Structure and anti-inflammatory activity of neo-clerodane diterpenoids from Scutellaria barbata.

Herein, 13 previously undescribed neo-clerodane diterpenoids (1-13) and 27 known analogs (14-40) were isolated from the aerial parts of Scutellaria barbata. Absolute configurations of undescribed compounds were assigned based on single-crystal X-ray diffraction analysis and comparison of experimental and circular dichroism. All isolates were evaluated for the inhibition of nitric oxide generation induced by lipopolysaccharide in RAW 264.7 macrophages. Compound 36 was found to be the most active with an IC50 value of 10.6 µM. Structure-activity relations of these neo-clerodane diterpenoids revealed that the α, ß-unsaturated-γ-lactone moiety with an exocyclic conjugated double bond was necessary for maintaining and increasing its activity. Further mechanistic studies show that compound 36 suppressed nitric oxide synthase enzymes (iNOS) expression without affecting iNOS activity. Additionally, compound 36 suppresses NF-κB signaling by inhibiting IκBα phosphorylation.

Synthesis and anticancer activity of novel histone deacetylase inhibitors that inhibit autophagy and induce apoptosis.

The combination of histone deacetylase (HDAC) and autophagy inhibitor has been considered as a novel cancer therapeutic strategy. To find novel HDAC inhibitors that can inhibit autophagy, several new series of oxazole- and thiazole-based HDAC inhibitors were designed and synthesized by replacing the phenyl cap in SAHA with 5-phenyloxazoles and 5-phenylthiazoles. The representative oxazole derivative, compound 21, showed better enzymatic inhibitory activity than SAHA (vorinostat). Compound 21 induced G2/M cell cycle arrest and its antiproliferative activity is 10-fold better than SAHA in multiple tumor cell lines. Western blot analysis showed that compound 21 can markedly increase the acetylation levels of tubulin, histone H3, and histone H4. Contrary to SAHA, compound 21 was found to inhibit autophagy. Additionally, compound 21 induced cell apoptosis via the Bax/Bcl-2 and caspase-3 pathways. Ultimately, compound 21 exhibited higher oral antitumor potency than SAHA in a A549 xenograft model. Our results indicated that compound 21 may be further developed as a promising anticancer agent.

Alteration of gut microbiota in high-fat diet-induced obese mice using carnosic acid from rosemary.

Rosmarinus officinalis (rosemary) is widely used as a food ingredient. Rosemary extract (containing 40% carnosic acid) exhibited potent antiobesity activity. However, the relationship between carnosic acid (CA) and changes in the gut microbiota of high-fat diet (HFD)-induced obese mice has not been fully investigated. C57BL/6 mice were fed a normal diet, an HFD, or an HFD containing 0.1% or 0.2% CA for 10 weeks. CA exhibited promising antiobesity effects and caused marked alterations in the gut microbiota of HFD-induced obese mice. CA caused the prevalence of probiotics and functional bacteria, including Akkermansia muciniphila, Muribaculaceae unclassified, and Clostridium innocuum group, and inhibited diabetes-sensitive bacteria, including Proteobacteria and Firmicutes. The ratio of Firmicutes to Bacteroidetes was regulated by CA in a dose-dependent manner, decreasing it from 13.22% to 2.42%. Additionally, CA reduced bile acid-metabolizing bacteria, such as Bilophila, Clostridium, Lactobacillus, and Leuconostoc. The results of the linear discriminant analysis and effect size analysis indicated that CA attenuated the microbial changes caused by HFD. The high CA (HCA) group (HFD containing 0.2% CA) exhibited a greater abundance of Verrucomicrobiae (including Akkermansia muciniphila, genus Akkermansia, family Akkermansiaceae, and order Verrucomicrobiales), Eubacterium, and Erysipelatoclostridium, and the low CA (LCA) group (HFD containing 0.1% CA) exhibited a greater abundance of Eisenbergiella, Intestinimonas, and Ruminococcaceae. Our results demonstrate that the antiobesity effects of CA might be strongly related to its prebiotic effects.

Bidirectional interaction of nobiletin and gut microbiota in mice fed with a high-fat diet.

