Major furocoumarins in grapefruit juice II: Phototoxicity, photogenotoxicity, and inhibitory potency vs. cytochrome P450 3A4 activity

Bergaptol, a Major Furocoumarin in Citrus: Pharmacological Properties and Toxicity

Bergaptol (5-hydroxypsoralen or 5-hydroxyfuranocoumarin) is a naturally occurring furanocoumarin widely found in citrus fruits, which has multiple health benefits. Nonetheless, no specific review articles on bergaptol have been published. Compiling updated information on bergaptol is crucial in guiding future research direction and application. The present review focuses on the research evidence related to the pharmacological properties and toxicity of bergaptol. Bergaptol has anti-inflammatory, antioxidant, anti-cancer, anti-osteoporosis, anti-microbial, and anti-lipidemic effects. It can inhibit the activities of cytochrome P450s (CYP), especially CYP2C9 and CYP3A4, thereby affecting the metabolism and concentrations of some drugs and toxins. Compared with other coumarins, bergaptol has the least potency to inhibit CYP3A4 in cancer cells. Instead, it can suppress drug efflux transporters, such as P-glycoprotein, thereby overcoming chemotherapeutic drug resistance. Furthermore, bergaptol has antimicrobial effects with a high potential for inhibition of quorum sensing. In vivo, bergaptol can be retained in plasma for longer than other coumarins. Nevertheless, its toxicity has not been clearly reported. In vitro study suggests that, unlike most furocoumarins, bergaptol is not phototoxic or photomutagenic. Existing research on bergaptol has mostly been conducted in vitro. Further in vivo and clinical studies are warranted to identify the safe and effective doses of bergaptol for its multimodal application.

Furocoumarins potentiate UVA-induced DNA damage in skin melanocytes

Epidemiological studies have found that high citrus fruit consumption was associated with higher risk of skin cancer. Citrus fruits and some vegetables contain furocoumarins, which may interact with ultraviolet radiation to induce skin cancer. We aimed to determine the effects of two furocoumarins, including 8-methoxypsoralen (8-MOP) and 6',7'-dihydroxybergamottin (DHB), on UVA-induced DNA damage in human epidermal melanocytes, the origin of melanoma. Our hypothesis was that these dietary furocoumarins increase UVA-induced DNA damage in melanocytes, compared to cells exposed to UV alone. We incubated melanocytes with 8-MOP or DHB, followed by exposure to physiological doses of UVA radiation. We used Western blots to quantify the UVA-induced DNA damage measured by the fraction of phosphorylated histone variant H2AX (γH2AX), which is a marker of DNA damage, relative to total H2AX (γH2AX/H2AX) in the presence or absence of furocoumarins. To quantify the UVA-induced change in γH2AX/H2AX, we calculated the UVA:Control ratio as the ratio of γH2AX/H2AX in UVA-exposed cells to that in cells without UVA (control). The mean UVA:Control ratios were borderline significantly higher for cells treated with 8-MOP and significantly higher for cells treated with DHB, compared to that of untreated cells. This study suggests that furocoumarins (particularly 8-MOP and DHB) enhance UVA-induced DNA damage in melanocytes, which is a potential novel mechanism for citrus and furocoumarins to elevate the risk of skin cancer.

Bergamottin: location, aggregation and interaction with the plasma membrane

Bioactive furanocoumarins, a group of natural secondary metabolites common in higher plants, are recognized for their benefits to human health and have been shown to have numerous biological properties. However, the knowledge of its biomolecular mechanism is not known. One of the main furanocoumarins is bergamottin (BGM), which is characterized by a planar three-ringed structure and a hydrocarbon chain, which give BGM its high lipid/water partition coefficient. Because of that, and although the biological mechanism of BGM is not known, BGM bioactive properties could be ascribed to its potential to interact with the biological membrane, modulating its structure, changing its dynamics and at the same time that it might interact with lipids. For our goal, we have applied molecular dynamics to determine the position of BGM in a complex membrane and discern the possibility of certain interactions with membrane lipids. Our findings establish that BGM tends to locate in the middle of the hydrocarbon layer of the membrane, inserts in between the hydrocarbon chains of the phospholipids in an oblique position with respect to the membrane plane, increasing the fluidity of the membrane. Significantly, BGM tends to be surrounded by POPC molecules but exclude the molecule of CHOL. Outstandingly, BGM molecules associate spontaneously creating aggregates, which does not preclude them from interacting with and inserting into the membrane. The bioactive properties of BGM could be ascribed to its membranotropic effects and support the improvement of these molecules as therapeutic molecules, giving place to new opportunities for potential medical improvements.Communicated by Ramaswamy H. Sarma.

