This study concluded that protective mechanism of icariin is a CEBP‐β/G‐CSF axis‐induced noncanonical NF‐κB activation, which provides the long‐term neuroprotective effects via anti‐inflammatory and antiapoptotic actions after ON ischemia.

Simultaneous Quantitative Analysis of Multiple Biotransformation Products of Xian-Ling-Gu-Bao, a Traditional Chinese Medicine Prescription, with Rat Intestinal Microflora by Ultra-Performance Liquid Chromatography Tandem Triple Quadrupole Mass Spectrometry

Xian-Ling-Gu-Bao (XLGB), a famous traditional Chinese medicine prescription consisted of six herbal medicines, was used for prevention and treatment of osteoporosis in China. As an oral formulation, the multiple components contained in XLGB were inevitably biotransformed by the intestinal microflora before absorption via the gastrointestinal tract. However, the dynamic profiles of biotransformation products of XLGB remain unknown. In this paper, a rapid and sensitive ultra-performance liquid chromatography tandem triple quadrupole mass spectrometry method was developed for the simultaneous quantitative analysis of multiple biotransformation products of XLGB with rat intestinal microflora. For 10 selected quantitative compounds, all calibration curves revealed good linearity (r2 &gt; 0.99) within the sampling ranges considered. The whole intra- and inter-day precisions (as relative standard deviation) of all analytes were &lt;13.5%, and the accuracies (as relative error) were in the range from −11.3 to 11.2%. The lower limits of quantification were 20, 10, 5, 20, 2, 2, 2, 5, 2 and 2 ng/mL for sweroside, timosaponin BII, epimedin C, asperosaponin VI, psoralen, isobavachin, icariside II, timosaponin AIII, isobavachalcone and icaritin, respectively. The matrix effects, extraction recoveries and stabilities were all satisfactory. Meanwhile, dynamic profiles of 21 additional biotransformation products were also monitored by their area-time curves. The analytical method was successfully applied to describe dynamic profiles of 31 biotransformation products of XLGB and the recipes with removal of a definite composed herbal medicine (Anemarrhenae Rhizoma or Rehmanniae Radix).

Pharmacokinetics and metabolism of icaritin in rats by UPLC-MS/MS

Icaritin (ICT) has distinct bioactivities, especially known for its beneficial effects on bone-related degenerative disorders; however, its pharmacokinetic properties remain unknown. A novel developed UPLC-MS/MS method for the determination of ICT and its main metabolite glucuronidated icaritin (GICT) was firstly applied to pharmacokinetic and metabolism studies of ICT in female rats, which were intraperitoneally given 40 mg/kg ICT. Following the protein precipitation of plasma samples with acetonitrile, ICT and GICT were separated on a C18 column using gradient elution mode and quantified in the multiple reaction monitoring mode. The linearities were acceptable for ICT (r = 0.9960) and GICT (r = 0.9968), and the lower limit of quantification values was 0.5 and 5 ng/ml, respectively. The accuracy fell in the range of 92.0%-103.1% and precisions were within 9.5%. Good linearity, accuracy, precision, and recovery were achieved for the UPLC-MS/MS method. ICT was predominantly and rapidly biotransformed to GICT which was slowly eliminated in vivo with a terminal half-life value of 4.51 hr. Pharmacokinetics of pure ICT eliminated biotransformation interference of Epimedium extract and disclosed genuine pharmacokinetic manner of ICT, as well as firstly elucidated low concentration and bioavailability of ICT in rat plasma.

Development and Validation of a HPLC-MS/MS Method for Simultaneous Determination of Twelve Bioactive Compounds in Epimedium: Application to a Pharmacokinetic Study in Rats

