Hyperhenrones: Prenylated α-pyrones with anti-inflammatory activity from Hypericum henryi.

Fourteen previously undescribed α-pyrone derivatives (1-14) together with four known analogs (15-18) were isolated from a traditional Chinese medicinal plant Hypericum henryi. Compounds (+)/(-)-1, 2, and 3 share a rare 6/6/4/6/6 polycyclic skeleton. Compound 14 was the first example of a 7,7-dimethyl-pyran-4-one moiety. Their structures were elucidated using comprehensive spectroscopic analyses and electronic circular dichroism calculations. The anti-inflammatory activities of 1-18 were screened in lipopolysaccharide-induced RAW264.7 cells. Among them, compounds 14, (+)-18, and (-)-18 exhibited inhibitory effects against nitric oxide production in LPS-induced RAW264.7 cells. Additionally, compound 14 suppressed the expression of cyclooxygenase-2 and inducible nitric oxide synthase in LPS-induced RAW264.7 cells. Furthermore, preliminary mechanism studies indicated that compound 14 suppressed the phosphorylation and degradation of the inhibitor of NF-κB, and this led to the inhibition of NF-κB activation.

Inhibition of Aß aggregation by naphtho-γ-pyrone derivatives from a marine-derived fungus, Aspergillus sp. MPUC239.

Alzheimer's disease (AD) is an important human disease that mainly causes cognitive impairments. Growing evidence has shown that amyloid-ß (Aß) peptide plays a key role in AD pathogenesis in what is known as the Aß cascade hypothesis. This hypothesis suggests the importance of suppressing Aß aggregation and Aß production. The latter process is governed by ß-site APP Cleaving Enzyme1 (BACE1) and γ-secretase. We, therefore, focused on Aß aggregation inhibitory activity, initially assessing numerous extracts derived from our marine-derived fungus collections. One EtOAc extract derived from an Aspergillus sp. exhibited Aß aggregation inhibitory activity. Eleven known compounds (1-11) were isolated from CHCl3 and EtOAc extracts derived from the fungus, and the structures were identified based on MS, NMR, and ECD spectra. Compounds 2, 6, and 10 inhibited Aß aggregation with IC50 values of 2.8, 3.9, and 8.1 µM, respectively. The protective effect on SH-SY5Y cells against Aß toxicity was also evaluated, and compounds 6 and 10 significantly alleviated Aß toxicity. BACE1 inhibitory activity was also examined, and compounds 4, 5, 7, 10, and 11 inhibited BACE1 activity with IC50 values of 14.9, 70.0, 36.5, 28.0, and 72.8 µM, respectively. These data suggest that compound 10 could be useful in AD treatment.

In vitro DPPH Radical Scavenging Activity of α-Pyrones from Odontonema strictum (Acanthaceae).

An ethyl acetate leaf extract from Odontonema strictum has been reported to have potent antihypertensive activity by inhibiting coronary artery contractions in porcine heart. However, the phytochemistry of the active fraction was unknown. Here we report, for the first time, the isolation and characterization of four known α-pyrones from the active fraction. The antioxidant activity of umuravumbolide (IC50 = 55.7±0.027 µg/mL), deacetylumuravumbolide (IC50 = 0.24±0.0002 µg/mL), dideacetylboronolide (IC50 = 149±0 µg/mL) and deacetylboronolide (IC50 = 24±0 µg/mL) was evaluated in vitro against 2,2-diphenyl-1-picrylhydrazyl radicals. Ascorbic acid was used as a positive control (IC50 = 1.73×10-3±0.3 µg/mL). The presence of 6-substituted 5,6-dihydro-α-pyrones and phenylpropanoid glucosides in the active fraction was suggested to be responsible for the antihypertensive activity. This is the first time that the antioxidant potential of these phytochemicals has been evaluated, and the results indicate that O. strictum has potential as an herbal medicine. Thus, further chemotaxonomic studies among the genera Odontonema and Tetradenia, a known source of α-pyrones, are recommended.

Protective effect of kavain in meristematic cells of Allium cepa L.