Nobiletin is abundant in citrus peels and demonstrates good anti-obesity bioactivity. However, its anti-obesity mechanisms still remain unclear. This study aims to explore the bidirectional interaction between nobiletin and gut microbiota in mice fed with a high-fat diet. For the colonic bioconversion, more demethylated metabolites with higher biological activity were found in feces than nobiletin in the 48 h excretion study and 8 week consecutive dosing study. Moreover, long-term oral intake of nobiletin would modify the gut microbiota with improved demethylation ability and enhanced production of short chain fatty acids. The comparison of metabolite profiles in mouse liver and feces indicated that gut microbiota might have a higher biotransformation activity on nobiletin than the host. Two bacteria at the genus level, Allobaculum and Roseburia, remained enriched by nobiletin after the 4- and 8-week feedings. They might correlate with the enhanced nobiletin biotransformation and actively contribute to the health benefits of nobiletin in vivo. These results suggested that the bidirectional interaction of nobiletin and gut microbiota played an important role on the anti-obesity effect of nobiletin.

Synthesis and structure-activity relationships of 5-phenyloxazole-2-carboxylic acid derivatives as novel inhibitors of tubulin polymerization.

A series of 5-phenyloxazole-2-carboxylic acid derivatives were synthesized, and their structure-activity relationships (SARs) were studied. N,5-diphenyloxazole-2-carboxamides 6, 7, and 9, which mimicked ABT751, showed improved cytotoxicity compared with ABT751. Compound 9 exhibited the highest antiproliferative activities against Hela A549, and HepG2 cancer cell lines, with IC50 values of 0.78, 1.08, and 1.27 µM, respectively. Furthermore, compound 9 showed selectivity for human cancer cells over normal cells, and this selectivity was greater than those of ABT751 and colchicine. Preliminary mechanism studies suggested that compound 9 inhibited tubulin polymerization and led to cell cycle arrest at G2/M phase. Molecular docking studies indicated that compound 9 bound to the colchicine binding site of tubulin. Our findings provided insights into useful SARs for further structural modification of inhibitors of tubulin polymerization.

Asymmetric Construction of Cyclobutanes via Direct Vinylogous Michael Addition/Cyclization of ß,γ-Unsaturated Amides.

The construction of cyclobutanes has attracted much attention because of its unique four-membered ring skeleton. Herein, we report the highly enantioselective direct vinylogous Michael reaction of ß,γ-unsaturated pyrazole amides and nitroolefin using a squaramide catalyst. Cyclobutane derivatives were obtained by subsequent cyclization in good yields (up to 85%) with excellent enantioselectivities (up to 99% ee). Importantly, the large-scale reaction experiment confirmed the reliability of the vinylogous reaction. Furthermore, the synthetic utility of the vinylogous adducts and cyclobutane derivatives has been realized.

Aged citrus peel (chenpi) extract causes dynamic alteration of colonic microbiota in high-fat diet induced obese mice.

Aged citrus peels (chenpi) have been used as a dietary supplement for gastrointestinal health maintenance in China. Recently, it was reported to exhibit anti-obesity activity. However, the relationship between the modulation effect of chenpi on gut microbiota and obesity prevention is not clearly understood. In this study, mice were fed with a high-fat diet (HFD), HFD supplemented with 0.25%- and 0.5%-chenpi extract, and normal diet, respectively, for 11 weeks. Chenpi extract significantly increased fecal short chain fatty acids by 43% for acetic acid and 86% for propionic acid. In addition, chenpi could decrease the prevalence of Proteobacteria and the ratio of Firmicutes to Bacteroidetes by about 88% and 70%, respectively. Moreover, this study was the first work to demonstrate the dynamics of two beneficial bacteria-Akkermansia spp. and Allobaculum spp. in a dose- and time-dependent manner for chenpi treatment via monitoring the dynamic change of the gut microbiota. Metagenomic analysis of the gut microbiota showed that several pathways, such as a two-component system, a tight junction, Staphylococcus aureus infection and others, were enhanced dynamically. The improved biological process of metabolism especially in benzoate derivatives might refer to the increased metabolic transformation of polymethoxyflavones from chenpi in the colon. Our study indicated that the modulation effect of chenpi on the gut microbiota may be an important pathway for its anti-obesity mechanisms.

Identification of bioactive compounds that contribute to the α-glucosidase inhibitory activity of rosemary.

