Antioxidant activity and principle constituents of Vietnam bitter tea Ilex kudingcha

The leaves of the plant Ilex kudingcha, a native Southern China and Northern Vietnam tree, has long been used indigenously as a tea called kudingcha (bitter tea) because of having bitter taste. In Vietnam, this tea is prescribed for headache, cold, hypertension, fever, and diabetes. There has been no investigation on the antioxidant principles of kudingcha so far. As part of a systematic search for antioxidant secondary metabolites from plants, we examined the antioxidant activity of Vietnam bitter tea by in vitro assays [1,2]. An EtOAc-soluble fraction of MeOH extract of kudingcha was found to display remarkable free radical scavenging and anti-lipid peroxidation activities, and significantly protected LDL oxidation mediated by either an ion Cu²⁺ or a free radical AAPH. Phytochemical analyses showed that this tea contains abundantly phenolic compounds and the principles were characterized as caffeic acid derivatives (1–8 and 10–14), including a new compound 3,5-di-O-caffeoyl epi-quinic acid n-butyl ester (14), and flavonols (9, 15, and 16). This suggests that dietary consumption of Vietnam kudingcha may provide beneficial effects on reducing cardiovascular and oxidative stress-related diseases.

Acknowledgements: This study was supported by research grants 2008 from Chosun University, Gwangju, Korea and Vietnam Institute of Medicinal Materials, Hanoi, Vietnam.

References: 1. Thuong, P. T. et al. (2005) Biol. Pharm. Bull. 28, 1095–1097. 2. Thuong, P. T. et al. (2007) Phytochemistry 68, 2432–2438