Mirabegron displays anticancer effects by globally browning adipose tissues.

Metabolic reprogramming in malignant cells is a hallmark of cancer that relies on augmented glycolytic metabolism to support their growth, invasion, and metastasis. However, the impact of global adipose metabolism on tumor growth and the drug development by targeting adipose metabolism remain largely unexplored. Here we show that a therapeutic paradigm of drugs is effective for treating various cancer types by browning adipose tissues. Mirabegron, a clinically available drug for overactive bladders, displays potent anticancer effects in various animal cancer models, including untreatable cancers such as pancreatic ductal adenocarcinoma and hepatocellular carcinoma, via the browning of adipose tissues. Genetic deletion of the uncoupling protein 1, a key thermogenic protein in adipose tissues, ablates the anticancer effect. Similarly, the removal of brown adipose tissue, which is responsible for non-shivering thermogenesis, attenuates the anticancer activity of mirabegron. These findings demonstrate that mirabegron represents a paradigm of anticancer drugs with a distinct mechanism for the effective treatment of multiple cancers.

Cryo-EM structure of the ß3-adrenergic receptor reveals the molecular basis of subtype selectivity.

The ß3-adrenergic receptor (ß3AR) is predominantly expressed in adipose tissue and urinary bladder and has emerged as an attractive drug target for the treatment of type 2 diabetes, obesity, and overactive bladder (OAB). Here, we report the cryogenic electron microscopy structure of the ß3AR-Gs signaling complex with the selective agonist mirabegron, a first-in-class drug for OAB. Comparison of this structure with the previously reported ß1AR and ß2AR structures reveals a receptor activation mechanism upon mirabegron binding to the orthosteric site. Notably, the narrower exosite in ß3AR creates a perpendicular pocket for mirabegron. Mutational analyses suggest that a combination of both the exosite shape and the amino-acid-residue substitutions defines the drug selectivity of the ßAR agonists. Our findings provide a molecular basis for ßAR subtype selectivity, allowing the design of more-selective agents with fewer adverse effects.

Pharmacokinetic Characterization of LW6, a Novel Hypoxia-Inducible Factor-1α (HIF-1α) Inhibitor in Mice.

LW6, an (aryloxyacetylamino)benzoic acid derivative, was recently identified to be an inhibitor of hypoxia-inducible factor-1α (HIF-1α), which is an attractive target for cancer therapeutics. Although LW6 is known to act by inhibiting the accumulation of HIF-1α, pharmacokinetics needs to be evaluated to assess its potential as an anti-tumor agent. Here, we investigated the plasma pharmacokinetics and metabolism of LW6 in mice. LW6 exhibited a small volume of distribution (0.5 ± 0.1 L/kg), and a short terminal half-life (0.6 ± 0.1 h). Following intravenous or oral administration, LW6 was rapidly converted to its active metabolite, (4-adamantan-1-yl-phenoxy)acetic acid (APA). Although LW6 was rapidly absorbed, its oral bioavailability, estimated using AUClast values, was low (1.7 ± 1.8%). It was slowly degraded in mouse liver microsomes (t1/2 > 1 h) and serum (t1/2 > 6 h). About 54% or 44.8% of LW6 was available systemically as APA in the mouse after a single intravenous or oral administration, respectively. Thus, our results indicated the need to simultaneously consider the active metabolite as well as the parent compound for successful evaluation during lead optimization.

Metabolite Profiling and Characterization of LW6, a Novel HIF-1α Inhibitor, as an Antitumor Drug Candidate in Mice.

A novel HIF (hypoxia-inducible factor)-1α inhibitor, the (aryloxyacetylamino)benzoic acid derivative LW6, is an anticancer agent that inhibits the accumulation of HIF-1α. The aim of this study was to characterize and determine the structures of the metabolites of LW6 in ICR mice. Metabolite identification was performed using a predictive multiple reaction monitoring-information dependent acquisition-enhanced product ion (pMRM-IDA-EPI) method in negative ion mode on a hybrid triple quadrupole-linear ion trap mass spectrometer (QTRAP). A total of 12 metabolites were characterized based on their MS/MS spectra, and the retention times were compared with those of the parent compound. The metabolites were divided into five structural classes based on biotransformation reactions: amide hydrolysis, ester hydrolysis, mono-oxidation, glucuronidation, and a combination of these reactions. From this study, 2-(4-((3r,5r,7r)-adamantan-1-yl)phenoxy)acetic acid (APA, M7), the metabolite produced via amide hydrolysis, was found to be a major circulating metabolite of LW6 in mice. The results of this study can be used to improve the pharmacokinetic profile by lowering the clearance and increasing the exposure relative to LW6.

