Anticancer activities as well as antiviral and virus-enhancing properties of aqueous fruit extracts from fifty-six European plant species.

Several plant-derived drugs are used in medical oncology today. Since only a small part of the flora has been tested for any kind of bioactivity intensive further screening may be rewarding. Fifty-six plant extracts were studied attempting to explore the feasibility of an assay that screens cytotoxic, antiviral and virus-enhancing activities in the same test. We made use of the property of an avian influenza virus replicating in a human breast cancer cell line. During the first 3 days of the test the cytotoxicity of the extracts was evaluated by phase-contrast microscopy. From the 4th day on when viral cytopathogenic effect became manifest we were able to identify antiviral and virus-enhancing activity among some of those extracts not showing cytotoxicity during the first 3 days of incubation. Aqueous extracts from the fruits of 56 plant species belonging to 22 families were screened. Twelve species exhibited cytotoxic, eight antiviral, five virus-enhancing and 31 no activity. These results show that the replication of a myxovirus in a human tumor cell offers the possibility of screening cytotoxic, antiviral and virus-enhancing activity in the same assay.