Modulation of esterified drug metabolism by tanshinones from Salvia miltiorrhiza ("Danshen")

Synthesis of Ketonylated Carbocycles via Excited-State Copper-Catalyzed Radical Carbo-Aroylation of Unactivated Alkenes

Carbocycles are core skeletons in natural and synthetic organic compounds possessing a wide diversity of important biological activities. Herein, we report the development of an excited-state copper-catalyzed radical carbo-aroylation of unactivated alkenes to synthesize ketonylated tetralins, di- and tetrahydrophenanthrenes, and cyclopentane derivatives. The reaction is operationally simple and features mild reaction conditions that tolerate a broad range of functional groups. Preliminary mechanistic studies suggest a reaction pathway beginning with photoexcitation of [CuI-BINAP]2 and followed by a single electron transfer (SET), radical aroylation of unactivated alkenes, radical cyclization, and re-aromatization, affording the desired ketonylated carbocycles.

Salvia miltiorrhiza Bge. (Danshen) for Inflammatory Bowel Disease: Clinical Evidence and Network Pharmacology-Based Strategy for Developing Supplementary Medical Application

Inflammatory bowel disease (IBD) is a non-specific colorectal disease caused by multifaceted triggers. Although conventional treatments are effective in the management of IBD, high cost and frequent side effects limit their applications and have turned sufferers toward alternative and complementary approaches. Salvia miltiorrhiza Bge (Danshen) is an herbal medicine that reportedly alleviates the symptoms of IBD. A large body of research, including clinical trials in which Danshen-based products or botanical compounds were used, has unmasked its multiple mechanisms of action, but no review has focused on its efficacy as a treatment for IBD. Here, we discussed triggers of IBD, collected relevant clinical trials and analyzed experimental reports, in which bioactive compounds of Danshen attenuated rodent colitis in the management of intestinal integrity, gut microflora, cell death, immune conditions, cytokines, and free radicals. A network pharmacology approach was applied to describe sophisticated mechanisms in a holistic view. The safety of Danshen was also discussed. This review of evidence will help to better understand the potential benefits of Danshen for IBD treatment and provide insights for the development of innovative applications of Danshen.

Directionally Modified Fluorophores for Super-Resolution Imaging of Target Enzymes: A Case Study with Carboxylesterases

In the need for improving the labeling quality of super-resolution imaging, multifarious fluorescent labeling strategies have sprang up. Among them, a small molecule inhibitor-probe (SMI-probe) shows its advancement in fine mapping due to its smaller size and its specific binding to a specific site. Herein, we report a novel protocol of mechanism-guided directional modification of fluorophores into fluorescent inhibitors for enzyme targeting, which could half the size of the SMI-probe. To confirm the feasibility of the strategy, carboxylesterase (hCE) inhibitors are designed and developed. Among the constructed molecule candidates, NIC-4 inhibited both isoforms of hCE1 and hCE2, with IC₅₀ values of 4.56 and 4.11 μM. The CE-targeting specificity of NIC-4 was confirmed by colocalizing with an immunofluorescent probe in fixed-cell confocal imaging. Moreover, NIC-4 was used in live-cell super-resolution microscopy, which indicates dotlike structures instead of the larger staining with the immunofluorescent probe. Moreover, it enables the real-time tracking of dynamic flow of carboxylesterases in live cells.

Carboxylesterase inhibitors from clinically available medicines and their impact on drug metabolism

Mammalian carboxylesterases (CES), the key members of the serine hydrolase superfamily, hydrolyze a wide range of endogenous substances and xenobiotics bearing ester or amide bond(s). In humans, most of identified CES are segregated into the CES1A and CES2A subfamilies. Strong inhibition on human CES (including hCES1A and hCES2A) may modulate pharmacokinetic profiles of CES-substrate drugs, thereby changing the pharmacological and toxicological responses of these drugs. This review covered recent advances in discovery of hCES inhibitors from clinically available medications, as well as their impact on CES-associated drug metabolism. Three comprehensive lists of hCES inhibitors deriving from clinically available medications including therapeutic drugs, pharmaceutical excipients and herbal medicines, alongside with their inhibition potentials and inhibition parameters, are summarized. Furthermore, the potential risks of hCES inhibitors to trigger drug/herb-drug interactions (DDIs/HDIs) and future concerns in this field are highlighted. Potent hCES inhibitors may trigger clinically relevant DDIs/HDIs, especially when these inhibitors are co-administrated with CES substrate-drugs with very narrow therapeutic windows. All data and knowledge presented here provide key information for the clinicians to assess the risks of clinically available hCES inhibitors on drug metabolism. In future, more practical and highly specific substrates for hCES1A/hCES2A should be developed and used for studies on CES-mediated DDIs/HDIs both in vitro and in vivo.

Tanshinones: An Update in the Medicinal Chemistry in Recent 5 Years

Tanshinones are an important type of natural products isolated from Salvia miltiorrhiza Bunge with various bioactivities. Tanshinone IIa, cryptotanshinone and tanshinone I are three kinds of tanshinones which have been widely investigated. Particularly, sodium tanshinone IIa sulfonate is a water-soluble derivative of tanshinone IIa and it is used in clinical in China for treating cardiovascular diseases. In recent years, there are increasing interests in the investigation of tanshinones derivatives in various diseases. This article presents a review of the anti-atherosclerotic effects, cardioprotective effects, anticancer activities, antibacterial activities and antiviral activities of tanshinones and structural modification work in recent years.

