A new anthraquinone, morinquinone, together with 18 known anthraquinones were isolated from the stems of Morinda elliptica Ridl. Their structures were elucidated on the basis of spectroscopic data. They each showed weak inhibitory activity against a susceptible strain of Staphylococcus aureus and a methicillin-resistant S. aureus. Damnacanthal was effective against Microsporum gypseum (MIC 1 μg/mL). Lucidin was active against Entamoeba histolytica (MIC 31.25 μg/mL) and Giardia intestinalis (MIC 7.8 μg/mL).
Keywords: Morinda elliptica; Rubiaceae; anthraquinones; antimicrobial activity.