Two new lignans from the roots of Pulsatilla koreana - Cuong, T D; Hung, T M; Kim, J C; Huh, J I; Kwack, S J; Kang, T S; Kim, J H; Jang, H S; Choi, J S; Lee, H K; Bae, K; Min, B S (Planta Med, 2011)