B-esterase measurements and other blood related biomarkers in loggerhead sea turtles (Caretta caretta) as indicators of health status.

The loggerhead sea turtle (Caretta caretta) has been selected as sentinel species by the Marine Strategy Framework Directive (MSFD) descriptor 10 in relation to marine litter. In this, and other protected species, there is a need to develop conservative pollution biomarkers equally informative of chemical exposures to those traditionally carried out in metabolic organs, such as the liver. With this aim, plasma from turtles undergoing rehabilitation at the Fundació Oceanogràfic rescue centre (Arca del Mar) were selected and tested for B-esterase measurements. Hydrolysis rates of acetylcholinesterase (AChE), butyrylcholinesterase (BChE) and carboxylesterases (CEs) using four commercial substrates were undertaken on 191 plasma samples. Results indicated that acetylthiocholine was the most adequate substrate of cholinesterases and butyrate esters for CE measures. The correlation of these parameters with well-established blood biochemistry measurements was analysed. B-esterase measures in wild specimens were discussed in relation to age group, pathology on admission to the rescue centre and season; moreover, contrasts with long-term resident turtles were also made. Although this study provides baseline data on B-esterase measures in a large sample size for this species, more complementary information is still needed in terms of population genetics, chemical exposures, and in relation to other biochemical parameters before they can be confidently applied in wild specimens within the regulatory MSFD.

The mechanistic basis for the toxicity difference between juvenile rats and mice following exposure to the agricultural insecticide chlorpyrifos.

At high exposure levels, organophosphorus insecticides (OPs) exert their toxicity in mammals through the inhibition of brain acetylcholinesterase (AChE) leading to the accumulation of acetylcholine in cholinergic synapses and hyperactivity of the nervous system. Currently, there is a concern that low-level exposure to OPs induces negative impacts in developing children and the chemical most linked to these issues is chlorpyrifos (CPF). Our laboratory has observed that a difference in the susceptibility to repeated exposure to CPF exists between juvenile mice and rats with respect to the inhibition of brain AChE. The basis for this difference is unknown but differences in the levels of the detoxification mechanisms could play a role. To investigate this, 10-day old rat and mice pups were exposed daily for 7 days to either corn oil or a range of dosages of CPF via oral gavage. Four hours following the last administration of CPF on day 16, brain, blood, and liver were collected. The inhibition of brain AChE activity was higher in juvenile rats as compared to juvenile mice. The levels of activity of the detoxification enzymes and the impact of CPF exposure on their activity were determined in the two species at this age. In blood and liver, the enzyme paraoxonase-1 (PON1) hydrolyzes the active metabolite of CPF (CPF-oxon), and the enzymes carboxylesterase (CES) and cholinesterase (ChE) act as alternative binding sites for CPF-oxon removing it from circulation and providing protection. Both species had similar levels of PON1 activity in the liver and serum. Mice had higher ChE activity in liver and serum than rats but, following CPF exposure, the percentage inhibition was similar between species at an equivalent dosage. Even though rats had slightly higher liver CES activity than mice, the level of inhibition following exposure was higher in rats. In serum, juvenile mice had an 8-fold higher CES activity than rats, and exposure to a CPF dosage that almost eliminated CES activity in rats only resulted in 22% inhibition in mice suggesting that the high serum CES activity in mice as compared to rats is a key component in this species difference. In addition, there was a species difference in the sensitivity of CES to inhibition by CPF-oxon with rats having a lower IC50 in both liver and serum as compared to mice. This greater enzyme sensitivity suggests that saturation of CES would occur more rapidly in juvenile rats than in mice, resulting in more CPF reaching the brain to inhibit AChE in rats.

Carbon nanomaterial functionalization with pesticide-detoxifying carboxylesterase.

