Matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF) mass spectrometry is a suitable method for examining polyflavonoid tannin oligomers as it is capable to determine aspects of their oligomeric structure and characteristics, which are otherwise too difficult to determine by other techniques. It has been possible to determine by MALDI-TOF for Rhizophora apiculata mangrove polyflvonoid tannins that: (i) procyanidins oligomers formed by catechin/epicatechin, epigallocatechin, and epicatechin gallate monomers are present in great proportions; (ii) oligomers, up to nonamers, in which the repeating unit at 528-529 Da is a catechin gallate dimer that has lost both the gallic acid residues and an hydroxy group which are the predominant species; (iii) oligomers of the two types covalently linked to each other also occur. (C) 2008 Wiley Periodicals, Inc.