Isoprenylated phenolic compounds with tyrosinase inhibition from Morus nigra.

A new isoprenylated sanggenon-type flavanone, nigrasin K (1), together with three known analogs (2-4) and five known Diels-Alder adducts (5-9), were isolated from the twigs of Morus nigra. Their structures were elucidated by spectroscopic methods. Sanggenon M (2), chalcomoracin (5), sorocein H (6), kuwanon J (7), sanggenon C (8), and sanggenon O (9) showed significant inhibitory effects on mushroom tyrosinase.

Inhibitory Effects of (2'R)-2',3'-dihydro-2'-(1-hydroxy-1-methylethyl)-2,6'-bibenzofuran-6,4'-diol on Mushroom Tyrosinase and Melanogenesis in B16-F10 Melanoma Cells.

(2'R)-2',3'-Dihydro-2'-(1-hydroxy-1-methylethyl)-2,6'-bibenzofuran-6,4'-diol (DHMB) is a natural compound extracted from Morus notabilis. It was found that DHMB acts as a competitive inhibitor against mushroom tyrosinase with a Ki value of 14.77 µM. Docking results further indicated that it could form strong interactions with one copper ion with a distance of 2.7 Å, suggesting the mechanism of inhibition might be due to chelating copper ions in the active site. Furthermore, melanin production in B16-F10 murine melanoma cells was significantly inhibited by DHMB in a concentration-dependent manner without cytotoxicity. The results of western blotting also showed that DHMB decreased 3-isobuty-1-methxlzanthine-induced mature tyrosinase expression. Taken together, these findings indicated that DHMB may be a new promising pigmentation-altering agent for agriculture, cosmetic, and therapeutic applications.

Benzbromarone, an old uricosuric drug, inhibits human fatty acid binding protein 4 in vitro and lowers the blood glucose level in db/db mice.

AIM: Fatty acid-binding protein 4 (FABP4) plays an important role in maintaining glucose and lipid homeostasis. The aim of this study was to find new inhibitors of FABP4 for the treatment of type 2 diabetes. METHODS: Human FABP4 protein was expressed, and its inhibitors were detected in 1,8-ANS displacement assay. The effect of the inhibitor on lipolysis activity was examined in mouse 3T3-L1 preadipocytes. The db/db mice were used to evaluate the anti-diabetic activity of the inhibitor. Molecular docking and site-directed mutagenesis studies were carried out to explore the binding mode between the inhibitor and FABP4. RESULTS: From 232 compounds tested, benzbromarone (BBR), an old uricosuric drug, was discovered to be the best inhibitor of FABP4 with an IC50 value of 14.8 µmol/L. Furthermore, BBR (25 µmol/L) significantly inhibited forskolin-stimulated lipolysis in 3T3-L1 cells. Oral administration of BBR (25 or 50 mg/kg, for 4 weeks) dose-dependently reduced the blood glucose level and improved glucose tolerance and insulin resistance in db/db mice. Molecular docking revealed that the residues Ser55, Asp76, and Arg126 of FABP4 formed important interactions with BBR, which was confirmed by site-directed mutagenesis studies. CONCLUSION: BBR is an inhibitor of FABP4 and a potential drug candidate for the treatment of type 2 diabetes and atherosclerosis.

2-Arylbenzofuran and tyrosinase inhibitory constituents of Morus notabilis.

Phytochemical investigation of the stem of Morus notabilis led to the isolation and characterization of 10 compounds of 2-arylbenzofurans (1-10), including two new compounds, (2'R)-2',3'-dihydro-2'-(1-hydroxy-1-methylethyl)-2,6'-bibenzofuran-6,4'-diol (1) and 5,6-dimethoxy-2-(3-hydroxy-5-methoxyphenyl)benzofuran (2). Moracins O (6) and P (10) showed inhibitory effects on mushroom tyrosinase with IC50 values being lower than that of kojic acid.

New isoprenylated flavones and stilbene derivative from Artocarpus hypargyreus.