Kavain is one of the main kavalactones of Piper methysticum (Piperaceae) with anxiolytic, analgesic, and antioxidant activities. Therefore, the aim of the study was to evaluate the cytotoxic, mutagenic, and antimutagenic potential of kavain in Allium cepa cells. Roots of A. cepa were transferred to the negative (2% acetone) and positive (10 µg/mL of Methylmethanesulfonate, MMS) controls and to the concentrations of kavain (32, 64 and 128 µg/mL) for 48 h. A total of 5,000 meristematic cells were analyzed under an optical microscope to determine the mitotic index, mean number of chromosomal alterations and percentage of damage reduction. Data were analyzed by Kruskal-Wallis test (p <0.05). All concentrations of kavain were not cytotoxic and did not show significant chromosomal changes when compared to 2% acetone. Kavain showed a cytoprotective effect in the pre (128 µg/mL) and in the post-treatment (32 and 64 µg/mL) and reduced damage against the mutagenic action of MMS in all concentrations of the pre and simultaneous and at the highest of post (128 µg/mL). Kavain promoted a significant reduction in micronuclei, nuclear buds and chromosomal losses in relation to MMS. The observed data indicate the importance of kavain for the inhibition of damage and chemoprevention.

Sodium dehydroacetate confers broad antibiotic tolerance by remodeling bacterial metabolism.

Antibiotic tolerance has been a growing crisis that is seriously threatening global public health. However, little is known about the exogenous factors capable of triggering the development of antibiotic tolerance, particularly in vivo. Here we uncovered that an previously approved food additive termed sodium dehydroacetate (DHA-S) supplementation remarkably impaired the activity of bactericidal antibiotics against various bacterial pathogens. Mechanistic studies indicated that DHA-S induced glyoxylate shunt and reduced bacterial cellular respiration by inhibiting the enzymatic activity of α-ketoglutarate dehydrogenase (α-KGDH). Furthermore, DHA-S mitigated oxidative stress imposed by bactericidal antibiotics and enhanced the function of multidrug efflux pumps. These actions worked together to induce bacterial tolerance to antibiotic killing. Interestingly, the addition of five exogenous amino acids, particularly cysteine and proline, effectively reversed antibiotic tolerance elicited by DHA-S both in vitro and in mouse models of infection. Taken together, these findings advance our understanding of the potential risks of DHA-S in the treatment of bacterial infections, and shed new insights into the relationships between antibiotic tolerance and bacterial metabolism.

α-Pyrones with glucose uptake-stimulatory activity from the twigs of Cryptocarya wrayi.

Five new α-pyrones, cryptowratones A-E (1-5), and five known congeners (6-10), together with four other known compounds 11-14 were isolated from the twigs of Cryptocarya wrayi. The structures of the new compounds were elucidated on the basis of extensive spectroscopic data analysis and ECD calculations. All α-pyrones except 6 were evaluated for their stimulatory effects on glucose uptake in vitro with CHO-K1/GLUT4 cells. The positive control insulin displayed an approximate 42 ± 0.14% promotion on glucose uptake at 25 µM, compared with the CHO-K1/GLUT4 group. Compounds 1a/2a, 2, 3, and 10 showed a more significant stimulation of glucose uptake than insulin (25 µM) by 36 ± 0.08%, 27 ± 0.12%, 28 ± 0.12%, and 25 ± 0.12% at 1.5 µM, respectively. Immunofluorescence assays indicated the glucose uptake-stimulatory activity of α-pyrones might be correlated with increased GLUT4 translocation.

Two new ɑ-pyrone derivatives from the endophytic Diaporthe sp. ECN371.

