Effect of valerian, valerian/hops extracts, and valerenic acid on glucuronidation in vitro

The physiology of bilirubin: health and disease equilibrium

Bilirubin has several physiological functions, both beneficial and harmful. In addition to reactive oxygen species-scavenging activities, bilirubin has potent immunosuppressive effects associated with long-term pathophysiological sequelae. It has been recently recognized as a hormone with endocrine actions and interconnected effects on various cellular signaling pathways. Current studies show that bilirubin also decreases adiposity and prevents metabolic and cardiovascular diseases. All in all, the physiological importance of bilirubin is only now coming to light, and strategies for increasing plasma bilirubin levels to combat chronic diseases are starting to be considered. This review discusses the beneficial effects of increasing plasma bilirubin, incorporates emerging areas of bilirubin biology, and provides key concepts to advance the field.

Valerenic Acid Promotes Adipocyte Differentiation, Adiponectin Production, and Glucose Uptake via Its PPARγ Ligand Activity

Although valerenic acid (VA) is an important marker compound for quantitative assessment of Valeriana officinalis products, little is known about its potential effects on adipocytes. We investigated the effects of VA on adipocyte differentiation, adiponectin production, and glucose uptake using 3T3-L1 adipocytes. The results showed that VA promoted adipocyte differentiation and increased the gene expression of adipogenesis and glucose uptake-related proteins, including peroxisome proliferator-activated receptor gamma (PPARγ), cytosine-cytosine-adenosine-adenosine-thymidine enhancer binding protein alpha (C/EBPα), adiponectin, and glucose transporter 4 (GLUT4). Additionally, cell cultures treated with VA had elevated adiponectin secretion and glucose uptake. The PPARγ luciferase assay indicated VA as a partial agonist of PPARγ, while the analysis using its antagonist, GW9662, and a docking simulation between PPARγ and VA revealed the binding site of VA as likely adjacent to the Ω loop pocket of PPARγ. Taken together, these results demonstrate that VA acts as a PPARγ partial agonist to promote adipocyte differentiation, adiponectin production, and glucose uptake.

The effect of supplementation with Scutellaria baicalensis on hepatic function

The dried root of the angiosperm Scutellaria baicalensis, also known as Chinese skullcap or Baikal skullcap, is widely used in traditional Chinese medicine, Korean traditional medicine and as a nutritional supplement; several studies have indicated that both the supplement and some of its ingredients may have clinically beneficial actions. However, the National Institutes of Health official guidance states that the use of Scutellaria "has been implicated in rare instances of clinically apparent liver injury" and that "the onset of symptoms and jaundice occurred within 6-24 weeks of starting skullcap, and the serum enzyme pattern was typically hepatocellular", with marked increases in serum alanine transaminase, aspartate transaminase, alkaline phosphatase and bilirubin levels. Careful perusal of all such published case reports showed that in each case the patient was concurrently taking at least one other supplement which had an established association with hepatic dysfunction. The authors hypothesised that long-term supplementation with Scutellaria baicalensis does not lead to hepatic dysfunction. The aim of this study was to test this hypothesis by assessing liver function before and after starting supplementation with Scutellaria baicalensis. Pre- and post-supplementation serum assays of alanine transaminase, aspartate transaminase, alkaline phosphatase and bilirubin were carried out in 17 patients (16 female) of average age 38.6 (standard error 4.4) years who had each taken 1335 mg dried root daily for an average of 444 (71) days. The mean baseline versus follow-up values for each liver function test were: alanine transaminase: 25.7 (2.6) IU/L v. 25.1 (1.7) IU/L; aspartate transaminase: 22.1 (1.1) IU/L v. 23.5 (1.3) IU/L; alkaline phosphatase: 63.7 (4.6) IU/L v. 63.3 (3.9) IU/L; and bilirubin: 6.1 (0.6) μM v. 6.0 (0.7) μM. None of these changes was statistically significant; indeed, three of the four parameters showed a non-significant decrease over time. Furthermore, none manifested clinical symptoms or signs of hepatic dysfunction during Scutellaria supplementation. These results suggest that daily intake of a relatively high level of Scutellaria baicalensis for over a year is not associated with any biochemical or clinical evidence of hepatic dysfunction. Indeed, Scutellaria baicalensis has been shown in murine experiments to have hepatoprotective actions.

