Antibacterial and In Silico Evaluation of β -lactamase Inhibitory Potential of Pinus sylvestris L. (Scots Pine) Essential Oil

Antibiotic resistance remains one of the global challenges that needs urgent attention, including finding alternative treatment options to conventional antibiotics and reversing resistance. Pinus sylvestris L. ( Pinaceae ) essential oil (EO) has several biological properties. In this study, the EO of P. sylvestris was extracted by hydro-distillation method, and twenty-six chemical constituents of the EO identified by gas chromatography-mass spectrophotometry were screened as potential inhibitors of β -lactamase in silico by molecular docking. Antibacterial activity of the EO against thirteen bacterial isolates was further evaluated. Terpineol was identified as the major phytoconstituent of the P. sylvestris needles EO. From the docking analysis, benzene, 1,3-bis(3-phenoxyphenoxy) and dichloroacetic acid, 1-adamantylmethyl ester showed good inhibitory potentials against AmpC and OXA-23 β -lactamase, respectively, binding to the important catalytic serine residues (Ser64 and Ser79, respectively) with lower binding affinity energies (benzene, 1,3-bis(3-phenoxyphenoxy) = −10.1 kcal/mol and dichloroacetic acid, 1-adamantylmethyl ester = −8.4 kcal/mol) compared to the FDA-approved β -lactamase inhibitor, avibactam (−6.5 and −6.6 kcal/mol for AmpC and OXA23 β -lactamase, respectively). The EO inhibited the growth of all the tested bacteria. Klebsiella pneumoniae and Micrococcus luteus were the most susceptible bacteria with an inhibition zone (ZI) of 24 mm each, while the ZI obtained for Proteus vulgaris was the lowest (ZI = 8 mm). The results obtained in this study showed that EO of P. sylvestris has potential as a treatment option for broad-spectrum bacterial infections and in the management of β -lactamase-related antibiotic resistance.