Two new stilbenoids, carasiphenol C (1) and Carasiphenol D (2), and one new dihydroaurone, carasinaurone (3), were isolated from the aerial parts of Caragana sinica, along with three known substances. Their structures were elucidated on the basis of spectroscopic methods and X-ray-diffraction analysis. Compound 2 showed significant biological activity against Pyricularia oryzae.
Introduction. ± Caragana sinica (Bucholz.) Rehd. (Leguminosae) is widely distributed in China. Its dried root named -Jinquegen× [1] has been used as a folk medicine. In the previous papers, we reported that the AcOEt extract of the root of Caragana sinica showed the effects of stimulating the proliferation, differentiation, and maturation of cultured osteoblasts in vitro [2]. In our lab, many oligostilbenes, some of which exhibited estrogenic activity, were isolated from this plant [3]. The aerial parts of the plant have scarcely been used and were always considered a waste product. However, our recent studies on the aerial parts of the plant showed that it can be a rich source of oligostilbenes. In this paper, we report the isolation and structure elucidation of two new oligostilbenes, carasiphenol C (1) and carasiphenol D (2), and a new dihydroaurone, carasinaurone (3), together with three known compounds, (À)ampelosin F, caraphenol A [4], and carasinols A [5], from the aerial parts of Caragana sinica. Carasiphenol D (2) showed significant activity against the mycelial growth of Pyricularia oryzae. The minimum inhibitory concentration (MIC) of 2 was 0.017 mm.
Results and Discussion. ± Carasiphenol C (1) was isolated as a yellowish, amorphous, optically active powder. Its molecular formula, C 42 H 32 O 9 , was deduced from the HR-ESI-MS (m/z 681.2130 ([M À H] , C 42 H 33 O 9 )). The structure of 2 was established by the 1 H-and 13 C-NMR spectra (Tables 1 and2) and their comparison with those of ampelopsin H [6], a tetramer of resveratrol, and confirmed by HMBC and NOE data (Fig.