Bioassay-guided isolation of constituents of Piper sarmentosum using a mitochondrial transmembrane potential assay - Pan, L; Matthew, S; Lantvit, D D; Zhang, X; Tran, N N; Chai, H; de Blanco, E JC; Soejarto, D D; Swanson, S M; Kinghorn, A D (J Nat Prod, 2011)