Trifluorinated Tetralins via I(I)/I(III)-Catalysed Ring Expansion: Programming Conformation by [CH2 CH2 ] → [CF2 CHF] Isosterism

Saturated, fluorinated carbocycles are emerging as important modules for contemporary drug discovery. To expand the current portfolio, the synthesis of novel trifluorinated tetralins has been achieved. Fluorinated methyleneindanes serve as convenient precursors and undergo efficient difluorinative ring expansion with in situ generated p‐TolIF₂ (>20 examples, up to >95 %). A range of diverse substituents are tolerated under standard catalysis conditions and this is interrogated by Hammett analysis. X‐ray analysis indicates a preference for the CH−F bond to occupy a pseudo‐axial orientation, consistent with stabilising σ_C−H→σ_C−F* interactions. The replacement of the symmetric [CH₂−CH₂] motif by [CF₂−CHF] removes the conformational degeneracy intrinsic to the parent tetralin scaffold leading to a predictable half‐chair. The conformational behavior of this novel structural balance has been investigated by computational analysis and is consistent with stereoelectronic theory.

Pentacyclic triterpenoid acids in Styrax as potent and highly specific inhibitors against human carboxylesterase 1A

Human carboxylesterase 1A1 (hCES1A) is a promising target for the treatment of hyperlipidemia and obesity-associated metabolic diseases. To date, the highly specific and efficacious hCES1A inhibitors are rarely reported. This study aims to find potent and highly specific hCES1A inhibitors from herbs, and to investigate their inhibitory mechanisms. Following large-scale screening of herbal products, Styrax was found to have the most potent hCES1A inhibition activity. After that, a practical bioactivity-guided fractionation coupling with a chemical profiling strategy was used to identify the fractions from Styrax with strong hCES1A inhibition activity and the major constituents in these bioactive fractions were characterized by LC-TOF-MS/MS. The results demonstrated that seven pentacyclic triterpenoid acids (PTAs) in two bioactive fractions from Styrax potently inhibit hCES1A, with IC50 values ranging from 41 nM to 478 nM. Among all the identified PTAs, epibetulinic acid showed the most potent inhibition activity and excellent specificity towards hCES1A. Both inhibition kinetic analyses and in silico analysis suggested that epibetulinic acid potently inhibited hCES1A in a mixed inhibition manner. Collectively, our findings demonstrate that some PTAs in Styrax are potent and highly specific inhibitors of hCES1A and these constituents can be used as promising lead compounds for the development of more efficacious hCES1A inhibitors.

Novel potent bifunctional carboxylesterase inhibitors based on a polyfluoroalkyl-2-imino-1,3-dione scaffold

An expanded series of alkyl 2-arylhydrazinylidene-3-oxo-3-polyfluoroalkylpropionates (HOPs) 3 was obtained via Cu(OAc)₂-catalyzed azo coupling. All were nanomolar inhibitors of carboxylesterase (CES), while moderate or weak inhibitors of acetylcholinesterase and butyrylcholinesterase. Steady-state kinetics studies showed that HOPs 3 are mixed type inhibitors of the three esterases. Molecular docking studies demonstrated that two functional groups in the structure of HOPs, trifluoromethyl ketone (TFK) and ester groups, bind to the CES active site suggesting subsequent reactions: formation of a tetrahedral adduct, and a slow hydrolysis reaction. The results of molecular modeling allowed us to explain some structure-activity relationships of CES inhibition by HOPs 3: their selectivity toward CES in comparison with cholinesterases and the high selectivity of pentafluoroethyl-substituted HOP 3p to hCES1 compared to hCES2. All compounds were predicted to have good intestinal absorption and blood-brain barrier permeability, low cardiac toxicity, good lipophilicity and aqueous solubility, and reasonable overall drug-likeness. HOPs with a TFK group and electron-donor substituents in the arylhydrazone moiety were potent antioxidants. All compounds possessed low cytotoxicity and low acute toxicity. Overall, a new promising type of bifunctional CES inhibitors has been found that are able to interact with the active site of the enzyme with the participation of two functional groups. The results indicate that HOPs have the potential to be good candidates as human CES inhibitors for biomedicinal applications.

Investigation of the inhibitory effect of protostanes on human carboxylesterase 2 and their interaction: Inhibition kinetics and molecular stimulations

Carboxylesterase 2 (CES 2), plays a pivotal role in endobiotic homeostasis and xenobiotic metabolism. Protostanes, the major constituents of the genus Alisma, display a series of pharmacological activities. Despite the extensive studies of pharmacological activities, the investigation on inhibitory effects of protostanes against CES 2 is rarely reported. In this study, the inhibitory activities of a library of protostanes (1-25) against human CES 2 were investigated for the first time, using 6,8-dichloro-9,9-dimethyl-7-oxo-7,9-dihydroacridin-2-yl benzoate (DDAB) as the specific fluorescent probe for human CES 2. Compounds 1, 2, 7, 8, 12, 13, 18, 19, and 25 showed strong inhibitory effects towards CES 2. For the most potent compounds 1, 7, 13, and 25, the inhibition kinetics were further investigated, and these four protostanes were all uncompetitive inhibitors against human CES 2 with the inhibition constant (K_i) values ranging from 0.89 μM to 2.83 μM. In addition, molecular docking and molecular dynamics stimulation were employed to analyze the potential interactions between these protostanes and CES 2, and amino acid residue Gln422 was identified to play a crucial role in the strong inhibition of protostanes towards CES 2.