A bifunctional enzyme belonging to cytochrome P450 family involved in the O-dealkylation and N-dealkoxymethylation toward chloroacetanilide herbicides in Rhodococcus sp. B2.

BACKGROUND: The chloroacetamide herbicides pretilachlor is an emerging pollutant. Due to the large amount of use, its presence in the environment threatens human health. However, the molecular mechanism of pretilachlor degradation remains unknown. RESULTS: Now, Rhodococcus sp. B2 was isolated from rice field and shown to degrade pretilachlor. The maximum pretilachlor degradation efficiency (86.1%) was observed at a culture time of 5 d, an initial substrate concentration 50 mg/L, pH 6.98, and 30.1 °C. One novel metabolite N-hydroxyethyl-2-chloro-N-(2, 6-diethyl-phenyl)-acetamide was identified by gas chromatography-mass spectrometry (GC-MS). Draft genome comparison demonstrated that a 32,147-bp DNA fragment, harboring gene cluster (EthRABCDB2), was absent from the mutant strain TB2 which could not degrade pretilachlor. The Eth gene cluster, encodes an AraC/XylS family transcriptional regulator (EthRB2), a ferredoxin reductase (EthAB2), a cytochrome P450 monooxygenase (EthBB2), a ferredoxin (EthCB2) and a 10-kDa protein of unknown function (EthDB2). Complementation with EthABCDB2 and EthABDB2, but not EthABCB2 in strain TB2 restored its ability to degrade chloroacetamide herbicides. Subsequently, codon optimization of EthABCDB2 was performed, after which the optimized components were separately expressed in Escherichia coli, and purified using Ni-affinity chromatography. A mixture of EthABCDB2 or EthABDB2 but not EthABCB2 catalyzed the N-dealkoxymethylation of alachlor, acetochlor, butachlor, and propisochlor and O-dealkylation of pretilachlor, revealing that EthDB2 acted as a ferredoxin in strain B2. EthABDB2 displayed maximal activity at 30 °C and pH 7.5. CONCLUSIONS: This is the first report of a P450 family oxygenase catalyzing the O-dealkylation and N-dealkoxymethylation of pretilachlor and propisochlor, respectively. And the results of the present study provide a microbial resource for the remediation of chloroacetamide herbicides-contaminated sites.

Mirabegron: The most promising adipose tissue beiging agent.

Accumulation of white adipose tissue (WAT) underlies the obesity epidemic, leading to current therapeutic techniques that are being investigated for their ability to activate/"beige" this tissue. Adipose tissue (AT) beiging has been reported through intermittent cold exposure (CE), exercise, and ß3-Adrenergic Receptor (ß3AR) agonists. But how AT beiging can help in the treatment of metabolic disorders like obesity and type 2 diabetes (T2D) remains largely unexplored. This review summarizes recent research on the use of ß3AR agonist, mirabegron (Myrbetriq®), in stimulating beiging in AT. Researchers have only recently been able to determine the optimal therapeutic dose of mirabegron for inducing beiging in subcutaneous/ inguinal WAT, where the benefits of AT activation are evident without the undesired cardiovascular side effects. To determine whether the effects that mirabegron elicits are metabolically beneficial, a comparison of the undisputed findings resulting from intermittent CE-induced beiging and the disputed findings from exercise-induced beiging was conducted. Given the recent in vivo animal and clinical studies, the understanding of how mirabegron can be metabolically beneficial for both lean and obese individuals is more clearly understood. These studies have demonstrated that circulating adipokines, glucose metabolism, and lipid droplet (LD) size are all positively affected by mirabegron administration. Recent studies have also demonstrated that mirabegron has similar outcomes to intermittent CE and displays more direct evidence for beiging than those produced with exercise. With these current findings, mirabegron is considered the most promising and safest ß3AR agonist currently available that has the potential to be used in the therapeutic treatment of metabolic disorders, and future studies into its interaction with different conditions may prove to be useful as part of a treatment plan in combination with a healthy diet and exercise.

Probing phenylcarbamoylazinane-1,2,4-triazole amides derivatives as lipoxygenase inhibitors along with cytotoxic, ADME and molecular docking studies.

