ANTIMICROBIAL STUDY OF THE RESINOUS EXUDATES AND OF DITERPENOIDS AND FLAVONOIDS ISOLATED FROM SOME CHILEAN PSEUDOGNAPHALIUM (ASTERACEAE)

The antimicrobial properties of the resinous exudates from twigs and l eaves of four Chilean species of Pseudognaphalium: P. viravira, P. rob ustum, P. heterotrichium and P. cheiranthifolium were tested against s ix Gram negative bacteria and five Gram positive bacteria. The extract s share similar antimicrobial activities against the Gram positive bac teria. The antimicrobial activity correlated very well with the presen ce in the resinous exudates of ent-16-kauren-19-oic acid and to a less er extent with the presence of ent-9(11),16-kauradien-19-oic. Introduc tion of an hydrophilic 3 beta-OH drastically reduced the antimicrobial activity of these compound. The activity was not correlated with the flavonoid content of those resinous exudates. (C) 1997 Elsevier Scienc e Ireland Ltd.