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We report here new chemical evidence for the generation of radical molecular ions of compounds with a conjugated pi-system (polyene) in ESI and HR-MALDI mass spectrometry. The oxidation potential of the neutral polyenes was calculated by cyclic-voltammetry and the results compared with those previously published for other complex conjugated compounds that have also been shown to form M*+ in ESI-MS. This study clearly demonstrates the correlation between the oxidation potential and the formation of the M*+ for the polyenes studied.

This paper reports the chemical evidence of the balance between radical molecular ions and protonatedmolecules of xanthophylls (an oxygen-containing carotenoid) with a conjugated pi-system (polyene) and oxygen as a heteroatom in ESI and HRESI mass spectrometry. The ionization energy of neutral xanthophylls was calculated by semi-empirical methods. The results were compared with those previously published for carotenoids and retinoids, which have also been shown in ESI-MS to form M(+*) and [M + H](+), respectively. This study demonstrates, for the first time, the correlation of an extended conjugation and the presence of oxygen in the formation and balance of M(+*) or [M + H](+) for the carotenoids, neoxanthin, lutein, violaxanthin and zeaxanthin.

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Fotoprotetores derivados de produtos naturais: perspectivas de mercado e interações entre o setor produtivo e centros de pesquisa thais Guaratini, daniel roberto callejon, dalton caprari pires e José norberto callegari Lopes Lychnoflora Pesquisa e Desenvolvimento em Produtos Naturais LTDA., Rua dos Técnicos, s/n, Incubadora Supera -Campus da USP, 14049-900 Ribeirão Preto -SP, Brasil Leonardo mandalho Lima, daniel Giannella neto e celso sustovich

We report here a general mechanism for the elimination of aromatic molecules from polyene containing natural products of several compound classes in tandem mass spectrometry.