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. 2023 Mar 6;4(9-10):293-301.
doi: 10.1002/ansa.202200060. eCollection 2023 Oct.

Characterization of triglycerides photooxidation under solar radiations: A stepwise Raman study

Ali Assi  1 , Rime Michael-Jubeli  1 , Carine Jacques-Jamin  2 , Arlette Baillet-Guffroy  1 , Hélène Duplan  2 , Ali Tfayli  1
Affiliations

Characterization of triglycerides photooxidation under solar radiations: A stepwise Raman study

Ali Assi et al. Anal Sci Adv. .

Abstract

Triglycerides (TGs) are one of the main components of the glycerolipid family. Their main task in cells is to store excess fatty acids. TG energy storage is mainly concentrated in adipocytes. TGs and free fatty acids constitute the majority (57.5%) of the skin surface lipids (SSLs). TGs are essential for the formation of the skin water barrier. This work is the second part of a global study that aims to evaluate the effect of solar radiations on SSLs using vibrational spectroscopy. In the first part of this work, a stepwise characterization of free fatty acids was performed, and different spectral descriptors were used to follow the different structural modifications during the photo-oxidation process, that is hydrogen abstraction, formation of hydroperoxides and peroxyl radicals as primary oxidation products and the formation of aldehydes, ketones, alcohol as secondary products. In this second part, the photo-oxidation of TGs was evaluated using Raman spectroscopy. A decrease in the CH2/CH3 stretching bands ratio that confirmed the hydrogen abstraction, an increase in the 1165/1740 cm-1 ((δ(OH) and υ(C-O))/ν(C=O) (ester)) ratio indicated the formation of secondary oxidation products such as hydroperoxides. And finally, an increase in the 1725/1740 cm-1 (υ(C=O) (ald.)/υ(C=O) (ester)) ratio and the trans ν(C=C)/cis ν(C=C) ratio highlighted the formation of aldehydes, alcohols, ketone, trans secondary products and others.

Keywords: lipid Peroxidation; malondialdehyde; skin surface lipids; solar radiations; triglycerides; vibrational spectroscopy.

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Conflict of interest statement

The author declares that there is no conflict of interest.

Figures

FIGURE 1
FIGURE 1
Raman spectra of Crystal and amorphous forms of 1,2‐palmitin‐3‐palmitolein (TG3). (A) 750‐1470 cm−1 region, (B) 1550‐1850 cm−1 region and (C) 2700‐3200 cm−1 region.
FIGURE 2
FIGURE 2
(I) Oxidation mechanism of polyunsaturated alkyl chain in triglyceride (TG) (* example of trilinolenin): [(I.A) hydrogen abstraction; (I.B) hydro‐peroxidation; (I.B′) peroxyl radicals formation; (I.C) cyclization; (I.D) formation of secondary oxidation products]. (II) Raman descriptors of trilinolein oxidation. (III) Raman descriptors of trilinolenin descriptors: [(II.A, III.A) CH2/CH3 stretching ratio; (II.B, III.B) (δ(OH) and υ(C–O)/υ(C=O) (ester) ratio; (II.C, III.C) υ(C=C)/υ(C=O) (ester) ratio; (II.D, III.D) υ(C=O) (aldehyde)/υ(C=C) ratio; (II.D′, III.D′) trans υ(C=C)/cis υ(C=C) ratio]., , , ,
FIGURE 3
FIGURE 3
(A–F) Raman spectra of trilinolein and trilinolenin at different UV doses.
See this image and copyright information in PMC

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