(−)-Xanthienopyran, a New Inhibitor of Superoxide Anion Generation by Activated Neutrophils, and Further Constituents of the Seeds of Xanthium strumarium - Lee, Chia-Lin; Huang, Po-Ching; Hsieh, Pei-Wen; Hwang, Tsong-Long; Hou, Yu-Yi; Chang, Fang-Rong; Wu, Yang-Chang (Planta Medica, 2008)