The geometries and spin densities of green tea catechin radicals are calculated using unrestricted B3LYP hydrid density functional calculations. The radicals which have the smallest value of Maximum Spin Density (MSD) are referred to the most stable radical species deriving from the absolute minimum energy of investigated compounds. In this study, we have calculated these values in gas phase and water solution. | TẠP CHÍ PHÁT TRIỂN KH CN TẬP 9 SÓ11 -2006 THEORETICAL STUDY OF THE SPIN DENSITY DISTRIBUTION OF THE GREEN TEA CATECHIN RADICALS Pham Thanh Quan Le Thanh Hung Tran Thi Ha Thai University of Technology VNU-HCM Manuscript Received on June 20 th 2006 Manuscript Revised November 2nd 2006 ABSTRACT The geometries and spin densities of green tea catechin radicals are calculated using unrestricted B3LYP hydrid density functional calculations. The radicals which have the smallest value of Maximum Spin Density MSD are referred to the most stable radical species deriving from the absolute minimum energy of investigated compounds. In this study we have calculated these values in gas phase and water solution. For green tea catechins their stable radicals have MSD values lying at - in gas phase and in water. Calculating some flavonoid stable radicals it was found that the MSD values lie at - in gas phase and - in water solution. These calculated data were compared with experimental data and were found to be in good agreement in predicting the stability of radicals. On the basic of the computed MSD values the stability of radicals can be explored and give a relative trend of the activity and scavenging of antioxidant radicals. Key words antioxidants phenolics flavonoids catechins spin density 1. INTRODUCTION Tea Camellia sinensis is believed to have a wide range of pharmaceutical properties including being antihypertensive antioxidative antiarteriosclerotic anticarcinogenic and hypochlolesterolemic. These diverse biological activities are thought to be attributed to a group of polyphenol compounds namely green tea catechins GTCs present in tea leaves. The content of GTCs varies among green tea black tea and oolong tea. Green tea refers to a nonfermented product in which GTCs are mostly preserved while black tea is oxidized during manufacturing process. Oolong tea is a partially fermented product in which GTCs are partially degraded 1 . The .
