Fast Isolation of Flavonoids from the Endemic Species Nolana ramosissima I.M. Johnst and Its Endothelium-Independent Relaxation Effect in Rat Aorta

The infusion of the desertic plant Nolana ramosissima I.M. Johnst showed vascular smooth muscle relaxation in rat aorta and the presence of several phenolic compounds, which were detected by high resolution UHPLC-Orbitrap-HESI-MS. In addition, five flavonoids were rapidly isolated from a methanolic extract using high-performance counter-current chromatography (HPCCC). The N. ramosissima extract showed endothelium-independent relaxation effect in rat aorta. Sixty-one compounds were detected in the infusion, mainly glycosylated flavonoids, flavanones and several oxylipins, suggesting that a synergistic effect between the compounds in the extracts could be responsible for the relaxation activity. Vascular activity experiments were done in isolated organ bath. In rat aorta, a nitric oxide inhibitor did not prevent the relaxation effects of the extract; however, a selective guanylyl cyclase inhibitor partially blunted this effect. The compound 5,3′-dihydroxy-4′7-dimethoxyflavone presented higher relaxation effect than 100 μg/mL of N. ramosissima extract. The extract and the isolated metabolites from N. ramosissima can show relaxation effects on rat aorta by a mechanism that is independent of the endothelium.

Detection of flavokavins (A, B, C) in cultivars of kava (Piper methysticum) using high performance thin layer chromatography (HPTLC)

Kava (Piper methysticum) is used to prepare the traditional beverage of the Pacific islands. In Europe, kava has been suspected to cause hepatoxicity with flavokavin B (FKB) considered as a possible factor. The present study describes an HPTLC protocol for rapid screening of samples. The objectives are: to detect the presence of flavokavins in extracts and to compare the FKB levels in different cultivars. Overall, 172 samples originating from four cultivars groups (noble, medicinal, two-days and wichmannii), were analysed. Results indicate that the ratio FKB/kavalactones is much higher in two-days (0.39) and wichmannii (0.32) compared to nobles (0.09) and medicinal cultivars (0.10). For each group, the ratios flavokavins/kavalactones do not change significantly between roots, stumps or basal stems and among clones, indicating that they are genetically controlled. This protocol has good accuracy and is cost efficient for routine analysis. We discuss how it could be used for quality control.

Countercurrent separation of natural products

An assessment of the technology and method development in countercurrent chromatography (CCC) and centrifugal partition chromatography (CPC), collectively referred to as countercurrent separation (CS), is provided. More than six decades of CS theory and applications are critically reviewed and developed into a practical guide to CS for natural products research. The necessary theoretical foundation is given for better use of CS in the separation of biological molecules of any size, small to large, and from any matrix, simple to complex. The three operational fundamentals of CS--instrumentation, biphasic solvent systems, and theory--are covered in a prismatic fashion. The goal of this review is to provide the necessary background and references for an up-to-date perspective of CS and to point out its potential for the natural products scientist for applications in natural products chemistry, metabolome, and proteome research involving organisms from terrestrial and marine sources.

Natural product isolation

Since the 1990s, interest in natural product research has increased considerably. Following several outstanding developments in the areas of separation methods, spectroscopic techniques, and sensitive bioassays, natural product research has gained new attention for providing novel chemical entities. This updated review deals with sample preparation and purification, recent extraction techniques used for natural product separation, liquid-solid and liquid-liquid isolation techniques, as well as multi-step chromatographic operations. It covers examples of papers published since the NPR review 'Modern separation methods' by Marston and Hostettmann,1 with major emphasis on methods developed and the research undertaken since 2000.

Performance characteristics of countercurrent separation in analysis of natural products of agricultural significance

A standard test mix consisting of 21 commercially available natural products of agricultural significance, termed the GUESSmix, was employed to measure the countercurrent chromatography performance characteristics of a very popular quaternary solvent system family made up of hexane-ethyl acetate-methanol-water (HEMWat). The polarity range of the GUESSmix combined with the elution-extrusion countercurrent chromatography (EECCC) technique and the newly developed reciprocal symmetry (ReS) and reciprocal shifted symmetry (ReSS) plots allow liquid-liquid distribution ratios ( K D) to be plotted for every compound eluted on a scale of zero to infinity. It was demonstrated that 16 of the 21 GUESSmix compounds are found in the optimal range of resolution (0.25 < K(D) < 16) of at least one HEMWat solvent system. The HEMWat solvent systems represented by the ratios 4:6:5:5, 4:6:4:6, and 3:7:4:6 possess the most densely populated optimal ranges of resolution for this standard mix. ReS plots have been shown to reveal the symmetrical reversibility of the EECCC method in reference to K(D) = 1. This study lays the groundwork for evaluation and comparison of solvent system families proposed in the literature, as well as the creation of new solvent system families with desired performance characteristics.

Apolar chromatography on Sephadex LH-20 combined with high-speed counter-current chromatography

A novel high yield isolation procedure for lipophilic cyclic peptide derivatives is presented. Destruxin (dtx) A, B, D, E, and E-diol retrieval from Metarhizium anisopliae culture broth was achieved with a three-step purification protocol. After liquid-liquid extraction column chromatography over Sephadex LH-20 served as enrichment step. High-speed counter-current chromatography (HSCCC) was used for the final purification. Within the first chromatographic step dtx D and dtx E-diol were separated in purities exceeding 90%. The separation of dtx A, B, and E was achieved from an enriched Sephadex LH-20 fraction by a HSCCC protocol using light petroleum-ethyl acetate-methanol-water = 2:5:2:5 (v/v) as eluent system. These derivatives were obtained in purities above 98% and total yields exceeding 40%.