Natural resin photo-oxidation

The first online TLC-MS attempt in the field of triterpenoids was done only in 2005 in the study of the photo-oxidation of natural di- and triterpenoid resins used as paint varnishes [10], The resinous samples were applied onto a cellulose-coated TLC plate, which afterward was subjected to direct MALDI-TOF-MS analysis without any development. The plates were only sprayed with a saturated ethanol solution of 2,5-dihydroxybenzoic acid as matrix to assist the ionization of compounds. Triterpenoids were observed as protonated molecules or as sodium clusters. Dammaradienone, dammaradienol, nor-a-amyrone, and dammarenolic, oleanonic, and ursonic acid were detected in dammar resin moronic acid, masticadienonic acid, and 3-0-acetyl-3-epi(iso)masticadienonic acid were found in mastic resin and diterpenoid abietane and pimarane acids were present in colophony. The induced aging process produced oxidized triterpenoids, which were observed in the MS spectra... 

Deterioration of paint films is promoted by photolysis, photo-oxidation, or photothermal reaction as a result of exposure to natural light. Specifically, UV light (wavelength 40-400 nm) decomposes some polymer structures. Polymer films, such as vinyl chloride resins, are gradually decomposed by absorbing the energy of UV light. 

Photo-oxidative degradation of electron-beam and UV cured di- and triacrylate resin films has been investigated [104,105]. The nature of the curing process and the photoinitiator are important in controlling the rate of photooxidation of the resin films. The inherent stability of the resin structure is dependent on the number of methylene protons which are alpha to the polyether oxygens. Electron beam cured resins are initially more photostable but eventually attain the same oxidation rate as for UV cured films. 

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