Phenolic Glycosides with antiproteasomal activity from Centaurea urvillei DC. subsp. urvillei.

A new flavanone glycoside, naringenin-7-O-ß-D-glucuronopyranoside, and a new flavonol glycoside, 6-hydroxykaempferol-7-O-ß-D-glucuronopyranoside were isolated together with 12 known compounds, 5 flavone glycoside; hispidulin-7-O-ß-D-glucuronopyranoside, apigenin-7-O-ß-D-methylglucuronopyranoside, hispidulin-7-O-ß-D-methylglucuronopyranoside, hispidulin-7-O-ß-D-glucopyranoside, apigenin-7-O-ß-D-glucopyranoside, a flavonol; kaempferol, two flavone; apigenin, and luteolin, a flavanone glycoside; eriodictyol-7-O-ß-D-glucuronopyranoside, and three phenol glycoside; arbutin, salidroside, and 3,5-dihydroxyphenethyl alcohol-3-O-ß-D-glucopyranoside from Centaurea urvillei subsp. urvillei. The structure elucidation of the new compounds was achieved by a combination of one- ((1)H and (13)C) and two-dimensional NMR techniques (G-COSY, G-HMQC, and G-HMBC) and LC-ESI-MS. The isolated compounds were tested for their antiproteasomal activity. The results indicated that kaempferol, a well known and widely distributed flavonoid in the plant kingdom, was the most active antiproteasomal agent, followed by apigenin, eriodictyol-7-O-ß-D-glucuronopyranoside, 3,5-dihydroxyphenethyl alcohol-3-O-ß-D-glucopyranoside, and salidroside, respectively.

Differential regulation of CFTRDeltaF508 degradation by ubiquitin ligases gp78 and Hrd1.

The most common mutation associated with cystic fibrosis is the deletion of phenylalanine 508 of cystic fibrosis transmembrane conductance regulator (CFTRDeltaF508). This mutation renders otherwise functional protein susceptible to ER-associated degradation (ERAD) and prevents CFTR from exiting the ER and trafficking to the plasma membrane. In this study, we demonstrate that RNAi-mediated silencing of gp78, an established ubiquitin ligase (E3) involved in ERAD, leads to accumulation of CFTRDeltaF508 protein in cells. gp78 facilitates the degradation of CFTRDeltaF508 by enhancing both its ubiquitination and interaction with p97/VCP. SVIP, which is the inhibitor of gp78, causes accumulation of CFTRDeltaF508. We showed that endogenous gp78 co-immunoprecipitates with Hrd1. Furthermore, the results indicate that silencing the expression of another ERAD E3, Hrd1, leads to stabilization of gp78 and decline in gp78 ubiquitination; thereby enhancing CFTRDeltaF508 degradation. The results support that gp78 is an E3 targeting CFTRDeltaF508 for degradation and Hrd1 inhibits CFTRDeltaF508 degradation by acting as an E3 for gp78.

Studies of the kinetics and thermochemistry of the forward and reverse reaction Cl + C6H6 = HCl + C6H5.

The laser flash photolysis resonance fluorescence technique was used to monitor atomic Cl kinetics. Loss of Cl following photolysis of CCl4 and NaCl was used to determine k(Cl + C6H6) = 6.4 x 10(-12) exp(-18.1 kJ mol(-1)/RT) cm(3) molecule(-1) s(-1) over 578-922 K and k(Cl + C6D6) = 6.2 x 10(-12) exp(-22.8 kJ mol(-1)/RT) cm(3) molecule(-1) s(-1) over 635-922 K. Inclusion of literature data at room temperature leads to a recommendation of k(Cl + C6H6) = 6.1 x 10(-11) exp(-31.6 kJ mol(-1)/RT) cm(3) molecule(-1) s(-1) for 296-922 K. Monitoring growth of Cl during the reaction of phenyl with HCl led to k(C6H5 + HCl) = 1.14 x 10(-12) exp(+5.2 kJ mol(-1)/RT) cm(3) molecule(-1) s(-1) over 294-748 K, k(C6H5 + DCl) = 7.7 x 10(-13) exp(+4.9 kJ mol(-1)/RT) cm(3) molecule(-1) s(-1) over 292-546 K, an approximate k(C6H5 + C6H5I) = 2 x 10(-11) cm(3) molecule(-1) s(-1) over 300-750 K, and an upper limit k(Cl + C6H5I) < or = 5.3 x 10(-12) exp(+2.8 kJ mol(-1)/RT) cm(3) molecule(-1) s(-1) over 300-750 K. Confidence limits are discussed in the text. Third-law analysis of the equilibrium constant yields the bond dissociation enthalpy D(298)(C6H5-H) = 472.1 +/- 2.5 kJ mol(-1) and thus the enthalpy of formation Delta(f)H(298)(C6H5) = 337.0 +/- 2.5 kJ mol(-1).