Chemotaxonomic differentiation of Rhizophora mangle L. and Laguncularia racemosa (L.) C.F. Gaertn. based on GC–MS and ATR–FTIR profiles of dichloromethane-soluble stem extractives

Abstract

Species-dependent variation in mangrove wood extractives remains insufficiently characterized, particularly at the compound and functional-group levels. Dichloromethane-soluble stem extractives from Rhizophora mangle L. and Laguncularia racemosa (L.) C.F. Gaertn. were comparatively characterized using gas chromatography–mass spectrometry (GC–MS) and attenuated total reflectance Fourier transform infrared spectroscopy. Extraction yielded 7.8% for R. mangle and 5.6% for L. racemosa on an oven-dry mass basis. GC–MS revealed distinct species-dependent profiles. R. mangle showed greater representation of phenolic and phenylpropanoid constituents, particularly eugenol and isoeugenyl acetate, together with lipid-derived compounds. L. racemosa was characterized predominantly by fatty acids, aldehydes, lactones, and esterified lipids, including palmitic acid and cis-13-octadecenoic acid. ATR–FTIR showed shared lignocellulosic functional groups but differences in aromatic-associated and oxygenated fingerprint-region absorptions. Compound assignments were considered tentative because retention-index validation and chromatographic deconvolution were not employed, while partial co-elution reduced confidence in some assignments. The combined profiles demonstrate distinct DCM-soluble extractive signatures and provide baseline evidence supporting chemotaxonomic differentiation of the two mangrove species. By comparatively characterizing the poorly documented DCM-soluble stem extractives of the species, this study addresses an important gap in mangrove stem-wood chemistry and provides a chemical baseline for future chemotaxonomic investigations.