Biotransformation of isoimperatorin and imperatorin by Glomerella cingulata and β-secretase inhibitory activity

Isoimperatorin attenuates bone loss by inhibiting the binding of RANKL to RANK

Osteoporosis, an immune disease characterized by bone mass loss and microstructure destruction, is often seen in postmenopausal women. Isoimperatorin (ISO), a bioactive, natural furanocoumarin isolated from many traditional Chinese herbal medicines, has therapeutic effects against various diseases; however, its effect on bone homeostasis remains unclear. In this study, we investigated the effect of ISO on the differentiation and activation of osteoclast and its molecular mechanism in vitro, and evaluated the effect of ISO on bone metabolism by ovariectomized (OVX) rat model. In vitro experiments showed that ISO affected RANKL-induced MAPK, NFAT, NFATc1 trafficking and expression, osteoclast F-actin banding, osteoclast-characteristic gene expression, ROS inhibitory activity, and calcium oscillations, NF-κB signaling pathway. In vivo experiments showed that oral administration of ISO effectively reduced bone loss caused by ovariectomy and retained bone mass.Collectively, ISO inhibits RANK/RANKL binding, thereby reducing the activity of NFATc1, calcium, and ROS and inhibiting osteoclast generation. In addition, ISO protects bone mass by slowing osteoclast production and downregulating NFATc1 gene and protein expression in the bone tissue microenvironment and inhibits OVX-induced bone loss in vivo.

Seven new 3,4-dihydro-furanocoumarin derivatives from Angelica dahurica

Objective

To study the chemical constituents of the roots of Angelica dahurica, a well-known Chinese herbal medicine named Baizhi in Chinese.

Methods

Compounds were separated by various chromatographies, and the structures of new compounds were elucidated based on the analysis of their spectroscopic and spectrometric data (1D, 2D NMR, HRESI MS, IR, and UV). The absolute configurations of new compounds were determined by the calculated electronic circular dichroism and chemical derivatization. The inhibitory activities of all isolates against nitric oxide (NO) production were evaluated using lipopolysaccharide-activated RAW 264.7 macrophage cells.

Results

Seven new 3,4-dihydro-furanocoumarin derivatives (1a/1b, 2a/2b, 3a/3b, 4) together with a known furanocoumarin (5) were isolated from the roots of A. dahurica. The new compounds included three pairs of enantiomers, (4S, 2''R)-angelicadin A (1a)/(4R, 2''S)-angelicadin A (1b), (4S, 2''S)-angelicadin A (2a)/(4R, 2''R)-angelicadin A (2b), and (4S, 2''S)-secoangelicadin A (3a)/(4R, 2''R)-secoangelicadin A (3b), together with (4R, 2''R)-secoangelicadin A methyl ester (4). The known xanthotoxol (5) inhibited the NO production with the half-maximal inhibitory concentration (IC50) value of (32.8 ± 0.8) µmol/L, but all the new compounds showed no inhibitory activities at the concentration of 100 µmol/L.

Conclusion

This is the first report of the discovery of 3,4-dihydro-furanocoumarins from A. dahurica. The results are not only meaningful for the understanding of the chemical constituents of A. dahurica, but also enrich the reservoir of natural products.

Synthesis of furocoumarin-stilbene hybrids as potential multifunctional drugs against multiple biochemical targets associated with Alzheimer's disease

A series of furocoumarin-stilbene hybrids has been synthesized and evaluated in vitro for inhibitory effect against acetylcholinesterase (AChE), butyrylcholinestarase (BChE), β-secretase, cyclooxygenase-2 (COX-2), and lipoxygenase-5 (LOX-5) activities including free radical-scavenging properties. Among these hybrids, 8-(3,5-dimethoxyphenyl)-4-(3,5-dimethoxystyryl)furochromen-2-one 4h exhibited significant anticholinesterase activity and inhibitory effect against β-secretase, COX-2 and LOX-5 activities. 2,2-Diphenyl-1-picrylhydrazyl (DPPH) radical scavenging activity and an in vitro cell-based antioxidant activity assay involving lipopolysaccharide induced reactive oxygen species production revealed that 4h has capability of scavenging free radicals. Molecular docking into AChE, BChE, β-secretase, COX-2 and LOX-5 active sites has also been performed.

