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Evidence for the Initial Steps of DHA Biohydrogenation by Mixed Ruminal Microorganisms from Sheep Involves Formation of Conjugated Fatty Acids.

Journal of agricultural and food chemistry (2018-01-02)
Noelia Aldai, Pierluigi Delmonte, Susana P Alves, Rui J B Bessa, John K G Kramer
ABSTRACT

Incubation of DHA with sheep rumen fluid resulted in 80% disappearance in 6 h. The products were analyzed as their fatty acid (FA) methyl esters by GC-FID on SP-2560 and SLB-IL111 columns. The GC-online reduction × GC and GC-MS techniques demonstrated that all DHA metabolites retained the C22 structure (no evidence of chain-shortening). Two new transient DHA products were identified: mono-trans methylene interrupted-DHA and monoconjugated DHA (MC-DHA) isomers. Identification of MC-DHA was confirmed by their predicted elution using equivalent chain length differences from C18 FA, their molecular ions, and the 22:5 products formed which were the most abundant at 6 h. The 22:5 structures were established by fragmentation of their 4,4-dimethyloxazoline derivatives, and all 22:5 products contained an isolated double bond, suggesting formation via MC-DHA. The most abundant c4,c7,c10,t14,c19-22:5 appeared to be formed by unknown isomerases. Results suggest that the initial biohydrogenation of DHA was analogous to that of C18 FA.

MATERIALS
Product Number
Brand
Product Description

Supelco
SLB®-IL111i Capillary GC Column, L × I.D. 30 m × 0.25 mm, df 0.20 μm
Supelco
SP®-2560 Capillary GC Column, L × I.D. 200 m × 0.25 mm, df 0.20 μm
Supelco
SLB®-IL111i Capillary GC Column, L × I.D. 60 m × 0.25 mm, df 0.20 μm
Supelco
SP®-2560 Capillary GC Column, L × I.D. 100 m × 0.25 mm, df 0.20 μm
Supelco
SLB®-5ms Capillary GC Column, L × I.D. 30 m × 0.25 mm, df 1.00 μm
Supelco
SLB®-5ms Capillary GC Column, L × I.D. 15 m × 0.25 mm, df 0.25 μm
Supelco
SLB®-5ms Capillary GC Column, L × I.D. 30 m × 0.25 mm, df 0.25 μm
Supelco
SLB®-5ms Capillary GC Column, L × I.D. 60 m × 0.25 mm, df 0.25 μm
Supelco
SLB®-5ms Capillary GC Column, L × I.D. 30 m × 0.25 mm, df 0.50 μm
Supelco
SLB®-5ms Capillary GC Column, L × I.D. 30 m × 0.32 mm, df 0.25 μm
Supelco
SLB®-5ms Capillary GC Column, L × I.D. 30 m × 0.32 mm, df 0.50 μm
Supelco
SLB®-5ms Capillary GC Column, L × I.D. 30 m × 0.25 mm, df 0.10 μm
Supelco
SLB®-5ms Capillary GC Column, L × I.D. 30 m × 0.53 mm, df 1.00 μm
Supelco
SP®-2560 Capillary GC Column, L × I.D. 75 m × 0.18 mm, df 0.14 μm
Supelco
SLB®-5ms Capillary GC Column, L × I.D. 10 m × 0.10 mm, df 0.10 μm
Supelco
SLB®-5ms Capillary GC Column, L × I.D. 15 m × 0.10 mm, df 0.10 μm
Supelco
SLB®-5ms Capillary GC Column, L × I.D. 20 m × 0.18 mm, df 0.18 μm
Supelco
SP®-2560 Capillary GC Column, L × I.D. 100 m × 0.25 mm, df 0.20 μm
Supelco
SLB®-IL111 Capillary GC Column, L × I.D. 200 m × 0.25 mm, df 0.20 μm
Supelco
SLB®-IL111 Capillary GC Column, L × I.D. 30 m × 0.25 mm, df 0.20 μm
Supelco
SLB®-IL111 Capillary GC Column, L × I.D. 100 m × 0.25 mm, df 0.20 μm
Supelco
SLB®-IL111 Capillary GC Column, L × I.D. 60 m × 0.25 mm, df 0.20 μm