Diterpenes of the pimarane type isolated from Viguiera arenaria: Promising in vitro biological potential as therapeutic agents for endodontics

Viguiera arenaria, family Asteraceae, is a plant that contains diterpenoids, which make this species potentially applicable in endodontics. More specifically, V. arenaria contains diterpenes of the pimarane type, which display various classic biological activities. This study evaluates the antibiofilm activity, the time-kill curve, and the inhibitory concentration index of diterpenes of the pimarane type (ent-pimara-8(14),15-dien-19-oic acid, ent-8(14),15-pimaradien-3β-ol, and ent-8(14),15-pimaradien-3β-19-oic acid sodium salt, designated diterpenes I, II, and III, respectively) toward nine anaerobic bacteria commonly found in endodontic infections; this study also assesses the cytotoxic activity of these diterpenes against human fibroblasts. According to the antibiofilm assay, diterpenes I, II, and III inhibit at least 50% of all the bacteria. On the basis of the time-kill curve experiments, the behavior of these diterpenes depends on the tested bacteria, diterpene concentration, and microorganism sensitivity. Synergism of diterpenes I and II with chlorhexidine (CDH) was higher against P. gingivalis (clinical isolate) and Aggregatibacter actinomycetemcomitans (ATCC). As for diterpene III, synergism with CDH is higher against P. micros. As revealed by the XTT assay, none of the diterpenes of the pimarane type tested here are cytotoxic. Hence, diterpenes I, II, and III are promising biomolecules and may provide therapeutic solutions in the field of endodontics. Key words: Antibacterial activity, Asteraceae, cytotoxicity, diterpenes, endodontic infection.