Rational drug design, synthesis, and biological evaluation of novel chiral tetrahydronaphthalene-fused spirooxindole as MDM2-CDK4 dual inhibitor against glioblastoma

Simultaneous inhibition of MDM2 and CDK4 may be an effective treatment against glioblastoma. A collection of chiral spirocyclic tetrahydronaphthalene (THN)-oxindole hybrids for this purpose have been developed. Appropriate stereochemistry in THN-fused spirooxindole compounds is key to their inhibitory activity: selectivity differed by over 40-fold between the least and most potent stereoisomers in time-resolved FRET and KINOMEscan® in vitro assays. Studies in glioblastoma cell lines showed that the most active compound ent-4g induced apoptosis and cell cycle arrest by interfering with MDM2 -P53 interaction and CDK4 activation. Cells treated with ent-4g showed up-regulation of proteins involved in P53 and cell cycle pathways. The compound showed good anti-tumor efficacy against glioblastoma xenografts in mice. These results suggested that rational design, asymmetric synthesis and biological evaluation of novel tetrahydronaphthalene fused spirooxindoles could generate promising MDM2-CDK4 dual inhibitors in glioblastoma therapy.

Natural Products as Modulators of CES1 Activity

Carboxylesterase (CES) 1 is the predominant esterase expressed in the human liver and is capable of catalyzing the hydrolysis of a wide range of therapeutic agents, toxins, and endogenous compounds. Accumulating studies have demonstrated associations between the expression and activity of CES1 and the pharmacokinetics and/or pharmacodynamics of CES1 substrate medications (e.g., methylphenidate, clopidogrel, oseltamivir). Therefore, any perturbation of CES1 by coingested xenobiotics could potentially compromise treatment. Natural products are known to alter drug disposition by modulating cytochrome P450 and UDP-glucuronosyltransferase enzymes, but this issue is less thoroughly explored with CES1. We report the results of a systematic literature search and discuss natural products as potential modulators of CES1 activity. The majority of research reports reviewed were in vitro investigations that require further confirmation through clinical study. Cannabis products (Δ ⁹-tetrahydrocannabinol, cannabidiol, cannabinol); supplements from various plant sources containing naringenin, quercetin, luteolin, oleanolic acid, and asiatic acid; and certain traditional medicines (danshen and zhizhuwan) appear to pose the highest inhibition potential. In addition, ursolic acid, gambogic acid, and glycyrrhetic acid, if delivered intravenously, may attain high enough systemic concentrations to significantly inhibit CES1. The provision of a translational interpretation of in vitro assessments of natural product actions and interactions is limited by the dearth of basic pharmacokinetic data of the natural compounds exhibiting potent in vitro influences on CES1 activity. This is a major impediment to assigning even potential clinical significance. The modulatory effects on CES1 expression after chronic exposure to natural products warrants further investigation. SIGNIFICANCE STATEMENT: Modulation of CES1 activity by natural products may alter the course of treatment and clinical outcome. In this review, we have summarized the natural products that can potentially interact with CES1 substrate medications. We have also noted the limitations of existing reports and outlined challenges and future directions in this field.

Rapid bioluminescence assay for monitoring rat CES1 activity and its alteration by traditional Chinese medicines

In traditional Chinese medicine herbs (TCM), including Radix Salviae Miltiorrhizae (Danshen), Radix Puerariae Lobatae (Gegen), Radix Angelicae Sinensis (Danggui), and Rhizoma Chuanxiong (Chuanxiong) are widely used for the prevention and treatment of cardiovascular diseases and also often co-administered with Western drugs as a part of integrative medicine practice. Carboxylesterase 1 (CES1) plays a pivotal role in the metabolisms of pro-drugs. Since (S)-2-(2-(6-dimethylamino)-benzothiazole)-4,5-dihydro-thiazole-4-carboxylate (NLMe) has recently been identified by us as a selective CES1 bioluminescent sensor, we developed a rapid method using this substrate for the direct measurement of CES1 activity in rats. This bioluminescence assay was applied to determine CES1 activity in rat tissues after a two-week oral administration of each of the four herbs noted above. The results demonstrated the presence of CES1 enzyme in rat blood and all tested tissues with much higher enzyme activity in the blood, liver, kidney and heart than that in the small intestine, spleen, lung, pancreas, brain and stomach. In addition, the four herbs showed tissue-specific effects on rat CES1 expression. Based on the CES1 biodistribution and its changes after treatment in rats, the possibility that Danshen, Gegen and Danggui might alter CES1 activities in human blood and kidney should be considered. In summary, a selective and sensitive bioluminescence assay was developed to rapidly evaluate CES1 activity and the effects of orally administered TCMs in rats.

Structure-based virtual screening leading to discovery of highly selective butyrylcholinesterase inhibitors with solanaceous alkaloid scaffolds

According to recent research advance, it is interesting to identify new, potent and selective inhibitors of human butyrylcholinesterase (BChE) for therapeutic treatment of both the Alzheimer's disease (AD) and heroin abuse. In this study, we carried out a structure-based virtual screening followed by in vitro activity assays, with the goal to identify new inhibitors that are selective for BChE over acetylcholinesterase (AChE). As a result, a set of new, selective inhibitors of human BChE were identified from natural products with solanaceous alkaloid scaffolds. The most active one of the natural products (compound 1) identified has an IC50 of 16.8 nM against BChE. It has been demonstrated that the desirable selectivity of these inhibitors for BChE over AChE is mainly controlled by three key residues in the active site cavity, i.e. residues Q119, A277, and A328 in BChE versus the respective residues Y124, W286, and Y337 in AChE. Based on this structural insight, future rational design of new, potent and selective BChE inhibitors may focus on these key structural differences in the active site cavity.

Potential Pharmacokinetic Herb-Drug Interactions: Have we Overlooked the Importance of Human Carboxylesterases 1 and 2?

Background:

Herbal products have grown steadily across the globe and have increasingly been incorporated into western medicine for healthcare aims, thereby causing potential pharmacokinetic Herb-drug Interactions (HDIs) through the inhibition or induction of drug-metabolizing enzymes and transporters. Human Carboxylesterases 1 (CES1) and 2 (CES2) metabolize endogenous and exogenous chemicals including many important therapeutic medications. The growing number of CES substrate drugs also underscores the importance of the enzymes. Herein, we summarized those potential inhibitors and inducers coming from herbal constituents toward CES1 and CES2. We also reviewed the reported HDI studies focusing on herbal products and therapeutic agents metabolized by CES1 or CES2.

