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.

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.

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.