Fatty acids, sterols and hydrocarbons in the leaves of mangroves from northern Australia and New Zealand

Fresh leaves were collected from 11 species of mangrove plants for lipid analyses. The species examined were Avicennia marina, Avicennia marina var resinifera, Xylocarpus granatum, Rhizophora stylosa, Rhizophora apiculata, Rhizophora mucronata, Ceriops tagal var. australis, Bruguiera sexangula, Bruguiera gymnorrhiza, Acanthus ilicifolius and Sonneralia caseolaris, which were cultivated from seedlings in a shadehouse at the Australian Institute of Marine Science (AIMS). Ten of these species can be found along the coast of north Queensland, while Avicennia marina var resinifera occurs in New Zealand.The leaves were cut into small pieces and ground in an agate mortar and pestle under CHCl3-MeOH (1:1). After extraction, an aliquot of the solvent extract was saponified and partitioned to give the neutral lipids and the acidic lipids. Sterols and hydrocarbons were isolated from the neutral fraction by normal-phase HPLC. The acidic lipids were methylated with H2SO4-MeOH and analysed by GC. The sterols were further treated and after extraction yielded the steryl methyl ethers, which were analysed by GC. The hydrocarbons were also analysed by GC. Moisture content was also determined on separate leaf samples. This research was undertaken to assess the importance of mangrove leaves as a source of organic material such as fatty acids, sterols and hydrocarbons for food webs within coastal ecosystems. Variations in fatty acid, sterol and hydrocarbon composition were examined for potential chemotaxonomic significance.