Pyrimethamine induces phototoxicity in human keratinocytes via lysosomal and mitochondrial dependent signaling pathways under environmental UVA and UVB exposure

Pyrimethamine (PYR) is used to treat parasitic infections including toxoplasmosis, pneumonia and cystoisosporiasis in HIV patients. Various oral medicines have shown phototoxicity therefore, we aimed to study the phototoxicity of PYR and its molecular mechanism involving stress responsive lysosomal protein Lamp2 and mitochondrial mediated signaling pathway under normal UVA/B exposure. We found that photodegradation and subsequent photoproduct formation was evident through LCMS/MS analysis. Photosensitized PYR produces ROS that cause damage to DNA, cell membrane and membrane bound organelles in human keratinocytes. PYR triggered cytotoxicity and phototoxicity that was evident through MTT and NRU assay respectively. Intracellular ROS generation caused phosphatidyl serine (PS) translocation in cell membrane, lysosome membrane permeabilization (LMP) and mitochondrial membrane potential (MMP) collapse that was further validated through caspase3 activation. DNA damage was measured as tail DNA formation and cell cycle arrest in G1 phase. Photosensitized PYR induces oxidative stress in the form of overexpression of Lamp2 that ultimately led to cellular apoptosis. Moreover, the effects of UVB were higher than UVA, probably due to its direct interaction with various macromolecules. We propose that photoexcited PYR may be harmful to human health even at normal sunlight exposure. Therefore, protective procedures should be practiced during PYR medication.

Mechanistic study of bergamottin-induced inactivation of CYP2C9

Bergamottin (BGM) is a major furanocoumarin constituent of grapefruit and is reported to have inhibitory effects on cytochrome P450 enzymes. This study investigated the chemical interactions between BGM and the enzyme CYP2C9. BGM exhibited time-, concentration-, and NADPH-dependent inhibition of CYP2C9. Co-incubation with diclofenac, a reversible inhibitor of CYP2C9, attenuated the time-dependent enzyme inhibition. Exhaustive dialysis did not restore enzyme activity post-inhibition. Glutathione (GSH) and catalase/superoxide dismutase failed to reverse BGM-induced CYP2C9 inactivation. A GSH trapping study suggested that BGM was metabolized to an epoxide and/or γ-ketoenal that may have been responsible for the enzyme inactivation. In conclusion, BGM can be characterized as a mechanism-based inactivator of CYP2C9 acting via the formation of an epoxide and/or γ-ketoenal.

Food constituent- and herb-drug interactions in oncology: Influence of quantitative modelling on Drug labelling

AIMS

Herbal products, spices and/or fruits are perceived as inherently healthy; for instance, St. John's wort (SJW) is marketed as a natural antidepressant and patients often self-administer it concomitantly with oncology medications. However, food constituents/herbs can interfere with drug pharmacokinetics, with risk of altering pharmacodynamics and efficacy. The objective of this work was to develop a strategy to prioritize herb- or food constituent-drug interactions (FC-DIs) to better assess oncology drug clinical risk.

METHODS

Physiologically based pharmacokinetic (PBPK) models were developed by integrating in vitro parameters with the clinical pharmacokinetics of food constituents in grapefruit juice (bergamottin), turmeric (curcumin) or SJW (hyperforin). Perpetrator files were linked to verified victim PBPK models through appropriate interaction mechanisms (cytochrome P450 3A, breast cancer resistance protein, P-glycoprotein) and applied in prospective PBPK simulations to inform the likelihood and magnitude of changes in exposure to osimertinib, olaparib or acalabrutinib.

