Lignans and Other Constituents from the Roots of the Vietnamese Medicinal Plant Pseuderanthemum palatiferum - Mai, Huong Doan Thi; Minh, Hang Nguyen Thi; Pham, Van Cuong; Bui, Kim Nga; Nguyen, Van Hung; Chau, Van Minh (Planta Medica, 2011)