A rapid and reliable HPLC-MS/MS method has been developed and validated for the simultaneous quantification of twelve bioactive compounds (baohuoside II, baohuoside I, sagittatoside A, sagittatoside B, magnoflorine, epimedin A, epimedin B, epimedin C, chlorogenic acid, neochlorogenic acid, cryptochlorogenic acid and icariin) in rat plasma. The collected plasma samples were prepared by protein precipitate with acetonitrile. The twelve compounds were separated on a CORTECS^®C18 column (4.6 mm × 150 mm, 2.7 μm) with a gradient mobile phase system of 0.1% (v/v) formic acid and acetonitrile at a flow rate of 0.3 mL/min. All of the analytes were quantitated using electrospray ionization (ESI) in negative ion mode with selected reaction monitoring (SRM). The intra- and inter-day accuracy ranged from −5.6% to 13.0%, and the precisions of the analytes were less than 10.9%. The mean recoveries of the analytes were in the range of 60.66% to 99.77% and the matrix effect ranged from 93.08% to 119.84%. Stability studies proved that the analytes were stable under the tested conditions, with a relative standard deviation (RSD) lower than 11.7%. The developed method was successfully applied to evaluating the pharmacokinetic study of twelve bioactive compounds after oral administration of Epimedium extract in rat.

Oral absorption, distribution, metabolism, and excretion of icaritin in rats by Q-TOF and UHPLC-MS/MS

Icaritin (ICT) displays numerous pharmacological activities for the treatment of various cancers, osteoporosis, inflammation, and angiocardiopathy. The absorption, distribution, metabolism, and excretion of ICT still remain unknown. ICT was administered to rats at 2 mg/kg for intravenous injection or 40 mg/kg for oral route. Major metabolite of ICT was identified using quadrupole time-of-flight (Q-TOF), and ICT and its major metabolite were quantified in plasma, tissues, urine, faeces, and bile by ultra-high performance liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS). A total of 24 metabolites of ICT in plasma were identified and mono C-7 glucuronide glucuronidated icaritin (GICT) was the major metabolite of ICT after oral administration. The absolute bioavailability of ICT was 4.33% although ICT was rapidly absorbed into the blood. For oral administration, concentrations of GICT at various time points was 6.38-8.81-fold higher than those of ICT, and the area under the curve (AUC) of GICT was about 8-fold higher than that of ICT, while AUC values of ICT and GICT were almost equal for intravenous injection. Approximately 65.7% ICT and 42.7% GICT were distributed in liver and kidney, respectively. Unabsorbed ICT was mainly excreted as the parent form in faeces with at least 60% of administered dose during 24 h, whereas absorbed ICT was predominantly excreted as GICT from urine with 2.74% of administered dose accounting for 63.28% of absorbed drug. ICT was rapidly absorbed into the blood although a large amount of ICT remained unabsorbed, and then rapidly and mainly metabolized to GICT. ICT mainly distributed in liver, while GICT predominantly distributed in kidney. Absorbed ICT and GICT were predominantly excreted via urine, and unabsorbed ICT was mainly excreted as the parent form in faeces. Copyright © 2017 John Wiley & Sons, Ltd.

Anti-Cancer Properties of the Naturally Occurring Aphrodisiacs: Icariin and Its Derivatives

Epimedium (family Berberidaceae), commonly known as Horny Goat Weed or Yin Yang Huo, is commonly used as a tonic, aphrodisiac, anti-rheumatic and anti-cancer agent in traditional herbal formulations in Asian countries such as China, Japan, and Korea. The major bioactive compounds present within this plant include icariin, icaritin and icariside II. Although it is best known for its aphrodisiac properties, scientific and pharmacological studies suggest it possesses broad therapeutic capabilities, especially for enhancing reproductive function and osteoprotective, neuroprotective, cardioprotective, anti-inflammatory and immunoprotective effects. In recent years, there has been great interest in scientific investigation of the purported anti-cancer properties of icariin and its derivatives. Data from in vitro and in vivo studies suggests these compounds demonstrate anti-cancer activity against a wide range of cancer cells which occurs through various mechanisms such as apoptosis, cell cycle modulation, anti-angiogenesis, anti-metastasis and immunomodulation. Of note, they are efficient at targeting cancer stem cells and drug-resistant cancer cells. These are highly desirable properties to be emulated in the development of novel anti-cancer drugs in combatting the emergence of drug resistance and overcoming the limited efficacy of current standard treatment. This review aims to summarize the anti-cancer mechanisms of icariin and its derivatives with reference to the published literature. The currently utilized applications of icariin and its derivatives in cancer treatment are explored with reference to existing patents. Based on the data compiled, icariin and its derivatives are shown to be compounds with tremendous potential for the development of new anti-cancer drugs.