Hunting small molecules as anti-inflammatory agents/drugs is an expanding and successful approach to treat several inflammatory diseases such as cancer, asthma, arthritis, and psoriasis. Besides other methods, inflammatory diseases can be treated by lipoxygenase inhibitors, which have a profound influence on the development and progression of inflammation. In the present study, a series of new N-alkyl/aralky/aryl derivatives (7a-o) of 2-(4-phenyl-5-(1-phenylcarbamoyl)piperidine-4H-1,2,4-triazol-3-ylthio)acetamide was synthesized and screened for their inhibitory potential against the enzyme 15-lipoxygenase. The simple precursor ethyl piperidine-4-carboxylate (a) was successively converted into phenylcarbamoyl derivative (1), hydrazide (2), semicarbazide (3) and N-phenylated 5-(1-phenylcarbamoyl)piperidine-1,2,4-triazole (4), then in combination with electrophiles (6a-o) through further multistep synthesis, final products (7a-o) were generated. All the synthesized compounds were characterized by FTIR, 1H, 13C NMR spectroscopy, EIMS, and HREIMS spectrometry. Almost all the synthesized compounds showed excellent inhibitory potential against the tested enzyme. Compounds 7c, 7f, 7d, and 7g displayed potent inhibitory potential (IC50 9.25 ± 0.26 to 21.82 ± 0.35 µM), followed by the compounds 7n, 7h, 7e, 7a, 7b, 7l, and 7o with IC50 values in the range of 24.56 ± 0.45 to 46.91 ± 0.57 µM. Compounds 7c, 7f, 7d exhibited 71.5 to 83.5% cellular viability by MTT assay compared with standard curcumin (76.9%) when assayed at 0.125 mM concentration. In silico ADME studies supported the drug-likeness of most of the molecules. In vitro inhibition studies were substantiated by molecular docking wherein the phenyl group attached to the triazole ring was making a π-δ interaction with Leu607. This work reveals the possibility of a synthetic approach of compounds in relation to lipoxygenase inhibition as potential lead compounds in drug discovery.

Degradation of butachlor and propanil by Pseudomonas sp. strain But2 and Acinetobacter baumannii strain DT.

Herbicides have been extensively used globally, resulting in severe environmental pollution. Novel butachlor-degrading Pseudomonas sp. strain But2 isolated from soil can degrade butachlor regardless of the concentration and grows without a lag phase. Specific degradation was increased at 0.01-0.1 mM, and did not change significantly at higher concentrations. During degradation, 2-chloro-N-(2,6-diethylphenyl) acetamide, 2,6-diethylaniline, and 1,3-diethylbenzene were formed, which indicated that deamination occurred. Moreover, Pseudomonas sp. strains could tolerate propanil at up to 0.8 mM. The mixed bacterial culture of Pseudomonas sp. But2 and Acinetobacter baumannii DT (a propanil-degrading bacterial strain) showed highly effective biodegradation of both butachlor and propanil in liquid media and soil. For example, under treatment with the mixed culture, the half-lives of propanil and butachlor were 1 and 5 days, respectively, whereas those for the control were 3 and 15 days. The adjuvants present in herbicides reduced degradation in liquid media, but did not influence herbicide removal from the soil. The results showed that the mixed bacteria culture is a good candidate for the removal of butachlor and propanil from contaminated soils.

Effects of fenclorim on rice physiology, gene transcription and pretilachlor detoxification ability.

BACKGROUND: Fenclorim (Fen) can effectively protect rice from pretilachlor (Pre) injury, but its effects on rice have not been formally evaluated; thus, the Fen mode of action for alleviating the phytotoxicity caused by Pre in rice is not clear. This study aimed to examine the biochemical and physiological effects of Fen on rice and to determine the changes induced by Fen at the transcriptome level. RESULT: The chlorophyll content of rice plants was significantly affected by Pre but not by Fen. The activity of oxidative stress enzymes showed that Fen did not elicit any changes in oxidative stress; however, it reduced lipid peroxidation and oxidative damage induced by Pre. Fen did not affect the uptake of Pre but did affect its persistence in rice. In a transcriptome experiment, Fen upregulated genes in a detoxification pathway. Overall, 25 genes related to detoxification were identified, including P450, GST, and GT. Moreover, qRT-PCR analysis showed that four P450 genes, CYP71Y83, CYP71K14, CYP734A2 and CYP71D55, and two GST genes, GSTU16 and GSTF5, were upregulated by Fen and/or Pre. CONCLUSION: Our work indicates that Fen acts in antioxidative defense in addition to enhancing the metabolism of herbicides in rice.

