Phenolic content and DPPH radical scavenging activity of the flowers and leaves of Trifolium repens.

In order to facilitate the quality control of Trifolium repens flowers and leaves, a RP-HPLC method with UV detection was developed for the simultaneous quantitative determination of flavonols and isoflavones. The total flavonoid and phenolic (TPC) contents were determined spectrophotometrically in a visible part of the light spectrum at 425 and 760 nm, respectively. Additionally, evaluation of the antioxidant properties of the plant materials was performed using the DPPH in vitro test. The results showed that the flowers are the richest source of phenolics ranging from 28.7 to 38.8 mg GAE/g, and flavonoids, calculated for hyperoside, up to 20 mg HP/g, which hydrolyzed mainly to flavonols (the quercetin level greater than 6 mg/g). T. repens is poor in isoflavones; similar quantities ofca. 0.2 mg/g were detected in the flowers and leaves. The flower and leaf extracts showed antioxidant activity towards DPPH with EC50 values ranging from 72.3 to 179.3 microg/mL. Significant linear correlations were found between antioxidant potentials of the studied plant materials and total phenolic and flavonoid contents determined by HPLC and spectrophotometric methods (R2 in the range of 0.97 - 0.99).

Study on the phenolic constituents of the flowers and leaves of Trifolium repens L.

The flowers and leaves of Trifolium repens L. (Fabaceae) were subjected to phytochemical investigation in order to identify their major chemical constituents and to evaluate in vitro antioxidant activity of the isolated compounds against DPPH˙. A total of 12 flavonoids, pterocarpan and methyl caffeate were isolated, then characterised by UV, MS, NMR spectroscopy and identified as quercetin and kaempferol 3-O-(6″-α-rhamnopyranosyl-2″-ß-xylopyranosyl)-ß-galactopyranosides (1, 2), kaempferol 3-O-(2″,6″-α-dirhamnopyranosyl)-ß-galactopyranoside, mauritianin (3), quercetin and kaempferol 3-O-(2″-ß-xylopyranosyl)-ß-galactopyranosides (4, 5), kaempferol and quercetin 3-O-ß-(6″-O-acetyl)-galactopyranosides (6, 7), trifolin (8), hyperoside (9), myricetin 3-O-ß-galactopyranoside (10), quercetin (11), ononin (12), medicarpin 3-O-ß-glucopyranoside (13) and methyl caffeate (14). Mauritianin, ononin, pterocarpan and methyl caffeate have been reported in this plant for the first time. The compounds 4, 7, 9, 10, and 11 were tested for their antioxidant effect against DPPH˙. All studied compounds were found to have potent activity, but the most effective in the test were compounds 9, 10 and 11 (EC(50) values in the range 7.51-9.52 µM).

Polyphenolic compounds in Scopolia caucasica Kolesn. ex Kreyer (Solanaceae).

The qualitative and quantitative determinations of coumarins, phenolic acids and flavonoids in the leaves and underground parts of Scopolia caucasica using paper chromatography and HPLC methods were described. From the leaves of this plant, kaempferol 3-O-(2-glucosyl)-galactoside-7-O-glucoside, kaempferol 3-O-(2-glucosyl)-galactoside and quercetin 3-O-glucoside were isolated and identified by spectroscopic methods (UV, 1H- and 13C-NMR).

Further flavonoids from the flowers of Prunus spinosa L.

Further seven flavonoids were isolated from the flowers of Prunus spinosa L.: quercetin 3-O-alpha-L-arabinopyranoside, 3-O-alpha-L-rhamnopyranoside, 3-O-beta-D-xylo-pyranoside, and 3-O-beta-glucopyranoside, kaempferol 3,7-di-O-alpha-L-rhamnopyranoside, kaempferol and quercetin 3-O-(4"-beta-D-glucopyranosyl)-alpha-L-rhamnopyranosides. Four of them have been found for the first time in this plant. Structural elucidation was performed by means of chemical and spectral methods (UV, LSI MS, 1D and 2D NMR).

Quantitative determination of coumarins, flavonoids and chlorogenic acid in the leaves and underground parts of some species of genus Scopolia Jacq.

The quantitative determination of coumarins, flavonoids and chlorogenic acid in the leaves and underground parts of Scopolia carniolica Jacq., S. lurida Dun. and S. sinensis Hemsl. using the RP-HPLC method has been described.

Flavonoids from some species of genus Scopolia Jacq.

Kaempferol 3-O-(2-glucosyl)-galactoside-7-O-glucoside was isolated from the leaves of Scopolia carniolica Jacq. and S. sinensis Hemsl. From the latter taxon as well as kaempferol 3-O-galactoside and 3-O-(2-glucosyl)-galactoside, kaempferol and quercetin 3-O-robinobiosides and quercetin 3-O-sophoroside have been obtained. Moreover, from the leaves of S lurida Dun. kaempferol and quercetin 3-O-glucosides and 3-O-rutinosides were isolated. The structures of compounds have been determined by means of chemical and spectral methods (UV, LSI MS, 1H and 13C NMR, 1H-1H COSY NMR).