Flavonoids from Cleistocalyx operculatus Buds and their Cytotoxic Activity

Abstract

Cleistocalyx operculatus (Roxb.) Merr and Perry (Myrtaceae) is a well-known medicinal plant, widely distributed and propagated in China, Vietnam and some other tropical countries. Several species of Cleistocalyx are used in folk medicine. In Vietnam, C. operculatus is commonly called “Voi”. The flower buds (“Nu Voi”) and leaves (“La Voi”) have been used to make a beverage since ancient times. 1 The buds are commonly used as an ingredient for tonic drinks in Southern China. 2 The water extract of C. operculatus buds was shown to increase the contractility and decrease the frequency of contraction in an isolated rat heart perfusion system. 3 It showed strong protective effects on lipid peroxidation in rat liver microsomes and on the H2O2induced trauma of PC12 cells. 4 C. operculatus extract showed inhibitory activity against the α-glucosidase, rat-intestinal maltase, sucrase activities, and is considered a promising material for preventing and treating diabetes. 5 Recently, the essential oil of the C. operculatus buds was investigated for its in vitro and in vivo anti-inflammatory activities. These results suggested that its essential oil might exert an anti-inflammatory effect by suppressing the expression of pro-inflammatory cytokines, which is mediated, at least in part, by blocking the NF-κB activation. 6