(S (S (ADVP (RB So)) (S (BASENP (DT the) (NNS researchers)) (VP (VBD investigated) (SBAR (WHADVP (WRB how)) (S (NP (BASENP (DT a) (JJ concentrated) (NN form)) (PP (IN of) (BASENP (DT the) (NN plant) (NN component) (NN parthenolide)))) (VP (MD would) (VP (VB affect) (NP (BASENP (NN leukemia) (NNS cells)) (CC and) (BASENP (JJ normal) (NNS cells)))))))))) (PERIOD .))