RESULTS

Reported FC-DIs with oncology drugs were well recovered, with absolute average fold error values of 1.10 (bergamottin), 1.05 (curcumin) and 1.01 (hyperforin). Prospective simulations with grapefruit juice and turmeric showed clinically minor to insignificant changes in exposure (<1.50-fold) to acalabrutinib, osimertinib and olaparib, but predicted 1.57-fold FC-DI risk between acalabrutinib and curcumin. Moderate DDI risk was expected when acalabrutinib, osimertinib or olaparib were dosed with SJW.

CONCLUSIONS

A model-informed decision tree based on mechanistic understanding of transporter and/or enzyme-mediated FC-DI is proposed based on bergamottin, curcumin and hyperforin FC-DI clinical data. Adopting this quantitative modelling approach should streamline herbal product safety assessments, assist in FC-DI management, and ultimately promote safe clinical use of oncology drugs.

Characterization of Oxygenated Heterocyclic Compounds and in vitro Antioxidant Activity of Pomelo Essential Oil

Purpose

Citrus essential oils are widely used for aromatherapy and the alternative treatment of chronic diseases. Beyond the aroma substances, they are known to contain bioactive nonvolatile components; however, little knowledge has been gained about nonvolatiles in the essential oil of pomelo (Citrus grandis Osbeck), the largest citrus fruit. The purpose of this study was to analyze the nonvolatile oxygenated heterocyclic compounds (OHCs) of pomelo essential oils and evaluate their in vitro antioxidant activities for further development.

Methods

Cold-pressed essential oil (CPEO) and distilled essential oil (DEO) were obtained from the peel of the Liangping pomelo cultivar. High-performance liquid chromatography (HPLC) coupled with a photodiode array and fluorescence detection method was developed to identify and quantify the OHCs of the two essential oils. Ferric reducing antioxidant power and 2,2-diphenyl-1-picrylhydrazyl (DPPH) and 2-phenyl-4,4,5,5-tetramethyl-imidazoline-1-oxyl 3-oxide (PTIO) radical scavenging assays were used to determine the antioxidative capabilities.

Results

Thirteen OHCs were identified in CPEO. Coumarins such as meranzin (2.0 mmol L⁻¹) and furanocoumarins such as isoimperatorin (1.3 mmol L⁻¹) composed the majority of nonvolatiles in CPEO. These OHCs were characterized by high proportion (58%) of side chain epoxides. Five OHCs, namely, auraptenol, 6ʹ,7ʹ-dihydroxybergamottin (6ʹ,7ʹ-DHB), imperatorin, isoimperatorin and 8-geranyloxypsoralen were first identified in pomelo CPEO. Eight OHCs were detected at trace amounts in pomelo DEO. Antioxidant assays showed that CPEO was multiple times more potent than DEO regarding the total reducing power and radical scavenging capacity. Clearance of PTIO, a stable reactive oxygen species, followed slow kinetics.

Conclusion

Coumarins and furanocoumarins, two families of OHCs, constituted most of the nonvolatile components in CPEO. The nonvolatiles contributed significantly to the in vitro antioxidant activity of CPEO. Pomelo CPEO showed good prospects as a potential long-lasting natural antioxidant.

New grapefruit cultivars exhibit low cytochrome P4503A4-Inhibition activity

Furanocoumarins are the main compounds responsible for the food-drug interactions known as the grapefruit effect, which is caused by the inhibition of CYP3A4-mediated drug metabolism. We evaluated the effects of two new, low-furanocoumarin grapefruit cultivars on CYP3A4 activity and the roles of different furanocoumarins, individually and together with other juice compounds, in the inhibition of CYP3A4 by grapefruit. Whereas a standard grapefruit cultivar inhibited CYP3A4 activity in a dose-dependent manner, neither of the two examined low-furanocoumarin cultivars had an inhibitory effect. Despite the fact that bergamottin and 6',7'-dihydroxybergamottin are weak inhibitors of CYP3A4, their relatively high levels in grapefruit make them the leading cause of the grapefruit effect. We found that furanocoumarins together with other juice compounds inhibit CYP3A4 in an additive manner. In silico docking simulation was employed, and differentiated between high- and low-potency inhibitors, suggesting that modeling may be useful for identifying potentially harmful food-drug interactions.

