Chemical constituents of MeOH-CH2Cl2 extract of the stem of Glycosmis pentaphylla RETZ (Rutaceae) collected in Papua New Guinea were studied. A novel naphthoquinone and a new acridone alkaloid called glycoquinone (1) and glycocitrine-III (2), respectively, were isolated along with twelve known compounds, and their structures were elucidated by spectrometric analyses. This is the first isolation of a naphthoquinone derivative from the genus Glycosmis.