Simultaneous determination of lysophospholipids by high-performance liquid chromatography with fluorescence detection

Chiral and Achiral Enantiomeric Separation of (±)-Alprenolol

The chiral separation of enantiomers is crucial for pharmacovigilance within drug discovery. Although a large number of prescribed medications are marketed as pure enantiomers, this is not always the case and many are in fact racemic mixtures. Drug scandals, such as that of Thalidomide in 1961, provide a clear example of the social and economic repercussions that can be caused by negligence of these chiral compounds. Two high performance liquid chromatography (HPLC) methods are presented to determine, separate and quantitate a commonly prescribed chiral beta blocker, (-)-Alprenolol. The first method utilises a chiral column to physically separate the two enantiomers of Alprenolol in 25 minutes, before quantitating with two detectors. Fluorimetry gave the better limit of detection of 0.16-0.41ng and a correlation coefficient of 0.999. The second method used an achiral column coupled with polarimetry to quantitate (-)-Alprenolol without the need for physical separation in 10 minutes. The limit of detection achieved was 27-37μg and demonstrated a correlation coefficient of -0.999.

Enzymatic methods for choline-containing water soluble phospholipids based on fluorescence of choline oxidase: Application to lyso-PAF

In this paper we present methods to determine water soluble phospholipids containing choline (wCh-PL). The analytes were hydrolyzed by the enzyme phospholipase D and the choline formed was oxidized by the enzyme Choline Oxidase (ChOx); the fluorescence changes of the ChOx are followed during the enzymatic reaction, avoiding the necessity of an indicating step. Both reactions (hydrolysis and oxidation) can be combined in two different ways: 1) a two-step process (TSP) in which the hydrolysis reaction takes place during an incubation time and then the oxidation reaction is carried out, the analytical signal being provided by the intrinsic fluorescence of ChOx due to tryptophan; 2) a one-step process (OSP) in which both enzymatic reactions are carried out simultaneously in the same test; in this case the analytical signal is provided by the ChOx extrinsic fluorescence due to a fluorescent probe (Ru (II) chelate) linked to the enzyme (ChOx-RuC). The analytical capabilities of these methods were studied using 1,2-dioctanoyl-sn-glycero-3-phosphocholine (C₈PC), a water soluble short alkyl chain Ch-PL as a substrate, and 1-O-hexadecyl-sn-glyceryl-3-phosphorylcholine (lyso-PAF). The analytical features of merit for both analytes using both methods were obtained. The TSP gave a 10-fold sensitivity and lower quantification limit (1.0*10^-5 M for lyso-PAF), but OSP reduced the determination time and permitted to use the same enzyme aliquot for several measurements. Both methods gave similar precision (RSD 7%, n = 5). The TSP was applied to the determination of C₈PC and lyso-PAF in spiked synthetic serum matrix using the standard addition method. The application of this methodology to PLD activity determination is also discussed.

A versatile, quantitative analytical method for pharmaceutical relevant lipids in drug delivery systems

Over the past few years, liposomal formulations as drug carrier systems have markedly advanced in pharmaceutical research and development. Therefore, analytical methods to characterize liposome-based formulations are required. One particular issue in liposome analysis is the imbalance of lipid ratios within the vesicle formulations and the detectability of degradation products such as lysophospholipids and fatty acids caused by hydrolysis, especially in low molar ranges. Here, a highly sensitive and selective reversed-phase high-performance liquid chromatography (rp-HPLC) method is described by the combination of an organic solvent/trifluoroacetic acid (TFA) triggered gradient and the application of an evaporative light scattering detector (ELSD). Gain setting adjustments of the ELSD were applied to obtain an optimal detection profile of the analyzed substances. This optimization provides simultaneous separation and quantification of 16 components, including different phosphatidylcholines, phosphatidylglycerols and their degradation products, as well as cholesterol. Parameters such as limit of detection (LOD) and limit of quantification (LOQ) were determined for each of the components and had ranges from 0.25-1.00mg/mL (LOD) and 0.50-2.50μg/mL (LOQ), respectively. The intra-day precision for all analytes is less than 3% (RSD) and inter-day precision is about 8%. The applicability of the method was verified by analyzing two different liposome formulations consisting of DSPC:DPPC:DSPG:Chol (35:35:20:10) and DSPC:DPPC:DSPG (38:38:24). For degradation studies, both formulations were stored at 4°C and at ambient temperature. Additionally, forced degradation experiments were performed to determine hydrolysis mass balances. A total recovery of 96-102% for phospholipid compounds was found. Analytical data revealed that the sensitivity, selectivity, accuracy, and resolution are appropriate for the detection and quantification of phospholipids and their hydrolysis products. These results as well as additional preliminary analyses of other relevant components used in liposomal formulations indicate that the developed method is suitable for the development, characterization, and stability testing of liposomal based biopharmaceuticals.