Diaportholides A (1) and B (2), two polyketides with ɑ-pyrone moieties, were isolated from the cultures of an endophytic Diaporthe sp. ECN371 isolated from Orixa japonica, together with four known polyketides, phomopsolide B (3), phomopsolidones A (4) and B (5), and 5-[(1R)-1-hydroxyethyl]-γ-oxo-2-furanbutanoic acid (6). The structures of 1 and 2 were determined by extensive analysis of NMR and MS spectroscopic data. Furthermore, the structure of 2 was confirmed by analyzing the single-crystal X-ray diffraction data. The luciferase reporter gene assay revealed that among all isolated compounds (1-6), 3, a known ɑ-pyrone derivative, exhibited agonistic activity against the peroxisome proliferator-activated receptor ɑ, which is an important regulator of lipid metabolism in humans.

Novel kojic acid derivatives with anti-inflammatory effects from Aspergillus versicolor.

Two novel kojic acid derivatives, kojicones A and B (1 and 2), along with the precursors kojic acid (3) and (2R,4R)-4-hydroxy-5-methoxy-2,4-dimethyl-2- [(2R)-2-methylbutyryloxy]-5-cyclohexen-1,3-dione (4), were isolated from a fungal strain Aspergillus versicolor. Their structures and absolute configurations were accurately confirmed by HRESIMS data, NMR analysis, and electronic circular dichroism (ECD) calculations. Kojicones A and B were the first examples of kojic acid adducts with cyclohexen-1,3-dione possessing unprecedented tricycle skeletons. Compounds 1-3 were found to have inhibition on the NO production of murine RAW 264.7 cells. They can also reduce the mRNA expression of four cytokines (IL-6, IL-1ß, TNF-α, and iNOS) and promote the expression of IL-4 at 20 µM. Moreover, kojic acid (3) could treat the DSS (dextran sulfate sodium)-induced colitis on mice with the effectiveness similar to that of the positive control. The results suggested that kojic acid and its derivatives could be a promising anti-inflammatory source for the medicinal and cosmetic industry.

Alternative Approach for Specific Tyrosinase Inhibitor Screening: Uncompetitive Inhibition of Tyrosinase by Moringa oleifera.

Tyrosinase (TYR) is a type III copper oxidase present in fungi, plants and animals. The inhibitor of human TYR plays a vital role in pharmaceutical and cosmetic fields by preventing synthesis of melanin in the skin. To search for an effective TYR inhibitor from various plant extracts, a kinetic study of TYR inhibition was performed with mushroom TYR. Among Panax ginseng, Alpinia galanga, Vitis vinifera and Moringa oleifera, the extracts of V. vinifera seed, A. galanga rhizome and M. oleifera leaf reversibly inhibited TYR diphenolase activity with IC50 values of 94.8 ± 0.2 µg/mL, 105.4 ± 0.2 µg/mL and 121.3 ± 0.4 µg/mL, respectively. Under the same conditions, the IC50 values of the representative TYR inhibitors of ascorbic acid and kojic acid were found at 235.7 ± 1.0 and 192.3 ± 0.4 µg/mL, respectively. An inhibition kinetics study demonstrated mixed-type inhibition of TYR diphenolase by A. galanga and V. vinifera, whereas a rare uncompetitive inhibition pattern was found from M. oleifera with an inhibition constant of Kii 73 µg/mL. Phytochemical investigation by HPLC-MS proposed luteolin as a specific TYR diphenolase ES complex inhibitor, which was confirmed by the inhibition kinetics of luteolin. The results clearly showed that studying TYR inhibition kinetics with plant extract mixtures can be utilized for the screening of specific TYR inhibitors.

Oral Ferric Maltol Does Not Adversely Affect the Intestinal Microbiome of Patients or Mice, But Ferrous Sulphate Does.

