Abstract
The flower buds of Camellia sinensis have been used as a food garnish in Japanese-style dishes: e.g. "Botebotecha" in Shimane prefecture. However, the chemical constituents and pharmacological properties of these flower buds have not yet been clarified. As a part of our characterization studies on the bioactive constituents of medicinal flower, we have isolated new acylated saponins, floratheasaponins A-J and chakasaponins I-VI, from the flower buds of C. sinensis cultivated in Japan and in China (Anhui, Fujian, Sichuan Province). In this time, the Me0H extract from the flower buds of C. sinensis cultivated in Fujian Province showed inhibitory effects on body weight gain and the weight of visceral fat in high-fat diet-fed mice and TSOD mice. The Me0H extract and its n-BuOH-soluble fraction also reduced food intake in normal diet-fed mice. From the n-BuOH-soluble fraction, an acylated saponin, chakasaponin I-III, was isolated as active constituents. Next, the mechanism of action on the anorectic effects was investigated. The n-BuOH-soluble fraction suppressed NPY mRNA levels in the hypothalamus, suggesting the suppression of an appetite signal. The inhibitory effects of the n-BuOH fraction and chakasaponins II on food intake were partly reduced by pretreatment with a high-dose of capsaicin. Furthermore, chakasaponin II enhanced the release of 5-HT from the isolated ilea of mice in vitro. These findings suggested that the active saponins suppressed the appetite signals in the hypothalamus through stimulation of the capsaicin-sensitive sensory nerves, probably vagal afferent nerves, or enhancement of 5-HT release from the ilea, leading to reduced food intake and body weight gain.