Anti-Melanogenic Effects of Bergamottin via Mitogen-Activated Protein Kinases and Protein Kinase B Signaling Pathways

In this study, we examined the inhibitory effects of bergamottin on melanogenesis in B16F10 murine melanoma cells, together with its effects on the mechanism of melanin synthesis. α-Melanocyte stimulating hormone-stimulated B16F10 cells were treated with various concentrations of bergamottin, with arbutin as a positive control. Bergamottin significantly decreased the melanin content and tyrosinase activity without showing any cytotoxicity. In addition, bergamottin treatment significantly downregulated the expression of tyrosinase-related protein-1,2 and tyrosinase by suppressing the expression of microphthalmia-associated transcription factor. The phosphorylation status of mitogen-activated protein kinases (MAPKs) and protein kinase B (AKT) was examined to determine the mechanism underlying the antimelanogenic effects of bergamottin. Bergamottin treatment increased the phosphorylation of extracellular signal-regulated kinase (ERK) and AKT, but decreased the phosphorylation of p38 and c-Jun N-terminal kinase in the B16F10 cells. Moreover, the use of PD98059 (ERK inhibitor) and LY294002 (AKT inhibitor) corroborated these findings, indicating that bergamottin inhibits melanogenesis via the MAPKase and AKT signaling pathway. Thus, bergamottin has potential for treating hyperpigmentation disorders and can be a promising chemical for skin-whitening in the cosmetic industry.

The photoactivity of natural products - An overlooked potential of phytomedicines?

BACKGROUND

Photoactivity, though known for centuries, is only recently shifting back into focus as a treatment option against cancer and microbial infections. The external factor light is the ingenious key-component of this therapy: Since light activates the drug locally, a high level of selectivity is reached and side effects are avoided. The first reported photoactive medicines were plant extracts. Synthetic entities (so-called photosensitizers PSs), however, paved the route towards the clinical approval of the so-called photodynamic therapy (PDT), and thus natural PSs took a backseat in the past.

HYPOTHESIS

Many isolated bioactive phytochemicals hold a hidden photoactive potential, which is overlooked due to the reduced common awareness of photoactivity.

METHODS

A systematic review of reported natural PSs and their supposed medicinal application was conducted by employing PubMed, Scifinder, and Web of Science. The identified photoactive natural products were compiled including information about their natural sources, their photoyield, and their pharmacological application. Furthermore, the common chemical scaffolds of natural PS are shown to enable the reader to recognize potentially overlooked natural PSs.

RESULTS

The literature review revealed over 100 natural PS, excluding porphyrins. The PSs were classified according to their scaffold. Thereby it was shown that some PS-scaffolds were analyzed in a detailed way, while other classes were only scarcely investigated, which leaves space for future discoveries. In addition, the literature revealed that many PSs are phytoalexins, thus the selection of the starting material significantly matters in order to find new PSs.

CONCLUSION

Photoactive principles are ubiquitous and can be found in various plant extracts. With the increasing availability of light-irradiation setups for the identification of photoactive natural products, we anticipate the discovery of many new natural PSs in the near future. With the accumulation of chemically diverse PSs, PDT itself might finally reach its clinical breakthrough as a promising alternative treatment against multi-resistant microbes and cancer types.

Phototoxicity of traditional chinese medicine (TCM)

Phototoxicity can cause toxic responses such as edemas and lesions, and is one of the severe adverse effects that largely limit the use of these phototoxic drugs. Some traditional Chinese medicines (TCMs) and their constituents have been reported to be phototoxic. However, to date, their phototoxicity information is still very limited, and lacks systemic investigation. This article presents the phototoxicity potential of various types of TCMs and their active components in an effort to provide valuable information for drug research and discovery to mitigate phototoxicity concerns. Some potential mechanisms of action (MoAs) of phototoxicity are discussed. In addition, in vivo and in vitro phototoxicity assays are summarized this review.