Biodegradation of propanil by Acinetobacter baumannii DT in a biofilm-batch reactor and effects of butachlor on the degradation process.

The herbicide, propanil, has been extensively applied in weed control, which causes serious environmental pollution. Acinetobacter baumannii DT isolated from soil has been used to determine the degradation rates of propanil and 3,4-dichloroaniline by freely suspended and biofilm cells. The results showed that the bacterial isolate could utilize both compounds as sole carbon and nitrogen sources. Edwards's model could be fitted well to the degradation kinetics of propanil, with the maximum degradation of 0.027 ± 0.003 mM h-1. The investigation of the degradation pathway showed that A. baumannii DT transformed propanil to 3,4-dichloroaniline before being completely degraded via the ortho-cleavage pathway. In addition, A. baumannii DT showed high tolerance to butachlor, a herbicide usually mixed with propanil to enhance weed control. The presence of propanil and butachlor in the liquid media increased the cell surface hydrophobicity and biofilm formation. Moreover, the biofilm reactor showed increased degradation rates of propanil and butachlor and high tolerance of bacteria to these chemicals. The obtained results showed that A. baumannii DT has a high potential in the degradation of propanil.

p97: An Emerging Target for Cancer, Neurodegenerative Diseases, and Viral Infections.

The AAA+ ATPase, p97, also referred to as VCP, plays an essential role in cellular homeostasis by regulating endoplasmic reticulum-associated degradation (ERAD), mitochondrial-associated degradation (MAD), chromatin-associated degradation, autophagy, and endosomal trafficking. Mutations in p97 have been linked to a number of neurodegenerative diseases, and overexpression of wild type p97 is observed in numerous cancers. Furthermore, p97 activity has been shown to be essential for the replication of certain viruses, including poliovirus, herpes simplex virus (HSV), cytomegalovirus (CMV), and influenza. Taken together, these observations highlight the potential for targeting p97 as a therapeutic approach in neurodegeneration, cancer, and certain infectious diseases. This Perspective reviews recent advances in the discovery of small molecule inhibitors of p97, their optimization and characterization, and therapeutic potential.

Discovery and Characterization of XY101, a Potent, Selective, and Orally Bioavailable RORγ Inverse Agonist for Treatment of Castration-Resistant Prostate Cancer.

We report the design, optimization, and biological evaluation of nuclear receptor RORγ inverse agonists as therapeutic agents for prostate cancer treatment. The most potent compound 27 (designated as XY101) exhibited cellular activity with an IC50 value of 30 nM in a cell-based reporter gene assay with good selectivity against other nuclear receptor subtypes. The cocrystal structure of 27 in complex with the RORγ ligand binding domain provided a solid structural basis for its antagonistic mechanism. 27 potently inhibited cell growth, colony formation, and the expression of AR, AR-V7, and PSA. 27 also exhibited good metabolic stability and a pharmacokinetic profile with oral bioavailability of 59% and a half-life of 7.3 h. Notably, 27 demonstrated promising therapeutic effects with significant tumor growth inhibition in a prostate cancer xenograft model in mice. The potent, selective, metabolically stable, and orally available RORγ inverse agonists represent a new class of compounds as potential therapeutics against prostate cancer.

Isolation, characterization, and structural elucidation of 4-methoxyacetanilide from marine actinobacteria Streptomyces sp. SCA29 and evaluation of its enzyme inhibitory, antibacterial, and cytotoxic potential.

Marine actinobacteria are less explored than their terrestrial counterparts as potential source of natural products. The present study was aimed to elucidate the bioactive potential of metabolites produced by marine-derived actinobacterial strain Streptomyces sp.SCA29 isolated from Havelock Island, Andaman and Nicobar Islands, India. The potential isolate SCA29 was identified as Streptomyces sp. by phenotypic, genotypic (16S-rRNA) and phylogenetic analyses. The crude bioactive compound was extracted using organic solvents. The compounds were subjected to separation and purification by column chromatography which yielded six fractions. Each fraction was assayed for inhibition of α-glucosidase and α-amylase enzymes, antagonistic activity against bacterial pathogens, and cytotoxic activity against various cell lines. The fraction F3c was considered to be highly active owing to its significant inhibition potential against α-glucosidase and α-amylase enzymes with IC50 values as 44.26 and 53.19 µg/mL, respectively. The active fraction showed antibacterial activity against test bacterial pathogens with the MIC value ranged from 3.90 to 31.25 µg/mL. The compound also exhibited concentration-dependent cytotoxicity on various cell lines without significant effect against human normal cells. The bioassay-guided fractionation of extract led to the identification of 4-methoxyacetanilide, an acetamide derivative. The structure of the bioactive compound was confirmed by HR-MS, NMR (1H and 13C) and FT-IR spectra, and by comparison with literature data.

