Résumé
C-Glycosides are important natural products with various bioactivities. In plant biosynthetic pathways, the C-glycosylation step is usually catalyzed by C-glycosyltransferases (CGTs), and most of them prefer to accept uridine 5'-diphosphate glucose (UDP-Glc) as sugar donor. No CGTs favoring UDP-rhamnose (UDP-Rha) as sugar donor has been reported, thus far. Herein, we report the first selective C-rhamnosyltransferase VtCGTc from the medicinal plant Viola tricolor. VtCGTc could efficiently catalyze C-rhamnosylation of 2-hydroxynaringenin 3-C-glucoside, and exhibited high selectivity towards UDP-Rha. Mechanisms for the sugar donor selectivity of VtCGTc were investigated by molecular dynamics (MD) simulations and molecular mechanics with generalized Born and surface area solvation (MM/GBSA) binding free energy calculations. Val144 played a vital role in recognizing UDP-Rha, and the V144T mutant could efficiently utilize UDP-Glc. This work provides a new and efficient approach to prepare flavonoid C-rhamnosides such as violanthin and iso-violanthin.
Résumé
Estrogen receptors (ERs) are members of nuclear receptors and related to several diseases such as cancer, inflammation and osteoporosis. ERs have two forms, ERα and ERβ, which have different functions and organism distributions. Compounds selectively targeting ERβ can regulate important physiological functions and avoid the side effects caused by targeting ERα. Therefore, selective ERβ ligands have received considerable research interest in recent years. In this article, different kinds of selective ERβ ligands were summarized and their structure-activity relationships were also analyzed.
Résumé
OBJECTIVE@#To determine the effect of tetramethylpyrazine (TMP) on the expression of migration inhibitory factor (MIF) in acute spinal cord injury (ASCI) in rats.@*METHODS@#Allen's weight-drop method was used to establish a rat model of ASCI at T10. A total of 110 adult SD rats were divided into a sham operation group (group S, n=10), a control group (group C, n=50), and a TMP group (group T, n=50). Spinal cord functionality was measured by a modified Rivilin loxotic plate degree, BBB score, and combined behavioral score (CBS) at 1, 3, 5, 7, 14 and 21 d postoperatively. The injured spinal cord tissue samples were harvested at 1, 3, 6, 12 h and 1, 3, 5, 7, 14, 21 d postoperatively (n=5 at each time point) and used to prepare continuous histological sections, in which the expression of MIF was analyzed by immunohistochemistry.@*RESULTS@#The degree in group T measured by modified Rivlin loxotic plate test after the ASCI was significantly higher than that in group C at 7, 14, and 21 d (P<0.05). BBB score in group T was significantly higher than that in group C at 5, 7, 14, and 21 d after the ASCI (P<0.05). CBS score in group C was significantly higher than that in group T at 5, 7, 14, and 21 d after the ASCI (P<0.05). The significantly low number of MIF positive cells was shown in group T when compared with that in group C at 12 h and 1, 3, 5, 7 d after the ASCI (P<0.05). As time passed, there was negative correlation between modified Rivlin loxotic plate degree and MIF expression and also between BBB score and MIF, and there was positive correlation between CBB score and MIF expression.@*CONCLUSION@#TMP has protective effect after the ASCI, and may promote the repair of injured spinal cord tissues. TMP may decrease the MIF expression in cells after the ASCI.