BACKGROUND AND AIMS: Altering dietary ferrous sulphate (FS) consumption exacerbates a murine model of colitis and alters the intestinal microbiome. We investigated the impact of oral ferric maltol (FM) and FS on mice with dextran sodium sulphate (DSS) induced colitis, and the microbiome of patients with iron deficiency. METHODS: Mice had acute colitis induced, with 2% DSS for 5 days, followed by water. During this period, groups of mice were fed standard chow (200 ppm iron, SC, n = 8), or SC with 200ppm FS supplementation (n = 16, FSS), or SC with 200 ppm FM supplementation (n = 16, FMS). Clinical, pathological and microbiome assessments were compared at days 1 and 10. Fecal bacterial gDNA was extracted and the microbiome assessed by sequencing. Statistical inferences were made using MacQIIME. Principal Coordinates Analysis were used to visualize beta-diversity cluster analysis. Ten patients with IDA were treated with FS, and six with inactive inflammatory bowel disease received FM, supplements for four weeks: pre- and mid-treatment fecal samples were collected: the microbiome was assessed (see above). RESULTS: In mice, after DSS treatment, there was a decrease in many genera in the SC and FSS groups: Lactobacillales increased in mice that received FMS. In humans, FS treatment led to an increase in five genera, but FM was not associated with any measurable change. The severity of DSS-induced colitis was greater with FSS than FMS. CONCLUSIONS: This study demonstrates differential and unique influences of ferric maltol and ferrous sulphate supplements on intestinal microbiota. These differences might contribute to the different side effects associated with these preparations.

Developmental toxicity, antioxidant, and marker enzyme assessment of swertiamarin in zebrafish (Danio rerio).

A secoiridoid glycoside called swertiamarin has been widely used as a herbal medicine for many decades. In particular, swertiamarin from the Enicostema axillare herb has been used as a multipurpose drug to treat innumerable health problems. As this medicine is consumed orally, its toxicity level should be determined. To examine the safety of this compound, toxicology work was done in zebrafish, and this is the first report to describe swertiamarin toxicity in zebrafish. Zebrafish embryos were used in this swertiamarin toxicity study, and morphological changes were observed. Further, the compound was also studied in adult zebrafish to determine the impact of the compound on the fish liver. Enzyme profiling with superoxide dismutase, glutathione peroxidase, catalase, reduced glutathione levels, glutathione S-transferase, lactate dehydrogenase, glutamic oxaloacetic transaminases, lipid peroxidation, Na+ /K+ -ATPase, and glutamic pyruvic transaminases) was evaluated (p ≤ 0.05). Results suggest that swertiamarin is a safe drug only at a low concentration (40 µM). This study also shows that even herbal medicinal compounds may be toxic to humans at higher dosages. Hence, irrespective of whether a drug is synthetic or natural, it needs to be tested for its toxicity before use in humans.

Yangonin modulates lipid homeostasis, ameliorates cholestasis and cellular senescence in alcoholic liver disease via activating nuclear receptor FXR.

BACKGROUND: Alcoholic liver disease (ALD) is a progressive disease beginning with simple steatosis but can progress to alcoholic steatohepatitis, fibrosis, cirrhosis, and even hepatocellular carcinoma. The morbidity of ALD is on the rise and has been a large burden on global healthcare system. It is unfortunately that there are currently no approved therapeutic drugs against ALD. Hence, it is of utmost urgency to develop the efficacious therapies. The ability of many molecular targets against ALD is under investigation. Farnesoid X receptor (FXR), a member of the ligand-activated transcription factor superfamily, has been recently demonstrated to have a crucial role in the pathogenesis and progression of ALD. PURPOSE: The purpose of the study is to determine whether Yangonin (YAN), a FXR agonist previously demonstrated by us, exerts the hepatoprotective effects against ALD and further to clarify the mechanisms in vitro and in vivo. STUDY DESIGN: The alcoholic liver disease model induced by Lieber-Decarli liquid diet was established with or without Yan treatment. METHODS: We determined the liver to body weight ratios, the body weight, serum and hepatic biochemical indicators. The alleviation of the liver histopathological progression was evaluated by H&E and immunohistochemical staining. Western blot and quantitative real-time PCR were used to demonstrate YAN treatment-mediated alleviation mechanisms of ALD. RESULTS: The data indicated that YAN existed hepatoprotective activity against ALD via FXR activation. YAN improved the lipid homeostasis by decreasing hepatic lipogenesis and increasing fatty acid ß-oxidation and lipoprotein lipolysis through modulating the related protein. Also, YAN ameliorated ethanol-induced cholestasis via inhibiting bile acid uptake transporter Ntcp and inducing bile acid efflux transporter Bsep and Mrp2 expression. Besides, YAN improved bile acid homeostasis via inducing Sult2a1 expression and inhibiting Cyp7a1 and Cyp8b1 expression. Furthermore, YAN attenuated ethanol-triggered hepatocyte damage by inhibiting cellular senescence marker P16, P21 and Hmga1 expression. Also, YAN alleviated ethanol-induced inflammation by down-regulating the inflammation-related gene IL-6, IL-1ß and TNF-α expression. Notably, the protective effects of YAN were cancelled by FXR siRNA in vitro and FXR antagonist GS in vivo. CONCLUSIONS: YAN exerted significant hepatoprotective effects against liver injury triggered by ethanol via FXR-mediated target gene modulation.

