Identification of two isomeric meroterpenoid naphthoquinones from Cordia linnaei by liquid chromatography-mass spectrometry and liquid chromatography-nuclear magnetic resonance spectroscopy - Ioset,J.R.; Wolfender,J.L.; Marston,A.; Gupta,M.P.; Hostettmann,K. (Phytochem Anal, 1999)