Hepatotoxicity of Herbal Supplements Mediated by Modulation of Cytochrome P450

Herbal supplements are a significant source of drug-drug interactions (DDIs), herb-drug interactions, and hepatotoxicity. Cytochrome P450 (CYP450) enzymes metabolize a large number of FDA-approved pharmaceuticals and herbal supplements. This metabolism of pharmaceuticals and supplements can be augmented by concomitant use of either pharmaceuticals or supplements. The xenobiotic receptors constitutive androstane receptor (CAR) and the pregnane X receptor (PXR) can respond to xenobiotics by increasing the expression of a large number of genes that are involved in the metabolism of xenobiotics, including CYP450s. Conversely, but not exclusively, many xenobiotics can inhibit the activity of CYP450s. Induction of the expression or inhibition of the activity of CYP450s can result in DDIs and toxicity. Currently, the United States (US) Food and Drug Administration does not require the investigation of the interactions of herbal supplements and CYP450s. This review provides a summary of herbal supplements that inhibit CYP450s, induce the expression of CYP450s, and/or whose toxicity is mediated by CYP450s.

Characterization and Purification of Bergamottin from Citrus grandis (L.) Osbeck cv. Yongjiazaoxiangyou and Its Antiproliferative Activity and Effect on Glucose Consumption in HepG2 cells

Bergamottin is a natural furanocoumarin compound with weak polarity. Characterization and quantification of bergamottin were carried out in different fruit tissues of various citrus cultivars. Among the four citrus tissues tested, i.e., flavedo, albedo, segment membrane (SM), and juice sacs (JS) in eight citrus cultivars, the highest bergamottin content was found in the flavedo of Citrus grandis (L.) Osbeck cv. Yongjiazaoxiangyou (YJZXY, 666.54 μg·g⁻¹ DW). A combination of silica gel column chromatography and high-speed counter-current chromatography (HSCCC) was established to efficiently purify bergamottin from the flavedo of YJZXY. Bergamottin showed significant antiproliferative activity on three cancer cell lines, i.e., human liver cancer HepG2, promyelocytic leukemia HL-60, and gastric cancer BGC-823 cells, which showed a marked inhibition effect on these cell lines in a dose-dependent manner. In addition, bergamottin significantly increased glucose consumption in HepG2 cells also in a dose-dependent manner, which is the first report of its potential in anti-diabetes applications.

Development of a comprehensive analytical method for furanocoumarins in grapefruit and their metabolites in plasma and urine using UPLC-MS/MS: a preliminary study

To develop a comprehensive analytical method for photoactive furanocoumarins, grapefruit (whole, flesh, peel and juice) was extracted using QuEChERS (Quick, Easy, Cheap, Effective, Rugged and Safe) method. Seven furanocoumarins: bergaptol, psoralen, 8-methoxypsoralen, bergapten, 6',7'-dihydroxybergamottin (6',7'-DHB), epoxybergamottin and bergamottin were determined in grapefruit using UPLC-MS/MS. The concentrations of furanocoumarins in the plasma and urine of six healthy young adults before and after ingestion of grapefruit or grapefruit juice were also determined. Recovery rates of furanocoumarins by QuEChERS method from matrix spike sample and laboratory calibrate sample were 125.7 ± 25.4% and 105.7 ± 6.3%, respectively. Bergamottin and 6',7'-DHB were predominant compounds in grapefruit flesh, juice and plasma, while bergaptol and 6',7'-DHB were major compounds detected in the urine. The results demonstrated that bergamottin and 6',7'-DHB were metabolized to bergaptol. Overall, the analytical methods developed in the present study can be applied to the analysis of various furanocoumarins in plant sources and biological samples.

The Distribution of Coumarins and Furanocoumarins in Citrus Species Closely Matches Citrus Phylogeny and Reflects the Organization of Biosynthetic Pathways