Chemistry, Pharmacology and Therapeutic Potential of Swertiamarin - A Promising Natural Lead for New Drug Discovery and Development.

Swertiamarin, a seco-iridoid glycoside, is mainly found in Enicostemma littorale Blume (E. littorale) and exhibits therapeutic activities for various diseases. The present study aimed to provide a review of swertiamarin in terms of its phytochemistry, physicochemical properties, biosynthesis, pharmacology and therapeutic potential. Relevant literature was collected from several scientific databases, including PubMed, ScienceDirect, Scopus and Google Scholar, between 1990 and the present. This review included the distribution of swertiamarin in medicinal plants and its isolation, characterization, physicochemical properties and possible biosynthetic pathways. A comprehensive summary of the pharmacological activities, therapeutic potential and metabolic pathways of swertiamarin was also included after careful screening and tabulation. Based on the reported evidence, swertiamarin meets all five of Lipinski's rules for drug-like properties. Thereafter, the physicochemical properties of swertiamarin were detailed and analyzed. A simple and rapid method for isolating swertiamarin from E. littorale has been described. The present review proposed that swertiamarin may be biosynthesized by the mevalonate or nonmevalonate pathways, followed by the seco-iridoid pathway. It has also been found that swertiamarin is a potent compound with diverse pharmacological activities, including hepatoprotective, analgesic, anti-inflammatory, antiarthritis, antidiabetic, antioxidant, neuroprotective and gastroprotective activities. The anticancer activity of swertiamarin against different cancer cell lines has been recently reported. The underlying mechanisms of all these pharmacological effects are diverse and seem to involve the regulation of different molecular targets, including growth factors, inflammatory cytokines, protein kinases, apoptosis-related proteins, receptors and enzymes. Swertiamarin also modulates the activity of several transcription factors, and their signaling pathways in various pathological conditions are also discussed. Moreover, we have highlighted the toxicity profile, pharmacokinetics and possible structural modifications of swertiamarin. The pharmacological activities and therapeutic potential of swertiamarin have been extensively investigated. However, more advanced studies are required including clinical trials and studies on the bioavailability, permeability and administration of safe doses to offer swertiamarin as a novel candidate for future drug development.

The p53/p21/p16 and PI3K/Akt signaling pathways are involved in the ameliorative effects of maltol on D-galactose-induced liver and kidney aging and injury.

Successive evidence has established that maltol, a flavor-enhancing agent, could provide resistance to oxidative stress-induced tissue injury in various animal models though its benefits for aging-induced liver and kidney injuries are still undetermined. In the present work, for demonstrating maltol's ameliorative effect and probable mechanism against aging-induced liver and kidney injuries, D-galactose (D-Gal)-induced animal in vivo and HEK293 cells in vitro models were established and results demonstrated that long-term D-Gal treatment increases the accumulation of advanced glycation end products (AGEs) in liver and kidney tissues, mitigates cell viability, and arrests the cycle. Interestingly, 4-weeks maltol treatment at 50 and 100 mg/kg activated aging-associated proteins including p53, p21, and p16 followed by inhibiting malondialdehyde (MDA)'s over-production and increasing the levels of antioxidant enzymes. Therefore, decreases in cytochrome P450 E1 (CYP2E1) and 4-hydroxydecene (4-HNE)'s immunofluorescence expression levels are confirmed. Furthermore, maltol improved oxidative stress injury by activating the phosphatidylinositol-3-kinase (PI3K)/protein kinase B (Akt) signaling pathway. In conclusion, the purpose of the present study was to estimate the mechanistic insights into maltol's role as an antioxidant in liver and kidney cell senescence and injury, which will reflect potential of therapeutic strategy for antiaging and aging-related disease treatment.

