A New ent-kaurene Diterpenoid Isolated from Leaves of Espeletia semiglobulata Cuatrec. and its Potential Antimicrobial Activity

The fraction of the neutral extraction leaves Espeletia semiglobulata Cuatrec. was subjected to chromatographic separation, it yielded four ent-kaurene type diterpenoids: three known [ent-kaur-16-en-19-al (I), ent-kaur-18-nor-16-en-4-ol (III), ent-kaur-16-en-19-ol (IV)] and a new one elucidated as ent-kaur-3-acetoxy-15-ene (II), based on physicochemical spectroscopic data FTIR, GC-MS, 1D 2D NMR. These compounds were antimicrobial bioassay studies. This showed significant inhibition potential against growth gram negative bacterial strains [Escherichia coli (ATCC 25922): 8 mm, Klebsiella pneumoniae 23357): 10 Pseudomonas aeruginosa 27853): mm], also fungal strain (Candida krusei: mm), at 2 mg/mL concentration. (III) (IV) failed show any results in screening five [Staphylococcus aureus 25923), Enterococcus faecalis 29212), 23357), Escherichia 25922) y 27853)] [Candida krusei 6558)]. reveal remarkable natural structure-activity relationship core regarding C-3 position (A ring perhydrophenanthrene unit), whose oxygenation or addition hydrogen bond acceptor donor group, improves activity.