A Novel Medium Poly(vinyl acetate-triallyl isocyanurate-divinylbenzene) Coupled with Oligo-β-Cyclodextrin for the Isolation of Puerarin from Pueraria Flavones

Preparation of Poly(glycidyl methacrylate) (PGMA) and Amine Modified PGMA Adsorbents for Purification of Glucosinolates from Cruciferous Plants

Glucosinolates (GLs) are of great interest for their potential as antioxidant and anticancer compounds. In this study, macroporous crosslinked copolymer adsorbents of poly (glycidyl methacrylate) (PGMA) and its amine (ethylenediamine, diethylamine, triethylamine)-modified derivatives were prepared and used to purify the GLS glucoerucin in a crude extract obtained from a cruciferous plant. These four adsorbents were evaluated by comparing their adsorption/desorption and decolorization performance for the purification of glucoerucin from crude plant extracts. According to the results, the strongly basic triethylamine modified PGMA (PGMA-III) adsorbent showed the best adsorption and desorption capacity of glucoerucin, and its adsorption data was a good fit to the Freundlich isotherm model and pseudo-second-order kinetics; the PGMA adsorbent gave the optimum decolorization performance. Furthermore, dynamic adsorption/desorption experiments were carried out to optimize the purification process. Two glass columns were serially connected and respectively wet-packed with PGMA and PGMA-III adsorbents so that glucoerucin could be decolorized and isolated from crude extracts in one process. Compared with KCl solution, aqueous ammonia was a preferable desorption solvent for the purification of glucoerucin and overcame the challenges of desalination efficiency, residual methanol and high operation costs. The results showed that after desorption with 10% aqueous ammonia, the purity of isolated glucoerucin was 74.39% with a recovery of 80.63%; after decolorization with PGMA adsorbent, the appearance of glucoerucin was improved and the purity increased by 11.30%. The process of using serially connected glass columns, wet-packed with PGMA and PGMA-III, may provide a simple, low-cost, and efficient method for the purification of GLs from cruciferous plants.

NMR Study on the Inclusion Complexes of β-Cyclodextrin with Isoflavones

The structure of the inclusion complexes of β-cyclodextrin (β-CD) with daidzein and daidzin in D2O were investigated using NMR spectroscopy. For the β-CD and daidzein system, two types of 1:1 complexes were formed with the daidzein deeply inserted into the CD cavity with different orientations. For the β-CD/daidzin system, a 1:1 complex was formed with the flavonoid part of daidzin entering the CD cavity from the wide rim. The inclusion complexes determined by NMR were constructed using molecular docking. Furthermore, the mixture of puerarin, daidzein and daidzin, which are the major isoflavonoid components present in Radix puerariae, was analyzed by diffusion-ordered spectroscopy (DOSY) alone and upon addition of β-CD in order to mimic chromatographic conditions and compare their binding affinities.

Extraction and isolation of phenolic compounds

Phenolic compounds constitute a major class of plant secondary metabolites that are widely distributed in the plant kingdom and show a large structural diversity. These compounds occur as aglycones or glycosides, as monomers or constituting highly polymerized structures, or as free or matrix-bound compounds. Furthermore, they are not uniformly distributed in the plant and their stability varies significantly. This greatly complicates their extraction and isolation processes, which means that a single standardized procedure cannot be recommended for all phenolics and/or plant materials; procedures have to be optimized depending on the nature of the sample and the target analytes, and also on the object of the study. In this chapter, the main techniques for sample preparation, and extraction and isolation of phenolic compounds have been reviewed-from classical solvent extraction procedures to more modern approaches, such as the use of molecularly imprinted polymers or counter-current chromatography.

NMR studies on puerarin and its interaction with beta-cyclodextrin

The interaction between puerarin and β-cyclodextrin (CD) has been studied in D(2)O, H(2)O/acetone-d(6), acetone-d(6) and DMSO-d(6) solutions by (1)H NMR spectroscopy. The NMR data obtained from hydroxy protons indicate that the formation of the inclusion complex between the two molecules is not stabilized by strong hydrogen bond interactions. The sugar part of puerarin as well as the A ring are outside the β-CD cavity while the B and C rings are located inside the cavity and the interaction is mainly stabilized by hydrophobic interactions. In DMSO at 30°C and in acetone-d(6)/H(2)O at temperature below -5°C, doubling of some signals indicated that, in these solvent systems, free rotation of the C-glycosyl bond was restricted due to the steric hindrance between the phenolic hydroxy group at C-7 and the bulky sugar moiety at C-8. In acetone, fast exchange of phenolic protons on the NMR timescale was observed, showing the effect of the solvent on the hindered rotation.