The fatty acid composition of seeds ofGinkgo biloba has been examined by a combination of capillary gas chromatography, silver ion high‐performance liquid chromatography and gas chromatography/mass spectrometry. Some of the fatty acids identified are unusual in plants and were rather different from those reported earlier. These include ananteiso‐methyl branched fatty acid, 14‐methylhexadecanoic acid, 5,9‐octadecadienoic acid, and 5,9,12‐octadecatrienoic acid. Fourier‐transform infrared spectroscopy confirmed that all of the double bonds were of thecis‐configuration.
Unusual fatty acids, with up to 34 carbon atoms and containing one or two bis-methylene-interrupted double-bond systems, have been identified in the sponge Haliclona cinerea from the Black Sea. These include the dienes-5,9-16:2, 7,11-18:2, 9,13-20:2, 13,17-24:2, 15,19-26:2, 17,21-28:2, 19,23-30:2 and 21,25-32:2; trienes-5,9,23-30:3, 5,9,24-31:3, 5,9,25-32:3, and 5,9,27-34:3; and the tetraenes-5,9,19,23-30:4, 5,9,21,25-32:4, and 5,9,23,27-34:4. In addition, 5,9,13-eicosatrienoic acid was present. Many of these do not appear to have been described before, and only 5,9-16:2 and 5,9,23-30:3 are found often in sponges. They were identified by using silver-ion high-performance liquid chromatography to simplify the complex mixture of fatty acids for subsequent analysis by gas chromatography-mass spectrometry as picolinyl ester derivatives. Deuteration with Wilkinson's catalyst in homogeneous solution confirmed the structures. We speculate that the di- and tetraenoic fatty acids arise by chain elongation of 5,9-hexadecadienoic acid, also a major component of the lipids, followed by further insertion of double bonds in the 5 and 9 positions. The trienes may be formed from 9-hexadecenoic acid by similar mechanisms.
Triacylglycerols of the seed oil ofTrichosanthes kirilowii have been resolved by high‐performance liquid chromatography (HPLC) in the silver‐ion and reverse‐phase modes. The fatty acids were identified by gas chromatography/mass spectrometry as the picolinyl esters. The main components arecis,cis‐C18:2n‐6 (38.2 mole%), C18:39c,11t,13c (punicic acid, 38.0 mole%), andcis‐C18:1n‐9 (11.8 mole%). Small amounts of C18:39c,11t,13t (α‐eleostearic acid) and C18:39t,11t,13c (catalpic acid) were detected. Silver‐ion HPLC exhibited excellent resolution in which fractions were resolved on the basis of the number and configuration of double‐bonds. In this instance, the strength of interaction of a conjugated trienoic double‐bond system with silver ions seemed to be between that of dienoic and monoenoic double bond systems. The triacylglycerols were also separated into 20 fractions by reverse‐phase HPLC, and the fractionation was achieved according to the partition number in which a conjugated trienoic double bond was not equivalent to three monoenoic double bonds in a molecule with a given chainlength. The principal triacylglycerol species are (C18:2n‐6) (C18:39c,11t,13c)2 (28.3 mol% of total), (C18:1n‐9)(C18:2n‐6) (C18: 39c,11t,13c) (19.0 mol%), and (C18:2n‐6)2(C18:39c,11t,13c) (16.2 mol%), while simple triacylglycerols such as (C18:39c11t,13c)3 and (C18:2n‐6)3 were present as minor components only (<1.0 mol%). Species esterified with conjugated trienoic acids comprise more than 96% of the total.Stereospecific analysis gave rise to insurmountable difficulties, but it is evident that there is some asymmetry in the distribution of fatty acids in the molecules.
Crystalline ciguatoxin isolated from moray eel (Lycodontis = G ymnothorax javanicus) viscera has an LD 50 of 0.45 g/kg (i.p., mice). It has a molecular weight of 1 1 1 1.7 0.2 daltons. 'H NMR studies have shown that it is a polar and highly oxygenated molecule belonging to the class of polyethers. On basic alumina ciguatoxin is reversibly converted to a chromatographically distinct less polar form, which is equally toxic and elicits typical ciguatoxin symptoms in mice.From parrotfish (Scarus sordidus), which originated on a ciguateric reef on Tarawa atoll (Kiribati), we have isolated two toxins that evoke ciguatera symptoms in mice at approximately equal levels. Chromatographic evidence suggests that the two toxins are identical with the two ciguatoxins of different polarity and that the less polar form is the previously described scaritoxin.
The wax esters of the roe oil of the amber fish, Seriola aureovittata, have been resolved by high-performance liquid chromatography (HPLC) in the silver-ion mode. Each of the fractions collected was transmethylated, and the fatty acids and alcohols were identified by gas chromatography/mass spectrometry (GC/MS) as the picolinyl esters and nicotinates, respectively. Their compositions were determined by GC. The fatty acid composition is complex, and the main components are C18:1n-9 (35.5 mo[%), C22:6n-3 (20.3 mo[%), and C16:1n-7 (10.7 mol%), while fatty alcohols are limited to saturated (C16:0, 60.3 mol%; C18:0, 15.3 mol%; C14:0, 5.1 mol%) and monoenoic alcohols (C18:1n-9, 6.5 mol%; C16:1n-7, 4.5 tool%) with traces (<0.1 mol%) of polyunsaturated fatty alcohols such as C20:3n-3, C20:4n-6, C20:5n-3, and C22:5n-3. Silver-ion HPLC exhibited excellent resolution in which fractions were resolved on the basis of the number and configuration of double bonds as well as the distribution pattern between the acid and alcohol moieties of the molecules with a given number of double bonds. The main wax ester fraction are those of monoenoic acid-saturated alcohol species, hexaenoic acid/saturated alcohol species, and pentaenoic acid/saturated alcohol species. Appreciable specificity was observed in the esterification of fatty acids with alcohols, and surprisingly, no saturated acid-monoenoic alcohol species were detected. JAOCS 72, 707-713 (1995).
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