Four carbon materials, spent coffee-ground biochar, carbon black, short CNTs, and nitrogen-doped few-layer graphene (N-graphene) were tested for their functionalization with a commercial carboxylesterase. Their robustness to variations in time and key physicochemical parameters (temperature and pH) was analysed. In general, carbon nanomaterials showed better performance than biochar, both in terms of binding capacity and resilience in harsh conditions, at statistically significant levels. Among the tested materials, functionalized N-graphene also showed the highest level of inhibition of carboxylesterase by pesticide exposure. Therefore, N-graphene was selected for biotechnological application of pesticide scavenging toxicity in T. thermophila, a ciliate bioindicator of water quality. While immobilization of the enzyme was not effective in the case of carbaryl, a methyl carbamate, in the case of the organophosphorus dichlorvos, a 1- or 30-min contact time with a water solution containing 5 times the LC100 - 0.5 mM - allowed 50% and 100% rescue of ciliate survival, respectively. These results suggest that functionalization with carboxylesterase may be of additional benefit compared to bare carbon in water clean-up procedures, especially for highly hydrophilic pesticides such as dichlorvos.

Human carboxylesterase 1A plays a predominant role in the hydrolytic activation of remdesivir in humans.

Remdesivir, an intravenous nucleotide prodrug, has been approved for treating COVID-19 in hospitalized adults and pediatric patients. Upon administration, remdesivir can be readily hydrolyzed to form its active form GS-441524, while the cleavage of the carboxylic ester into GS-704277 is the first step for remdesivir activation. This study aims to assign the key enzymes responsible for remdesivir hydrolysis in humans, as well as to investigate the kinetics of remdesivir hydrolysis in various enzyme sources. The results showed that remdesivir could be hydrolyzed to form GS-704277 in human plasma and the microsomes from human liver (HLMs), lung (HLuMs) and kidney (HKMs), while the hydrolytic rate of remdesivir in HLMs was the fastest. Chemical inhibition and reaction phenotyping assays suggested that human carboxylesterase 1 (hCES1A) played a predominant role in remdesivir hydrolysis, while cathepsin A (CTSA), acetylcholinesterase (AchE) and butyrylcholinesterase (BchE) contributed to a lesser extent. Enzymatic kinetic analyses demonstrated that remdesivir hydrolysis in hCES1A (SHUTCM) and HLMs showed similar kinetic plots and much closed Km values to each other. Meanwhile, GS-704277 formation rates were strongly correlated with the CES1A activities in HLM samples from different individual donors. Further investigation revealed that simvastatin (a therapeutic agent for adjuvant treating COVID-19) strongly inhibited remdesivir hydrolysis in both recombinant hCES1A and HLMs. Collectively, our findings reveal that hCES1A plays a predominant role in remdesivir hydrolysis in humans, which are very helpful for predicting inter-individual variability in response to remdesivir and for guiding the rational use of this anti-COVID-19 agent in clinical settings.

FumDSB Can Reduce the Toxic Effects of Fumonisin B1 by Regulating Several Brain-Gut Peptides in Both the Hypothalamus and Jejunum of Growing Pigs.

Fumonisin B1 (FB1) is the most common food-borne mycotoxin produced by the Fusarium species, posing a potential threat to human and animal health. Pigs are more sensitive to FB1 ingested from feed compared to other farmed livestock. Enzymatic degradation is an ideal detoxification method that has attracted much attention. This study aimed to explore the functional characteristics of the carboxylesterase FumDSB in growing pigs from the perspective of brain-gut regulation. A total of 24 growing pigs were divided into three groups. The control group was fed a basal diet, the FB1 group was supplemented with FB1 at 5 mg/kg feed, and the FumDSB group received added FumDSB based on the diet of the FB1 group. After 35 days of animal trials, samples from the hypothalamus and jejunum were analyzed through HE staining, qRT-PCR and immunohistochemistry. The results demonstrated that the ingestion of FB1 can reduce the feed intake and weight gain of growing pigs, indicating that several appetite-related brain-gut peptides (including NPY, PYY, ghrelin and obestatin, etc.) play important roles in the anorexia response induced by FB1. After adding FumDSB as detoxifying enzymes, however, the anorexia effects of FB1 were alleviated, and the expression and distribution of the corresponding brain-gut peptides exhibited a certain degree of regulation. In conclusion, the addition of FumDSB can reduce the anorexia effects of FB1 by regulating several brain-gut peptides in both the hypothalamus and the jejunum of growing pigs.

