Potent inhibition of human tyrosinase inhibitor by verproside from the whole plant of Pseudolysimachion rotundum var. subintegrum.

Affinity-based ultrafiltration-mass spectrometry coupled with ultraperformance liquid chromatography-quadrupole time-of-flight mass spectrometry was utilised for the structural identification of direct tyrosinase ligands from a crude Pseudolysimachion rotundum var. subintegrum extract. False positives were recognised by introducing time-dependent inhibition in the control for comparison. The P. rotundum extract contained nine main metabolites in the UPLC-QTOF-MS chromatogram. However, four metabolites were reduced after incubation with tyrosinase, indicating that these metabolites were bound to tyrosinase. The IC50 values of verproside (1) were 31.2 µM and 197.3 µM for mTyr and hTyr, respectively. Verproside showed 5.6-fold higher efficacy than that of its positive control (kojic acid in hTyr). The most potent tyrosinase inhibitor, verproside, features a 3,4-dihydroxybenzoic acid moiety on the iridoid glycoside and inhibits tyrosinase in a time-dependent and competitive manner. Among these three compounds, verproside is bound to the active site pocket with a docking energy of -6.9 kcal/mol and four hydrogen bonding interactions with HIS61 and HIS85.

Compound K ameliorates airway inflammation and mucus secretion through the regulation of PKC signaling in vitro and in vivo.

Background: Cigarette smoke (CS) is considered a principal cause of chronic obstructive pulmonary disease (COPD) and is associated with mucus hypersecretion and airway inflammation. Ginsenoside compound K (CK), a product of ginsenoside metabolism, has various biological activities. Studies on the effects of CK for the treatment of COPD and mucus hypersecretion, including the underlying signaling mechanism, have not yet been conducted. Methods: To study the protective effects and molecular mechanism of CK, phorbol 12-myristate 13-acetate (PMA)-induced human airway epithelial (NCI-H292) cells were used as a cellular model of airway inflammation. An experimental mouse COPD model was also established via CS inhalation and intranasal administration of lipopolysaccharide. Mucin 5AC (MUC5AC), monocyte chemoattractant protein-1, tumor necrosis factor-α (TNF-α), and interleukin-6 secretion, as well as elastase activity and reactive oxygen species production, were determined through enzyme-linked immunosorbent assay. Inflammatory cell influx and mucus secretion in mouse lung tissues were estimated using hematoxylin and eosin and periodic acid-schiff staining, respectively. PKCδ and its downstream signaling molecules were analyzed via western blotting. Results: CK prevented the secretion of MUC5AC and TNF-α in PMA-stimulated NCI-H292 cells and exhibited a protective effect in COPD mice via the suppression of inflammatory mediators and mucus secretion. These effects were accompanied by an inactivation of PKCδ and related signaling in vitro and in vivo. Conclusion: CK suppressed pulmonary inflammation and mucus secretion in COPD mouse model through PKC regulation, highlighting the compound's potential as a useful adjuvant in the prevention and treatment of COPD.

Daphnodorin C isolated from the stems of Daphne kiusiana Miquel attenuates airway inflammation in a mouse model of chronic obstructive pulmonary disease.

BACKGROUND: Since long-term or high-dose use of COPD medication causes adverse effects in patients with COPD, more effective and safer ways to manage COPD symptoms are required. Daphne kiusiana Miquel is a medicinal plant, but its anti-COPD efficacy was little studied. PURPOSE: We investigated the anti-COPD activity and molecular mechanism of action of active compounds isolated from D. kiusiana to find drug candidates for COPD. METHODS: We isolated seven compounds (1-7) in an ethyl acetate (EtOAc) fraction from D. kiusiana, and determined that seven compounds effectively control the inflammatory responsiveness in both PMA-stimulated lung epithelial cells (in vitro) and/or in COPD model mice using cigarette smoke- and lipopolysaccharides-exposed animals in vivo. RESULTS: We show that the ethyl acetate (EtOAc) fraction from D. kiusiana. suppresses inflammatory response in both PMA-stimulated human lung epithelial cells (in vitro) and COPD model mice (in vivo). The EtOAc fraction effectively suppresses various inflammatory responses, such as mucus secretion, ROS production, bronchial recruitment of inflammatory cells, and release of proinflammatory cytokines. Additionally, we isolated three compounds with anti-inflammatory efficacy from the EtOAc fraction, out of which daphnodorin C was the most effective. Finally, we demonstrated that daphnodorin C negatively regulates inflammatory gene expression by suppressing NF-κB and specific MAPK signaling pathways (JNK and p38) in vitro and in vivo. CONCLUSIONS: These results suggest that daphnodorin C could be a promising therapeutic alternative for managing COPD symptoms.

