Anti-Inflammatory, Antibacterial, Anti-Biofilm, and Anti-Quorum Sensing Activities of the Diterpenes Isolated from Clinopodium bolivianum

This study reports for the first time the isolation of four diterpenoid compounds: 15-Hydroxy-12-oxo-abietic acid (1), 12 alpha-hydroxyabietic acid (2), (-)-Jolkinolide E (3), and 15-Hydroxydehydroabietic acid (4) from Clinopodium bolivianum (C. bolivianum). The findings demonstrate that both the dichloromethane/methanol (DCMECB) extract of C. bolivianum and the isolated compounds exhibit significant anti-inflammatory (inhibition of NF-kappa B activation), antibacterial (primarily against Gram-positive bacteria), and anti-biofilm (primarily against Gram-negative bacteria) activities. Among the isolated diterpenes, compounds 3 and 4 showed notable anti-inflammatory effects, with IC50 values of 17.98 mu M and 23.96 mu M for compound 3, and 10.79 mu M and 17.37 mu M for compound 4, in the HBEC3-KT and MRC-5 cell lines. Regarding their antibacterial activity, compounds 3 and 4 were particularly effective, with MIC values of 0.53-1.09 mu M and 2.06-4.06 mu M, respectively, against the S. pneumoniae and S. aureus Gram-positive bacteria. Additionally, these compounds demonstrated significant anti-biofilm and anti-quorum sensing activities, especially against Gram-negative bacteria (H. influenzae and L. pneumophila). We also explain how compound 3 (BIC = 1.50-2.07 mu M, Anti-QS = 0.31-0.64 mu M) interferes with quorum sensing due to its structural homology with AHLs, while compound 4 (BIC = 4.65-7.15 mu M, Anti-QS = 1.21-2.39 mu M) destabilises bacterial membranes due to the presence and position of its hydroxyl groups. These results support the traditional use of C. bolivianum against respiratory infections caused by both Gram-positive and Gram-negative bacteria. Furthermore, given the increasing antibiotic resistance and biofilm formation by these bacteria, there is a pressing need for the development of new, more active compounds. In this context, compounds 3 and 4 isolated from C. bolivianum offer promising potential for the development of a library of new, more potent, and selective drugs.