The evaluation of the oxidative state of native-LDL: three methods compared

Lemon grass (Cymbopogon citratus (D.C) Stapf) polyphenols protect human umbilical vein endothelial cell (HUVECs) from oxidative damage induced by high glucose, hydrogen peroxide and oxidised low-density lipoprotein

The aromatic herb Cymbopogon citratus Stapf is widely used in tropical and subtropical countries in cooking, as a herbal tea, and in traditional medicine for hypertension and diabetes. Some of its properties have been associated with the in vitro antioxidant effect of polyphenols isolated from their aerial parts. However, little is known about C. citratus effects on endothelial cells oxidative injury. Using chromatographic procedures, a polyphenol-rich fraction was obtained from C. citratus (CCF) and their antioxidant properties were assessed by cooper-induced LDL oxidation assay. The main constituents of the active CCF, identified by high-performance liquid chromatography with diode-array detection and mass spectrometry (HPLC-DAD-MS), were chlorogenic acid, isoorientin and swertiajaponin. CCF 10 and 100 μg/ml diminishes reactive oxidative species (ROS) production in human umbilical vein endothelial cell (HUVECs), challenged with high D-glucose (60% inhibition), hydrogen peroxide (80% inhibition) or oxidised low-density lipoprotein (55% inhibition). CCF 10 or 100 μg/ml did not change nitric oxide (NO) production. However, CCF was able to inhibit vasoconstriction induced by the thromboxane A2 receptor agonist U46619, which suggest a NO-independent vasodilatador effect on blood vessels. Our results suggest that lemon grass antioxidant properties might prevent endothelial dysfunction associated to an oxidative imbalance promoted by different oxidative stimuli.

Open tubular capillary electrochromatography: a new technique for in situ enzymatic modification of low density lipoprotein particles and their protein-free derivatives

Electrochromatography with open tubular capillaries coated with human low density lipoprotein (LDL) particles and their protein-free derivatives was studied as a method for their in situ enzymatic modification. LDL particles as monolayers or their protein-free derivatives (lipid microemulsions) were coated on 50 microm i.d. capillaries, which resemble tiny human blood vessels in size, the arterioles. The immobilized LDL particles were exposed to sphingomyelinase, phospholipase A2 or alpha-chymotrypsin at 25 and 37 degrees C. The mobility of the electro-osmotic flow was employed as a surface charge indicator, and the retention factors of steroids were used as hydrophobicity indicators. Moreover, the capillaries were, for the first time, coated with lipid microemulsions containing either LDL-derived or commercial lipids, and the immobilized microemulsions were treated with sphingomyelinase in capillary. The results demonstrate that open tubular capillaries provide a good microreactor for the in situ modification of LDL particles and lipid microemulsions. The technique only requires extremely low quantities of LDL particles, lipid microemulsions, and enzymes. It allows quick and easy alteration of the reaction conditions, and the enzymes can be collected and reused. Asymmetrical flow field flow fractionation provides useful information on the size of the enzymatically modified LDL particles.