A specific, accurate, and sensitive measure of total plasma malondialdehyde by HPLC.

Malondialdehyde (MDA) is one of the most commonly reported biomarkers of lipid peroxidation in clinical studies. The reaction of thiobarbituric acid (TBA) with MDA to yield a pink chromogen attributable to an MDA-TBA2 adduct is a common assay approach with products being quantified by ultraviolet-Vis assay as nonspecific TBA-reactive substances (TBARS) or chromatographically as MDA. The specificity of the TBARS assay was compared with both chromatographic assays for total plasma MDA. The levels of total plasma MDA were significantly lower than the plasma TBARS in each of the samples examined, and interestingly, the interindividual variation apparent in the level of plasma MDA was not evident in the plasma TBARS assay. Each of the four online chromatographic detectors yielded a precise, sensitive, and accurate determination of total plasma MDA, and selected-ion monitoring was the most-accurate assay (101.3%, n = 4). The online diode array detectors provided good assay specificity (peak purity index of 999), sensitivity, precision, and accuracy. This research demonstrates the inaccuracy that is inherent in plasma TBARS assays, which claim to quantify MDA, and it is proposed that the TBARS approach may limit the likelihood of detecting true differences in the level of lipid peroxidation in clinical studies.

Isolation of natural products by low-pressure column chromatography.

This chapter describes the isolation of natural products using low-pressure column chromatography (LPLC) and provides a brief summary of the adsorption and size exclusion processes involved in LPLC. Different types of stationary phases used in both adsorption and size exclusion LPLC are also presented with specific examples. Various operational parameters in relation to column packing (both wet and dry), column equilibration, sample application, and column development, and a summary of generic procedures for adsorption and size exclusion LPLC are also incorporated in this chapter. Throughout the chapter, several specific examples of the application of LPLC for the isolation of various natural products including alkaloids, coumarins, flavones, and saponins from various plants are given. Many of these examples include a combination of adsorption and size exclusion chromatography to obtain specific compounds.

Evaluation of quality control strategies in Scutellaria herbal medicines.

The statutory regulation of herbal medicines is under review within the United Kingdom (UK) and by 2011 all herbal medicines will require either a Product Licence or a Traditional Herbal Registration. The species Scutellaria baicalensis has been shown to possess anti-inflammatory, anti-viral and anti-tumor properties and is one of the most widely used Chinese herbal extracts in Eastern and Western medicines. The bioactivity of this herbal medicine is due to the radical scavenging activities of the flavone components of which there are more than 60. This research has characterised 5 key flavones in 18 extracts of Scutellaria using a combination of HPLC with DAD and MS detection. Employing an internal standard approach, the validated HPLC method afforded good sensitivity and excellent assay precision. Assays for the ferric reducing antioxidant power (FRAP) and total phenol determinations enabled determination of the antioxidant coefficient (PAC) of each Scutellaria extract. The potential usefulness of employing multivariate statistical analysis using a combination of the key parameters collected namely, FRAP activity, total phenol content, levels of 5 flavone biomarkers and the PAC as a means of quality evaluation of the Scutellaria herbal extracts was investigated. The PAC value was predicted by soft independent modelling of class analogy (SIMCA) as being the most discriminatory parameter and applying this ranking the herbal extracts were grouped into 3 clusters. The second most influential parameter in determining the clustering of the samples was the level of baicalin in each extract. It is proposed that the PAC value alone or in combination with a chromatographic fingerprint of key biomarkers [e.g. baicalin or (baicalin+baicalein)] may be useful indicators to adopt for the quality control of S. baicalensis.

Differentiation of opium and poppy straw using capillary electrophoresis and pattern recognition techniques.

Opium samples from four different locations and poppy straw from different plant varieties have been assayed using micellar capillary electrophoresis incorporating a sweeping technique. Individual alkaloids (morphine, codeine, papaverine, noscapine, thebaine, oripavine, reticuline and narceine) were quantitatively determined in the different samples by a validated capillary electrophoresis method. Unsupervised pattern recognition of the opium samples and the poppy straw samples using hierarchical cluster analysis (HCA) and principal component analysis (PCA), showed distinct clusters. Supervised pattern recognition using soft independent modelling of class analogy (SIMCA) was performed to show individual groupings and allow unknown samples to be classified according to the models built using the CZE assay results.

Eremostachiin: a new furanolabdane diterpene glycoside from Eremostachys glabra.

The reversed-phase preparative HPLC analysis of the methanol extract of the rhizomes of Eremostachys glabra (Lamiaceae) led to the isolation of two furanolabdane diterpene glycosides, phlomisoside II, and beta-D-glucopyranosyl-(1-->2)-beta-D-glucopyranosyl ester of phlomisoic acid (named eremostachiin), the latter being a novel natural product. The structure of the new compound has been elucidated unambiguously by HRMS and a series of 1D- and 2D-NMR spectroscopic techniques. The free radical scavenging activity of these compounds was assessed using the DPPH assay.