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.

[Construction and application of pharmacophore model of human carboxylesterase 2 inhibitors].

According to human carboxylesterase 2(hCE2) inhibitors reported in the literature, the pharmacophore model of hCE2 inhibitors was developed using HipHop module in Discovery Studio 2016. The optimized pharmacophore model, which was validated by test set, contained two hydrophobic, one hydrogen bond acceptor, and one aromatic ring features. Using the pharmacophore model established, 5 potential hCE2 inhibitors(CS-1,CS-2,CS-3,CS-6 and CS-8) were screened from 20 compounds isolated from the roots of Paeonia lactiflora, which were further confirmed in vitro, with the IC_(50) values of 5.04, 5.21, 5.95, 6.64 and 7.94 µmol·L~(-1), respectively. The results demonstrated that the pharmacophore model exerted excellent forecasting ability with high precision, which could be applied to screen novel hCE2 inhibitors from Chinese medicinal materials.

Discovery of hCES2A inhibitors from Glycyrrhiza inflata via combination of docking-based virtual screening and fluorescence-based inhibition assays.

Human carboxylesterase 2 (hCES2A) is a key target to ameliorate the intestinal toxicity triggered by irinotecan that causes severe diarrhea in 50%-80% of patients receiving this anticancer agent. Herbal medicines are frequently used for the prevention and treatment of the intestinal toxicity of irinotecan, but it is very hard to find strong hCES2A inhibitors from herbal medicines in an efficient way. Herein, an integrated strategy via combination of chemical profiling, docking-based virtual screening and fluorescence-based high-throughput inhibitor screening assays was utilized. Following the screening of a total of 73 herbal products, licorice (the dried root of Glycyrrhiza species) was found with the most potent hCES2A inhibition activity. Further investigation revealed that the chalcones and several flavonols in licorice displayed strong hCES2A inhibition activities, while isoliquiritigenin, echinatin, naringenin, gancaonin I and glycycoumarin exhibited moderate inhibition of hCES2A. Inhibition kinetic analysis demonstrated that licochalcone A, licochalcone C, licochalcone D and isolicoflavonol potently inhibited hCES2A-mediated fluorescein diacetate hydrolysis in a reversible and mixed inhibition manner, with Ki values less than 1.0 µM. Further investigations demonstrated that licochalcone C, the most potent hCES2A inhibitor identified from licorice, dose-dependently inhibited intracellular hCES2A in living HepG2 cells. In summary, this study proposed an integrated strategy to find hCES2A inhibitors from herbal medicines, and our findings suggested that the chalcones and isolicoflavonol in licorice were the key ingredients responsible for hCES2A inhibition, which would be very helpful to develop new herbal remedies or drugs for ameliorating hCES2A-associated drug toxicity.

Chemoproteomics-Enabled De Novo Discovery of Photoswitchable Carboxylesterase Inhibitors for Optically Controlled Drug Metabolism.

Herein, we report arylazopyrazole ureas and sulfones as a novel class of photoswitchable serine hydrolase inhibitors and present a chemoproteomic platform for rapid discovery of optically controlled serine hydrolase targets in complex proteomes. Specifically, we identify highly potent and selective photoswitchable inhibitors of the drug-metabolizing enzymes carboxylesterases 1 and 2 and demonstrate their pharmacological application by optically controlling the metabolism of the immunosuppressant drug mycophenolate mofetil. Collectively, this proof-of-concept study provides a first example of photopharmacological tools to optically control drug metabolism by modulating the activity of a metabolizing enzyme. Our arylazopyrazole ureas and sulfones offer synthetically accessible scaffolds that can be expanded to identify specific photoswitchable inhibitors for other serine hydrolases, including lipases, peptidases, and proteases. Our chemoproteomic platform can be applied to other photoswitches and scaffolds to achieve optical control over diverse protein classes.

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.

Toxicological screening of marine red algae Champia parvula (C. Agardh) against the dengue mosquito vector Aedes aegypti (Linn.) and its non-toxicity against three beneficial aquatic predators.

