RESUMO
Employing a combination of liquid chromatography electrospray ionization and paper spray ionization high-resolution tandem mass spectrometry, extracts from cupuassu (Theobroma grandiflorum) pulp prepared with either water, methanol, acetonitrile or combinations thereof were subjected to metabolite fingerprinting. Among the tested extractors, 100% methanol extracted preferentially phenols and cinnamic acids derivatives, whereas acetonitrile and acetonitrile/methanol were more effective in extracting terpenoids and flavonoids, respectively. And while liquid chromatography- mass spectrometry detected twice as many metabolites as paper spray ionization tandem mass spectrometry, the latter proved its potential as a screening technique. Comprehensive structural annotation showed a high production of terpenes, mainly oleanane triterpene derivatives. of the mass spectra Further, five major metabolites with known antioxidant activity, namely catechin, citric acid, epigallocatechin-3'-glucuronide, 5,7,8-trihydroxyflavanone, and asiatic acid, were subjected to molecular docking analysis using the antioxidative enzyme peroxiredoxin 5 (PRDX5) as a model receptor. Based on its excellent docking score, a pharmacophore model of 5,7,8-trihydroxyflavanone was generated, which may help the design of new antioxidants.
RESUMO
On-surface degradation of sildenafil (an adequate substrate as it contains assorted functional groups in its structure) promoted by the Fenton (Fe2+ /H2 O2 ) and Fenton-like (Mn+ /H2 O2 ; Mn+ = Fe3+ , Co2+ , Cu2+ , Mn2+ ) systems was investigated by using paper spray ionization mass spectrometry (PS-MS). The performance of each system was compared by measuring the ratio between the relative intensities of the ions of m/z 475 (protonated sildenafil) and m/z 235 (protonated lidocaine, used as a convenient internal standard and added to the paper just before the PS-MS analyzes). The results indicated the following order in the rates of such reactions: Fe2+ /H2 O2 â« H2 O2 â« Cu2+ /H2 O2 > Mn+ /H2 O2 (Mn+ = Fe3+ , Co2+ , Mn2+ ) ~ Mn+ (Mn+ = Fe2+ , Fe3+ , Co2+ , Cu2+ , Mn2 ). The superior capability of Fe2+ /H2 O2 in causing the degradation of sildenafil indicates that Fe2+ efficiently decomposes H2 O2 to yield hydroxyl radicals, quite reactive species that cause the substrate oxidation. The results also indicate that H2 O2 can spontaneously decompose likely to yield hydroxyl radicals, although in a much smaller extension than the Fenton system. This effect, however, is strongly inhibited by the presence of the other cations, ie, Fe3+ , Co2+ , Cu2+ , and Mn2+ . A unique oxidation by-product was detected in the reaction between Fe2+ /H2 O2 with sildenafil, and a possible structure for it was proposed based on the MS/MS data. The on-surface reaction of other substrates (trimethoprim and tamoxifen) with the Fenton system was also investigated. In conclusion, PS-MS shows to be a convenient platform to promptly monitor on-surface oxidation reactions.