To investigate the bioactive compounds that contribute to the α-glucosidase inhibitory activity of rosemary, phenolics and triterpene acids were characterized and quantified using quadrupole-Orbitrap mass spectrometry and enzyme assay. Two phenolic diterpenes (carnosol and hydroxy p-quinone carnosic acid) and two triterpene acids (betulinic acid and ursolic acid) were identified as potent α-glucosidase inhibitors. Carnosol, a major diterpene in rosemary, showed significant α-glucosidase inhibitory activity with IC50 value of 12 µg mL-1, and its inhibition mode was competitive. The inhibition mechanism of carnosol on α-glucosidase was further investigated by a combination of surface plasmon resonance (SPR) spectroscopy, fluorescence quenching studies and molecular-modeling techniques. The SPR assay suggested that carnosol had a high affinity to α-glucosidase with equilibrium dissociation constant (KD) value of 72.6 M. Fluorescence quenching studies indicated that the binding between carnosol and α-glucosidase was spontaneous and mainly driven by hydrophobic forces. Molecular docking studies revealed that carnosol bound to the active site of α-glucosidase. Furthermore, the oral administration of carnosol at 30 mg kg-1 significantly reduced the postprandial blood glucose levels of normal mice. This is the first report on the α-glucosidase inhibition and hypoglycemic activity of phenolic diterpenes, and these results could facilitate the utilization of rosemary as a dietary supplement for the treatment of diabetes.

Synthesis and Biological Evaluation of Novel Resveratrol-NSAID Derivatives as Anti-inflammatory Agents.

Long-term use of nonsteroidal antiinflammatory drugs (NSAIDs) may cause serious side effects such as gastric mucosal damage. Resveratrol, a naturally dietary polyphenol, exhibited anti-inflammatory activity and a protective effect against gastric mucosa damage induced by NSAIDs. In this regard, we synthesized a series of resveratrol-based NSAIDs derivatives and evaluated their anti-inflammatory activity against nitric oxide (NO) overproduction in lipopolysaccharide (LPS)-stimulated RAW264.7 macrophages. We identified mono-substituted resveratrol-ibuprofen combination 21 as the most potent anti-inflammatory agent, which is more active than a physical mixture of ibuprofen and resveratrol, individual ibuprofen, or individual resveratrol. In addition, compound 21 exerted potent inhibitory effects on the LPS-induced expression of tumor necrosis factor-α (TNF-α) and interleukin-1ß (IL-1ß). Furthermore, compound 21 significantly increased the survival rate in an LPS-induced acute inflammatory model and produced markedly less gastric damage than ibuprofen. It was found that compound 21 may be a potent anti-inflammatory agent for the treatment of inflammation-related diseases.

Total synthesis and cytotoxic activities of longamide B, longamide B methyl ester, hanishin, and their analogues.

The marine alkaloids, longamide B (1), longamide B methyl ester (2), hanishin (3), and a series of non-naturally occurring analogues were synthesized in an efficient manner from inexpensive commercially available dl-aspartic acid dimethyl ester. The cytotoxicities of these natural products (1-3) and their analogues (9-15) were evaluated against human lung adenocarcinoma (A549) and human prostate cancer (PC3) cells. This is the first evaluation of the cytotoxicities of these alkaloids in these cancer cell lines and it revealed that analogue 15 had comparable cytotoxic activity to its natural parent compound, (±)-hanishin (3). This study provides useful information for further structural modification of these alkaloids in order to develop novel antitumor agents.

Coumarins with α-glucosidase and α-amylase inhibitory activities from the flower of Edgeworthia gardneri.

The flower of Edgeworthia gardneri is consumed in beverages in Tibet and has potential health benefits for diabetes. As a part of our continuous studies on dietary supplements for diabetes, two monomers, five dimers and one trimer of coumarins were isolated from the flowers of E. gardneri. One dimer was a new compound (1) and its structure was determined by spectroscopic methods, including multiple NMR techniques and mass spectrometry. The inhibitory activities of all coumarins against α-amylase and α-glucosidase were evaluated. Compound 4 displayed potent inhibitory effect on both α-amylase and α-glucosidase, with an IC50 of 90 and 86µg/mL, respectively. The IC50 of compound 3 against α-glucosidase was 18.7µg/mL, and its inhibition mode was noncompetitive. Based on the fluorescence analysis, the binding constant and the number of binding sites of compound 3 were calculated as 2.05×10(5) and 1.24, respectively. Furthermore, the interaction between compound 3 and α-glucosidase was a spontaneous process that was driven mainly by hydrophobic force. This study could facilitate the utilization of E gardneri as functional food ingredient.

α-Glucosidase Inhibition and Antihyperglycemic Activity of Phenolics from the Flowers of Edgeworthia gardneri.