Preclinical studies and clinical evaluation of compounds from the genus Epimedium for osteoporosis and bone health

The morbidity and mortality associated with fractures due to osteoporosis or "porous bone" contributes significantly to global healthcare costs and will increase exponentially with ageing populations. In menopausal women, the onset of menopause and rapid estrogen withdrawal leads to osteoporotic fractures. Healthy bone requires the coordinated remodeling function of osteoclasts, osteoblasts, and osteocytes in the basic bone multicellular unit, regulated by estrogen, RANKL/OPG, ROS, growth factors, and other kinase signaling pathways. Anti-osteoporotic drugs in current use such as hormone replacement therapy, selective estrogen receptor modulators, and bisphosphonates are designed to target these pathways, but all have their limitations. Extracts of the dried aerial parts of the traditional Chinese medicinal plant Epimedium (Berberidaceae) has long been used for bone health. Some nine Epimedium prenylflavonoid compounds have been reported to target estrogen signaling and other bone morphogenesis pathways in mesenchymal stem cell, osteoblast, and osteoclast cell lineages. Epimedium prenylflavonoids and enriched extracts can exert beneficial effects on bone health in estrogen-deficient and other osteoporosis animal models. The development of sensitive and rapid mass chromatographic techniques to quantify compounds extracted from Epimedium, including icariin and icaritin, has been used to standardize production and to study the pharmacokinetics and metabolism of Epimedium in animal models and humans. Recent clinical trials have reported positive effects on bone health, suggesting that compounds or extracts of Epimedium have the potential to be developed as agents, alone or in combination with other drugs, to prevent or delay the onset of osteoporosis and reduce the risk of hip fractures.

Comparative Pharmacokinetics Study of Icariin and Icariside II in Rats

To explore the pharmacokinetic properties of icariin (ICA) and icariside II (ICA II) following intragastric and intravenous administration in rats, a rapid and sensitive method by using ultra-performance liquid chromatography–tandem mass spectroscopy (UPLC-MS/MS) was developed and validated for the simultaneous quantification of ICA and ICA II in rat plasma. The quantification was performed by using multiple reaction monitoring of the transitions m/z 677.1/531.1 for ICA, 515.1/369.1 for ICA II and 463.1/301.1 for diosmetin-7-O-β-d-glucopyranoside (IS). The assay showed linearity over the concentration range of 1.03–1032 ng/mL, with correlation coefficients of 0.9983 and 0.9977. Intra- and inter-day precision and accuracy were within 15%. The lower limit of quantification for both ICA and ICA II was 1.03 ng/mL, respectively. The recovery of ICA and ICA II was more than 86.2%. The LC-MS/MS method has been successfully used in the pharmacokinetic studies of ICA and ICA II in rats. The results indicated that 91.2% of ICA was transformed into ICA II after oral administration by rats, whereas only 0.4% of ICA was transformed into ICA II after intravenous administration. A comparison of the pharmacokinetics of ICA and ICA II after oral administration revealed that the C_max and AUC_0–t of ICA II were 3.8 and 13.0 times higher, respectively, than those of ICA. However, after intravenous administration, the C_max and AUC_0–t of ICA II were about only 12.1% and 4.2% of those of ICA. These results suggest that ICA and ICA II have distinct pharmacokinetic properties, and the insights obtained facilitate future pharmacological action studies.

Chemical Constituents, Quality Control, and Bioactivity of Epimedii Folium (Yinyanghuo)

Epimedii Folium (Yinyanghuo in Chinese) is one of the most commonly used traditional Chinese medicines. Its main active components are flavonoids, which exhibit multiple biological activities, such as promotion of bone formation and sexual function, protection of the nervous system, and prevention of cardiovascular diseases. Flavonoids also show anti-inflammatory and anticancer effects. Various effective methods, including genetic and chemical approaches, have been developed for the quality control of Yinyanghuo. In this review, the studies conducted in the last decade about the chemical constituents, quality control, and bioactivity of Yinyanghuo are summarized and discussed.