Induction of Mild Hyperbilirubinemia: Hype or Real Therapeutic Opportunity?

Observational epidemiological studies showed that mild hyperbilirubinemia has beneficial effects on the prevention of cardiovascular disease, type 2 diabetes mellitus, and metabolic syndrome. In mammals, bilirubin plays a major role as a potent antioxidant. Uridine 5'-diphospho-glucuronosyl transferase (UGT)1A1 variants coding for bilirubin UDP-glucuronosyl transferase resulting in mild hyperbilirubinemia (as in Gilbert syndrome (GS)) may confer a strong genetic advantage. Strategies to boost bioavailability of bilirubin or to mimic GS represent an attractive approach to prevent many oxidative stress and inflammation-mediated diseases. Even a tiny, micromolar increase in serum bilirubin concentrations substantially decreases the risk of oxidative stress-mediated diseases. There are several possible ways to achieve this, including lifestyle changes, changes in dietary patterns, regular physical activities, or use of chemical drug or of specific plant products either in the form of regular food items or nutraceuticals. Further basic and experimental research is required to fully uncover this promising therapeutic field.

Valerian: no evidence for clinically relevant interactions

In recent popular publications as well as in widely used information websites directed to cancer patients, valerian is claimed to have a potential of adverse interactions with anticancer drugs. This questions its use as a safe replacement for, for example, benzodiazepines. A review on the interaction potential of preparations from valerian root (Valeriana officinalis L. root) was therefore conducted. A data base search and search in a clinical drug interaction data base were conducted. Thereafter, a systematic assessment of publications was performed. Seven in vitro studies on six CYP 450 isoenzymes, on p-glycoprotein, and on two UGT isoenzymes were identified. However, the methodological assessment of these studies did not support their suitability for the prediction of clinically relevant interactions. In addition, clinical studies on various valerian preparations did not reveal any relevant interaction potential concerning CYP 1A2, 2D6, 2E1, and 3A4. Available animal and human pharmacodynamic studies did not verify any interaction potential. The interaction potential of valerian preparations therefore seems to be low and thereby without clinical relevance. We conclude that there is no specific evidence questioning their safety, also in cancer patients.

An overview of the evidence and mechanisms of herb-drug interactions

Despite the lack of sufficient information on the safety of herbal products, their use as alternative and/or complementary medicine is globally popular. There is also an increasing interest in medicinal herbs as precursor for pharmacological actives. Of serious concern is the concurrent consumption of herbal products and conventional drugs. Herb-drug interaction (HDI) is the single most important clinical consequence of this practice. Using a structured assessment procedure, the evidence of HDI presents with varying degree of clinical significance. While the potential for HDI for a number of herbal products is inferred from non-human studies, certain HDIs are well established through human studies and documented case reports. Various mechanisms of pharmacokinetic HDI have been identified and include the alteration in the gastrointestinal functions with consequent effects on drug absorption; induction and inhibition of metabolic enzymes and transport proteins; and alteration of renal excretion of drugs and their metabolites. Due to the intrinsic pharmacologic properties of phytochemicals, pharmacodynamic HDIs are also known to occur. The effects could be synergistic, additive, and/or antagonistic. Poor reporting on the part of patients and the inability to promptly identify HDI by health providers are identified as major factors limiting the extensive compilation of clinically relevant HDIs. A general overview and the significance of pharmacokinetic and pharmacodynamic HDI are provided, detailing basic mechanism, and nature of evidence available. An increased level of awareness of HDI is necessary among health professionals and drug discovery scientists. With the increasing number of plant-sourced pharmacological actives, the potential for HDI should always be assessed in the non-clinical safety assessment phase of drug development process. More clinically relevant research is also required in this area as current information on HDI is insufficient for clinical applications.