Larval toxicity of ethanolic extract of C. parvula (Ex-Cp) was prominent in the second and the third instars at the maximum lethal dosage of 100 ppm with 98 and 97 % mortality rate respectively. The LC50 and LC90 was displayed at 43 ppm and 88 ppm dosage respectively. Correspondingly, the sub-lethal dosage (65 ppm) of Ex-Cp significantly alters the carboxylesterase (α and ß), GST and CYP450 enzyme level in both III and IV instar larvae in dose-dependent manner. Similarly, the Ex-Cp displayed significant repellent activity (97 %) with a maximum level of protection time (210 min). Photomicrography assay of Ex-Cp (65 ppm) were toxic to dengue larvae as compared to control. The non-target toxicity of Ex-Cp against the beneficial mosquito predators displayed less toxicity at the maximum dosage of 600 ppm as compared to Temephos. Thus the present research delivers the target and non-target toxicity of red algae C. parvula against the dengue mosquito vector.

Construction and application of a high-content analysis for identifying human carboxylesterase 2 inhibitors in living cell system.

Human carboxylesterase 2 (hCE2), one of the most principal drug-metabolizing enzymes, catalyzes the hydrolysis of a variety of endogenous esters, anticancer agents, and environmental toxicants. The significant roles of hCE2 in both endobiotic and xenobiotic metabolism sparked great interest in the discovery and development of efficacious and selective inhibitors. However, the safe and effective inhibitors of hCE2 are scarce, due to the lack of efficient screening and evaluation systems for complex biological systems. To offer a solution to this problem, a high-content analysis (HCA)-based cell imaging and multiparametric assay method was constructed for evaluating the inhibitory effect and safety of hCE2 inhibitors in living cell system. In this study, we first established a cell imaging-based method for identifying hCE2 inhibitors at the living cell level with hCE2 fluorescent probe NCEN. Meanwhile, two nuclear probes, Hoechst 33342 and PI, were integrated to evaluate the potential cytotoxicity of compounds simultaneously. Then, the accuracy of the HCA-based method was verified by the LC-FD-based method with a positive inhibitor BNPP, and the results showed that the HCA-based method exhibited excellent precision, robustness, and reliability. Finally, the newly established HCA-based multiparametric assay panel was successfully applied to re-evaluate a series of reported hCE2 inhibitors in living cells. In summary, the HCA-based multiparametric method could serve as an efficient tool for the accuracy measurement inhibitory effect and cytotoxicity of compounds against hCE2 in living cell system. Graphical abstract.

Effect of food contamination and collection material in the measurement of biomarkers in saliva of horses.

This study aims to evaluate the effect of the presence of food and the material used in a panel of biomarkers in saliva of horses. For the food effect study, clean saliva was incubated with a known amount of food consisting of oats, hay or grass. Significant changes were observed when saliva was incubated with oats for total protein (P = .050) and phosphorus (P = .008), with grass for total protein (P = .037), salivary alpha-amylase (sAA, P = .018), total esterase (TEA, P = .018), butyrilcholinesterase (BChE, P = .037), adenosine deaminase (ADA, P = .037), and total bilirubin (P = .018), and with hay for sAA (P = .018), phosphorus (P = .037), γ-glutamyl transferase (gGT, P = .004), and creatine kinase (CK, P = .016). For the material-based collection study, saliva using a sponge and a cotton role at the same time were collected and compared. Lower values were obtained in clean saliva collected with cotton role compared to sponge for sAA (P = .030), TEA (P = .034), BChE (P = .003), gGT (P = .002) and cortisol (P < .001) In conclusion, the presence of food and the material used for its collection, can influence the results obtained when analytes are measured in saliva of horses.

Molluscicidal activity and physiological toxicity of quaternary benzo[c]phenanthridine alkaloids (QBAs) from Macleaya cordata fruits on Oncomelania hupensis.

