Chemical Constituents of Papulaspora immersa, an Endophyte from Smallanthus sonchifolius (Asteraceae), and Their Cytotoxic Activity

Papulaspora immersa H. H. HOTS ON was isolated from roots and leaves of Smallanthus sonchifolius (POEPP. and ENDL.) H. ROB. (Asteraceae), traditionally known as Yacon. The fungus was cultured in rice, and, from the AcOEt fraction, 14 compounds were isolated. Among them, (22E,24R)-8,14-epoxyergosta-4,22-diene-3,6-dione (4), 2,3-epoxy-1,2,3,4-tetrahydronaphthalene-c-1,c-4,8-triol (10), and the chromone papulasporin (13) were new secondary metabolites. The spectral data of the known natural products were compared with the literature data, and their structures were established as the (24R)stigmast 4 en 3 one (1), 24-methylenecycloartan-3 beta-ol (2), (22E,24R)-ergosta-4,6,8(14),22-tetraen-3-one (3), (-)-(3R,4R)-4-hydroxymellein (5), (-)-(3R)-5-hydroxymellein (6), 6,8-dihydroxy-3-methylisocoumarin (7), (-)-(4S)-4,8-dihydroxy-alpha-tetralone (8), naphthalene-1,8-diol (9), 6,7,8-trihydroxy-3-methylisocoumarin (11), 7-hydroxy-2,5-dimethylchromone (12), and tyrosol (14). Compound 4 showed the highest cytotoxic activity against the human tumor cell lines MDA-MB435 (melanoma), HCT-8 (colon), SF295 (glioblastoma), and HL-60 (promyelocytic leukemia), with IC(50) values of 3.3, 14.7, 5.0 and 1.6 mu m, respectively. Strong synergistic effects were also observed with compound 5 and some of the isolated steroidal compounds.

Fundacao de Amparo a Pesquisa do Estado de Sao Paulo (FAPESP)[04/07935-6]

Fundacao de Amparo a Pesquisa do Estado de Sao Paulo (FAPESP)[08/09540-0]

Fundacao de Amparo a Pesquisa do Estado de Sao Paulo (FAPESP)[05/56259-6]

Conselho Nacional de Desenvolvimento Cientifico e Tecnologico (CNPq)

Financiadora de Estudos e Projetos (FINEP)

Coordenacao de Aperfeicoamento de Pessoal de Nivel Superior (CAPES)