The seed fatty acid composition and the distribution of Delta 5-olefinic acids in the triacylglycerols of some Taxares (Cephalotaxus and Podocarpus)

The fatty acid compositions of the seeds from four Cephalotaxus species or varieties (plum yews; Cephalotaxaceae) and two Podocarpus species (podocarp s; Podocarpaceae) have been established. These compositions were compared w ith those previously published for some Taxaceae species (Taxus and Torreya ). Cephalotaxaceae; Podocarpaceae, and Taxaceae belong to the Taxares subor der. Delta 5-Olefinic acids are present in the seed lipids from all species analyzed. In Cephalotaxus, Podocarpus, and Torreya, the prominent Delta 5- olefinic acid that occurs is the trienoic acid 5,11,14-20:3 (sciadonic) aci d, comprising from 6.7 to 26.4% of total fatty acids. In these species, the Delta 5,11 structure is largely favored over the Delta 5,9 structure: the 5,9-18:2 (taxoleic) and 5,9,12-18:3 (pinolenic) acids are at the limit of d etection, in contrast to Taxus and most Pinaceae species, where these two D elta 5-olefinic acids generally predominate. 14-Methylhexadecanoic acid, an habitual though minor component of Pinaceae and Ginkgo biloba seed lipids, could not be detected in Cephalotaxus species studied here and was tentati vely identified in trace amounts only in one Podocarpus species. In additio n to sciadonic acid, Cephalotaxus and Podocarpus seeds are characterized by unusually high amounts of 11,14-20:2 acid, in the range of 3.1-12.0%. This contrasts with most of the 170 species of conifers analyzed so far (from t he families Pinaceae, Cupressaceae, Taxodiaceae, Taxaceae, and Sciadopityac eae, which belong to the Pinares suborder), where this acid is generally le ss than or equal to 2%. A close resemblance between Torreya grandis and thr ee of the Cephalotaxus species analyzed might be indicative of some phyleti c relationship between the families Cephalotaxaceae and Taxaceae. C-13 nucl ear magnetic resonance spectroscopy of the seed oils from C. drupaceae and P. andinus has shown that Delta 5-olefinic acids are apparently excluded fr om the internal position of triacylglycerols, which is a characteristic com mon to all Coniferales species analyzed so far, and consequently of great a ntiquity.