Search

Robinia pseudoacacia flower is a natural product with many biological activities, including antioxidation. To further develop its antioxidation, the extract was fermented by Aspergillus niger FFCC 3112 in the medium with carbon to nitrogen ratio of 1.4:1 and initial pH of 4.2 for 3.5 days to form the best antioxidant activity of the fermentation product by strain screening, single factor optimization, and response surface methodology. Further analysis, isolation and activity determination showed that a main chemical component, kaempferol-3-O-α-L-rhamnopyranosyl-(1→6)-β-D-galactopyranosyl-7-O-α-L-rhamnopyranoside, in the extract was completely hydrolyzed to kaempferol-7-O-α-L-rhamnopyranoside and kaempferol with better antioxidant activity through biotransformation, which was the basis for improving the antioxidant activity of fermentation products. Moreover, the mechanism of antioxidant and the contribution of phenolic hydroxyl groups were investigated by density functional theory. The result indicated that the antioxidant capacity of kaempferol-7-O-α-L-rhamnopyranoside and kaempferol increased with the increase of solvent polarity. In high-polarity solvents, they mainly scavenge free radicals through single electron transfer followed by proton transfer.

An effective high-speed countercurrent chromatography (HSCCC) method was established for separation and purification of (S)-dehydrovomifoliol from the leaves of Nitraria sibirica Pall. (NS). HSCCC was performed with a two-phase solvent systems composed of n-hexane-ethyl acetate-methanol-water (1:5:1:5, v/v) at a flow rate of 2mL/min. From 1g crude sample of NS, 23mg (S)-dehydrovomifoliol was obtained at purity of 95%. The chemical structure was confirmed by MS, 1H NMR, and 13C NMR. (S)-dehydrovomifoliol was isolated from Nitraria genus for the first time.

A combined chromatographic method using high-speed counter-current chromatography (HSCCC) and Sephadex LH-20 chromatography was established for bioassay-guided separation and purification of water-soluble antioxidants from Carthamus tinctorius L florets. The crude sample II obtained by an initial cleanup step on the AB-8 macroporous resin exhibited a potential ABTS radical cation scavenging activity with the SC50 value of 49.28 mu g/mL. The HSCCC separation was performed with a two-phase solvent system composed of n-butanol-0.1 mol/L HCl (1:1, v/v) at a flow rate of 1.2 mL/min. After a single run, 3 mg hydroxysafflor yellow A (HSYA) with 98% purity was separated as a major component from 20 mg of crude sample II. In order to increase the yield and investigate the minor components, the sample size of HSCCC separation was enlarged to 1 g. Then, HSCCC fractions were subjected to Sephadex LH-20 chromatography and eluted with distilled water at a flow rate of 1.5 mL/min to remove the acid and further separate the components. This separation yielded 184.0 mg of HSYA (1), 10.0 mg of 5,4'-dihydroxyflavone-3,6-di-O-beta-D-glucoside-7-O-beta-D-glucuronide (2), 3.0 mg of 3-O-caffeoylquinic acid (3), and 3.2 mg of 4-O-beta-D-glucosyl-trans-p-coumaric acid (4) from 1 g crude sample II of C tinctorius L. florets. The purity of the separated compounds were over 95% by HPLC analysis, and their chemical structures were confirmed by MS, H-1 NMR and C-13 NMR. Compounds 3 and 4 were found from this plant for the first time. Antioxidant activities assayed in vitro by ABTS radical cation scavenging showed that the SC50 values of the above four compounds were 44.39 +/- 1.62 mu g/mL, 78.13 +/- 1.00 mu g/mL, 21.85 +/- 1.96 mu g/mL, and 31.44 +/- 2.06 mu g/mL, respectively.

Chickpea is known as a plant that is rich in protein, carbohydrates, and nutrition, and its seeds and sprouts have been processed into various health foods. In the present study, four isoflavones were purified from the seeds and sprouts of chickpea by high speed countercurrent chromatography (HSCCC) using two biphasic solvent systems composed of n-hexane-ethyl acetate-methanol-water (5:5:5:5, v/v) and ethyl acetate-water (1:1 v/v). The results indicated that 14.2 mg of formononetin, 15.7 mg of biochanin A, 9.1 mg of ononin, 11.3 mg of biochanin A-7-O-β-D-glucoside were obtained from 150 mg of sprout extracts with the purity of 92.26%, 95.86%, 95.32%, and 96.56%, respectively. Compared with the sprouts, separation of seed extracts yielded less amounts of biochanin A-7-O-β-D-glucoside and biochanin A with lower purity. The results indicate that four main isoflavones in chickpea, i.e., isoflavones, formononetin, biochanin A, ononin, and biochanin A-7-O-β-D-glucoside, are substantially increased by biosynthesis during the seed germination.