Estudo fitoquímico de Onychopetalum amazonicum R.E. Fr. (Annonaceae)

Abstract

The Onychopetalum genus (Annonaceae) has restricted distribution to the Amazon region, being constituted of two species: Onychopetalum amazonicum (RE Fr.) and Onychopetalum periquino (Rusby). The present work describes the phytochemical study of this species. The plant material (leaves, twigs and bark), collected in the Adolpho Ducke Forest Reserve (RFAD), from previously marked individual was submitted to hydrodistillation to obtain essential oils and acid-base treatment to obtain alkaloid fractions. The GC-MS analysis of the essential oils enabled the identification of 41 constituents, highlighting as majority in the leaves, the (E) caryophyllene (17.0%), while in the bark and twigs was observed (epi)-α-cadinol (24.1 and 14.0%, respectively). The analysis of the spectrometric profile for APCI-IT-MSn of the fractions obtained from analytical scale make possible choose the leaf alkaloidal fraction for the isolation of alkaloids not yet described in Onychopetalum genus. The analysis by HPLC, in preparative scale, of the leaf alkaloidal fraction of O. amazonicum, led to the isolation of the alkaloids nornuciferine, anonaine, asimilobine and O-methylisopiline (aporphine); isocorypalmine and stepholidine (tetrahydrodroprotoberberíne) and norjuzifine (benzyl-tetrahydroisoquinolíne), whose structures were characterized by MS and NMR (1D and 2D) techniques, together with the comparison with literature data. This is the first report of these alkaloids in Onychopetalum genus. In addition, antimicrobial tests performed for the first time with the essential oils showed mild activity for the essential oil from the bark which inhibited the growth of Staphylococcus epidermidis, Escherichia coli and Kocuria rhizophila, being observed a MIC =62,5 for the three strains