Methods:

We searched in PubMed for manuscript published in English after Jan 1, 2000 combining terms “carboxylesterase 1”, “carboxylesterase 2”, “inhibitor”, “inducer”, “herb-drug interaction”, “inhibitory”, and “herbal supplement”. We also searched specific websites including FDA and EMA. The data of screened papers were analyzed and summarized.

Results:

The results showed that more than 50 natural inhibitors of CES1 or CES2, including phenolic chemicals, triterpenoids, and tanshinones were found from herbs, whereas only few inducers of CES1 and CES2 were reported. Systemic exposure to some commonly used drugs including oseltamivir, irinotecan, and clopidogrel were changed when they were co-administered with herb products such as goldenseal, black cohosh, ginger, St. John’s Wort, curcumin, and some Chinese compound formula in animals.

Conclusion:

Nonclinical and clinical studies on HDIs are warranted in the future to provide safety information toward better clinical outcomes for the combination of herbal products and conventional drugs.

Sodium tanshinone IIA sulfonate attenuates cardiac dysfunction and improves survival of rats with cecal ligation and puncture-induced sepsis

Cardiac dysfunction, a common consequence of sepsis, is the major contribution to morbidity and mortality in patients. Sodium tanshinone IIA sulfonate (STS) is a water-soluble derivative of Tanshinone IIA (TA), a main active component of Salvia miltiorrhiza Bunge, which has been widely used in China for the treatment of cardiovascular and cerebral system diseases. In the present study, the effect of STS on sepsis-induced cardiac dysfunction was investigated and its effect on survival rate of rats with sepsis was also evaluated. STS treatment could significantly decrease the serum levels of C-reactive protein (CRP), procalcitonin (PCT), cardiac troponin I (cTn-I), cardiac troponin T (cTn-T), and brain natriuretic peptide (BNP) in cecal ligation and puncture (CLP)-induced) septic rats and improve left ventricular function, particularly at 48 and 72 h after CLP. As the pathogenesis of septic myocardial dysfunction is attributable to dysregulated systemic inflammatory responses, several key cytokines, including tumor necrosis factor-α (TNF-α), interleukin-1β (IL-1β), interleukin-6 (IL-6), interleukin-10 (IL-10) and high mobility group protein B1 (HMGB1), were detected to reveal the possible mechanism of attenuation of septic myocardial dysfunction after being treated by STS. Our study showed that STS, especially at a high dose (15 mg·kg^-1), could efficiently suppress inflammatory responses in myocardium and reduce myocardial necrosis through markedly reducing production of myocardial TNF-α, IL-6 and HMGB1. STS significantly improved the 18-day survival rate of rats with sepsis from 0% to 30% (P < 0.05). Therefore, STS could suppress inflammatory responses and improve left ventricular function in rats with sepsis, suggesting that it may be developed for the treatment of sepsis.

A Review of Danshen Combined with Clopidogrel in the Treatment of Coronary Heart Disease

OBJECTIVE

Danshen, the root of Salvia miltiorrhiza Bunge, is a traditional herbal medicine in China, which has been used to treat irregular menstruation, cold hernia, and abdominal pain for thousands of years. Danshen is frequently used in combination with drugs to treat cardiovascular diseases. Clopidogrel is a commonly used drug for treating coronary heart disease, but clopidogrel resistance restricts its development. Therefore, the clinical efficacy of Danshen combined with clopidogrel treats coronary heart disease and the relationship between Danshen and clopidogrel metabolism enzymes is suggested for future investigations.

MATERIALS AND METHODS

The information was collected by searching online databases, and the RevMan 5.3 software was used to perform meta-analysis.

RESULTS

Twenty-two articles, including 2587 patients, were enrolled after the evaluation. Meta-analysis showed that Danshen combined with clopidogrel was more effective than clopidogrel alone in treating coronary heart disease by improving clinical curative effect, reducing the frequency of angina pectoris, improving electrocardiogram results, shortening the duration of angina pectoris, and easing adverse reactions. Danshen inhibited carboxylesterase 1 and most enzyme of cytochrome P450, especially cytochrome P450 1A2, which may affect the metabolism of clopidogrel.

CONCLUSION

Danshen combined with clopidogrel may compensate for individual differences of clopidogrel resistance among individuals in the treatment of coronary heart disease. Meanwhile, the inhibitory effect of Danshen on cytochrome P450 and carboxylesterase 1 could be partly responsible for the synergistic and attenuating effects of Danshen combined with clopidogrel.

Discovery of dihydrooxazolo[2,3-a]isoquinoliniums as highly specific inhibitors of hCE2

Human carboxylesterase 2 (hCE2) is one of the most abundant esterases distributed in human small intestine and colon, which participates in the hydrolysis of a variety of ester-bearing drugs and thereby affects the efficacy of these drugs. Herein, a new compound (23o) with a novel skeleton of dihydrooxazolo[2,3-a]isoquinolinium has been discovered with strong inhibition on hCE2 (IC₅₀ = 1.19 μM, K_i = 0.84 μM) and more than 83.89 fold selectivity over hCE1 (IC₅₀ > 100 μM). Furthermore, 23o can inhibit hCE2 activity in living HepG2 cells with the IC₅₀ value of 2.29 μM, indicating that this compound has remarkable cell-membrane permeability and is capable for inhibiting intracellular hCE2. The SAR (structure–activity relationship) analysis and molecular docking results demonstrate that the novel skeleton of oxazolinium is essential for hCEs inhibitory activity and the benzyloxy moiety mainly contributes to the selectivity of hCE2 over hCE1.

