In this communication the antibacterial activity of filifolinol (1), naringenin (2) 3-O-methylgalangin (3) and pinocembrin (4) isolated from the resinous exudates of Heliotropium filifolium and H. sinuatum, were evaluated by flow cytometry against Staphylococcus aureus and Salmonella tiphymurium. The results showed that filifolinol (1) and naringenin (2) were inactive in the range of concentrations used (10 to 1000 μg/mL). On the other hand, pinocembrin (4) produced a decrease in cell surface at 500 μg/mL and the total disappearance of both bacterial populations at 1000 μg/mL. Also, 3-O-methylgalangin (3) showed the total disappearance at 1000 μg/mL of both bacterial populations and a decrease at 200 μg/mL for S. typhimurium and at 500 μg/mL for S. aureus
