Phytochemical Study of the Alkaloidal Fractions of Unonopsis duckei R. E. Fr. Guided by Electrospray Ionisation Ion-trap Tandem Mass Spectrometry

IntroductionThe Unonopsis genus is a promising source of aporphinoid alkaloids, substances with great biological potential. These alkaloids have a well-defined mass spectrometry fragmentation pattern that, together with previous phytochemical knowledge, can guide the isolation of alkaloids not yet described for the genus. ObjectiveIsolate substances not yet described in the Unonopsis genus, guided by alkaloidal profile analyses of stem barks, twigs and leaves of Unonopsis duckei using electrospray ionisation ion-trap tandem mass spectrometry (ESI-IT/MSn). MethodsMethanolic extracts from stem barks, twigs and leaves were submitted to a liquid-liquid, acid-base partitioning treatment to obtain the alkaloidal fractions. These fractions were analysed by direct infusion into an ESI-IT/MSn system. The major alkaloids observed for each fraction were submitted to fragmentation analysis. ResultsThe MS fragmentation patterns revealed the presence of alkaloids previously reported for Annonaceae, including nornuciferine, anonaine, asimilobine, liriodenine and lysicamine, known for the Unonopsis genus, as well as others that were not yet described for this genus. In this way, the proaporphine alkaloid glaziovine was isolated, as well as a mixture of the aporphine alkaloids glaucine and norglaucine, all described for the first time in the Unonopsis genus. ConclusionMass spectrometry monitoring was fundamental to prioritise the isolation of substances not yet identified for the Unonopsis genus, dismissing known compounds and simplifying the phytochemical study. Copyright (c) 2013 John Wiley & Sons, Ltd. The MS monitoring of the alkaloidal fractions of the Unonopsis duckei was fundamental to prioritise the isolation of substances not yet identified for the Unonopsis genus, dismissing known compounds and simplifying the phytochemical study. The presence of alkaloids previously reported for Annonaceae family, nornuciferine (3), anonaine (4), asimilobine (5), lysicamine (6) and liriodenine (7) was detected. The proaporphine alkaloid glaziovine (1) and the aporphine alkaloids glaucine (2a) and norglaucine (2b) are described for the first time in the Unonopsis genus.