Validation of LC-MS/MS methods for the determination of mirabegron and eight metabolites in human plasma in a paediatric population.

Mirabegron is the first registered ß3-adrenoceptor agonist for treatment of overactive bladder as an alternative to antimuscarinics. Previously four liquid chromatography-tandem mass spectrometry assays were published to determine mirabegron and eight metabolites (M5, M8, M11-M16) in human plasma. In order to support paediatric development, the assays were further optimized to reduce the required blood volume and increase the sensitivity. The assays were miniaturized by using 96-well supported liquid extraction plates (mirabegron, M5, M16) or 96-well mixed-mode cation exchange solid phase extraction plates (M8, M11-M15) and a more sensitive MS-system was used. For the analytes, up to fivefold increase in assay sensitivity was achieved. The required blood sample volume was reduced from 10 to 2 mL for each timepoint. Validation demonstrated that the assays were accurate, precise and selective in the determination of mirabegron and metabolites. The assays were successfully applied to evaluate the pharmacokinetics of mirabegron in a paediatric population.

Beta-3 Adrenoceptor Signaling Pathways in Urothelial and Smooth Muscle Cells in the Presence of Succinate.

Succinate, an intermediate metabolite of the Krebs cycle, can alter the metabolomics response to certain drugs and controls an array of molecular responses in the urothelium through activation of its receptor, G-protein coupled receptor 91 (GPR91). Mirabegron, a ß3-adrenergic receptor (ß3-AR) agonist used to treat overactive bladder syndrome (OAB), increases intracellular cAMP in the detrusor smooth muscle cells (SMC), leading to relaxation. We have previously shown that succinate inhibits forskolin-stimulated cAMP production in urothelium. To determine whether succinate interferes with mirabegron-mediated bladder relaxation, we examined their individual and synergistic effect in urothelial-cell and SMC signaling. We first confirmed ß3-AR involvement in the mirabegron response by quantifying receptor abundance by immunoblotting in cultured urothelial cells and SMC and cellular localization by immunohistochemistry in rat bladder tissue. Mirabegron increased cAMP levels in SMC but not in urothelial cells, an increase that was inhibited by succinate, suggesting that it impairs cAMP-mediated bladder relaxation by mirabegron. Succinate and mirabegron increased inducible nitric oxide synthesis and nitric oxide secretion only in urothelial cells, suggesting that its release can indirectly induces SMC relaxation. Succinate exposure decreased the expression of ß3-AR protein in whole bladder in vivo and in SMC in vitro, indicating that this metabolite may lead to impaired pharmacodynamics of the bladder. Together, our results demonstrate that increased levels of succinate in settings of metabolic stress (e.g., the metabolic syndrome) may lead to impaired mirabegron and ß3-AR interaction, inhibition of cAMP production, and ultimately requiring mirabegron dose adjustment for its treatment of OAB related to these conditions.

Promiscuous activity of C-acyltransferase from Pseudomonas protegens: synthesis of acetanilides in aqueous buffer.

Amide bond formation has considerable significance in synthetic chemistry. Although the C-acyltransferase from Pseudomonas protegens has been found to catalyze C-C bond formation in nature as well as in in vitro experiments with non-natural substrates, it is now shown that the enzyme is also able to catalyze amide formation using aniline derivatives as substrates with promiscuous activity. Importantly, the amide formation was enabled in aqueous buffer. Identifying phenyl acetate as the most suitable acetyl donor, the products were obtained with up to >99% conversion and up to 99% isolated yield.

Metabolic Hydrolysis of Aromatic Amides in Selected Rat, Minipig, and Human In Vitro Systems.