Novel oxazoliniums are highly specific inhibitors of hCE2 over hCE1 and have good cell-membrane permeability for inhibiting intracellular hCE2.

Potent, Irreversible Inhibition of Human Carboxylesterases by Tanshinone Anhydrides Isolated from Salvia miltiorrhiza ("Danshen")

The roots of Salvia miltiorrhiza ("Danshen") have been used in Chinese herbal medicine for centuries for a host of different conditions. While the exact nature of the active components of this material are unknown, large amounts of tanshinones are present in extracts derived from these samples. Recently, the tanshinones have been demonstrated to be potent human carboxylesterase (CE) inhibitors, with the ability to modulate the biological activity of esterified drugs. During the course of these studies, we also identified more active, irreversible inhibitors of these enzymes. We have purified, identified, and synthesized these molecules and confirmed them to be the anhydride derivatives of the tanshinones. These compounds are exceptionally potent inhibitors ( K_i < 1 nM) and can inactivate human CEs both in vitro and in cell culture systems and can modulate the metabolism of the esterified drug oseltamivir. Therefore, the coadministration of Danshen extracts with drugs that contain the ester chemotype should be minimized since, not only is transient inhibition of CEs observed with the tanshinones, but also prolonged irreversible inhibition arises via interaction with the anhydrides.

Human carboxylesterases: a comprehensive review

Mammalian carboxylesterases (CEs) are key enzymes from the serine hydrolase superfamily. In the human body, two predominant carboxylesterases (CES1 and CES2) have been identified and extensively studied over the past decade. These two enzymes play crucial roles in the metabolism of a wide variety of endogenous esters, ester-containing drugs and environmental toxicants. The key roles of CES in both human health and xenobiotic metabolism arouse great interest in the discovery of potent CES modulators to regulate endobiotic metabolism or to improve the efficacy of ester drugs. This review covers the structural and catalytic features of CES, tissue distributions, biological functions, genetic polymorphisms, substrate specificities and inhibitor properties of CES1 and CES2, as well as the significance and recent progress on the discovery of CES modulators. The information presented here will help pharmacologists explore the relevance of CES to human diseases or to assign the contribution of certain CES in xenobiotic metabolism. It will also facilitate medicinal chemistry efforts to design prodrugs activated by a given CES isoform, or to develop potent and selective modulators of CES for potential biomedical applications.

Facile synthesis of 1,2-dione-containing abietane analogues for the generation of human carboxylesterase inhibitors

Recently, a series of selective human carboxylesterase inhibitors have been identified based upon the tanshinones, with biologically active molecules containing a 1,2-dione group as part of a naphthoquinone core. Unfortunately, the synthesis of such compounds is complex. Here we describe a novel method for the generation of 1,2-dione containing diterpenoids using a unified approach, by which boronic acids are joined to vinyl bromo-cyclohexene derivatives via Suzuki coupling, followed by electrocyclization and oxidation to the o-phenanthroquinones. This has allowed the construction of a panel of miltirone analogues containing an array of substituents (methyl, isopropyl, fluorine, methoxy) which have been used to develop preliminary SAR with the two human carboxylesterase isoforms. As a consequence, we have synthesized highly potent inhibitors of these enzymes (Ki < 15 nM), that maintain the core tanshinone scaffold. Hence, we have developed a facile and reproducible method for the synthesis of abietane analogues that have resulted in a panel of miltirone derivatives that will be useful tool compounds to assess carboxylesterase biology.

Salvia miltiorrhiza: A Potential Red Light to the Development of Cardiovascular Diseases

Salvia miltiorrhiza Bunge, also known as Danshen in Chinese, has been widely used to treat cardiovascular diseases (CVD) in China and other Asia countries. Here, we summarize literatures of the historical traditional Chinese medicine (TCM) interpretation of the action of Salvia miltiorrhiza, its use in current clinical trials, its main phytochemical constituents and its pharmacological findings by consulting Pubmed, China Knowledge Resource Integrated, China Science and Technology Journal, and the Web of Science Databases. Since 2000, 39 clinical trials have been identified that used S. miltiorrhiza in TCM prescriptions alone or with other herbs for the treatment of patients with CVD. More than 200 individual compounds have been isolated and characterized from S. miltiorrhiza, which exhibited various pharmacological activities targeting different pathways for the treatment of CVD in various animal and cell models. The isolated compounds may provide new perspectives in alternative treatment regimes and reveal novel chemical scaffolds for the development of anti-CVD drugs. Meanwhile, there are also some rising concerns of the potential side effects and drug-drug interactions of this plant. The insights gained from this study will help us to better understanding of the actions of this herb for management of cardiovascular disorders. As an herb of red root, S. miltiorrhiza will act as a potential red light to prevent the development of CVD.

Iron-Catalyzed Synthesis of Tetrahydronaphthalenes via 3,4-Dihydro-2H-pyran Intermediates

The development of an iron(III)-catalyzed synthetic strategy toward functionalized tetrahydronaphthalenes is described. This approach is characterized by its operational simplicity and is distinct from currently available procedures that rely on [4 + 2]-cycloadditions. Our strategy takes advantage of the divergent reactivity observed for simple aryl ketone precursors to gain exclusive access to tetrahydronaphthalene products (23 examples). Detailed mechanistic investigations identified pyrans as reactive intermediates that afford the desired tetrahydronaphthalenes in high yields upon iron(III)-catalyzed Friedel-Crafts alkylation.

