CYTOTOXIC ACTIVITY OF A METHANOL EXTRACT OF PHALLUSIA-NIGRA (TUNICATA, ASCIDIACEA)

Tunicates have been reported to be a rich source of biologically activ e compounds. In this study, we demonstrate the presence of cytotoxic s ubstances in Phallusia nigra, a common tunicate from Brazilian coastal waters, An extract of tunicate tissue was obtained by homogenizing th e visceral organs from 50 specimens in methanol, followed by filtratio n and concentration in a rotary vacuum evaporator. Finally, the concen trate was partitioned with chloroform to remove lipids. The resulting extract possessed antimitotic and hemolytic activity. The former was d emonstrated as a delay in the development of sea urchin eggs by partia lly inhibiting the process of cleavage (first cleavage, EC(50) +/- SEM = 3.44 +/- 0.84 mg/ml). The <500 molecular fraction of the extract ob tained by ultrafiltration also inhibited cell proliferation (the numbe r of viable cells was decreased by 68% with 500 mu g/ml) and DNA synth esis of T47D cells derived from human breast carcinoma as measured by [H-3]-thymidine incorporation (66% of the control value after 24-h inc ubation with 100 mu g/ml). Dose-dependent hemolysis obtained with P, n igra extract on mouse erythrocytes had an EC(50) +/- SEM = 1.12 +/- 10 .02 mg/ml for a 0.5% erythrocyte suspension. Hemolysis could be reduce d by pre-incubating the cells with choline-containing phospholipid. Sp hingomyelin (40 mu g/ml) increased the EC(50) by twofold to 2.86 +/- 0 .04 mg/ml, but phosphatidylcholine (80 mu g/ml) did not modify hemolys is.