Schistosomiasis is a serious worldwide parasitic disease. One of the best ways to control schistosomiasis is to control the population of Oncomelania hupensis snails. We sought to identify a high-efficiency biogenic molluscicide against Oncomelania with low toxicity, to avoid chemical molluscicide contamination and toxicity in aquatic organisms. We extracted quaternary benzo[c]phenanthridine alkaloids (QBAs) from Macleaya cordata fruits. Molluscicidal activity of the QBAs against Oncomelania was determined using bioassay. Our results showed that the extracted QBAs had a strong molluscicidal effect. In treatment of O. hupensis with QBAs for 48 h and 72 h, the lethal concentration (LC50) was 2.89 mg/L and 1.29 mg/L, respectively. The molluscicidal activity of QBAs was close to that of niclosamide (ethanolamine salt), indicating that QBAs have potential development value as novel biogenic molluscicides. We also analyzed physiological toxicity mechanisms by examining the activity of several important detoxification enzymes. We measured the effect of the extracted QBAs on the activities of glutathione S-transferase (GST), carboxylesterase (CarE), acid phosphatase (ACP), and alkaline phosphatase (AKP) in the liver of O. hupensis. We found that the effects of QBAs on detoxification metabolism in O. hupensis were time and concentration dependent. The activities of GST, CarE, AKP, and ACP in the liver of snails increased significantly in the early stage of treatment (24 h), but decreased sharply in later stages (120 h), compared with these activities in controls. GST, CarE, AKP, and ACP activity in the liver of snails treated with LC50 QBAs for 120 h decreased by 62.3%, 78.1%, 59.2%, and 68.6%, respectively. Our results indicate that these enzymes were seriously inhibited by the extracted QBAs and the detoxification and metabolic functions of the liver gradually weakened, leading to poisoning, which could be the main cause of death in O. hupensis snails.

Demethylbellidifolin isolated from Swertia bimaculate against human carboxylesterase 2: Kinetics and interaction mechanism merged with docking simulations.

In this study, forty-nine kinds of traditional Chinese medicines (TCMs) were evaluated for their inhibitory activities against human carboxylesterase 2 (HCE 2) using a human liver microsome (HLM) system. Swertia bimaculata showed significant inhibition on HCE 2 at 10 µg/mL among forty-nine kinds of TCMs. The extract of Swertia bimaculata was separated by preparative HPLC to afford demethylbellidifolin (1) identified by MS, 1H NMR, and 13C NMR spectra. Demethylbellidifolin (1) was assayed for its inhibitory HCE 2 effect by HCE 2-mediated DDAB hydrolysis, and its potential IC50 value was 3.12 ±â€¯0.64 µM. Demethylbellidifolin (1) was assigned as a mixed-type competitive inhibitor with the inhibiton constant Ki value of 6.87 µM by Lineweaver-Burk and slope plots. Living cell imaging was conducted to corroborate its inhibitory HCE 2 activity. Molecular docking indicated potential interactions of demethylbellidifolin (1) with HCE 2 through two hydrogen bonds of the C-3 and C-5 hydroxy groups with amino acid residues Glu227 and Ser228 in the catalytic cavity, respectively.

A natural inhibitor from Alisma orientale against human carboxylesterase 2: Kinetics, circular dichroism spectroscopic analysis, and docking simulation.

As a part of our searching for natural human carboxylesterase 2 (human CES 2) inhibitors from traditional Chinese medicine, we found that the extract of Alisma orientale significantly inhibited human CES 2 in vitro. The investigation on A. orientale led to the isolation of a new protostane-type triterpenoid alismanin I (1). Its structure was determined according to HRESIMS, 1D and 2D NMR spectra. Alismanin I (1) displayed significantly inhibitory activity against human CES 2 with IC50 value of 1.31 ±â€¯0.09 µM assayed by human CES 2-mediated DDAB hydrolysis. According to its inhibition kinetic result, compound 1 was a noncompetitive type inhibitor, and its Ki was 3.65 µM. Its inhibitory effect was confirmed in living cell level through a visual manner. The potential interaction mechanism of compound 1 with human CES 2 was also analyzed by circular dichroism (CD) spectrum and molecular docking.

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.