Selective Carboxylesterase Inhibitors for Improving Efficacy, Safety and Rational use of Ester-Containing Drugs

In clinical practice, a large number of prodrugs and active drugs containing an ester, carbamate or amide moiety are used. Carboxylesterase (CaE, EC 3.1.1.1) is the key enzyme of hydrolytic metabolism of such drugs in the body, it largely determines their pharmacokinetics, bioavailability, efficacy and possible toxic effects. Using CaE selective inhibitors as components of combined drug therapy it is possible us to regulate the rate of hydrolytic transformation of ester-containing drugs and opens the possibility of their rational use. The development of effective and selective CaE inhibitors suitable for in vivo application is a new promising approach in medicinal chemistry and pharmacology that allows to improve the efficacy, bioavailability and reduce the side effects of ester-containing drugs.

Overexpression of AtEDT1 promotes root elongation and affects medicinal secondary metabolite biosynthesis in roots of transgenic Salvia miltiorrhiza

Medicinal secondary metabolites (salvianolic acids and tanshinones) are valuable natural bioactive compounds in Salvia miltiorrhiza and have widespread applications. Improvement of medicinal secondary metabolite accumulation through biotechnology is necessary and urgent to satisfy their increasing demand. Herein, it was demonstrated that the overexpression of the transcription factor Arabidopsis thaliana-enhanced drought tolerance 1 (AtEDT1) could affect medicinal secondary metabolite accumulation. In this study, we observed that the transgenic lines significantly conferred drought tolerance phenotype. Meanwhile, we found that the overexpression of AtEDT1 promoted root elongation in S. miltiorrhiza. Interestingly, we also found that the overexpression of AtEDT1 determined the accumulation of salvianolic acids, such as rosmarinic acid, lithospermic acid, salvianolic acid B, and total salvianolic acids due to the induction of the expression levels of salvianolic acid biosynthetic genes. Conversely, S. miltiorrhiza plants overexpressing the AtEDT1 transgene showed a decrease in tanshinone synthesis. Our results demonstrated that the overexpression of AtEDT1 significantly increased the accumulation of salvianolic acids in S. miltiorrhiza. Further studies are required to better elucidate the functional role of AtEDT1 in the regulation of phytochemical compound synthesis.

Structure-Activity Relationships of Pentacyclic Triterpenoids as Potent and Selective Inhibitors against Human Carboxylesterase 1

Human carboxylesterase 1 (hCE1), one of the most important serine hydrolases distributed in liver and adipocytes, plays key roles in endobiotic homeostasis and xenobiotic metabolism. This study aimed to find potent and selective inhibitors against hCE1 from phytochemicals and their derivatives. To this end, a series of natural triterpenoids were collected and their inhibitory effects against human carboxylesterases (hCEs) were assayed using D-Luciferin methyl ester (DME) and 6,8-dichloro-9,9-dimethyl-7-oxo-7,9-dihydroacridin-2-yl benzoate (DDAB) as specific optical substrate for hCE1, and hCE2, respectively. Following screening of a series of natural triterpenoids, oleanolic acid (OA), and ursolic acid (UA) were found with strong inhibitory effects on hCE1 and relative high selectivity over hCE2. In order to get the highly selective and potent inhibitors of hCE1, a series of OA and UA derivatives were synthesized from OA and UA by chemical modifications including oxidation, reduction, esterification, and amidation. The inhibitory effects of these derivatives on hCEs were assayed and the structure-activity relationships of tested triterpenoids as hCE1 inhibitors were carefully investigated. The results demonstrated that the carbonyl group at the C-28 site is essential for hCE1 inhibition, the modifications of OA or UA at this site including esters, amides and alcohols are unbeneficial for hCE1 inhibition. In contrast, the structural modifications on OA and UA at other sites, such as converting the C-3 hydroxy group to 3-O-β-carboxypropionyl (compounds 20 and 22), led to a dramatically increase of the inhibitory effects against hCE1 and very high selectivity over hCE2. 3D-QSAR analysis of all tested triterpenoids including OA and UA derivatives provide new insights into the fine relationships linking between the inhibitory effects on hCE1 and the steric-electrostatic properties of triterpenoids. Furthermore, both inhibition kinetic analyses and docking simulations demonstrated that compound 22 was a potent competitive inhibitor against hCE1-mediated DME hydrolysis. All these findings are very helpful for medicinal chemists to design and develop highly selective and more potent hCE1 inhibitors for biomedical applications.

Salvia miltiorrhiza Roots against Cardiovascular Disease: Consideration of Herb-Drug Interactions

Salvia miltiorrhiza root (Danshen) is widely used in Asia for its cardiovascular benefits and contains both hydrophilic phenolic acids and lipophilic tanshinones, which are believed to be responsible for its therapeutic efficacy. This review summarized the effects of these bioactive components from S. miltiorrhiza roots on pharmacokinetics of comedicated drugs with mechanic insights regarding alterations of protein binding, enzyme activity, and transporter activity based on the published data stemming from both in vitro and in vivo human studies. In vitro studies indicated that cytochrome P450 (CYP450), carboxylesterase enzyme, catechol-O-methyltransferase, organic anion transporter 1 (OAT1) and OAT3, and P-glycoprotein were the major targets involved in S. miltiorrhiza-drug interactions. Lipophilic tanshinones had much more potent inhibitory effects towards CYPs activities compared to hydrophilic phenolic acids, evidenced by much lower K_i values of the former. Clinical S. miltiorrhiza-drug interaction studies were mainly conducted using CYP1A2 and CYP3A4 probe substrates. In addition, the effects of coexisting components on the pharmacokinetic behaviors of those noted bioactive compounds were also included herein.

