Abstract
The opportunistic pathogen Acinetobacter baumannii is a particularly problematic nosocomial threat worldwide, leading to high morbidity and mortality rates due to its multiple resistance mechanisms, including the production of lipolytic enzymes. Herein, the aerial parts of three coniferous plants, Pinus canariensis C. Sm. (PC), Cupressus lusitanica Mill. (CL), and Cupressus arizonica Greene. (CA), were extracted and fractionated. Among these, the CA extract followed by CL and then PC, exhibited the highest inhibition of bacterial lipase activity, with half-maximal inhibitory concentration (IC(50)) values of 1117 ± 87, 1278 ± 62, and 1926 ± 104 µg/mL, respectively. The methylene chloride fractions of CA and CL extracts exhibited the highest inhibition of bacterial lipase activity, with IC(50) (940 ± 25 µg/mL and 1103 ± 155 µg/mL), respectively. The metabolite profile of the three extracts, along with their most active fractions, were determined using liquid chromatography-quadrupole-time-of-flight tandem mass spectrometry (LC-QTOF-MS/MS). Interestingly, the metabolite profiles of CL extracts were established here for the first time. A total of 99 secondary metabolites from diverse classes were identified across all samples. Among these, four metabolites were isolated: 3,5-di-p-coumaroylquinic acid, epicatechin, cupressuflavone, and rutin. The biflavonoid cupressuflavone showed the lowest IC(50) value (3812 ± 450 µg/mL). Additionally, partial least squares was applied to assess the key metabolites contributing to the differentiation of the studied bioactivity. Consequently, this study provides novel insights into the bioactivity potential of coniferous plants, demonstrating their value as a natural source of antivirulence agents against the A. baumannii lipase enzyme.