Three new isoprenylated flavones, hypargyflavones A-C (1-3, resp.), and one novel stilbene derivative, hypargystilbene A (4), together with seven known compounds, 5-11, were isolated from the stems of Artocarpus hypargyreus Hance. The structures were elucidated by spectroscopic methods. Hypargyflavone A (1), cudraflavone C (8), brosimone I (10), and norartocarpin (11) showed inhibitory effects on pancreatic lipase.

[Progress of anti-tumor study based on BRAF].

BRAF is one of the most important pro-oncogenes, which is mutated in approximately 8% of human tumors. The most common BRAF mutation is a valine-to-glutamate transition (V600E) that is expressed primarily in melanoma, colorectal cancer and thyroid carcinoma. MEK/ERK is constitutively activated in the cells expressing BRAFV600E, leading to tumor development, invasion, and metastasis. Therefore, BRAFV600E is a therapeutic target for melanoma and some other BRAFV600E tumors. Vemurafenib, a BRAFV600E inhibitor, which was approved by FDA for the treatment of late-stage melanoma in 2011, produces improved rates of overall and progression-free survival in patients with the BRAFV600E mutation, making a dramatic breakthrough in melanoma treatment. Vemurafenib is also an individual target drug based on genetic diagnosis. However, its therapeutic success is limited by the emergence of drug resistance. Therefore, it is important to explore the mechanisms underlying the resistance for developing new inhibitor drugs and for preventing or delaying the resistance evolution to BRAF inhibitor drugs. In this review, we described the role of BRAFV600E as an anti-tumor drug target and the development of BRAF inhibitors. We also discussed the mechanisms leading to resistance of BRAFV600E inhibitors. Furthermore, therapeutic strategies that might be employed to overcome acquired resistance were proposed.

Pharmacological inhibition of diacylglycerol acyltransferase 1 reduces body weight gain, hyperlipidemia, and hepatic steatosis in db/db mice.

AIM: To test whether pharmacological inhibition of Diacylglycerol acyltransferase 1 (DGAT1) by a small-molecule inhibitor H128 can improve metabolism disorders in leptin receptor-deficient db/db mice. METHODS: To investigate the effect of H128 on intestinal fat absorption,db/db mice were acutely given a bolus of corn oil by gavage. The mice were further orally administered H128 (3 and 10 mg/kg) for 5 weeks. Blood glucose, lipids, insulin, ALT, and AST as well as hepatic triglycerides were measured. The insulin tolerance test was performed to evaluate insulin sensitivity. The expression of genes involved in fatty acid oxidation was detected by RT-PCR. RESULTS: Oral administration of H128 (10 mg/kg) acutely inhibited intestinal fat absorption following a lipid challenge in db/db mice. Chronic treatment with H128 significantly inhibited body weight gain, decreased food intake, and induced a pronounced reduction of serum triglycerides. In addition, H128 treatment markedly ameliorated hepatic steatosis, characterized by decreased liver weight, lipid droplets, and triglyceride content as well as serum ALT and AST levels. Furthermore, H128 treatment increased the expression of the CPT1 and PPARα genes in liver, suggesting that H128 enhanced fatty acid oxidation in db/db mice. However, neither blood glucose nor insulin tolerance was affected by H128 treatment throughout the 5-week experimental period. CONCLUSION: DGAT1 may be an effective therapeutic target for the treatment of obesity, hyperlipidemia and hepatic steatosis.

New isoprenylated 2-arylbenzofurans and pancreatic lipase inhibitory constituents from Artocarpus nitidus.

Two new isoprenylated 2-arylbenzofurans, artonitidin A (=(2'R)-2',3'-dihydro-2'-(1-hydroxy-1-methylethyl)-5',7-bis(3-methylbut-2-en-1-yl)-2,4'-bi-1-benzofuran-6,6'-diol; and artonitidin B (=5-[6-hydroxy-7-(3-methylbut-2-en-1-yl)-1-benzofuran-2-yl]-4-(3-methylbut-2-en-1-yl)benzene-1,3-diol; together with 14 known compounds, were isolated from the stems of Artocarpus nitidus Trec. The structures were elucidated by spectroscopic methods. Norartocarpin, cudraflavone C, brosimone I, artotonkin, albanin A, and artopetelin M showed inhibitory effects on pancreatic lipase with IC(50) values ranging from 1.8+/-0.1 to 63.8+/-3.6 microM.