Abstract
Licorice, the root and rhizome of Glycyrrhiza uralansis Fisch, is one of the most frequently used Traditional Chinese Medicines in rigorous clinical trials to remove toxins and sputum, and to relieve coughing. However, the aerial parts are not used so widely at present. It has been reported that the aerial parts have many bioactivities such as anti-microbial and anti-HIV activities. In this study, we aimed to discover the bioactive compounds from the leaves of G. uralensis. Four new compounds, licostilbene A-B (1-2) and licofuranol A-B (3-4), together with eight known flavonoids (5-12), were isolated and identified from the leaves of G. uralensis. Their structures were elucidated mainly by the interpretation of high-resolution electrospray mass spectrometry (HR-ESI-MS) and nuclear magnetic resonance (NMR) spectroscopic data. Compared with quercetin, which showed a 50% inhibitory concentration (IC(50)) value of 4.08 μg/mL, compounds 1-9 showed significant anti-inflammatory activities by inhibiting lipopolysaccharide (LPS)-induced nitric oxide (NO) production with IC(50) values of 2.60, 2.15, 3.21, 3.25, 2.00, 3.45, 2.53, 3.13 and 3.17 μg/mL, respectively. The discovery of these active compounds is important for the prevention and treatment of inflammation.