The release of aromatic amines from drugs and other xenobiotics resulting from the hydrolysis of metabolically labile amide bonds presents a safety risk through several mechanisms, including geno-, hepato- and nephrotoxicity. Whilst multiple in vitro systems used for studying metabolic stability display serine hydrolase activity, responsible for the hydrolysis of amide bonds, they vary in their efficiency and selectivity. Using a range of amide-containing probe compounds (0.5-10 µM), we have investigated the hydrolytic activity of several rat, minipig and human-derived in vitro systems - including Supersomes, microsomes, S9 fractions and hepatocytes - with respect to their previously observed human in vivo metabolism. In our hands, human carboxylesterase Supersomes and rat S9 fractions systems showed relatively poor prediction of human in vivo metabolism. Rat S9 fractions, which are commonly utilised in the Ames test to assess mutagenicity, may be limited in the detection of genotoxic metabolites from aromatic amides due to their poor concordance with human in vivo amide hydrolysis. In this study, human liver microsomes and minipig subcellular fractions provided more representative models of human in vivo hydrolytic metabolism of the aromatic amide compounds tested.

Biotransformation of Dimethenamid-P by the basidiomycete Irpex consors.

Twenty-nine basidiomycetes were screened in surface and liquid cultures for their capability to biotransform the chloroacetamide herbicide Dimethenamid-P (DMTA-P). The basidiomycete Irpex consors converted 70% of the herbicide (0.5 g L-1 DMTA-P) in liquid cultures within 6 days, applying a minimal medium under non-ligninolytic conditions. Nine transformation products of DMTA-P were identified by liquid chromatography-mass spectrometry analysis of the culture supernatants. The four main metabolites were isolated and subjected to GC-MS analysis and NMR spectroscopy. The analyses revealed that the thiophene ring was oxidized at three different positions. Metabolite M1 was identified as the S-oxide, which was isolable and relatively stable at room temperature. In metabolite M2, one methyl substituent of the thiophene ring was hydroxylated. The two metabolites M3A and M3B were diastereomers, but fully separated by HPLC. Here, oxidation of the aromatic CH carbon resulted in prototropic rearrangement to an αß-unsaturated thiolactone. None of the three major metabolites of DMTA-P has been described before.

Discovery of a Potential HER2 Inhibitor from Natural Products for the Treatment of HER2-Positive Breast Cancer.

Breast cancer is one of the most lethal types of cancer in women worldwide due to the late stage detection and resistance to traditional chemotherapy. The human epidermal growth factor receptor 2 (HER2) is considered as a validated target in breast cancer therapy. Even though a substantial effort has been made to develop HER2 inhibitors, only lapatinib has been approved by the U.S. Food and Drug Administration (FDA). Side effects were observed in a majority of the patients within one year of treatment initiation. Here, we took advantage of bioinformatics tools to identify novel effective HER2 inhibitors. The structure-based virtual screening combined with ADMET (absorption, distribution, metabolism, excretion and toxicity) prediction was explored. In total, 11,247 natural compounds were screened. The top hits were evaluated by an in vitro HER2 kinase inhibition assay. The cell proliferation inhibition effect of identified inhibitors was evaluated in HER2-overexpressing SKBR3 and BT474 cell lines. We found that ZINC15122021 showed favorable ADMET properties and attained high binding affinity against HER2. Moreover, ZINC15122021 showed high kinase inhibition activity against HER2 and presented outstanding cell proliferation inhibition activity against both SKBR3 and BT474 cell lines. Results reveal that ZINC15122021 can be a potential HER2 inhibitor.

Comprehensive spectroscopic probing the interaction and conformation impairment of bovine serum albumin (BSA) by herbicide butachlor.

Butachlor is an effective herbicide to deal with undesired weeds selectively and is used at high levels in Asian countries. However, its interaction and impairment effect on BSA was still not clear. In this study, we investigated the interaction between butachlor and bovine serum albumin (BSA) by multi-spectroscopic methods including UV absorption, circular dichroism (CD) spectra, Fourier transform infrared (FTIR) spectra and fluorescence spectra under physiological conditions (pH=7.4). The results revealed that there was a static quenching of BSA induced by butachlor stemmed from the formation of complex. Based on thermodynamic data, the interaction of butachlor with BSA was due to happen, and van der Waals force as well as hydrogen bond were the major forces contributed to the interaction. The binding constant Kb and number of binding site of butachlor with BSA were 5.158×10(5) and 1.372 at 303K, respectively. The distance r between donor (BSA) and acceptor (butachlor) was 0.113nm, obtained according to the Förster theory. The results revealed that butachlor induced conformational changes in BSA but the secondary structure of BSA was still retained. In addition, the microenvironment around chromophore residues of BSA, for example, tryptophan, changed as well, resulting from the formation of more hydrogen bonds.