Targeting Apoptosis and Multiple Signaling Pathways with Icariside II in Cancer Cells

Cancer is the second leading cause of deaths worldwide. Despite concerted efforts to improve the current therapies, the prognosis of cancer remains dismal. Highly selective or specific blocking of only one of the signaling pathways has been associated with limited or sporadic responses. Using targeted agents to inhibit multiple signaling pathways has emerged as a new paradigm for anticancer treatment. Icariside II, a flavonol glycoside, is one of the major components of Traditional Chinese Medicine Herba epimedii and possesses multiple biological and pharmacological properties including anti-inflammatory, anti-osteoporosis, anti-oxidant, anti-aging, and anticancer activities. Recently, the anticancer activity of Icariside II has been extensively investigated. Here, in this review, our aim is to give our perspective on the current status of Icariside II, and discuss its natural sources, anticancer activity, molecular targets and the mechanisms of action with specific emphasis on apoptosis pathways which may help the further design and conduct of preclinical and clinical trials. Icariside II has been found to induce apoptosis in various human cancer cell lines of different origin by targeting multiple signaling pathways including STAT3, PI3K/AKT, MAPK/ERK, COX-2/PGE2 and β-Catenin which are frequently deregulated in cancers, suggesting that this collective activity rather than just a single effect may play an important role in developing Icariside II into a potential lead compound for anticancer therapy. This review suggests that Icariside II provides a novel opportunity for treatment of cancers, but additional investigations and clinical trials are still required to fully understand the mechanism of therapeutic effects to further validate it in anti-tumor therapy.

The profiling and identification of the metabolites of 8-prenylkaempferol and a study on their distribution in rats by high-performance liquid chromatography with diode array detection combined with electrospray ionization ion trap time-of-flight multistage mass spectrometry

8-Prenylkaempferol is a prenylflavonoid that has various bioactivities and benefits for human health. A high-performance liquid chromatography with a diode array detector combined with electrospray ionization ion trap time-of-flight multistage mass spectrometry (HPLC-DAD-ESI-IT-TOF-MS(n) ) method was established to profile and identify the metabolites of 8-prenylkaempferol in rat in vivo and in vitro, and to study the distribution of these metabolites in rats for the first time. A total of 38 metabolites were detected and tentatively identified, 30 of which were identified as new compounds. The new in vivo metabolic reactions in rats of prenylflavonoids of isomerization, polymerization, sulfation, amino acid conjugation, vitamin C conjugation and other known metabolic reactions were found in the metabolism of 8-prenylkaempferol. The numbers of detected metabolites in feces, urine, plasma, small intestine, stomach, kidneys, liver, heart, lungs, spleen and hepatic S9 fraction were 31, 19, 1, 20, 13, 8, 7, 3, 3, 1 and 11, respectively. This indicated that small intestine and stomach were the major organs in which the 8-prenylkaempferol metabolites were distributed. Furthermore, 16 metabolites were determined to have bioactivities based on the literature and 'PharmMapper' analysis. These findings are useful for better comprehension of the effective forms, target organs and pharmacological actions of 8-prenylkaempferol. Moreover, they provide a reference for the study of the metabolism and distribution of prenylflavonoid aglycone compounds.

Pharmacological effects and pharmacokinetic properties of icariin, the major bioactive component in Herba Epimedii

Herba Epimedii is an important medicinal plant which has been used in various traditional Chinese formulations for thousands of years as well as in modern proprietary traditional Chinese medicine products. It has extensive clinical indications, especially for the treatment of sexual dysfunction and osteoporosis. There have been more than 260 chemical moieties identified in the genus Epimedium most of which belong to flavonoids. Icariin is the most abundant constituent in Herba Epimedii. Icariin is pharmacologically bioactive and demonstrates extensive therapeutic capacities such as osteoprotective effect, neuroprotective effect, cardiovascular protective effect, anti-cancer effect, anti-inflammation effect, immunoprotective effect and reproductive function. Particularly, the significant osteogenic effect of icariin made it a promising drug candidate in bone tissue engineering. The current review paper aims to summarize the literatures reporting the pharmacological effects of icariin. The pharmacokinetic properties of bioactive ingredients in Herba Epimedii have also been discussed.