Selective Inhibitors of Human Liver Carboxylesterase Based on a β-Lapachone Scaffold: Novel Reagents for Reaction Profiling

Carboxylesterases (CEs) are ubiquitous enzymes that are responsible for the metabolism of xenobiotics, including drugs such as irinotecan and oseltamivir. Inhibition of CEs significantly modulates the efficacy of such agents. We report here that β-lapachone is a potent, reversible CE inhibitor with K_i values in the nanomolar range. A series of amino and phenoxy analogues have been synthesized, and although the former are very poor inhibitors, the latter compounds are highly effective in modulating CE activity. Our data demonstrate that tautomerism of the amino derivatives to the imino forms likely accounts for their loss in biological activity. A series of N-methylated amino derivatives, which are unable to undergo such tautomerism, were equal in potency to the phenoxy analogues and demonstrated selectivity for the liver enzyme hCE1. These specific inhibitors, which are active in cell culture models, will be exceptionally useful reagents for reaction profiling of esterified drugs in complex biological samples.

De Novo Sequencing and Assembly Analysis of the Pseudostellaria heterophylla Transcriptome

Pseudostellaria heterophylla (Miq.) Pax is a mild tonic herb widely cultivated in the Southern part of China. The tuberous roots of P. heterophylla accumulate high levels of secondary metabolism products of medicinal value such as saponins, flavonoids, and isoquinoline alkaloids. Despite numerous studies on the pharmacological importance and purification of these compounds in P. heterophylla, their biosynthesis is not well understood. In the present study, we used Illumina HiSeq 4000 sequencing platform to sequence the RNA from flowers, leaves, stem, root cortex and xylem tissues of P. heterophylla. We obtained 616,413,316 clean reads that we assembled into 127, 334 unique sequences with an N50 length of 951 bp. Among these unigenes, 53,184 unigenes (41.76%) were annotated in a public database and 39, 795 unigenes were assigned to 356 KEGG pathways; 23,714 unigenes (8.82%) had high homology with the genes from Beta vulgaris. We discovered 32, 095 DEGs in different tissues and performed GO and KEGG enrichment analysis. The most enriched KEGG pathway of secondary metabolism showed up-regulated expression in tuberous roots as compared with the ground parts of P. heterophylla. Moreover, we identified 72 candidate genes involved in triterpenoids saponins biosynthesis in P. heterophylla. The expression profiles of 11 candidate unigenes were analyzed by quantitative real-time PCR (RT-qPCR). Our study established a global transcriptome database of P. heterophylla for gene identification and regulation. We also identified the candidate unigenes involved in triterpenoids saponins biosynthesis. Our results provide an invaluable resource for the secondary metabolites and physiological processes in different tissues of P. heterophylla.

Challenges and Opportunities with Non-CYP Enzymes Aldehyde Oxidase, Carboxylesterase, and UDP-Glucuronosyltransferase: Focus on Reaction Phenotyping and Prediction of Human Clearance

Over the years, significant progress has been made in reducing metabolic instability due to cytochrome P450-mediated oxidation. High-throughput metabolic stability screening has enabled the advancement of compounds with little to no oxidative metabolism. Furthermore, high lipophilicity and low aqueous solubility of presently pursued chemotypes reduces the probability of renal excretion. As such, these low microsomal turnover compounds are often substrates for non-CYP-mediated metabolism. UGTs, esterases, and aldehyde oxidase are major enzymes involved in catalyzing such metabolism. Hepatocytes provide an excellent tool to identify such pathways including elucidation of major metabolites. To predict human PK parameters for P450-mediated metabolism, in vitro-in vivo extrapolation using hepatic microsomes, hepatocytes, and intestinal microsomes has been actively investigated. However, such methods have not been sufficiently evaluated for non-P450 enzymes. In addition to the involvement of the liver, extrahepatic enzymes (intestine, kidney, lung) are also likely to contribute to these pathways. While there has been considerable progress in predicting metabolic pathways and clearance primarily mediated by the liver, progress in characterizing extrahepatic metabolism and prediction of clearance has been slow. Well-characterized in vitro systems or in vivo animal models to assess drug-drug interaction potential and intersubject variability due to polymorphism are not available. Here we focus on the utility of appropriate in vitro studies to characterize non-CYP-mediated metabolism and to understand the enzymes involved followed by pharmacokinetic studies in the appropriately characterized surrogate species. The review will highlight progress made in establishing in vitro-in vivo correlation, predicting human clearance and avoiding costly clinical failures when non-CYP-mediated metabolic pathways are predominant.

Enhancement of Oral Bioavailability of Curcumin by a Novel Solid Dispersion System

The objective of this study was to improve the solubility and bioavailability of curcumin by a new curcumin dripping pills (Cur-DPs) formulation using melt mixing methods. The optimal formulation consisted of Polyethoxylated 40 hydrogenated castor oil (Cremophor RH40), Poloxamer 188, and Polyethylene glycol 4000 (PEG 4000). Differential scanning calorimetry (DSC), powder X-ray diffraction (PXRD), and Fourier-transform infrared spectroscopy (FT-IR) were used to verify the forming of Cur-DPs. All the physical characterization information proved the formation of Cur-DPs, and the results demonstrated the superiority of the dripping pills in dissolution rates. The pharmacokinetic study of Cur-DPs was performed in rats compared to the pure curcumin suspension. The oral bioavailability of poorly water-soluble curcumin was successfully improved by CUR-DPs. And the stability of prepared Cur-DP was also in a good state in 3 months. These results identified the Cur-DPs was an effective new approach for pharmaceutical application.

Physiologically based pharmacokinetic modeling of impaired carboxylesterase-1 activity: effects on oseltamivir disposition

BACKGROUND AND OBJECTIVE

Human carboxylesterase-1 (CES1) is an enzyme that is primarily expressed in the liver, where it plays an important role in the metabolism of many commonly used medications. Ethanol (alcohol)-mediated inhibition of CES1 and loss-of-function polymorphisms in the CES1 gene can markedly reduce this enzyme's function. Such alterations in CES1 activity may have important effects on the disposition of substrate drugs. The aim of this study is to develop a physiologically based pharmacokinetic (PBPK) model to predict changes in CES1 substrate drug exposure in humans with CES1 activity impaired by ethanol or loss-of-function CES1 genetic polymorphisms.

