O presente trabalho descreve o isolamento, a partir do caule de Annona amazonica, do ácido acantóico, um diterpeno do tipo pimaradieno que possui várias e importantes atividades biológicas descritas na literatura. Neste estudo foi verificado que este composto apresenta significante atividade tripanocida contra as formas epimastigotas de Trypanosoma cruzi. Também foi constatado que este diterpeno é o constituinte majoritário da planta, encontrado em cerca de 65% do extrato hexânico, demonstrando que A. amazonica é uma nova fonte natural renovável desta substância. Além do ácido acantóico, a investigação química resultou no isolamento dos alcalóides liriodenina e cassiticina, entre outros compostos, tais como terpenos, esteróides e ácidos graxos. Adicionalmente, é descrita a completa e inequívoca atribuição dos deslocamentos químicos de RMN de 1 H e 13 C da cassiticina.The present work reports the isolation of acanthoic acid, a promising pimaradiene-type diterpene with several important biological activities described in the literature, from the stems of Annona amazonica. We found that acanthoic acid has significant trypanocidal activity against the epimastigote forms of Trypanosoma cruzi. This diterpene is the major constituent of the plant, comprising at least 65% of the hexane extract, demonstrating that A. amazonica is a new renewable natural source for this compound. The chemical investigation also resulted in the isolation of the alkaloids liriodenine and cassythicine, and other compounds including terpenes, sterols, and fatty acids. Additionally, the complete and unequivocal 1 H and 13 C NMR chemical shift assignments for cassythicine are provided.
Keywords: Annona amazonica, Annonaceae, acanthoic acid, cassythicine, trypanocidal activity
IntroductionThe family Annonaceae, comprised of tropical and subtropical species with about 135 genera and more than 2500 species and widely distributed in South and Central America, Africa, Asia, and Australia, 1 is known for its edible fruits and the medicinal properties of several species. 2 In Brazil, there are 26 genera with about 260 species, including the genus Annona, which contains approximately 120 species. 3 Chemical investigations of species of Annonaceae have revealed their high chemical diversity in terms of secondary metabolites, such as alkaloids, acetogenins, terpenoids and lactones. These compounds have shown important biological activities, including antiparasitic, in particular against Leishmania sp., Plasmodium falciparum, and Trypanosoma cruzi. [4][5][6][7][8][9][10][11][12] Annona amazonica R.E. Fries is a tropical tree that grows up to 20-25 m tall and 35-60 cm in diameter, and is found from Panama to South America. In Brazil this species commonly occurs in the Amazon, mainly in the states of Amazonas and Pará. 13 To the best of our knowledge, only one previous phytochemical study has described the isolation and identification of cyanogenic constituents from this species. 14 Here we describe the isolation and structural identification of the chemica...