Biodistribution evaluation of icaritin in rats by ultra-performance liquid chromatography-tandem mass spectrometry

ETHNOPHARMACOLOGICAL RELEVANCE

Icaritin (ICT) is a major bioactive prenylflavonoid derivative contained in the Epimedium which is a widely used herbal medicine for the treatment of infertility, impotence, cardiovascular and skeletal diseases listed in the Chinese Pharmacopoeia. The aim of this study is to investigate the tissue distribution of ICT in rats by ultra-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) MATERIALS AND METHODS: ICT was intraperitoneally administrated to rats for 7 consecutive days at dose levels of 20, 40 and 60 mg/kg/day, respectively. Various tissue homogenates were pretreated by protein precipitation with acetonitrile. ICT and internal standard coumestrol were separated on a BEH C18 column with a gradient mobile phase and detected using precursor-product ion transitions of m/z 367.1→297.1 for ICT and 267.0→211.1 for coumestrol at the negative ionization mode, respectively.

RESULTS

ICT was widely distributed in rat's various tissues and its concentrations in tissues increased with elevated doses. A sensitive and reliable UPLC-MS/MS method was firstly established to quantify ICT in rat tissues. The lower limit of quantification was 0.5 ng/mL based on 100 μL of tissue homogenates. The intra- and inter-day accuracy at all levels fell in the ranges of 90.8-103.4% and 91.6-100.3%, and the intra- and inter-day precision (RSD) were in the ranges of 2.9-10.5% and 2.6-9.1%, respectively.

CONCLUSIONS

The UPLC-MS/MS showed good accuracy, precision and recovery and was suitable for the quantification of ICT in rat tissues. Wide distribution of ICT could helpfully elucidate systemic effects and various functions of ICT.

Icariin stimulates the osteogenic differentiation of rat bone marrow stromal cells via activating the PI3K-AKT-eNOS-NO-cGMP-PKG

Icariin, a prenylated flavonol glycoside isolated from Epimedii herba, has been found to be a potent stimulator of osteogenic differentiation and has potential application in preventing bone loss. However, the signaling pathway underlying its osteogenic effect remains unclear. We hypothesized that the osteogenic activity of icariin is related to the nitric oxide (NO) signal pathway and PI3K/AKT pathway in its upstream. Rat bone marrow stromal cells (rBMSCs) were cultured in osteogenic medium and treated with icariin or together with L-NAME, ODQ, PDE5, and/or LY294002 (the inhibitor of NOS, sGC, cGMP, and PI3K respectively), and effects were examined on the expression of signal messengers (NOS, NO, sGC, cGMP, PKG and PI3K) and the levels of osteogenic markers (alkaline phosphatase or ALP, osteocalcin and calcified nodules). It was found that icariin dose-dependently increased ALP activity, and treatment at the optimal concentration (10(-5)M) increased NOS activity, iNOS and eNOS expression, NO production, sGC and cGMP contents and PKG expression besides the phosphorylation of AKT. The addition of L-NAME, ODQ and PDE5 significantly inhibited the icariin effects on above markers respectively. The addition of LY294002 decreased the p-AKT level, NOS activity, eNOS expression and NO production significantly, but had no significant effect on iNOS expression. The addition of any of the four inhibitors also abolished the osteogenic effect of icariin on rBMSCs as indicated by ALP activity, osteocalcin synthesis, calcium deposition and the number and areas of calcified nodules. These results suggest that the osteogenic effect of icariin involves the PI3K-AKT-eNOS-NO-cGMP-PKG signal pathway. Furthermore, dosage response studies showed that icariin at 10(-6)M (a physiologically achievable concentration in vivo) also activated this signal pathway.

Herb-drug interaction of Epimedium sagittatum (Sieb. et Zucc.) maxim extract on the pharmacokinetics of sildenafil in rats

Epimedium sagittatum (Sieb. et Zucc.) Maxim is one of the herbs used to treat erectile dysfunction in Traditional Chinese Medicine. Sildenafil is a phosphodiesterase 5 inhibitor used to treat erectile dysfunction in Western Medicine. This study evaluates the herbal-drug interaction of Epimedium sagittatum extract on the pharmacokinetics of sildenafil in rats by ultra-performance liquid chromatography. The rat plasma was sampled from each anesthetized rat after pretreatment with 3-days Epimedium sagittatum extract (1/2 g/kg/day) and intravenous injection with sildenafil (10/30 mg/kg). The pharmacokinetic data demonstrate that the area under the concentration-time curve (AUC) of sildenafil (10 mg/kg) was significantly decreased in groups that received a high dose of Epimedium sagittatum extract. In conclusion, the study demonstrates that there was significant herb-drug interaction of Epimedium sagittatum extract on the pharmacokinetics of sildenafil at low and high daily doses, suggesting co-administration use of Epimedium sagittatum extract and sildenafil in clinical practice should be prevented due to possible herb-drug interactions.