Iridoid compounds from the aerial parts of Swertia mussotii Franch. with cytotoxic activity.

One new secoiridoid compound swertiamarin B (1), along with a known compound lytanthosalin (2), were isolated from ethanol extract of the aerial parts of Swertia mussotii. Their structures were elucidated by the detailed analysis of comprehensive spectroscopic data. All compounds were first isolated from the Swertia genus. Their antitumor activities were evaluated for four human tumor cell lines (HCT-116, HepG2, MGC-803 and A549). Compounds 1 and 2 showed excellent cytotoxic activities toward the MGC-803 cell lines with IC50 values 3.61 and 12.04 µM, respectively.

Swertiamarin supplementation prevents obesity-related chronic inflammation and insulin resistance in mice fed a high-fat diet.

Obesity is characterized by low-grade chronic inflammation, which underlies insulin resistance and non-alcoholic fatty liver disease (NAFLD). Swertiamarin is a secoiridoid glycoside that has been reported to ameliorate diabetes and NAFLD in animal models. However, the effects of swertiamarin on obesity-related inflammation and insulin resistance have not been fully elucidated. Thus, this study investigated the effects of swertiamarin on inflammation and insulin resistance in high-fat diet (HFD)-induced obese mice. C57BL/6 mice were fed a HFD or HFD containing swertiamarin for 8 weeks. Obesity-induced insulin resistance and inflammation were assessed in the epididymal white adipose tissue (eWAT) and livers of the mice. Swertiamarin attenuated HFD-induced weight gain, glucose intolerance, oxidative stress, and insulin resistance, and enhanced insulin signalling in mice. Compared to HFD-fed mice, the swertiamarin-treated mice exhibited increased lipolysis and reduced adipocyte hypertrophy and macrophage infiltration in eWAT. Moreover, swertiamarin alleviated HFD-mediated hepatic steatosis and inflammation by suppressing activation of the p38 MAPK and NF-κB pathways within the eWAT and liver of obese mice. In conclusion, supplementation with swertiamarin attenuated weight gain and hepatic steatosis, and alleviated obesity-associated inflammation and insulin resistance, in obese mice.

Swertiamarin from Enicostemma littorale, counteracts PD associated neurotoxicity via enhancement α-synuclein suppressive genes and SKN-1/NRF-2 activation through MAPK pathway.

The elusive targets and the multifactorial etiology of Parkinson's disease (PD) have hampered the discovery of a potent drug for PD. Furthermore, the presently available medications provide only symptomatic relief and have failed to mitigate the pathogenesis associated with PD. Therefore, the current study was aimed to evaluate the prospective of swertiamarin (SW), a secoiridoid glycoside isolated from a traditional medicinal plant, Enicostemma littorale Blume to ameliorate the characteristic features of PD in Caenorhabditis elegans. SW (25 µM) administration decreased the α-synuclein (α-syn) deposition, inhibited apoptosis and increased dopamine level mediated through upregulating the expression of genes linked to ceramide synthesis, mitochondrial morphology and function regulation, fatty acid desaturase genes along with stress responsive MAPK (mitogen-activated protein kinase) pathway genes. The neuroprotective effect of SW was evident from the robust reduction of 6-hydroxydopamine (6-OHDA) induced dopaminergic neurodegeneration independent of dopamine transporter (dat-1). SW mediated translational regulation of MAPK pathway genes was observed through increase expression of SKN-1 and GST-4. Further, in-silico molecular docking analysis of SW with C. elegans MEK-1 showed a promising binding affinity affirming the in-vivo results. Overall, these novel finding supports that SW is a possible lead for drug development against the multi- factorial PD pathologies.

