A new hydroperoxyquinolone alkaloid, glycopentaphyllone (1), along with nine compounds (2-10), was isolated from the fruits of Glycosmis pentaphylla. Their structures were elucidated on the basis of spectroscopic methods. The absolute configuration of glycopentaphyllone at C-2' was established as S-configuration by applying Mosher's method. In addition, the completed assignments of C-13 NMR as well as 2D NMR spectral data of compound 5 were reported herein for the first time. Also, all isolates were evaluated for antibacterial activity against Escherichia coli TISTR 780, Salmonella typhimurium TISTR 292, Staphylococcus aureus TISTR 1466, and Methicillin-resistant S. aureus SK1. (C) 2012 Phytochemical Society of Europe. Published by Elsevier B.V. All rights reserved.