Recent developments in the field of the determination of constituents of TCMs in body fluids of animals and human

Although traditional Chinese medicines (TCMs) play important role in drug discovery and human health, the actual value of TCMs has not been fully recognized worldwide due to its complex components and uncontrollable quality. For the modernization and globalization of TCMs, it is important to establish selective, sensitive and feasible analytical methods for determination and quantification of bioactive components of TCMs in body fluids primarily due to the low concentration, the complex nature of the biological matrices, and multi-components and their metabolites present in biological fluids. The present review summarizes the current extraction techniques, chromatographic separation and spectroscopic (especially mass spectrometric) analysis methods and new trends on the analysis of bioactive components and metabolites of TCMs in biological fluids. In addition, the importance of establishment of pharmacokinetics and bioavailability profiles and simultaneous determination of multi-active components in TCMs is discussed to provide proper examples of analytical methods for pharmacological and clinical studies of TCMs.

Functions and action mechanisms of flavonoids genistein and icariin in regulating bone remodeling

Increasingly natural products particularly flavonoids are being explored for their therapeutic potentials in reducing bone loss and maintaining bone health. This study has reviewed previous studies on the two better known flavonoids, genistein and icariin, their structures, functions, action mechanisms, relative potency, and potential application in regulating bone remodeling and preventing bone loss. Genistein, an isoflavone abundant in soy, has dual functions on bone cells, able to inhibit bone resorption activity of osteoclasts and stimulate osteogenic differentiation and maturation of bone marrow stromal progenitor cells (BMSCs) and osteoblasts. Genistein is an estrogen receptor (ER)-selective binding phytoestrogen, with a greater affinity to ERβ. Genistein inhibits tyrosine kinases and inhibits DNA topoisomerases I and II, and may act as an antioxidant. Genistein enhances osteoblastic differentiation and maturation by activation of ER, p38MAPK-Runx2, and NO/cGMP pathways, and it inhibits osteoclast formation and bone resorption through inducing osteoclastogenic inhibitor osteoprotegerin (OPG) and blocking NF-κB signaling. Icariin, a prenylated flavonol glycoside isolated from Epimedium herb, stimulates osteogenic differentiation of BMSCs and inhibits bone resorption activity of osteoclasts. Icariin, whose metabolites include icariside I, icariside II, icaritin, and desmethylicaritin, has no estrogenic activity. However, icariin is more potent than genistein in promoting osteogenic differentiation and maturation of osteoblasts. The existence of a prenyl group on C-8 of icariin molecular structure has been suggested to be the reason why icariin is more potent than genistein in osteogenic activity. Thus, the prenylflavonoids may represent a class of flavonoids with a higher osteogenic activity.

Oral absorption and excretion of icaritin, an aglycone and also active metabolite of prenylflavonoids from the Chinese medicine Herba Epimedii in rats

Icaritin (ICT) is a main aglycone and also active intestinal metabolite of prenylflavonoids from the Chinese medicine Herba Epimedii. In the present study, the oral absorption and excretion of this compound was investigated using rats for exploring its fate in the body, so as to better understanding its in vivo pharmacological activities. The free (parent) and total (parent plus conjugated metabolites) ICT concentrations in rat plasma, urine and bile, after intravenous (i.v.) and oral administration both at 5mg/kg, were determined before and after enzymatic hydrolysis with β-glucuronidase/sulphatase, respectively, by a HPLC-UV method. The results showed that free ICT plasma concentration after i.v. dose was rapidly decreased with average t(1/2, λ) of 0.43 h, while the total ICT concentration was decreased slowly with t(1/2, λ) of 6.86 h. The area under the curve of ICT conjugated metabolites was about 11-fold higher than that of free ICT. The majority of ICT in the body was excreted from the bile with 68.05% of dose over 8 h after i.v. dosing, in which only 0.15% was in parent form. While very little amount of ICT was excreted from the urine with 3.01% of dose over 24 h, in which the parent form was 0.62%. After oral administration, very little amount of parent ICT was detected only in 0.5, 1 or 2 h plasma samples with the concentration less than LOQ, however, its total plasma concentration after enzymatic hydrolysis treatment was at relative high level with average maximum concentration of 0.49 μg/ml achieved at 1h post dose. The oral bioavailability of ICT was 35% of dose, estimated by its total plasma drug concentrations. It is concluded that ICT can be easily absorbed into the body, and then rapidly conversed to its conjugated metabolites, and finally removed from the body mainly by biliary excretion.