Partial inhibition of mitochondrial complex I ameliorates Alzheimer's disease pathology and cognition in APP/PS1 female mice.

Alzheimer's Disease (AD) is a devastating neurodegenerative disorder without a cure. Here we show that mitochondrial respiratory chain complex I is an important small molecule druggable target in AD. Partial inhibition of complex I triggers the AMP-activated protein kinase-dependent signaling network leading to neuroprotection in symptomatic APP/PS1 female mice, a translational model of AD. Treatment of symptomatic APP/PS1 mice with complex I inhibitor improved energy homeostasis, synaptic activity, long-term potentiation, dendritic spine maturation, cognitive function and proteostasis, and reduced oxidative stress and inflammation in brain and periphery, ultimately blocking the ongoing neurodegeneration. Therapeutic efficacy in vivo was monitored using translational biomarkers FDG-PET, 31P NMR, and metabolomics. Cross-validation of the mouse and the human transcriptomic data from the NIH Accelerating Medicines Partnership-AD database demonstrated that pathways improved by the treatment in APP/PS1 mice, including the immune system response and neurotransmission, represent mechanisms essential for therapeutic efficacy in AD patients.

Identification of Tyrosinase Inhibitors and Their Structure-Activity Relationships via Evolutionary Chemical Binding Similarity and Structure-Based Methods.

Tyrosinase is an enzyme that plays a crucial role in the melanogenesis of humans and the browning of food products. Thus, tyrosinase inhibitors that are useful to the cosmetic and food industries are required. In this study, we have used evolutionary chemical binding similarity (ECBS) to screen a virtual chemical database for human tyrosinase, which resulted in seven potential tyrosinase inhibitors confirmed through the tyrosinase inhibition assay. The tyrosinase inhibition percentage for three of the new actives was over 90% compared to 61.9% of kojic acid. From the structural analysis through pharmacophore modeling and molecular docking with the human tyrosinase model, the pi-pi interaction of tyrosinase inhibitors with conserved His367 and the polar interactions with Asn364, Glu345, and Glu203 were found to be essential for tyrosinase-ligand interactions. The pharmacophore features and the docking models showed high consistency, revealing the possible essential binding interactions of inhibitors to human tyrosinase. We have also presented the activity cliff analysis that successfully revealed the chemical features related to substantial activity changes found in the new tyrosinase inhibitors. The newly identified inhibitors and their structure-activity relationships presented here will help to identify or design new human tyrosinase inhibitors.

Antimicrobial substances from Amazonian Aniba (Lauraceae) species.

Extracts and six isolated substances from Aniba (Lauraceae) Amazonian species A. parviflora, A. panurensis and A. rosaeodora were analysed in vitro to their antibacterial, antiparasitic and antiplasmodial activities. NMR and MS experiments led to the identification of three styrylpyrones (5,6-dihydrokawain [I], 4-methoxy-11,12-methylenedioxy-6-trans-styryl-pyran-2-one [II] and rel-(6R,7S,8S,5'S)-4'-methoxy-8-(11,12-dimethoxyphenyl-7-[6-(4-methoxy-2-pyranyl)]-6-(E)-styryl-1'-oxabicyclo[4,2,0]oct-4'-en-2'-one [III]), a pyridine alkaloid (anibine [IV]) and two kavalactones (tetrahydroyangonin [V] and dihydromethysticin [VI]). The best antibacterial result was observed at the hexane fraction of A. panurensis (MIC 7.8 µg/mL against the three bacteria). Equal MIC were observed by the extract and dichloromethane fraction of A. panurensis against S. simulans and S. aureus; and 15.62 µg/mL against MRSA. Similarly, only A. panurensis extracts showed in vitro activities against Tripanossoma cruzi and Leishmania amazonensis parasites. In Plasmodium falciparum assay, 5,6-dihydrokawain was considered an active antimalarial (14.03 µM), and substances II (132.94 µM) and III (41.84 µM) presented moderate activities.