Chemical Constituents of Thai Citrus hystrix and Their Antiausterity Activity against the PANC-1 Human Pancreatic Cancer Cell Line

Human pancreatic cancer cells have an extreme tolerance to nutrition starvation, enabling them to survive in a hypovascular tumor microenvironment. Searching for agents that preferentially inhibit cancer cell viability under nutrition starvation conditions is a novel antiausterity strategy in anticancer drug discovery. In the present study, a hexane extract of the peels of Citrus hystrix fruits showed preferential cytotoxicity against PANC-1 human pancreatic cancer cells using a nutrient-deprived medium. Phytochemical investigation of this bioactive extract led to the isolation of 10 coumarins (1-10) including a new furanocoumarin (1). The isolated compounds were tested for their preferential cytotoxic activity against three different human pancreatic cancer cell lines [PANC-1, MIA PaCa-2, and PSN-1]. Among these, bergamottin (7) was identified as the most active constituent. In real-time live imaging, 7 was found to induce cell shrinkage, membrane blebbing, and disintegration of organelles in PANC-1 cells. Bergamottin (7) was also found to inhibit PANC-1 cell migration and colony formation. Mechanistically, 7 inhibited key survival proteins in the Akt/mTOR signaling pathway. Bergamottin (7) and related compounds are potential antiausterity candidates for drug development against pancreatic cancer.

Biotransformation of furanocoumarins by fungi: preparation of imperation analogs

Imperation analogs have the furanocoumarin skeleton, with the isopentenyl group, which displayed significant bioactivities. The biotransformation of furanocoumarins imperation, isoimperation and phellopterin (1-3) by fungi has been proved to be an efficient method for the structural modification. Ten transformed furanocoumarin analogs were obtained by fungal biotransformation, including one new highly oxygenated furanocoumarin (4c). Aspergillus niger AS 3.739 displayed selectively transformed capability toward furanocouamrins (1-3) with one or two major products. So, seven hydroxylation and hydrolysis derivatives have been prepared efficiently. Additionally, the biotransformation of phellopterin gave multiple products (4a, 4b, 4c) by Cunninghamella blakesleana AS 3.970. The biotransformation time-courses of furanocoumarins have been established, which suggested the preferred incubation time. The bioactivities of furanocoumarin analogs have been investigated in an in vitro bioassay. And, furanocoumarins 1-3, 2a, and 2c displayed moderate anti-osteoporosis activities using MCET3-E1 cell line at the concentrations of 1, 10, and 100 μM.

In vivo metabolite profiles of isoimperatorin and phellopterin in rats analyzed using HPLC coupled with diode array detector and electrospray ionization ion trap time-of-flight mass spectrometry technique

Isoimperatorin (IP) and phellopterin (PP) are two furocoumarins existing in Angelicae Dahuricae Radix. There is an isopentenyloxyl substituted at C-5 in IP, and an isopentenyloxyl and a methoxyl substituted at C-8 and C-5, respectively, in PP. To elucidate the in vivo metabolic characteristics of PP and IP, HPLC coupled with diode array detector and electrospray ionization ion trap time-of-flight mass spectrometry technique was used. In total, 111 metabolites, including 53 new ones, were identified from the urine and plasma samples of rats after oral administration of IP and PP, respectively. The metabolites were formed through eight reactions on IP and PP: oxidation, hydroxylation-hydrogenation, carboxylation on the isopentenyloxyl, O-dealkylation, hydroxylation on the furocoumarin nucleus, ring-opening reaction on the furan ring and reduction or ring-opening reaction on the lactone ring. Among these, hydroxylation on the furocoumarin nucleus was found for the first time for in vivo metabolites of PP and IP, and the ring-opening reaction on the furan ring or lactone ring was found for the first time for in vivo metabolites of isopentenyloxyl furocoumarins. The research gave us a new insight into the in vivo metabolic profiles of IP and PP, which could help us better understand their important roles as two active constituents of Angelicae Dahuricae Radix.

