title: Study on the photostability of guaiazulene by high-performance liquid chromatography/mass spectrometry and gas chromatography/mass spectrometry.
abstract: The photostability of guaiazulene (1,4-dimethyl-7-isopropylazulene; GA), a natural azulenic compound used in cosmetic and health-care products, as well as in pharmaceutical preparations, was investigated in solution (methanol, ethanol, acetonitrile), by different techniques: gas chromatography/mass spectrometry (GC/MS) and high-performance liquid chromatography combined with atmospheric pressure chemical ionization mass spectrometry and UV detection (LC/APCI-MS and HPLC/UV). A solar simulator (xenon-arc lamp) was used as UV-A radiation source. The study involved: monitoring compound decomposition, identifying products of photodegradation (PPs), assessing the role of oxygen and evaluating the kinetics of the process. Minor PPs are volatile compounds and were characterized by GC/MS, while oligomeric polyoxygenated compounds, tentatively characterized on the basis of MS and MS/MS spectra, were found to be the main photoproducts. The photodegradation was found to be enhanced by the presence of oxygen; nevertheless, determination of the singlet oxygen quantum yield for GA gave a lower value than that for the reference standard Rose Bengal. The obtained results and the developed stability-indicating methods (GC/MS and LC/MS) are of interest for stability studies and/or quality control purposes of GA as raw material or cosmetic products.
authors.affiliation: Department of Pharmaceutical Science, University of Bologna, Italy.
authors.forename: Jessica
authors.initials: J
authors.lastname: Fiori
authors.forename: Roberto
authors.initials: R
authors.lastname: Gotti
authors.forename: Angelo
authors.initials: A
authors.lastname: Albini
authors.forename: Vanni
authors.initials: V
authors.lastname: Cavrini
mesh_terms: D000975:Antioxidants / Q000737:chemistry*; D052176:Azulenes / Q000737:chemistry*; D002851:Chromatography, High Pressure Liquid; D004355:Drug Stability; D008401:Gas Chromatography-Mass Spectrometry / Q000379:methods*; D010777:Photochemistry; D012717:Sesquiterpenes / Q000737:chemistry*; D045789:Sesquiterpenes, Guaiane; D021241:Spectrometry, Mass, Electrospray Ionization / Q000379:methods*; D053719:Tandem Mass Spectrometry / Q000379:methods*
chemical_list: D000975:Antioxidants; D052176:Azulenes; D012717:Sesquiterpenes; D045789:Sesquiterpenes, Guaiane; C004451:guaiazulene