Down-regulation of LPCAT expression increases platelet-activating factor level in cirrhotic rat liver: potential antiinflammatory effect of silybin

Cholestasis is one of the major causes of liver diseases. A chronic accumulation of toxic bile acids in the liver, which occurs in this condition, can induce fibrosis and cirrhosis. Inflammation is a fundamental component of acute and chronic cholestatic liver injury. Platelet-activating factor (PAF) is a proinflammatory lipid which may be generated by two independent pathways called the de novo and remodeling pathway being the last responsible for the synthesis of PAF during inflammation. In recent years a key role in PAF remodeling has been attributed to lysophosphatidylcholine acyltransferase (LPCAT) enzymes. Although the knowledge on their characteristic is growing, the exact mechanism of LPCAT in pathological conditions remains still unknown. Here, we reported that the level of lyso-PAF and PAF significantly increased in the liver of cirrhotic vs. control rats together with a significant decrease in both mRNA abundance and protein level of both LPCAT1 and LPCAT2. Acyltransferase activities of both LPCAT1 and LPCAT2 were parallel decreased in the liver of cirrhotic animals. Interestingly, treatment with silybin strongly decreased the level of both pro-inflammatory lipids and restored the activity and expression of both LPCAT1 and LPCAT2 of cirrhotic liver. Silybin effect was specific for LPCAT1 and LPCAT2 since it did not affect LPCAT3 mRNA abundance of cirrhotic liver.

Levels of gingival tissue platelet activating factor after conventional and regenerative periodontal surgery

The hypothesis, a relationship between gingival tissue platelet activating factor (PAF) levels and healing after periodontal surgery, was tested by measuring PAF levels in gingival tissues collected from sites that had undergone flap surgery and guided tissue regeneration (GTR) or flap surgery alone. Using a split-mouth design, 20 intrabony defects were randomly assigned to treatment with flap surgery and GTR (group 1) or with flap surgery alone (group 2). Gingival tissue samples were obtained at surgery (baseline) and at 6-month follow-up evaluation visit. One half of each sample was used for analysis of PAF levels by high-performance liquid chromatography, and the other half of the sample was used for histomorphometric analysis that included measurements of number and diameter of blood vessels. PAF levels and diameter of blood vessels were significantly decreased (p < 0.01), and the number of blood vessels was significantly increased (p < 0.05) in both groups after 6 months compared to the baseline values. Postoperative number of blood vessels were significantly higher in group 1 (p < 0.05), whereas there was no significant difference in postoperative PAF levels between the two groups (p > 0.05). Based on the reported results, it is suggested that a decrease in gingival PAF levels might be found after conventional and regenerative periodontal surgery.

Levels of platelet activating factor in gingival crevice fluid following periodontal surgical therapy

BACKGROUND AND OBJECTIVE

Elevated levels of platelet activating factor (PAF), a potent inflammatory phospholipid mediator, have been previously detected in gingival tissues and gingival crevice fluid (GCF) in periodontal disease. However, the role of this mediator during wound healing after periodontal surgery remains unclear. The hypothesis, a relationship between PAF levels and periodontal healing, was tested by measuring PAF levels in GCF samples collected from sites that had undergone guided tissue regeneration (GTR) or flap surgery.

MATERIAL AND METHODS

Using a split-mouth design, 30 intrabony defects were randomly assigned to treatment with GTR (group 1) or to flap surgery (group 2). GCF was sampled pre-operatively and at 6-, 12- and 24-wk follow-up evaluation visits. PAF levels in GCF were analyzed by high-performance liquid chromatography (HPLC).

RESULTS

Both treatment modalities significantly reduced the probing pocket depth and improved the clinical attachment level (p < 0.01). Compared with pre-operative values, the GCF volume and PAF levels were significantly decreased at postoperative weeks 6, 12 and 24 in both groups (p < 0.01). There were also significant differences in GCF volume and PAF levels at all time points up to 24 wks in both groups (p < 0.01). No statistically significant differences were observed in any of the parameters investigated between the two groups (p > 0.05).

CONCLUSION

PAF is detectable in GCF by HPLC and showed a continuous decrease at all the time points monitored following periodontal surgical therapy. This suggests that changes in the levels of this mediator in GCF might be useful for monitoring the progress of periodontal repair and regeneration.

Analysis of free and esterified ergosterol in tomato products

A new extraction and chromatographic procedure to quantify free and esterified ergosterol in tomato products was devised. The extraction solution was composed of a dichloromethane/methanol mixture in a 2:1 (v/v) ratio. This extraction solvent allowed for higher ergosterol recovery from tomato products (an average of 25% more) compared to hexane, which is frequently employed for ergosterol extraction. Both free and esterified ergosterol were determined by HPLC reverse-phase chromatography employing a Nova-Pak C-18 column (300 x 3.9 mm), filled with 4 mm average particle size and a guard column of the same material. The elution was performed at a flow rate of 1 mL. min(-1) with a linear gradient of solvent A (methanol/water, 80:20, v/v) and solvent B (dichloromethane). The gradient, starting at sample injection, was from 0 to 50% B for 20 min for the free ergosterol analysis and additional 15 min at 50% B to analyze the ergosterol esters. This technique has proven to be more sensitive for ergosterol determination than other reported chromatographic procedures. Moreover, ergosterol esters, extracted from various fungal sources, separated well and were easily quantified.