An infrared absorption study of autoxidized methyl linoleate

Abstract

Summary A study has been made of the infrared absorption spectra of autoxidized methyl linoleate in samples ranging from PV 1 to PV 940 m.e./kg. Principal changes occur in the frequency range 3400–3550 cm−1 where bonded−OH groups absorb and at 1650–1775 cm−1 where >c=0 groups absorb. Two maxima were observed in oxidized samples in the −OH absorption range: one sharp and distinct at 3467–70 cm−1 which increased in intensity with increase in PV and a broad band which increased with increasing PV until it resolved into a true maximum at 3430 cm−1. Reduction of typical oxidized samples with KI reagent resulted in disappearance of the 3430 cm−1 band and appearance of a new band above 3500 cm−1. The band at 3430 cm−1 was attributed to −OOH groups associated by hydrogen bridging. The band at 3467 cm−1 and the band appearing above 3500 cm−1 were attributed to −OH groups, the band at the higher frequency resulting directly from reduction of a hydroperoxide. Absorption due to ketone and aldehyde carbonyl groups appeared only as an indefinite shoulder on the band due to the ester carbonyl. These were resolved by using the intensity of the sample with PV 1 as Io and that for the oxidized samples as I. A plot of Log Io/I then revealed three maxima. These indicate the presence of two and possibly three carbonyl containing substances other than the ester carbonyl in autoxidized methyl linoleate. Absorption in the two critical frequency ranges of fractions of autoxidized methyl linoleate eluted from an adsorption column correlate with interpretations made from ultraviolet absorption studies of the same substances.

Photochemical oxidation of fatty acid esters with and without chlorophyll

“…Both types of compounds absorb at 2.8 to 2.9 microns (hydroxyl stretching vibrations) and at 10.36 microns (bending vibrations of carbon-hydrogen groups attached to a trans double bond). The hydroxyl absorption band parallels the content of peroxidic and other hydroxyls and was found to be in agreement with the findings of previous workers (1,11,21,35), including the observation that hydroxyl absorption occurs a a lower wavelength than does hydroperoxyl. These absorption curves are not included because they were all similar to those of the products of methyl linoleate (Figures 2, 3).…”

Spectroscopic evaluation of human tear lipids

“…Curve fitting showed these bands to be centered at 3450, 3347 and 3200 cm −1 . All of these peaks are characteristic of hydrogen bonded OH moieties as nonhydrogen bonded OH bands appear between 3700 and 3500 cm −1 (Dugan et al, 1949). Lipid hydroperoxides in olive oil exhibit a band at 3447 cm −1 (van de Voort et al, 1994), fatty acids, such as oleic acid in olive oil display bands at 3310 and 3200 cm −1 (Ismail et al, 1993), however no bands were detectable in our spectra of palmitic acid (data not shown).…”

UVA Light In vivo Reaches the Nucleus of the Guinea Pig Lens and Produces Deleterious, Oxidative Effects

“…1). The intensity of OH stretching bands (3600±3100 cm À1 ) re¯ects the degree of oxidation present in a lipid sample (Dugan et al, 1949), as well as the amount of hydroxylcontaining lipids such as sphingolipids and cholesterol. The level of lipid hydroxyl was elevated by 30 % in the lens nucleus of UVA-exposed guinea pigs (P 0 .…”