Binding effect of proline-rich-proteins (PRPs) on in vitro antimicrobial activity of the flavonoids

The interaction of the cyanidin, pelargonidin, catechin, myrecetin and kaempferol with casein and gelatin, as proline rich proteins (PRPs), was studied. The binding constants calculated for both flavonoid-casein and flavonoid-gelatin were fairly large (105–107 M−1) indicating strong interaction. Due to higher proline content in gelatin, the binding constants of flavonoid-gelatin (2.5 × 105–6.2 × 107 M−1) were found to be higher than flavonoid-casein (1.2 × 105–5.0 × 107 M−1). All the flavonoids showed significant antibacterial activity against the tested strains. Significant loss in activity was observed due to the complexation with PRPs confirming that binding effectively reduced the concentration of the free flavonoids to be available for antibacterial activity. The decline in activity was corresponding to the values of the binding constants. Though the activities of free catechin and myrecetin were higher compared to pelargonidin, cyanidin and kaempferol yet the decline in activity of catechin and myrecetin due to complexation with casein and gelatin was more pronounced.

Enantiomeric separation of zolmitriptan by CE with a sulfated β-cyclodextrin chiral selector / 中国药科大学学报

Aim:To develop a practical chiral CE method for the quantitative determination of the unwanted enantiomer[( R )-enantiomer]presented in zolmitriptan. Methods:The background electrolyte was 20 mmol/L sodium dihydrogenphosphate solution with 1% S-β-CD,adjusted to pH 3.50 with phosphoric acid. A fused-silica capillary(60 cm×50 μm ID,effective length 51.5 cm)was used at 20 ℃ for the separation. The applied voltage was -30 kV. The samples were loaded by hydrodynamic injection(50 mbar pressure,6 s). UV was measured at 220 nm. Results:Zolmitriptan and its chiral impurity were baseline resolved ( R s=6.66). The linearity was good over the concentration range from 4 to 80 μg/mL( r =0.999 8) of ( R )-enantiomer. The injection precision (expressed as CV%) was 2.83%. The average recovery was 99.97%( n =9). The limit of detection was 1.5 μg/mL. The host-guest complex binding constants were 964 and 905 mol-1 for ( R )-enantiomer and zolmitriptan,respectively. Conclusion:The method is suitable for the determination of ( R )-enantiomer in zolmitriptan and binding constants of zolmitriptan enantiomers to S-β-CD.

Binding of 4-methyl umbelliferyl-α-D-glucopyranoside to Vicia faba lectin: Fluorescence-quenching studies.

On binding to Vicia faba lectin, the fluorescence of 4-methylumbelliferyl-α-Dglucopyranoside was quantitatively quenched showing that the interaction of 4- methylumbelliferyl-α-D-glucopyranoside took place in a binding environment. The binding of the fluorescent sugar was saccharide specific as evidenced by the reversal of 4-methylumbelliferyl- α-D-glucopyranoside fluorescence quenching by D-fructose. The association constant, Ka, values for the 4-methylumbelliferyl-α-D-glucopyranoside was determined by competition study employing reversal of fluorescence quenching of 4-methylumbelliferyl-α- D-glucopyranoside by D-fructose. The Ka value obtained for D-fructose was 1·07 ± 0·03 × 104 M–1 and for 4-methylumbelliferyl-α-D-glucopyranoside was 1·60 ± 0·05 × 104 M–1 at 15°C. The Ka values of 2·51 ± 0·06 × 104 M–1, l·26 ± 0·02 × 104 Μ–1 and 0·56 ± 0·01 × 104 M–1, respectively at 10°, 20° and 30°C were obtained from the Chipman equation. The relative fluorescence quenching, Δ Fa, at infinite concentration of the free saccharide sites of Vicia faba lectin [P’] was 93·5% at 30°C and the binding constant for 4-methylumbelliferyl-α-Dglucopyranoside lectin interaction as derived by Yank and Hanaguchi equation was 0·63 ± 0·01 × 104 M–1.