The flowers of Edgeworthia gardneri are consumed as an herbal tea in Tibet with potential health benefits. To complement the current knowledge regarding the chemical composition and antihyperglycemic activity of the flower of E. gardneri, two new phenolics, gardnerol A and B (1 and 2), along with 19 known phenolics were isolated from the flower of E. gardneri. All isolates were evaluated for their inhibitory activity against α-glucosidase. Compound 5, identified as the major constituent of the flower of E. gardneri, showed a significant α-glucosidase inhibitory activity and acted as a competitive inhibitor. The oral administration of compound 5 at a dose of 300 mg/kg significantly reduced the postprandial blood glucose levels of normal and streptozotocin (STZ)-induced diabetic mice. Furthermore, compound 5 significantly decreased the fasting blood glucose levels in STZ-induced diabetic mice.

Structural investigation and biological activity of sesquiterpene lactones from the traditional Chinese herb Inula racemosa.

Five new sesquiterpene lactones, racemosalactones A-E (1-5), along with 19 known sesquiterpene latones (6-24), were isolated from the roots of Inula racemosa. Their structures were elucidated by extensive spectroscopic analysis, and the absolute configuration of 2 was deduced from X-ray diffraction analysis. Compounds 1, 6, 8, 10, 12, 14, and 17 exhibited antiproliferative activities with IC50 values ranging from 0.38 to 4.19 µg/mL against human non-small-cell lung cancer A549, hepatocellular carcinoma HepG2, and human fibrosarcoma HT1080 cells. Compounds 6 and 8 exhibited antiproliferative activities against endothelial cells with IC50 values of 2.4 and 2.5 µg/mL, respectively. Furthermore, compounds 6 and 8 both inhibited endothelial cell tube formation at 1.0 µg/mL. A method for the rapid and straightforward preparative-scale isolation of compound 6 from alantolides is described.

Synthesis and structure-activity relationships of N-methyl-5,6,7-trimethoxylindoles as novel antimitotic and vascular disrupting agents.

Several new series of 5,6,7-trimethoxyindole derivatives were synthesized and their structure-activity relationships (SARs) were studied. Some of these compounds exhibited strong antiproliferative activities in the submicromolar range. N-Methyl-5,6,7-trimethoxylindoles 21 and 31 displayed the highest antiproliferative activities, with IC50 values ranging from 22 to 125 nM in four human cancer cell lines and activated human umbilical vein endothelial cells (HUVECs). In addition to vascular disrupting activity verified by in vitro assays, compounds 21 and 31 displayed much higher selectivity for activated HUVECs versus quiescent HUVECs than those of colchicine and combretastatinA-4. The polymerization of cancer cell tubulin was inhibited and the cell cycle was arrested in the G2/M phase after treatment with 21 and 31. It was showed that 21 disrupted tumor vasculature by use of in vivo assay. Our results suggest that these two new compounds we synthesized may become the promising leads for the development of vascular disrupting agents.

Isolation, modification and cytotoxic evaluation of flavonoids from Rhododendron hainanense.

OBJECTIVES: The aim of this study was to search for antitumour activity of flavonoid compounds. The cytotoxic activity of these compounds in vitro was evaluated against the human leukaemia (HL-60) and human hepatoma (SMMC-7721) cell lines. METHODS: Eight natural flavonoids (1-8) were isolated from the aerial parts of Rhododendron hainanense and a series of modified flavonoid derivatives (9-18) were obtained from the natural product matteucinol (1), using simple synthetic methods. Antitumour inhibitory activity of these flavonoids was assessed using the sulforhodamine B method. KEY FINDINGS: Most of the compounds exhibited good pharmacological activity and the preliminary structure-activity relationships were described. Within the series of flavonoid derivatives in this study, compounds 3 (2,3-dihydro-5-hydroxy-7-methoxy-2-(4-methoxyphenyl)-6,8-dimethyl-4H-1-benzopyran-4-one) and 16 (5-hydroxy-7, 4'-dimethoxy-6, 8-dimethylflavan) exhibited strong inhibitory activity against the HL-60 cell line with IC50 values (the drug concentration that resulted in a 50% reduction in cell viability or inhibition of the biological activity) of 15.2 and 13.2 µm, respectively. CONCLUSIONS: Renewed attention to flavonoid derivatives revealed the possibility that compounds 3 and 16 could be considered as lead compounds for the development of new antitumour agents. Our results have not only enriched the family of active flavonoids from natural sources, but have encouraged the synthesis of flavonoid analogues for improving cytotoxic activity.