Leishmanicidal compounds of Nectria pseudotrichia, an endophytic fungus isolated from the plant Caesalpinia echinata (Brazilwood)

BACKGROUND In a screen of extracts from plants and fungi to detect antileishmanial activity, we found that the ethyl acetate extract of the fungus Nectria pseudotrichia, isolated from the tree Caesalpinia echinata (Brazilwood), is a promising source of bioactive compounds. OBJECTIVES The aims of this study were to isolate and determine the chemical structures of the compounds responsible for the antileishmanial activity of the organic extract from N. pseudotrichia. METHODS Compounds were isolated by chromatographic fractionation using semi-preparative high-performance liquid chromatography, and their chemical structures were determined by analytical and spectral data and by comparison with published data. The antileishmanial activity of the isolated compounds was evaluated in intracellular amastigote forms of Leishmania (Viannia) braziliensis expressing firefly luciferase as reporter gene, and cytotoxicity was determined in Vero and THP-1 mammalian cell lines by MTT assay. FINDINGS Fractionation of the extract yielded seven compounds: 10-acetyl trichoderonic acid A (1), 6′-acetoxy-piliformic acid (2), 5′,6′-dehydropiliformic acid (3), piliformic acid (4), hydroheptelidic acid (5), xylaric acid D (6), and cytochalasin D (7). Compounds 1, 2 and 3 are reported here for the first time. Compounds 1, 2, and 5 were more active, with IC50 values of 21.4, 28.3, and 24.8 µM, respectively, and showed low toxicity to Vero and THP-1 cells. MAIN CONCLUSIONS N. pseudotrichia produces secondary metabolites that are more toxic to intracellular amastigote forms of L. (V.) braziliensis than to mammalian cells.

Synthesis and cytotoxicity evaluation of thiosemicarbazones and their thiazole derivatives

ABSTRACT The aims of this study were to synthesize a series of thiosemicarbazones and their thiazole derivatives, to investigate their cytotoxic activity against three human cancers and normal (Vero cells) cell lines, and to evaluate the pro-apoptotic potential of the most active compounds. Materials and Methods: The thiosemicarbazones were obtained by reacting an aromatic aldehyde with thiosemicarbazide (yield 71-96%), which were subjected to a cyclization with α-bromoacetophenone to yield the required thiazole heterocycles (yield 63-100%). All the synthesized compounds were screened at 50 µM concentration against three cell lines representing HL60 (promyelocytic leukemia), Jurkat (acute lymphoblastic leukemia), and MCF-7 (breast cancer). The pro-apoptotic effect was measured by flow cytometry as the percentage of cells with hypodiploid DNA. Results: Three thiazole compounds showed activity against at least one tumor cell line (IC50 = 43-76 µM) and low cytotoxicity against Vero cells (IC50 > 100 M). The most active compound of this series induced 91% and 51% DNA fragmentation in HL60 and MCF-7 cell lines, respectively, suggesting that this compound triggered apoptosis in these cells. Conclusion: Among the synthesized compounds, one in particular was found to exert antiproliferative and pro-apoptotic activity on tumor cells and can be considered promising as a lead molecule for the design of new analogues with improved activity.

RESUMO O estudo teve como objetivo a síntese de uma série de tiossemicarbazonas e seus derivados tiazólicos e a avaliação da atividade citotóxica contra três linhagens de células tumorais humanas e células normais (Vero), a fim de se avaliar o potencial pró-apoptótico dos compostos mais ativos. As tiossemicarbazonas foram obtidas por reação entre um aldeído aromático e tiossemicarbazida (rend. 71-96%), as quais foram submetidas à ciclização com α-bromoacetofenona, fornecendo os heterociclos tiazólicos desejados (rend. 63-100%). Todos os compostos sintetizados foram testados na concentração de 50 µM contra três linhagens de células tumorais: HL60 (leucemia promielocítica), Jurkat (leucemia linfoblástica aguda) e MCF-7 (câncer de mama). O efeito pró-apoptótico foi avaliado por citometria de fluxo como porcentagem de células com DNA hipodiplóide. Três compostos tiazólicos foram ativos contra, pelo menos, uma linhagem tumoral (CI50=43-76 µM), com baixa citotoxicidade contra células Vero (CI50 > 100 M). O composto mais ativo dessa série induziu fragmentação do DNA de 91% e 51% nas linhagens HL60 e MCF-7, respectivamente, sugerindo que este composto ativou a apoptose nessas células. Dentre os compostos sintetizados, um em particular apresentou atividade antiproliferativa e pró-apoptótica em células tumorais e pode ser considerado composto protótipo promissor na busca por novos análogos com atividade melhorada.