Abstract
ent-16-Kauren-19-oic acid is a bacteriolytic diterpenoid present in the resin of the
medicinal plant Pseudognaphalium vira vira. The compound and its methyl ester showed strong activity against gram-positive bacteria,
whereas the derivative 3β-hydroxy-ent-kauren-19-oic acid was inactive against all assayed bacteria at the maximal concentration
used (250 µg/mL). The bacteriolytic effect of ent-16-kauren-19-oic acid (5 µg/mL) was confirmed with cultures of Bacillus cereus and Staphylococcus aureus, whereas the methyl derivative (12 µg/mL) showed only a bacteriostatic effect. Both
compounds stimulated oxygen consumption and proton conduction of whole cells, as reflected
by an abrupt increase in the extracellular pH. These results indicate that ent-16-kauren-19-oic acid acts as a respiratory chain uncoupler, and that this function
is strongly affected by minor structural substitutions, suggesting a tight activity-structure
relationship. The ultimate effect of the uncoupling mechanism demonstrated by ent-16-kauren-19-oic acid is bacterial lysis. The disruption of the bacterial membrane
integrity caused by the diterpenoid compound was determined using SYTOX Green stain
and visualized by fluorescence microscopy.
Key words
ent‐16‐kauren‐19‐oic acid -
Pseudognaphalium vira vira
- Asteraceae - diterpenoid - antibacterial activity - respiratory chain uncoupler
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Dr. Marcela Wilkens
Departamento de Biología
Facultad de Química y Biología
Universidad de Santiago de Chile
Casilla 40
Correo 33
Estación Central
Santiago
Chile
Telefon: + 56 27 18 11 21
Fax: + 56 26 81 21 08
eMail: mwilkens@usach.cl