It was demonstrated that anthraquinone-rich extracts, obtained from the phototoxic vegetal species Heterophyllaea

pustulata Hook f. (Rubiaceae), exhibited bacteriostatic activity on Micrococcus luteus ATCC 9341, selectively inhibiting

both oxacillin-sensitive and resistant Staphylococcus aureus, and antifungal activity against important opportunist

microorganisms and against those involved in superficial mycosis, all from nosocomial origin. The acute in vitro

both oxacillin-sensitive and resistant Staphylococcus aureus, and antifungal activity against important opportunist

microorganisms and against those involved in superficial mycosis, all from nosocomial origin. The acute in vitro

microorganisms and against those involved in superficial mycosis, all from nosocomial origin. The acute in vitro

cytotoxicity evaluation of each anthraquinone (AQ) isolated from these bioactive extracts, on a mammalian eukaryotic cell

line (Vero cells), allowed us to establish the non-cytotoxic concentration range, which was used to evaluate the

antimicrobial effect. Four from nine AQs tested, soranjidiol, rubiadin, damnacanthal and (S)-5,5'-bisoranjidiol, showed in

vitro bacteriostatic/bactericide activity against S. aureus. The action mechanism seems to involve an increase in the levels

of superoxide anion and/or singlet oxygen molecular. Moreover, the effect of actinic irradiation as a boosting agent for the

of superoxide anion and/or singlet oxygen molecular. Moreover, the effect of actinic irradiation as a boosting agent for the

production of both reactive oxygen species as well as its influence on antibacterial effect was assessed.