Antimicrobial terpenes from oleoresin of ponderosa pine treePinus ponderosa: A defense mechanism against microbial invasion

The oleoresin of the ponderosa pine,Pinus ponderosa (Pinaceae) exhibited broad antimicrobial activity. In order to identify the active compounds, the oleoresin was steam distilled to give a distillate and residue. The distillate contained mainly monoterpenes and some sesquiterpenes, while the residue consisted chiefly of four structurally related diterpene acids. An antimicrobial assay with the pure compounds indicated that the monoterpenes were active primarily against fungi, but there was also some activity against gram-positive bacteria. The diterpene acids, in contrast, only exhibited activity against gram-positive bacteria. Although not all of the identified sesquiterpenes could be tested, longifolene showed activity only against gram-positive bacteria. Therefore, it appears that the oleoresin ofP. ponderosa functions as a biochemical defense against microbial invasion.