Citrus plants are able to produce defense compounds such as coumarins and furanocoumarins to cope with herbivorous insects and pathogens. In humans, these chemical compounds are strong photosensitizers and can interact with medications, leading to the "grapefruit juice effect". Removing coumarins and furanocoumarins from food and cosmetics imply additional costs and might alter product quality. Thus, the selection of Citrus cultivars displaying low coumarin and furanocoumarin contents constitutes a valuable alternative. In this study, we performed ultra-performance liquid chromatography coupled with mass spectrometry analyses to determine the contents of these compounds within the peel and the pulp of 61 Citrus species representative of the genetic diversity all Citrus. Generally, Citrus peel contains larger diversity and higher concentrations of coumarin/furanocoumarin than the pulp of the same fruits. According to the chemotypes found in the peel, Citrus species can be separated into 4 groups that correspond to the 4 ancestral taxa (pummelos, mandarins, citrons and papedas) and extended with their respective secondary species descendants. Three of the 4 ancestral taxa (pummelos, citrons and papedas) synthesize high amounts of these compounds, whereas mandarins appear practically devoid of them. Additionally, all ancestral taxa and their hybrids are logically organized according to the coumarin and furanocoumarin pathways described in the literature. This organization allows hypotheses to be drawn regarding the biosynthetic origin of compounds for which the biogenesis remains unresolved. Determining coumarin and furanocoumarin contents is also helpful for hypothesizing the origin of Citrus species for which the phylogeny is presently not firmly established. Finally, this work also notes favorable hybridization schemes that will lead to low coumarin and furanocoumarin contents, and we propose to select mandarins and Ichang papeda as Citrus varieties for use in creating species devoid of these toxic compounds in future breeding programs.

Evaluation of chemical phototoxicity, focusing on phosphorylated histone H2AX

Histone H2AX is a minor component of nuclear histone H2A. The phosphorylation of histone H2AX at Ser 139, termed γ-H2AX, was originally identified as an early event after the direct formation of DNA double-strand breaks (DSBs) by ionizing radiation. Now, the generation of γ-H2AX is also considered to occur in association with secondarily formed DSBs by cellular processing such as DNA replication and repair at the site of the initial damage, including DNA adducts, crosslinks, and UV-induced photolesions. Therefore, γ-H2AX is currently attracting attention as a new biomarker for detecting various genotoxic insults. We have determined the toxic impact of various environmental stresses such as chemicals, light and/or their coexposure using γ-H2AX, and found that the γ-H2AX assay exhibited high sensitivity and a low false-positive rate as a detection system of genotoxic potential. In this review, we introduced our recent findings concerning the evaluation of chemical phototoxicity, focusing on γ-H2AX.

Cytotoxic activity and composition of petroleum ether extract from Magydaris tomentosa (Desf.) W. D. J. Koch (Apiaceae)

The petroleum ether extract of Magydaris tomentosa flowers (Desf.) W. D. J. Koch has been analyzed by GC-MS. It is mainly constituted by furanocoumarins such as xanthotoxin, xanthotoxol, isopimpinellin, and bergaptene. Other coumarins such as 7-methoxy-8-(2-formyl-2-methylpropyl) coumarin and osthole also occurred. The antiproliferative activity of Magydaris tomentosa flower extract has been evaluated in vitro on murine monocye/macrophages (J774A.1), human melanoma (A375) and human breast cancer (MCF-7) tumor cell lines, showing a major activity against the latter.

Antiviral activity of angelicin against gammaherpesviruses

Human gammaherpesviruses including Epstein-Barr virus (EBV) and Kaposi's sarcoma-associated herpesvirus (KSHV) are important pathogens as they persist in the host and cause various malignancies. However, few antiviral drugs are available to efficiently control gammaherpesvirus replication. Here we identified the antiviral activity of angelicin against murine gammaherpesvirus 68 (MHV-68), genetically and biologically related to human gammaherpesviruses. Angelicin, a furocoumarin naturally occurring tricyclic aromatic compound, efficiently inhibited lytic replication of MHV-68 in a dose-dependent manner following the virus entry. The IC50 of angelicin antiviral activity was estimated to be 28.95μM, while the CC50 of angelicin was higher than 2600μM. Furthermore, incubation with angelicin efficiently inhibited 12-O-tetradecanoylphorbol-13-acetate (TPA)-induced lytic replication of human gammaherpresviruses in both EBV- and KSHV-infected cells. Taken together, these results suggest that MHV-68 can be a useful tool to screen novel antiviral agents against human gammaherepsviruses and that angelicin may provide a lead structure for the development of antiviral drug against gammaherpesviruses.

Almorexant effects on CYP3A4 activity studied by its simultaneous and time-separated administration with simvastatin and atorvastatin

PURPOSE

To characterise further the previously observed cytochrome P450 3A4 (CYP3A4) interaction of the dual orexin receptor antagonist almorexant.

