The sterol and fatty acid compositions of seven tropical seagrasses from North Queensland, Australia

Abstract

The sterol and fatty acid compositions of fresh leaves of the seagrasses Cymodocea serrulata, Enhalus acoroides, Halodule uninervis, Halophila ovalis, H. ovata, H. spinulosa and Thalassia hemprichii are reported. The major fatty acids were palmitic acid, linoleic acid and linolenic acid as expected. H. ovalis and H. ovata were characterized by the relatively high abundance ( ca 5%) of the acid hexadeca-7,10,13-trienoic acid (16:3<7 > ). The sterol compositions were typical of higher plants, with sitosterol and stigmasterol accounting for 60–90% of the observed sterols. 28-Isofucosterol was a major sterol (20–30%) only in the Halophila spp. Cluster analysis of the sterol composition data clearly separated the Halophila spp. from the other seagrasses and enabled the distinction of Enhalus sp. from Cymodocea, Halodule and Thalassia spp. The seagrass species were clearly separated into five chemical groups using the combined fatty acid and sterol composition data and the need for a reappraisal of the taxonomic position of Halophila was indicated.