Comparison of the mass spectrum from hydrogenated and non-hydrogenated samples showed that the TMS ether of methyl 5,8-dihydroxy octadecanoate was derived from the TMS ether of methyl 5,8-dihydroxy-9,12-octadecadienoate. This was evidenced by the molecular ion at m/z 470 and by the characteristic fragments resulting from cleavage around the double bonds and oxygenated C atoms [8]. Thus RP-HPLC peak 2 (Fig.

1) proved to be 5,8-diHOD. RP-HPLC peak 2* was analyzed as a part of RP-HPLC peak 2, due to overlap. Hydrogenation of the TMS ether derivative showed peaks stemming from cleavage around an oxygenated C-atom. The molecular ion at m/z 370 evidenced that this compound was TMS ether of lactonized 5,8-dihydroxyoctadecanoate. Selleckchem SAHA HDAC Comparing the hydrogenated sample with the non-hydrogenated sample showed that TMS ether of lactonized find more 5,8-dihydroxy octadecanoate probably originated from lactonized 5,8-diHOD. GC/MS analysis of monohydroxy fatty acids (RP-HPLC peak 3) In the GC chromatogram of the hydrogenated monohydroxy fatty acids of RP-HPLC peak 3 (Fig. 1) as TMS ethers of methyl ester derivatives, one prominent peak was present. The mass spectrum identified it as a mixture of the TMS ethers of methyl 8-hydroxy octadecanoate,

methyl 10-hydroxy octadecanoate and a small Necrostatin-1 amount of methyl 9-hydroxy octadecanoate. Also, a small peak of methyl 13-hydroxy octadecanoate was present in the GC chromatogram. In the GC/MS analysis of the corresponding non-hydrogenated monohydroxy fatty acids as TMS ethers of methyl ester derivatives, three peaks were visible in the GC chromatogram. Reference compounds indicated that GC peak 1 (18.3 min) was TMS ether of methyl 8-hydroxy octadecadienoate because of the fragmentation pattern and retention time of the non-hydrogenated sample [7]. The mass spectrum of Oxymatrine TMS ether of methyl 10-hydroxy octadecanoate, GC peak 2 (18.4 min), showed that this compound originated from 10-hydroxy octadecadienoic acid (10-HOD). The mass spectrum of GC peak 4

(19.1 min) and the mass spectra of reference compounds showed that TMS ethers of methyl 13-hydroxy octadecanoate and methyl 9-hydroxy decanoate were derived from 13-hydroxy octadecadienoic acid (13-HOD) and 9-hydroxy octadecadienoic acid (9-HOD), respectively. Thus, RP-HPLC peak 3 (Fig. 1) was composed of 8-HOD (20), 10-HOD (18), 13-HOD (1) and 9-HOD (1). GC/MS analysis of monohydroxy fatty acids eluting after RP-HPLC peak 3 (Fig. 1) as TMS ethers of methyl ester derivatives showed that a small amount of 8-HOM was also present (data not shown). Characteristics of oxylipin formation Incubation with [U-13C] 18:2 showed that all oxygenated fatty acid products (RP-HPLC peak 1 to peak 3, Fig. 1) represented a mixture of converted 18:2 from endogenous and exogenous sources. The conversion of 500 nmol exogenously supplied 18:2 was about 50% of the total conversion, as judged by the ratio of [U-13C] labeled fragments to unlabeled fragments on GC/MS.