Investigations were undertaken on the antiviral action of an hydroalco
holic extract from Haemanthus albiflos bulb, reported here as an effic
ient agent against RNA viruses. Poliovirus propagated on HeLa cells wi
th different concentrations of the extract was used in the assays. The
effect on cellular RNA, DNA and protein synthesis as well as on viral
RNA synthesis was evaluated by measuring the radioactivity incorporat
ed using labelled precursors. A 0.2 muL/mL concentration of the plant
extract showed an inhibition of cellular RNA, DNA and protein synthesi
s compared with the control of 44%, 40% and 52%, respectively. At the
same concentration a 90% decrease of the viral RNA synthesis was obser
ved over 210 min.