Rapid identification of isoprenylated flavonoids constituents with inhibitory activity on bacterial neuraminidase from root barks of paper mulberry (Broussonetia papyrifera).

This study was to assess the possibility of using competitive and slow binding experiments with affinity-based ultrafiltration UPLC-QTof-MS analysis to identify potent bacterial neuraminidase (bNA) inhibitors from the Broussonetia papyrifera roots extract. To isolate unbound compounds from the enzyme-binding complex, the root bark extracts were either incubated in the absence of bNA, in the presence of bNA, or with the time-dependent bNA before the ultrafiltration was performed. Thirteen flavonoids were separated from the target extract, and their inhibitory activities were tested against bNA. The isolated flavonoids exhibited potent inhibition against NA (IC50 = 0.7-54.0 µM). Our kinetic analysis of representative active flavonoids (1, 2, and 6) showed slow and time-dependent reversible inhibition. Additionally, chalcones exhibited noncompetitive inhibition characteristics, whereas flavonols and flavans showed mixed-type behavior. The computational results supported the experimental behaviors of flavonoids 2, 6, 10, and 12, indicating that bounded to the active site, but flavonoids 6 and 10 binds near but not accurately at the active site. Although this is mixed-type inhibition, their binding can be considered competitive.

Transforming Growth Factor ß Inhibits MUC5AC Expression by Smad3/HDAC2 Complex Formation and NF-κB Deacetylation at K310 in NCI-H292 Cells.

Airway mucus secretion is an essential innate immune response for host protection. However, overproduction and hypersecretion of mucus, mainly composed of the gel- forming MUC5AC protein, are significant risk factors for patients with asthma and chronic obstructive pulmonary disease (COPD). The transforming growth factor ß (TGFß) signaling pathway negatively regulates MUC5AC expression; however, the underlying molecular mechanism is not fully understood. Here, we showed that TGFß significantly reduces the expression of MUC5AC mRNA and its protein in NCI-H292 cells, a human mucoepidermoid carcinoma cell line. This reduced MUC5AC expression was restored by a TGFß receptor inhibitor (SB431542), but not by the inhibition of NF-κB (BAY11-7082 or Triptolide) or PI3K (LY294002) activities. TGFß-activated Smad3 dose-dependently bound to MUC5AC promoter. Notably, TGFß-activated Smad3 recruited HDAC2 and facilitated nuclear translocation of HDAC2, thereby inducing the deacetylation of NF-κB at K310, which is essential for a reduction in NF-κB transcriptional activity. Both TGFß-induced nuclear translocation of Smad3/HDAC2 and deacetylation of NF-κB at K310 were suppressed by a Smad3 inhibitor (SIS3). These results suggest that the TGFß-activated Smad3/HDAC2 complex is an essential negative regulator for MUC5AC expression and an epigenetic regulator for NF-κB acetylation. Therefore, these results collectively suggest that modulation of the TGFß1/Smad3/HDAC2/NF-κB pathway axis can be a promising way to improve lung function as a treatment strategy for asthma and COPD.

Longifolioside A inhibits TLR4-mediated inflammatory responses by blocking PKCδ activation in LPS-stimulated THP-1 macrophages.