METHODS

The antiviral drug oseltamivir, an ethyl ester prodrug that is rapidly converted in vivo to the active metabolite oseltamivir carboxylate (OSC) by CES1 was used as a probe drug for CES1 activity. Oseltamivir PBPK models integrating in vitro and in vivo data were developed and refined. Then the changes in oseltamivir and OSC exposure in humans with CES1 impaired by ethanol or polymorphisms were simulated using a PBPK model incorporating in vitro inhibition and enzyme kinetic data. Model assumptions were verified by comparison of simulations with observed and published data. A sensitivity analysis was performed to gain a mechanistic understanding of the exposure changes of oseltamivir and OSC.

RESULTS

The simulated changes in oseltamivir and OSC exposures in humans with CES1 impaired by ethanol or polymorphism were similar to the observed data. The observed exposures to oseltamivir were increased by 46 and 37 % for the area under the plasma concentration-time curve from time zero to 6 h (AUC6) and from time zero to 24 h (AUC24), respectively, with co-administration of ethanol 0.6 g/kg. In contrast, only a slight change was observed in OSC exposure. The simulated data show the same trend as evidenced by greater change in exposures to oseltamivir (27 and 26 % for AUC(6) and AUC(24), [corrected] respectively) than OSC (≤6 %).

CONCLUSIONS

The PBPK model of impaired CES1 activity correctly predicts observed human data. This model can be extended to predict the effects of drug interactions and other factors affecting the pharmacokinetics of other CES1 substrate drugs.

Efficient synthesis of tetrahydronaphthalene- or isochroman-fused spirooxindoles using tandem reactions

The cascade reaction involving a Michael–aldol or vinylogous Henry-acetalization relay is described. We have used the cascade reaction to assemble tetrahydronaphthalene- or isochroman-fused spirooxindoles and other drug-like spirocyclic scaffolds.

Diterpenoids of terrestrial origin

This review covers the isolation and chemistry of diterpenoids from terrestrial as opposed to marine sources and includes labdanes, clerodanes, pimaranes, abietanes, kauranes, gibberellins, cembranes and their cyclization products. The literature from January to December 2013 is reviewed.

Synergistic effects of clopidogrel and fufang danshen dripping pills by modulation of the metabolism target and pharmacokinetics

Background and Objective. The aim was to evaluate the synergistic effects of clopidogrel and FDDP by modulating the metabolism target and the pharmacokinetics. Methods. The inhibition effect of FDDP on the CES1 was first investigated by the molecular simulation method, and the synergistic effects on the pharmacokinetics of CPGS were studied as follows: SD rats were treated with oral clopidogrel alone at a dosage of 30 mg/kg or the combination of clopidogrel and FDDP at dosages of 30 mg/kg and 324 mg/kg, respectively, for 21 days. The concentrations of CPGS in the blood plasma samples were determined and the calculated concentrations were used to determine the pharmacokinetic parameters. Results. 20 compounds in FDDP potentially interacted with CES1 target. The CPGS showed a two-compartment model pharmacokinetic profile. The concentration-time course of CPGS was not changed by FDDP, but FDDP decreased the peak plasma concentration and area under the curve of CPGS. Conclusion. The CES1's activity could be partly inhibited by FDDP through the molecular simulation investigation. The concentration-time course of CPGS was altered slightly by FDDP. The results demonstrated the synergistic effects of clopidogrel and FDDP by modulating both the pharmacokinetics and the target metabolism.

Cytochrome P450 enzyme mediated herbal drug interactions (Part 2)

To date, a number of significant herbal drug interactions have their origins in the alteration of cytochrome P450 (CYP) activity by various phytochemicals. Among the most noteworthy are those involving St. John's wort and drugs metabolized by human CYP3A4 enzyme. This review article is the continued work from our previous article (Part 1) published in this journal (Wanwimolruk and Prachayasittikul, 2014[ref:133]). This article extends the scope of the review to six more herbs and updates information on herbal drug interactions. These include black cohosh, ginseng, grape seed extract, green tea, kava, saw palmetto and some important Chinese medicines are also presented. Even though there have been many studies to determine the effects of herbs and herbal medicines on the activity of CYP, most of them were in vitro and in animal studies. Therefore, the studies are limited in predicting the clinical relevance of herbal drug interactions. It appeared that the majority of the herbal medicines have no clear effects on most of the CYPs examined. For example, the existing clinical trial data imply that black cohosh, ginseng and saw palmetto are unlikely to affect the pharmacokinetics of conventional drugs metabolized by human CYPs. For grape seed extract and green tea, adverse herbal drug interactions are unlikely when they are concomitantly taken with prescription drugs that are CYP substrates. Although there were few clinical studies on potential CYP-mediated interactions produced by kava, present data suggest that kava supplements have the ability to inhibit CYP1A2 and CYP2E1 significantly. Therefore, caution should be taken when patients take kava with CYP1A2 or CYP2E1 substrate drugs as it may enhance their therapeutic and adverse effects. Despite the long use of traditional Chinese herbal medicines, little is known about the potential drug interactions with these herbs. Many popularly used Chinese medicines have been shown in vitro to significantly change the activity of human CYP. However, with little confirming evidence from clinical studies, precaution should be exercised when patients are taking Chinese herbal medicines concomitantly with drugs that are CYP substrates. Currently there is sufficient evidence to indicate that herbal drug interactions can occur and may lead to serious clinical consequence. Further clinical trial research should be conducted to verify these herbal drug interactions. Education on herbal drug interactions and communication with patients on their use of herbal products is also important.