Absolute stereostructures of alismalactone 23-acetate and alismaketone-a 23-acetate, new seco-protostane and protostane-type triterpenes with vasorelaxant effects from Chinese Alismatis rhizoma - Yoshikawa, M; Murakami, T; Ikebata, A; Ishikado, A; Murakami, N; Yamahara, J; Matsuda, H (Chem Pharm Bull, 1997)