Metabolite profiling of four major flavonoids of Herba Epimedii in zebrafish

The zebrafish model organism was applied first in a metabolic study of icariin, baohuoside I, epimedin A and epimedin C, which are flavonoids in Herba Epimedii. Metabolites of these compounds in zebrafish after exposure for 24 h were identified by HPLC-ESI-MS, whereby the separation was performed with a Zorbax C-18 column using a gradient elution of 0.05% formic acid acetonitrile-0.05% formic acid water. The quasi-molecular ions of compounds were detected in simultaneous negative and positive ionization modes. Metabolic products of icariin and epimedin C via cleavage of glucose residue instead of rhamnose residues were found, which coincided with the results using regular metabolic analysis methods. In addition, the zebrafish model was used to predict the metabolism of the trace component epimedin A, whose metabolic mechanisms haven't been clearly elucidated with the current metabolism model. The metabolic pathway of epimedin A in zebrafish was similar to those of its homologue icariin and epimedin C. Our study demonstrated that the zebrafish model can successfully imitate the current models in elucidating metabolic pathways of model flavonoids, which has advantages of lower cost, far less amount of compound needed, easy set up and high performance. This novel model can also be applied in quickly predicting the metabolism of Chinese herb components, especially trace compounds.

Analysis of biliary excretion of icariin in rats

Icariin is a bioactive herbal ingredient isolated from Epimedii Herba. This study evaluates the distribution of icariin in rats by microdialysis sampling and high-performance liquid chromatography with ultraviolet detection (HPLC-UV). Microdialysis probes were simultaneously placed in the jugular vein, brain striatum, and bile duct of each anesthetized rat for sampling after the administration of icariin (dose=10 or 20 mg/kg) via the femoral vein. The role of P-glycoprotein (P-gp) on icariin distribution was assessed by pretreatment with cyclosporine (CsA, dose=20 mg/kg). This study is the first report of the biliary excretion of icarin in rats, defined as the blood-to-bile distribution (k value), calculated by dividing the area under the concentration-time curve (AUC) of icariin in bile by that in blood (k=AUCbile/AUCblood). The k values were 19.0±5.9 and 18.8±3.8 at the doses of 10 and 20 mg/kg, respectively. The decreased biliary excretion of icariin due to pretreatment with CsA was evidenced by the reduced k values (18.8±3.8 vs 9.9±1.9, p=0.005). This work demonstrates that biliary excretion is the major elimination pathway for icariin disposition and that transporters, such as P-gp, might be related to icariin's biliary excretion.

A rapid screening method for prenylated flavonoids with ultra-high-performance liquid chromatography/electrospray ionisation mass spectrometry in licorice root extracts

Due to their substitution with an isoprenoid group, prenylated flavonoids have an increased affinity for biological membranes and target proteins, enhancing their potential bioactivity. Although many prenylated flavonoids have been described, there are no methods that specifically screen for their presence in complex mixtures, prior to purification. We describe a method based on ultra-high-performance liquid chromatography (UHPLC) with electrospray ionisation mass spectrometry (ESI-MS) that allows rapid screening for prenylated flavonoids in multi-component plant extracts. Identification of the prenylated flavonoids is based on screening for neutral losses of 42 u and 56 u in the positive-ion mode MS(2) and MS(3) spectra within the MS chromatograms. In addition, this method discriminates between a prenyl chain and a ring-closed prenyl (pyran ring), based on the ratio of the relative abundances of the ions that lose 42 u and 56 u (42:56). The application of this screening method on a 70% aq. ethanol, ethanol and ethyl acetate extract of the roots of Glycyrrhiza glabra indicated the presence of 70 mono- and di-prenylated flavonoids. In addition, of each prenylated flavonoid the type of prenylation, chain or pyran ring was determined.