Evaluation of the inhibition of human carboxylesterases (CESs) by the active ingredients from Schisandra chinensis.

1. Schisandra chinensis, also called wuweizi in Chinese, is the fruit of Schisandra chinensis (Turcz.) Baill., and has been officially utilized as an astringent tonic for more than two thousand years in China. This study aims to evaluate the inhibition of carboxylesterases (CESs) by the major ingredients isolated from Schisandra chinensis, including Anwuligan, Schisandrol B, Schisanhenol, deoxyschizandrin, and Schisandrin B. 2. In vitro human liver microsomes (HLMs)-catalyzed hydrolysis of 2-(2-Benzoyl-3-methoxyphenyl) benzothiazole (BMBT) and fluorescein diacetate (FD) was employed as the probe reaction for CES1 and CES2, respectively. Initial screening, inhibition kinetics determination (inhibition type and parameters (Ki)), and in silico docking method were carried out. 3. Schisandrin B showed strong inhibition on the activity of CES1, and the activity of CES2 was strongly inhibited by Anwuligan and Schisandrin B. Schisandrin B exhibited noncompetitive inhibition towards CES1 and CES2. Anwuligan showed competitive inhibition towards CES2. The inhibition kinetic parameters (Ki) were calculated to be 29.8, 0.6, and 8.1 uM for the inhibition of Schisandrin B on CES1, Anwuligan on CES2, and Schisandrin B on CES2. In silico docking showed that hydrogen bonds and hydrophobic interactions contributed to the inhibition of Schisandrin B on CES1, Anwuligan on CES2, and Schisandrin B on CES2. All these information will be helpful for understanding the adverse effects of Schisandra chinensis due to the inhibition of CESs-catalyzed metabolism.

Bysspectin A, an unusual octaketide dimer and the precursor derivatives from the endophytic fungus Byssochlamys spectabilis IMM0002 and their biological activities.

Bysspectin A (1), a polyketide-derived octaketide dimer with a novel carbon skeleton, and two new precursor derivatives, bysspectins B and C (2 and 3), were obtained from an organic extract of the endophytic fungus Byssochlamys spectabilis that had been isolated from a leaf tissue of the traditional Chinese medicinal plant Edgeworthia chrysantha, together with a known octaketide, paecilocin A (4). Their structures were determined by HRMS, 1D and 2D NMR spectroscopic analysis. A plausible route for their biosynthetic pathway is proposed. Compounds 1-3 were tested for their antimicrobial activities. Only compound 3 was weakly active against Escherichia coli and Staphyloccocus aureus with MIC values of 32 and 64 µg/mL, respectively. Further, the inhibitory effects on human carboxylesterases (hCE1, hCE2) of compounds 1 and 4 were evaluated. The results demonstrated that bysspectin A (1) was a novel and highly selective inhibitor against hCE2 with the IC50 value of 2.01 µM. Docking simulation also demonstrated that active compound 1 created interaction with the Ser-288 (the catalytic amino-acid in the catalytic cavity) of hCE2 via hydrogen bonding, revealing its highly selective inhibition toward hCE2.

Role of geraniol against lead acetate-mediated hepatic damage and their interaction with liver carboxylesterase activity in rats.

In this study, the effect of geraniol (50 mg/kg for 30 d), a natural antioxidant and repellent/antifeedant monoterpene, in a rat model of lead acetate-induced (500 ppm for 30 d) liver damage was evaluated. Hepatic malondialdehyde increased in the lead acetate group. Reduced glutathione unchanged, but glutathione S-transferase, glutathione reductase, as well as carboxylesterase activities decreased in geraniol, lead acetate and geraniol + lead acetate groups. 8-OhDG immunoreactivity, mononuclear cell infiltrations and hepatic lead concentration were lower in the geraniol + lead acetate group than the lead acetate group. Serum aspartate aminotransferase and alanine aminotransferase activities increased in the Pb acetate group. In conclusion, lead acetate causes oxidative and toxic damage in the liver and this effect can reduce with geraniol treatment. However, we first observed that lead acetate, as well as geraniol, can affect liver carboxylesterase activity.