LC-MS application in dereplication studies of Phorbas amaranthus extract.

LC-MS application in dereplication studies of Phorbas amaranthus extract.
Fernanda B. da Silva1, Alessandra L. Valverde2, Quezia B. Cass3, Letícia S. S. Schmitz4, Dhiego B. Rigato4, Paula C. Jimenez4, Letícia V. Costa-Lotufo5, Roberto C.C. Martins1
1. Instituto de Pesquisa de Produtos Naturais Walter Mors- UFRJ-Rio de Janeiro, RJ, Brazil
2. Instituto de Química, Universidade Federal Fluminense, Niterói, RJ, Brazil
3. Departamento de Química – UFSCar, São Carlos, SP, Brazil
4.Departamento de Ciências do Mar- UNIFESP, Santos, SP, Brazil
5. Departamento de Farmacologia- USP, São Paulo, SP, Brazil
[email protected]

Phorbas sponges are known to be rich sources of structurally unique and biologically active secondary metabolites. For the genus Phorbas, substances such as phorbazoles, phorbasides1, phorboxazoles2, phorbasin3, gagunins, e phorbaketals4 have been identified. Among the substances already described specifically for P. amaranthus specie are: anthosterones, phorbasterones5 and amaranzole3. Herein, specimens of P. amaranthus were collected in Fernando de Noronha and the extract was obtained from maceration with ethanol and methanol/ethyl acetate 1:1. The extract was evaluated for antitumor activity against the HCT-116 (colorectal carcinoma) and MCF-7 (breast carcinoma) human cell lines, through the MTT assay. Dereplication was applied to the crude extract. Liquid chromatography coupled with the high resolution mass spectrometer QToF mass was employed. The mass spectrum showed a large amount of signals, which indicates the diversity of metabolites present in the extract. For error calculation the following formula was used E = (theoretical value - experimental value / theoretical value) x 100 and considered 5ppm as error limit.
The extract showed cytotoxic activity against HCT-116 (inhibition at 50ug/mL >95%) and MCF-7 (inhibition at 50ug/mL >80%) cells. Phorbasides (except phorbaside B) and phorbasterones, have already showed good cytotoxic results for HCT-116 cells1,5 and could be the compounds responsible for this activity. Thus, studies to identify and isolate the active substances are underway.
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