METHODS

Pharmacokinetic interactions were investigated (n = 14 healthy male subjects in two treatment groups) between almorexant at steady-state when administered either concomitantly or 2 h after administration of single doses of simvastatin (40 mg) or atorvastatin (40 mg).

RESULTS

Almorexant dose-dependently increased simvastatin exposure (AUC0-∞) when administered concomitantly [geometric mean ratios (90 % CI): 2.5 (2.1, 2.9) (100 mg), 3.9 (3.3, 4.6) (200 mg)], but not Cmax [3.7 (3.0, 4.5) for both doses]. Time-separated administration resulted in relevant reductions of the interaction [AUC0-∞: 1.4 (1.2, 1.7) (100 mg), 1.7 (1.5, 2.0) (200 mg); Cmax: 1.5 (1.3, 1.9) (100 mg), 1.9 (1.6, 2.4) (200 mg)]. Similar results were obtained for hydroxyacid simvastatin. Independent of almorexant dose and relative time of administration, AUC0-∞ and Cmax of atorvastatin increased (ratios ranged from 1.1 to 1.5). AUC0-∞ and Cmax of o-hydroxy atorvastatin decreased dose-independently [AUC0-∞: 0.8 (0.8, 0.9) (100 mg), 0.6 (0.5, 0.6) (200 mg); Cmax: 0.3 (0.3, 0.4) (100 mg), 0.2 (0.2, 0.3) (200 mg)] when atorvastatin was concomitantly administered. Cmax of o-hydroxy atorvastatin slightly decreased (0.8 for both doses) following time-separated administration; AUC0-∞ was unchanged.

CONCLUSIONS

Whereas almorexant increased simvastatin exposure dose- and relative time of administration-dependently, atorvastatin exposure increased to a smaller extent and irrespective of dose and time. This suggests that the observed interaction of almorexant with simvastatin is mainly caused by intestinal CYP3A4 inhibition, whereas the interaction with atorvastatin is more due to hepatic CYP3A4 inhibition.

Phototoxicity of herbal plants and herbal products

Plants are used by humans in daily life in many different ways, including as food, herbal medicines, and cosmetics. Unfortunately, many natural plants and their chemical constituents are photocytotoxic and photogenotoxic, and these phototoxic phytochemicals are widely present in many different plant families. To date, information concerning the phototoxicity and photogenotoxicity of many plants and their chemical constituents is limited. In this review, we discuss phototoxic plants and their major phototoxic constituents; routes of human exposure; phototoxicity of these plants and their constituents; general mechanisms of phototoxicity of plants and phototoxic components; and several representative phototoxic plants and their photoactive chemical constituents.

NMR evaluation of total statin content and HMG-CoA reductase inhibition in red yeast rice (Monascus spp.) food supplements

BACKGROUND

Red yeast rice (i.e., rice fermented with Monascus spp.), as a food supplement, is claimed to be blood cholesterol-lowering. The red yeast rice constituent monacolin K, also known as lovastatin, is an inhibitor of the hydroxymethylglutaryl-CoA (HMG-CoA) reductase. This article aims to develop a sensitive nuclear magnetic resonance (NMR) method to determine the total statin content of red yeast rice products.

METHODS

The total statin content was determined by a 400 MHz 1H NMR spectroscopic method, based on the integration of the multiplet at δ 5.37-5.32 ppm of a hydrogen at the hexahydronaphthalene moiety in comparison to an external calibration with lovastatin. The activity of HMG-CoA reductase was measured by a commercial spectrophotometric assay kit.

RESULTS

The NMR detection limit for total statins was 6 mg/L (equivalent to 0.3 mg/capsule, if two capsules are dissolved in 50 mL ethanol). The relative standard deviations were consistently lower than 11%. The total statin concentrations of five red yeast rice supplements were between 1.5 and 25.2 mg per specified daily dose. A dose-dependent inhibition of the HMG-CoA reductase enzyme activity by the red yeast rice products was demonstrated.

CONCLUSION

A simple and direct NMR assay was developed to determine the total statin content in red yeast rice. The assay can be applied for the determination of statin content for the regulatory control of red yeast rice products.