Herbal remedies, mood, and cognition

Herbal medicines were the "sole" source of medicine for thousands of years, in every culture since the advent of human civilization. Today, patients are increasing the use of these botanicals for numerous conditions, such as mood and cognition. This article will explore commonly used herbal remedies for mood and cognition functioning. It is imperative that nurses and nurse practitioners obtain expertise with these botanicals with regard to efficacy, adverse effects and contraindications, possible drug interactions, and safety considerations.

Effects of Andrographis paniculata and Orthosiphon stamineus extracts on the glucuronidation of 4-methylumbelliferone in human UGT isoforms

The effects of Andrographis paniculata and Orthosiphon stamineus extracts on the in vitro glucuronidation of 4-methylumbelliferone (4MU) by recombinant human UGTs, UGT1A1, UGT1A3, UGT1A6, UGT1A7, UGT1A8, UGT1A10, UGT2B7 and UGT2B15 were determined. The potential inhibitory effects of both of the extracts on the activity of each of the UGT isoforms were investigated using 4MU as the substrate. Incubations contained UDP-glucuronic acid (UDPGA) as the cofactor, MgCl₂, cell lysate of respective isoform, and 4MU at the approximate apparent K_m or S₅₀ value of each isoform. Final concentrations of Andrographis paniculata and Orthosiphon stamineus extracts used were 0.025, 0.25, 2.5, 25 and 50 μg/mL and 0.01, 0.10, 1.0, 10 and 50 μg/mL respectively. Both extracts variably inhibited the activity of most of the isoforms in a concentration dependent manner. Andrographis paniculata extract was the better inhibitor of all the isoforms studied (IC₅₀ 1.70 μg/mL for UGT1A3, 2.57 μg/mL for UGT1A8, 2.82 μg/mL for UGT2B7, 5.00 μg/mL for UGT1A1, 5.66 μg/mL for UGT1A6, 9.88 μg/mL for UGT1A7 and 15.66 μg/mL for UGT1A10). Both extracts showed less than 70% inhibition of UGT2B15, so the IC₅₀ values were >50μg/mL. The inhibition of human UGTs by Andrographis paniculata and Orthosiphon stamineus extracts in vitro suggests a potential for drug-herbal extract interactions in the therapeutic setting.

Hepatic metabolism and biliary excretion of valerenic acid in isolated perfused rat livers: role of Mrp2 (Abcc2)

The study was designed to investigate the hepatic metabolism and transport system of valerenic acid, a main active constituent of valerian, in isolated perfused livers from Wistar and Mrp2-deficient TR(-) rats. After administration of 20 microM valerenic acid, the formation of seven valerenic acid glucuronides (M1-M7), namely two glucuronides of valerenic acid (M6, M7), four glucuronides of hydroxylated valerenic acid (M1, M3, M4, M5), and one glucuronide of hydroxylated dehydro-valerenic acid (M2) in bile and perfusate was quantified by HPLC. The hepatic extraction ratio and clearance of valerenic acid were very high in Wistar and TR(-) rats (E: 0.983 +/- 0.006 vs. 0.981 +/- 0.004; Cl: 35.4 +/- 0.21 mL/min vs. 35.3 +/- 0.14 mL/min). However, biliary excretion and efflux of conjugates differed greatly in TR(-) rats. While cumulative biliary excretion of unconjugated valerenic acid and the glucuronides M1-M7 dropped dramatically to 1-9%, their efflux into perfusate increased 1.5- to 10-fold. This indicates that valerenic acid and its glucuronides are eliminated into bile by Mrp2. In summary, valerenic acid was metabolized to several conjugates, whereby the canalicular transporter Mrp2 mediated biliary excretion of the parent drug and its glucuronides.