Antiproliferative effects of compounds derived from plants of Northeast Brazil

Ten compounds derived from plants indigenous to Northeast Brazil were exami ned for antiproliferative effects on human cells in vitro. The effects of t hese phytochemicals on cell growth were determined by the MTT microtitre as say with 3-day continuous drug exposure, Three human cell lines were used: CEM leukaemia, SW1573 lung tumour and CCD922 normal skin fibroblasts, Four active compounds were found with IC50 values less than 10 mu g/mL in the tw o cancer cell lines. Oncocalyxones A and C, both 1,4-anthracenediones from Auxemma oncocalyx (Boraginaceae), showed cytotoxicity with mean IC50 values of 0.8-2, 7-8 and 12-13 mu g/mL against GEM, SW1573 and CCD922, respective ly. One diterpene and one flavonoid, both from Egletes viscosa (Compositae) , were also active. 12-Acetoxy-hawtriwaic acid lactone was cytotoxic with m ean IC50 values of 6, 10 and 10 mu g/mL, respectively, 4,5-Dihydroxy-3,3,7, 8-tetramethoxy flavone (ternatin) was only growth-inhibitory with mean IC50 values of 2, 1 and 10 mu g/mL, respectively, These four most active compou nds were examined further for their effects on DNA integrity and on DNA syn thesis. All but ternatin caused substantial DNA damage and marked inhibitio n of 5-bromo-2'-deoxyuridine incorporation within 24 h, This study demonstr ated the antiproliferative activity of four novel phytochemicals, three of which are DNA-reactive and inhibit DNA synthesis, Further studies are warra nted to evaluate these compounds for antitumour potential. Copyright (C) 20 00 John Wiley & Sons, Ltd.