Longifolioside A is an iridoid glucoside compound isolated from Pseudolysimachion rotundum var. subintegrum, which has been used in traditional herbal medicines to treat respiratory inflammatory diseases. Logifolioside A is a potent antioxidant; however, its underlying pharmacological mechanisms of action in inflammatory diseases are unknown. Here, we investigated the inhibitory effects of longifolioside A in lipopolysaccharide (LPS)-stimulated toll-like receptor 4 (TLR4) signal transduction systems using human THP-1 macrophages and HEK293 cells stably expressing human TLR4 protein (293/HA-hTLR4). Longifolioside A significantly reduced the release of inflammatory cytokines such as interleukin (IL)-6, -8, and tumor necrosis factor (TNF)-α in LPS-stimulated THP-1 macrophages. Furthermore, longifolioside A inhibited the expression of inflammatory mediator genes such as inducible nitric oxide synthase (iNOS) and cyclooxygenase (COX)-2 that produce nitric oxide (NO) and prostaglandin E2 (PGE2), respectively. Longifolioside A suppressed the phosphorylation of PKCδ, IRAK4, IKKα/ß, IκBα, and mitogen-activated protein (MAP) kinases (ERK 1/2 and JNK, but not p38), thereby inactivating the nuclear localization of NF-κB and AP-1, and thus decreasing the expression of inflammatory response genes. Notably, longifolioside A disrupted the interaction between human TLR4 and the TIR domain-containing adaptor protein (TIRAP), an early step during TLR4 activation, thereby reducing IL-8 secretion in 293/HA-hTLR4 cells. This inhibitory effect was comparable to that of TAK-242 (a TLR4 inhibitor, or resatorvid). Our results indicate that longifolioside A prevents inflammatory response by suppressing TLR4 activation required for NF-κB and AP-1 activation.

Inhibition effects of mangosenone F from Garcinia mangostana on melanin formation in B16F10 cells.

Melanogenesis can be controlled by tyrosinase inhibition or by blocking the maturation processes of tyrosinase and its related proteins. Mangostenone F was isolated from the seedcases of Garcinia mangostana . Mangostenone F was shown to be inactive against tyrosinase (IC50 > 200 µM) but was a potent α-glucosidase inhibitor in vitro (IC50 = 21.0 µM). Mangostenone F was found to inhibit production of melanin in the mouse melanoma cell line B16F10. Importantly, unlike most glycosidase inhibitors, mangostenone F displayed very low cytotoxicity (EC50 > 200 µM). The Western blot for expression levels of proteins involved in melanogenesis showed that mangostenone F down-regulated tyrosinase and TRP-2 expression. Treating B16F10 cells with mangostenone F significantly increased the susceptibility of tyrosinase to endoglycosidase H digestion, indicating that tyrosinase was unable to mature fully and pass to the trans-golgi apparatus. Consistent with these data, in lysate assays, mangostenone F was shown to be a better inhibitor of α-glucosidases than deoxynojirimycin, a representative glycosidase inhibitor.

Anticholinesterase potential of flavonols from paper mulberry (Broussonetia papyrifera) and their kinetic studies.

It is necessary to develop food additives to help treat chronic disorders like neurodegenerative diseases from medicinal plants. Ethanol extracts of paper mulberry were found to display significant inhibition against cholinesterases, enzymes that are strongly linked with Alzheimer's disease (AD). The active components were identified as prenylated flavonols (2-4) that inhibited two related human cholinesterases in a dose-dependent manner, with IC50's ranging between 0.8 and 3.1µM and between 0.5 and 24.7µM against human acetylcholinesterase (hAChE) and butylcholinesterase (BChE), respectively. Prenyl groups within these flavonols were found to play a critical role for inhibition because the parent compound 1, quercetin, was inactive (IC50>500µM) towards the target enzymes. Flavonols (2-4) showed mixed inhibition kinetics as well as slow and time-dependent reversible inhibition toward hAChE. The affinity between protein and inhibitors was investigated using fluorescence quenching. The affinity constants (KSA) of inhibitors increased in proportion to their inhibitory potencies.

α-Glucosidase inhibition and antihyperglycemic activity of prenylated xanthones from Garcinia mangostana.

