Phytochemical study of the alkaloidal fractions of Unonopsis duckei R. E. Fr. guided by electrospray ionisation ion-trap tandem mass spectrometry.
BACKGROUND
The 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.


OBJECTIVE
Isolate 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/MS(n) ).


METHODS
Methanolic 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/MS(n) system. The major alkaloids observed for each fraction were submitted to fragmentation analysis.


RESULTS
The 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.


CONCLUSIONS
Mass 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.
Department of Chemistry, Federal University of Amazonas, 69077-000, Manaus, AM, Brazil.
Felipe M A
FM
da Silva
Afonso D L
AD
de Souza
Hector H F
HH
Koolen
Andersson
A
Barison
Mayara E
ME
Vendramin
Emmanoel V
EV
Costa
Antonio G
AG
Ferreira
Maria Lúcia B
ML
Pinheiro
D000470:Alkaloids / Q000032:analysis* / Q000737:chemistry; D029061:Annonaceae / Q000737:chemistry*; D001060:Aporphines / Q000032:analysis; D004149:Dioxoles / Q000032:analysis; D024301:Plant Bark / Q000737:chemistry; D018515:Plant Leaves / Q000737:chemistry; D021241:Spectrometry, Mass, Electrospray Ionization / Q000379:methods*; D053719:Tandem Mass Spectrometry / Q000379:methods*
D000470:Alkaloids; D001060:Aporphines; D004149:Dioxoles; C069090:lysicamine; C098138:anonaine; C002753:nornuciferine; C054614:asimilobine; C007847:glaziovine; C005004:glaucine
ESI-MS; Unonopsis duckei; alkaloidal profile; aporphine alkaloids; glaucine; glaziovine; norglaucine; proaporphine