Isoimperatorin attenuates airway inflammation and mucus hypersecretion in an ovalbumin-induced murine model of asthma

Isoimperatorin (IMP), an active natural furocoumarin, has numerous pharmacologic effects, including anti-inflammatory, analgesic, antispasmodic, and anticancer activities. This study aimed to evaluate the preventive activity of IMP in an ovalbumin (OVA)-induced murine model of asthma and to investigate its possible molecular mechanisms. Female BALB/c mice were sensitized on days 0 and 14 via intraperitoneal injection of 20μg OVA. On days 21-23 after the initial sensitization, the mice received an airway challenge with OVA (1% w/v in PBS) for 1h; meanwhile, IMP (10 or 30mg/kg once daily) was administered by gavage on days 18-23. Our results revealed that IMP significantly lowered the productions of interleukin (IL)-4, IL-5, IL-13, eotaxin, and immunoglobulin (Ig)E in bronchoalveolar lavage fluid (BALF), plasma, or lung tissues. Histological studies showed that IMP inhibited OVA-induced inflammatory cell infiltration and mucus production in the respiratory tract. In addition, pretreatment with IMP suppressed the activation of p38 mitogen-activated protein kinase (p38 MAPK), extracellular-signal-regulated kinases 1/2 (ERK1/2), and nuclear factor-κB (NF-κB). Together, these results suggest that IMP effectively inhibits airway inflammation and mucus hypersecretion by downregulating the levels of Th2 cytokines and inhibiting NF-κB and MAPK pathways.

Imperatorin-pharmacological meaning and analytical clues: profound investigation

Imperatorin, a furanocoumarin derivative, has many documented pharmacological properties which make it a candidate for possible drug development. In this review, the activity on the central nervous system, the anticancer and antiviral properties and the influence on the cardiovascular system are described. The aim of this review is also to present an overview of the techniques used for the analysis, isolation, and separation of imperatorin from plant material from the practical perspective.

Mechanism-based inactivation of cytochrome P450 2B6 by isoimperatorin

Isoimperatorin (IIMP), a 6,7-furanocoumarin derivative, occurs in many common medicinal herbs. Human exposure to IIMP mainly results from intake of fruits, foods and medicinal herbs. We examined the irreversible inhibitory effect of IIMP on cytochrome P450 2B6. IIMP was found to cause time-dependent inhibition of CYP2B6. In addition, the loss of CYP2B6 activity occurred in a NAPDH- and concentration-dependent manner. About 60% of activity of CYP2B6 was suppressed after its incubation with IIMP at 25 μM for 9 min. Enzyme kinetic studies were performed, kinact for IIMP was found to be 0.071 min(-1), and KI was 17.1 μM, respectively. Glutathione and catalase/superoxide dismutase showed little protective effects on CYP2B6 against the inactivation by IIMP. S-Mephenytoin, a substrate of CYP2B6, mildly prevented the enzyme from the inactivation induced by IIMP. The estimated partition ratio of the inactivation was approximately 211. Additionally, a γ-ketoenal intermediate was identified in microsomal incubations with IIMP. CYPs 2B6, 2D6, and 1A2 were the major enzymes responsible for the metabolic activation of IIMP. In conclusion, IIMP is a mechanism-based inactivator of CYP2B6. The formation of γ-ketoenal intermediate may be responsible for the enzyme inactivation.

Biotransformation of 20(R)-panaxadiol by the fungus Rhizopus chinensis

Microbial transformation of 20(R)-panaxadiol by the fungus Rhizopus chinensis CICC 3043 yielded seven metabolites. Their structures were elucidated on the basis of extensive spectroscopic analyses. R. chinensis could catalyze hydroxylation and further dehydrogenation at C-24 of 20(R)-panaxadiol, as well as hydroxylation at C-7, C-15, C-16, and C-29. Three of these compounds at 10μM could moderately inhibit growth of HepG2 human hepatocellular carcinoma cells with an inhibition rate of about 40%. Three compounds (also at 10μM) showed approximately 30% inhibition on NF-κB transcriptional activity in SW480 human colon carcinoma cells stably transfected with NF-κB luciferase reporter and induced by LPS.