An ethanol extract of the fruit case of Garcinia mangostan, whose most abundant chemical species are xanthones, showed potent α-glucosidase inhibitory activity (IC(50)=3.2 µg/ml). A series of isolated xanthones (1-16) demonstrated modest to high inhibition of α-glucosidase with IC(50) values of 1.5-63.5 µM. In particular, one hitherto unknown xanthone 16 has a very rare 2-oxoethyl group on C-8. Kinetic enzymatic assays with a p-nitrophenyl glucopyranoside indicated that one of them, compound (9) exhibited the highest activity (K(i)=1.4 µM) and mixed inhibition. Using, a physiologically relevant substrate, maltose, as substrate, many compounds (6, 9, 14, and 15) also showed potent inhibition which ranged between 17.5 and 53.5 µM and thus compared favorably with deoxynojirimycin (IC(50)=68.8 µM). Finally, the actual pharmacological potential of the ethanol extract was demonstrated by showing that it could elicit reduction of postprandial blood glucose levels. Furthermore, the most active α-glucosidase inhibitors (6, 9, and 14) were proven to be present in high quantities in the native seedcase by a HPLC chromatogram.

Xanthones with neuraminidase inhibitory activity from the seedcases of Garcinia mangostana.

This study was designed to gain deeper insights into the molecular properties of natural xanthones as neuraminidase inhibitors. A series of xanthones 1-12 was isolated from the seedcases of Garcinia mangostana and evaluated for bacteria neuraminidase inhibitory activity. Compounds 11 and 12 emerged to be new xanthones (mangostenone F, mangostenone G) which we fully spectroscopically characterized. The IC(50) values of compounds 1-12 were determined to range between 0.27-65.7 microM. The most potent neuraminidase inhibitor 10 which has an IC(50) of 270 nM features a 5,8-diol moiety on the B ring. Interestingly, structure-activity studies reveal that these xanthones show different kinetic inhibition mechanisms depending upon the arrangement of hydroxyl groups in the B ring. Compound 6 possessing a 6,7-diol motif on the B-ring operated under the enzyme isomerization model (k(5)=0.1144 microM(-1) s(-1), k(6)=0.001105 s(-1), and K(i)(app)=7.41 microM), whereas compound 10 possessing a 5,8-diol unit displayed simple reversible slow-binding inhibition (k(3)=0.02294 microM(-1) s(-1), k(4)=0.001025 s(-1), and K(i)(app)=0.04468 microM).

Polyphenols from Broussonetia papyrifera displaying potent alpha-glucosidase inhibition.

The organic extract of the roots of Broussonetia papyrifera showed extremely high alpha-glucosidase inhibitory activity with an IC50 of around 10 microg/mL. Due to its potency, subsequent bioactivity-guided fractionation of the chloroform extract led to 12 polyphenols, 1-12, 4 of which were identified as chalcones (1-4), another 4 as flavans (5-8), 2 as flavonols (9 and 10), and 2 others as the novel species benzofluorenones (11 and 12). Broussofluorenone A (11) and broussofluorenone B (12) emerged as new compounds possessing the very rare 5,11-dioxabenzo[b]fluoren-10-one skeleton. These compounds (1-12) were evaluated for alpha-glucosidase inhibitory activity to identify their inhibitory potencies and kinetic behavior. The most potent inhibitor, 10 (IC50=2.1 microM, Ki=2.3 microM), has an inhibitory activity slightly higher than that of the potent alpha-glucosidase inhibitor deoxynojirimycin (IC50=3.5 microM). The novel alpha-glucosidase inhibitors 11 (IC50=27.6 microM) and 12 (IC50=33.3 microM) are similar in activity to sugar-derived alpha-glucosidase inhibitors such as voglibose (IC50=23.4 microM). Interestingly, major constituents (1, 2, 6, 7, 9, and 10) of B. papyrifera displayed significant inhibitory activity with IC50 values of 5.3, 11.1, 12.0, 26.3, 3.6, and 2.1 microM, respectively. In kinetic studies, chalcones (1-4) exhibited noncompetitive inhibition characteristics, whereas the others (5-12) showed mixed behavior.