Isolation of high-purity peptide Val-Val-Tyr-Pro from Globin Peptide using MCI gel column combined with high-speed counter-current chromatography

Preparative separation of 1,1-diphenyl-2-picrylhydrazyl inhibitors originating from Saxifraga sinomontana employing medium-pressure liquid chromatography in combination with reversed-phase liquid chromatography

Traditional Tibetan medicines elaborately document the health benefits of Saxifraga sinomontana. However, there have been limited reports on its chemical make-up, presumably because of the complicated separation and purification process. In this work, a methanolic extract of Saxifraga sinomontana was utilized for targeted separation of 4 key 1,1-diphenyl-2-picrylhydrazyl inhibitors employing the medium-pressure liquid chromatography, reversed-phase liquid chromatography in combination with on-line reversed-phase liquid chromatography-1,1-diphenyl-2-picrylhydrazyl detection. Pre-treatment of the sample was carried out by employing medium-pressure liquid chromatography using MCI GEL® CHP20P as the stationary phase, furnishing 2.4 g of fraction Fr3 and 3.4 g of fraction Fr4 (the percentage retrieval was 32.7%). The 1,1-diphenyl-2-picrylhydrazyl inhibitors contained in fractions Fr3 and Fr4 were subjected to additional separation using a C18 (ReproSil-Pur C18 AQ) column and yielded 106.2 mg of Fr3-1, 246.9 mg of Fr3-2, 248.5 mg of Fr4-1 and 41.8 mg of Fr4-2. The degree of purity, structures and 1,1-diphenyl-2-picrylhydrazyl inhibition activity of the isolated DPPH inhibitors were determined, and four 1,1-diphenyl-2-picrylhydrazyl inhibitors including two new diarylnonanoids (3-methoxy-4-hydroxyphenol-(6'-O-galloyl)-1-O-β-d-glucopyrano side with IC₅₀ of 39.6 μM, 3,4,5-trimethoxyphenyl-(6'-O-galloyl)-1-O-β-d-glucopyranoside with IC₅₀ of 46.9 μM, saximonsin A with IC₅₀ of 11.4 μM, and saximonsin B with IC₅₀ of 20.6 μM) were isolated with a percentage purity above 95%. The methodology thus evolved has good efficacy for preparatively isolating high-purity 1,1-diphenyl-2-picrylhydrazyl inhibitors from extracts of Saxifraga sinomontana and could be efficiently utilized for rapidly isolating 1,1-diphenyl-2-picrylhydrazyl inhibitors from other natural products.

Large-scale preparative isolation of bergenin standard substance from Saxifraga atrata using polyamide coupled with MCI GEL® CHP20P as stationary phases in medium pressure chromatography

In this study, polyamide and MCI GEL® CHP20P were employed as stationary phases in medium pressure chromatography (MPC) for the efficient preparative separation of bergenin from Saxifraga atrata. Ethanol-water, methanol-water, and acetonitrile-water mobile phases all showed good enrichment capacity for bergenin fraction when polyamide was used as a stationary phase. After 5 cycles of polyamide MPC using acetonitrile/water, 1.2 g of bergenin fraction was isolated from 180 g Saxifraga atrata herb. Further purification of this fraction was conducted using MCI GEL® CHP20P styrene-divinylbenzene beads. The bergenin fraction was separated into two fractions, and after three runs of MPC, 714.2 mg of bergenin with purity above 99% was obtained. The results demonstrate that the combination of polyamide and styrene-divinylbenzene MPC can be utilized for preparative isolation of compounds from natural products with high yield and purity.

Hydroxypropyl-β-cyclodextrin encapsulated stationary phase based on silica monolith particles for enantioseparation in liquid chromatography

Hydroxypropyl-β-cyclodextrin-encapsulated stationary phase incorporated on silica monolith particles was prepared by physical embedding, providing a new method for the development of chiral stationary phase for enantioseparation in liquid chromatography. Ground silica monolith particles of about 2.0 μm were prepared via sol-gel reaction followed by differential sedimentation. Initially, the silica monolith particles were pretreated with 3-trimethoxysilyl propyl methacrylate to attach double-bonded ligands onto the surface, then a network structure was formed onto the surface of the particle using N-isopropyl acrylamide as functional monomer. Hydroxypropyl-β-cyclodextrin was encapsulated inside N-isopropyl acrylamide copolymerized layer on the surface of silica monolith particles. The effect of the amount of chiral selector on the chromatographic efficiency of the chiral stationary phase was examined. The glass lined stainless steel columns (1 mm internal diameter, 300 mm length) were packed with the stationary phase for estimation of the efficiency by separation of phenylsuccinic acid, oxybutynin, equol, and naproxen enantiomers in high-performance liquid chromatography, with the resolutions of 1.54, 1.72, 2.54, and 2.31, respectively. The column to column repeatabilities through relative standard deviation were found better than 3%. The experimental results indicate that the sol-gel ground silica particles modified with β-cyclodextrin provide a promising way for the separation of chiral enantiomers.

