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 | Hydroxy Fatty Acids |
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| Hydroxy fatty acids are ubiquitous natural products in both plant and animal species. The majority of hydroxy fatty acids are formed by the action of lipoxygenase enzymes, although cytochrome P450 plays a minor role in their biosynthesis. This product group mirrors our fatty acid group in that we have tried to offer the principle hydroxylated metabolites of all key polyunsaturated fatty acids. |
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| The products of 15-Lipoxygenase |
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| The biological role of the hydroxy fatty acids has not been clear until fairly recently. Several divergent lines of evidence now point to a prominent role in the regulation of gene expression. For example, 15-HETE has been implicated in the induction of cytokine expression and pro-inflammatory gene activation in bronchial epithelial cells. 12-HETE has been shown to induce integrin and other cell-surface active molecule expression in prostatic tissue. Finally, the discovery of alterations in gene expression in vascular endothelial cells induced by HODEs may have far reaching implications in atherosclerosis research. Plants also have been shown to undergo stress-response gene activation under the influence of hydroxy fatty acids, indicating that this may be a conserved cell transformation pathway. |
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| An unusual hydroxy fatty acid listed in this section is 12(S)-HHTrE. This unique trans-trans 17-carbon hydroxy fatty acid can result from either cyclooxygenase or non-enzymatic free-radical oxygenation. Although it has been shown to be an excellent substrate for 15-hydroxy prostaglandin dehydrogenase, its biological role remains obscure. |
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| Like the polyunsaturated fatty acids, hydroxy fatty acids are also susceptible to autoxidation. Likewise, they exhibit similar solubilities. Hence, the care and use protocols suggested for fatty acids should also be applied to the hydroxy fatty acids. |
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| Quantification of hydroxy fatty acids is performed by UV spectroscopy using the absorbance of the diene chromophore between 234-237 nm. Unfortunately, the extinction coefficients reported for the same hydroxy fatty acid may differ by up to 20%. To eliminate the confusion resulting from the conflicting extinction coefficients in the published literature, we have gravimetrically determined the extinction coefficients for many of the hydroxy fatty acids in this section. Only the empirically obtained values are reported for each compound. |
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| We have been called on several times to produce uncommon hydroxy fatty acid regioisomers or the hydroxylated metabolites of unusual fatty acid substrates. Our working knowledge and a large inventory of various purified animal and plant lipoxygenases often makes such a custom synthesis feasible. Please let us know of any hydroxy fatty acid of interest to you that is not found in these pages. |
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| Suggestions for further reading |
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- Ingram, C.D. and Brash, A.R. Characterization of HETEs and related conjugated dienes by UV spectroscopy. Lipids 23, 340-344 (1988).
- Honn, K.V., et al. Fatty acid modulation of tumor cell adhesion to microvessel endothelium and experimental metastasis. Prostaglandins 44, 413-429 (1992).
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