Onychopetalum is an Amazonian botanical genus close-related with Bocageopsis and Unonopsis, whose species are used in traditional medicine. Although these genera are widely investigated from the phytochemical viewpoint, the knowledge about Onychopetalum remains almost unexplored. In order to perform a comprehensive characterization of isoquinoline-derived alkaloids from Onychopetalum amazonicum, an integrative approach based on the alkaloid profile analysis by leaf spray mass spectrometry (LS-MS), followed by a robust dereplication through high-performance liquid chromatography coupled with diode array detector and atmospheric pressure chemical ionization tandem mass spectrometry, (HPLC-DAD-APCI-MS/MS) and nuclear magnetic resonance (NMR) analysis was adopted. LS-MS allowed the tentative identification of reticuline, norjuziphine, nornuciferine, O-methylisopiline, nuciferine, N-methyl-O-methylisopiline, anonaine, and N-methylanonaine. HPLC-DAD-MS/MS analysis supported the tentative identification of N-methylasimilobine, asimilobine, norushinsunine, N-methylisopiline, isopiline, liriodenine, and lysicamine. Moreover, the integration of MS and NMR data allowed the additional identification of stepholidine and isocorypalmine. The applied integrative approach proposed herein enabled a comprehensive analysis of the alkaloid content from the O. amazonicum, showing to be a useful strategy for the dereplication of isoquinoline-derived alkaloids.

Unonopsis (Annonaceae) is a neotropical genus constituted by nearly fifty species, with fifteen described in Brazil. In the state of Amazonas seven species are found, including U. guatterioides, which displays problems from the botanical viewpoint. Previous studies showed this genus as a promising source of aporphinoid alkaloids. In order to investigate the potential of the leaf alkaloid fingerprint for chemotaxonomic approaches, twelve Unonopsis specimens, representing five species commonly found in the state of Amazonas were subjected to acid-base partitioning to yield the respective alkaloidal fractions. These fractions were analysed by direct infusion electrospray ionization multiple stage mass spectrometry (ESI-MSn). The obtained data were treated through chemometric tools [principal components analysis (PCA) and hierarchical cluster analysis (HCA)]. Multivariate analysis pointed to aporphine, proaporphine and tetrahydroprotoberberine alkaloids as the responsible compounds for segregation of the investigated species, being these alkaloids tentatively identificated by multiple stage mass spectrometry. The alkaloid fingerprint along with multivariate analysis provided a simple and effective approach to differentiateUnonopsis species commonly found in the state of Amazonas.

The continuous search for antimicrobial candidates pushes the pursuit of compounds in the most diverse organisms. Amphibians are known as a prolific source of antibacterial peptides. Based on the rich biodiversity of the Amazon region the unexplored green-tree frog (Hypsiboas cinerascens) was studied for its skin secretion peptide content. Chromatographic separations and established tandem mass spectrometry (MS/MS) methods were used for sequencing the primary structures of the purified compounds. De novo sequencing lead to the identification of five new peptides related to hylaseptin P1, displaying an aminated C-terminal. Sequencing of the complementary deoxyribonucleic acid (cDNA) analysis allowed the disambiguation of isobaric amino-acids for C-01. Matrix assisted laser desorption ionization (MALDI) was carried out, demonstrating the in situ co-occurrence of the identified peptides in the dorsal skin. The major peptide C-01 was synthesized and assayed against a selection of microorganisms displaying minimal inhibitory concentrations (MICs) ranging from 4 to 16 µM.

Polycarpol, a recurrent lanostane-type triterpene in Annonaceae family, was confirmed by thin layer chromatography and mass spectrometry analysis in the aerial parts (twigs and trunk barks) of Unonopsis duckei R.E. Fr., U. floribunda Diels, U. rufescens(Baill.) R.E. Fr., U. stipitata Diels, Onychopetalum amazonicum R.E. Fr. and Bocageopsis pleiospermaMaas. Its chemotaxonomic significance was discussed for these three genera, as well for the Annonaceae family. In addition, the antimicrobial activity against several strains of microorganisms was evaluated for the first time for this compound, being observed significant antibacterial activity against Staphylococcus aureus (ATCC 6538), Staphylococcus epidermidis (ATCC 1228) and Escherichia coli (ATCC 10538 and ATCC 10799) with minimal inhibitory concentration values between 25 and 50 μg ml−1.

Por meio de técnicas cromatográficas, um novo peptídeo aniônico, denominado otacidina, foi isolado das secreções cutâneas de três anuros brasileiros Osteocephalus taurinus. O sequenciamento de novo dos aminoácidos foi realizado por meio de análises por espectrometria de massas por tempo de vôo acoplada à ionização dessortiva de matriz por laser (MALDI-TOF-MS/MS). O potencial antimicrobiano deste novo metabólito foi avaliado contra cepas de Escherichia coli e Pseudomonas aeruginosa, sendo observadas concentrações inibitórias mínimas (MICs) de 37,4 e 78,4 mM, respectivamente. Este trabalho é apenas o segundo relato de um peptídeo aniônico com propriedades antimicrobianas, isolado da pele de um anfíbio.

By means of chromatographic techniques, a novel anionic peptide, named otacidin, was isolated from the skin secretions of tree Brazilian anurans Osteocephalus taurinus. The de novo sequencing of the amino acids was performed by matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF-MS/MS) analyses. The antimicrobial potential of this novel metabolite was evaluated against Escherichia coli and Pseudomonas aeruginosa, being observed minimum inhibitory concentration (MICs) of 37.4 and 78.4 mM, respectively. This work is just the second report of an antimicrobial anionic peptide from an amphibian.