A well-documented obstacle in the synthesis of functionalized rhodamine dyes is the generation of regioisomers which are difficult to separate. These isomers occur due to the use of unsymmetrical anhydride reagents, which possess two potential points of reactivity where condensation with meta-aminophenols can take place. In this report we describe a method which eliminates this problem by using phthalaldehydic acids as anhydride replacements. These reagents provide only one point of reactivity for the aminophenol, thus allowing direct access to single isomer tetramethylrhodamines and avoiding isomer generation altogether. A range of functionalities are shown to be tolerated at the 5- and 6-position of the dye compounds which are prepared in up to gram quantities using our method. The scope of the method is further demonstrated by the preparation of additional rhodamine family members Rhodamine B and X-Rhodamine.
Endothelial apoptosis is a driving force in atherosclerosis development. Oxidized low‐density lipoprotien (oxLDL) pormotes inflammatory and thrombotic processes. Baicalein, a flavonoid obtained from the root of Chinese medicinal herb Scutellaria baicalensis, possesses a multitude of pharmacological activities including anti‐oxidant, anti‐inflammation and anti‐tumor. In this present study, we tested the hypothesis that baicalein could protects vascular endothelial cells against the proatherosclerotic stressor oxLDL and explored the possible mechanisms. Human umbilical vein endothelial cells (HUVECs) were incubated with baicalein (2.5–20 μM) for 2 hours and then incubated with oxLDL (150 μg/ml) for an additional 24 hours. Our results showed that baicalein ameliorated the oxLDL‐diminished eNOS protein expression and reduced the oxLDL‐induced adhesion molecules and the adherence of monocytic THP‐1 cells to HUVECs. Furthermore, several apoptotic features caused by oxLDL including ROS production, intracellular calcium accumulation, mitochondrial membrane potential collapse, disturbed the balance of bcl‐2 family proteins, and triggered subsequent cytochome c release to cytosol and activation of caspase‐3 were attenauted by pretreatment with baicalein. Findings from this study suggest that baicalein may have clinical implications in the prevention of atherosclerotic vascular disease.
Endothelial dysfunction caused by oxidized low‐density lipoprotein (oxLDL) plays a pivotal role in atherosclerosis. Kaempferol is a flavonoid present in various natural sources including apples, onions, leeks, citrus fruits, grapes, red wines, ginkgo biloba etc. Here we investigated the protective effects of kaempferol against oxLDL‐induced damage in human umbilical vein endothelial cells (HUVECs). The MTT assay showed that 2 hours pre‐incubation with kaempferol markedly restored the oxLDL‐induced viability loss in HUVECs in a concentration‐dependent manner. This effect was accompanied by a significant decrease in lactate dehydrogenase (LDH) release. Moreover, kaempferol imposed preventive effects on suppressing the production of reactive oxygen species (ROS), and restoring the activities of antioxidant enzyme superoxide dismutase (SOD). Pre‐incubation of kaempferol with HUVECs led to the reduction of apoptosis. Finally, kaempferol can efficiently prevent the disturbance of Bcl‐2 family protein, and triggered subsequent cytochrome c release into cytosol and activation of caspase‐3. Taken together, findings from our study suggest that kaempferol can effectively protect HUVECs against oxidative stress induced by oxLDL, which may be important for preventing atherosclerotic vascular disease.
Oxidized low‐density lipoprotein (oxLDL) is a proatherogenic molecule that accumulates in the vascular wall and contributes to the pathogenesis of vascular dysfuntion.LOX‐1, a lectin‐like oxLDL receptor, is responsible for binding and uptake of oxLDL in endothelial cells. It has been well documented that the activation of LOX‐1 can stimulate the formation of ROS and initiate a cascade of redox‐sensitive singnaling events. Ginkgo biloba extract (GbE), extracted from the leaves of the Ginkgo biloba tree, has been well known about its benefits in cardiovascular and neurological system. In this study, incubation of primary human umbilical vein endothelial cell culture (HUVECs) with oxidized low‐density lipoprotein (oxLDL) was to examine whether GbE protects against oxLDL‐induced endothelial dysfuntion and the underlying mechanisms were explore. Our results showed that GbE reduced ROS production and up‐regulation of LOX‐1 caused by oxLDL. In addition, oxLDL enhances cyclooxygenase 2 (COX‐2) expression through p38 MAPK phosphorylation and consequent NF‐κB translocation. These oxLDL‐induced endothelial dysfuntion were ameliorated dose dependently by GbE. Findings from this study suggest that GbE prevent oxidized LDL‐induced endothelial dysfuntion through down‐regulation of LOX‐1‐mediated singaling implying that GbE has a potential ability in the prevention of atherosclerotic vascular disease.
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