Studies of the interaction between isoimperatorin and human serum albumin by multispectroscopic method: identification of possible binding site of the compound using esterase activity of the protein

Isoimperatorin is one of the main components of Prangos ferulacea as a linear furanocoumarin and used as anti-inflammatory, analgesic, antispasmodic, and anticancer drug. Human serum albumin (HSA) is a principal extracellular protein with a high concentration in blood plasma and carrier for many drugs to different molecular targets. Since the carrying of drug by HSA may affect on its structure and action, we decided to investigate the interaction between HSA and isoimperatorin using fluorescence and UV spectroscopy. Fluorescence data indicated that isoimperatorin quenches the intrinsic fluorescence of the HSA via a static mechanism and hydrophobic interaction play the major role in the drug binding. The binding average distance between isoimperatorin and Trp 214 of HSA was estimated on the basis of the theory of Förster energy transfer. Decrease of protein surface hydrophobicity (PSH) was also documented upon isoimperatorin binding. Furthermore, the synchronous fluorescence spectra show that the microenvironment of the tryptophan residues does not have obvious changes. Site marker compettive and fluorescence experiments revealed that the binding of isoimperatorin to HSA occurred at or near site I. Finally, the binding details between isoimperatorin and HSA were further confirmed by molecular docking and esterase activity inhibition studies which revealed that drug was bound at subdomain IIA.

Two new oxidation products obtained from the biotransformation of asiatic acid by the fungus Fusarium avenaceum AS 3.4594

Asiatic acid (AA) is a natural triterpenoid possessing anti-inflammatory, anticancer, neuroprotective, and hepatoprotective activities. Structural modification of AA may provide valuable information for further structure-activity relationship analysis. Biotransformation is an efficient, specific, and environment friendly technology for structural modification of complicated natural products. In this study, the capabilities of twenty-five strains of filamentous fungi to transform AA were screened. Two new and one known oxidation products metabolized by Fusarium avenaceum AS 3.4594 were isolated. Their chemical structures were characterized as 2-oxo-3β,15α,23-trihydroxyurs-12-en-28-oic acid (1), 3-oxo-2,15α,23-trihydroxyurs-1,12-dien-28-oic acid (2), and 2-oxo-3β,23-dihydroxyurs-12-en-28-oic-acid (3) by extensive analysis of spectroscopic data.

Biotransformation of turmerones by Aspergillus niger

Biotransformation studies conducted on (+)-(S)-ar-turmerone (1) and (+)-(S)-dihydro-ar-turmerone (2) by the fungus Aspergillus niger have revealed that 1 was metabolized to give four oxidized metabolites, (+)-(7S)-hydroxydehydro-ar-todomatuic acid (3), (+)-(7S,10E)-12-hydroxydehydro-ar-todomatuic acid (4), (+)-(7S,10E)-7,12-dihydroxydehydro-ar-todomatuic acid (5), and (+)-(7S)-15-carboxy-9,13-epoxy-7-hydroxy-9,13-dehydro-ar-curcumene (6), and (+)-(S)-dihydro-ar-turmerone (2) was metabolized to (+)-7,11-dihydroxy-ar-todomatuic acid (7). Metabolites 3-7 were characterized using spectroscopic techniques. Metabolites 3-7 inhibited acetylcholinesterase (AChE) although less so than the parent substrates.

Biotransformation of bergapten and xanthotoxin by Glomerella cingulata

The biotransformation of bergapten (1) by the fungus Glomerella cingulata gave the corresponding reduced acid, 6,7-furano-5-methoxy hydrocoumaric acid (2), a new compound. Xanthotoxin (3) was also converted to the corresponding reduced acid cnidiol b (4) and demethylated metabolite xanthotoxol (5) by G. cingulata. The structure of the new compound 2 was elucidated by high-resolution mass spectrometry, extensive NMR techniques, including (1)H NMR and (13)C NMR, (1)H-(1)H correlation spectroscopy, heteronuclear multiple quantum coherence, and heteonuclear multiple bond coherence. The methyl ester or methyl ether or methyl ester and ether derivatives of 2 and 4 were synthesized. All compounds were tested for the beta-secretase (BACE1) inhibitory activity in vitro. The methyl ester and ether derivative 8 was shown to possess BACE1 inhibitory activity, and a IC(50) value was 0.64 +/- 0.04 mM.