Targeted isolation of 1,1-diphenyl-2-picrylhydrazyl inhibitors from Saxifraga atrata using medium- and high- pressure liquid chromatography combined with online high performance liquid chromatography-1,1-diphenyl-2- picrylhydrazyl detection

Traditional Tibetan medicine (TTM) is a valuable source of novel therapeutic lead molecules inspired by natural products (NPs). The health benefits of Saxifraga atrata are well documented in TTM, but reports on its chemical composition are limited, most likely due to the complicated purification process. Herein, target separation and identification of 4 main radical scavenging compounds from the methanolic extract of S. atrata was were performed using medium- and high-pressure liquid chromatography coupled with online HPLC-DPPH detection. The sample was pretreated using medium pressure liquid chromatography with MCI GELⓇ CHP20P styrene-divinylbenzene beads as a stationary phase, yielding 1.4 g of the target DPPH inhibitors (Fr4, 11.9% recovery). The compounds were further purified and isolated using HPLC on RP-C18 (ReproSil-Pur C18 AQ) followed by HILIC (Click XIon) column separation, resulting in 2.8 mg of fraction Fr4-1-1, 6.8 mg of fraction Fr4-2, 244.9 mg of the Fr4-3-1 sample, and 38.3 mg of Fr4-4-1. The structure and purity of the target compounds were determined, and four compounds (ethyl gallate, 11-O-galloylbergenin, rutin and isoquercitrin) were isolated with >95% purity. The developed methodology is efficient for targeted isolation of high-purity radical scavengers from NP extracts and could be used for rapid identification and isolation of DPPH inhibitors from various NPs.

Recent progress in separation prediction of counter-current chromatography

As a liquid-liquid partition chromatography, counter-current chromatography has advantages in large sample loading capacity without irreversible adsorption, which has been widely applied in separation and purification fields. The main factors, including partition coefficient, two-phase solvent systems, apparatus, and operating parameters greatly affect the separation process of counter-current chromatography. To promote the applications of counter-current chromatography, it is essential to develop theoretical research to master the principles of counter-current chromatographic separations so as to achieve predictions before laborious trials. In this article, recent progress about separation prediction methods are reviewed from a point of the steady and unsteady state of the mass transfer process of counter-current chromatography and its mass transfer characteristics, and then it is divided into three aspects: prediction of partition coefficient, modeling the thermodynamic process of counter-current chromatography, and modeling the dynamic process of counter-current chromatography.

Strategy for the separation of strongly polar antioxidant compounds from Lycium barbarum L. via high-speed counter-current chromatography

In the separation of strongly polar antioxidant compounds from natural products using high-speed counter-current chromatography that is target-guided by 2,2-diphenyl-1-picrylhydrazyl high-performance liquid chromatography experimentation, low adsorption ability is encountered due to the strong polarity of the target compounds. In this study, a strategy of novel partition coefficient value calculation was proposed for overcoming this problem. The partition coefficient value was expressed as the ratio of the antioxidant activities of the upper phase and the lower phase. This strategy was used in high-speed counter-current chromatography with a hydrophilic organic/salt-containing aqueous two-phase system for bioassay-guided separation of strongly polar antioxidant compounds from Lycium barbarum L. The antioxidant activity was determined via the radical scavenging activity method using 2,2-diphenyl-1-picrylhydrazyl radicals. A hydrophilic organic/salt-containing aqueous two-phase system of 95% EtOH - sat. (NH₄)₂SO₄ (1:1.8, v/v) was successfully used to separate Lycium barbarum L. extract. Five fractions were collected via high-speed counter-current chromatography separation. The antioxidant activity of the third fraction was the highest. Three compounds were separated via MCI gel column chromatography and Sephadex LH-20 column chromatography from the third fraction, and their antioxidant activities were determined. The antioxidant activities of the three compounds were higher than that of the third fraction. These results demonstrate that this strategy can be used to separate strongly polar antioxidant compounds from natural products.