In the present study the structure of proanthocyanidins from Polyalthia longifolia leaves was characterized with C-13 nuclear magnetic resonance, high performance liquid chromatography electrospray ionization mass spectrometry, and matrix-assisted laser desorption/ionization time-of-flight mass spectrometry analyses. The results showed that the proanthocyanidins were mixture of homopolymers of B-type procyanidins with degree of polymerization up to 14-mer. Furthermore, the antioxidant activity of the proanthocyanidins was studied through 2,2-diphenyl-1-picrylhydrazyl and 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulphonic acid) free-radical scavenging activities, and ferric reducing/antioxidant power assays. In addition, antityrosinase activity of the proanthocyanidins was investigated. The IC50 for 2,2-diphenyl-1-picrylhydrazyl and 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulphonic acid) free-radical scavenging activity of the proanthocyanidins were 89.32 +/- 12.07 and 76.79 +/- 5.88 mu g/mL, respectively; the ferric reducing/antioxidant power value was 710.54 +/- 142.82 mg ascorbic acid equivalent/g dry weight. The IC50 for antityrosinase activity was 773.09 +/- 1.47 mu g/mL. In conclusion, the proanthocyanidins from P. longifolia leaves exhibited potent antioxidant and antityrosinase activities. This research would provide scientific evidence for the use of proanthocyanidins from P. longifolia leaves as antioxidant and antityrosinase agents. (C) 2014, The Society for Biotechnology, Japan. All rights reserved.