Bioguided identification of antifungal and antiproliferative compounds from the Brazilian orchid Miltonia flavescens Lindl.

The Orchidaceae family is appreciated worldwide for the beauty of its flowers, and hundreds of species of this family occur in Brazil. Yet little is known about the potential of orchids for therapeutic application. We have investigated bioactive compounds produced by the South Brazilian orchid Miltonia flavescens Lindl. Bioguided studies with the fungus Cladosporium herbarum allowed the identification of hydrocinnamic acid as the active antifungal compound. In addition, the chloroform fraction exhibited an interesting activity against human cancer cells, and 5,7-dihydroxy-6,4'-dimethoxyflavone isolated from this fraction was found to be active against seven human cancer cell lines, including NCI/ADR-RES ovary sarcoma, with an IC50 value of 2.6 microg/mL. This is the first report on the cytostatic activity of this flavone against human ovary sarcoma.