<scp> <i>Pinus nigra</i> </scp> and <scp> <i>Pinus brutia</i> </scp> Extracts Inhibit Quorum Sensing in <scp> <i>Pseudomonas aeruginosa</i> PAO1 </scp> with Minimal Impact on Fibroblast Cell Viability and Calcium Deposition

ABSTRACT Pine species, beyond their use in the wood industry, are valuable sources of bioactive compounds. This study investigates the effects of methanol extracts from Pinus nigra ( P. nigra ) and Pinus brutia ( P. brutia ) on quorum sensing (QS) activity and related genes in Pseudomonas aeruginosa ( P. aeruginosa ). Additionally, we examined their impact on the viability and calcium deposition of L929 fibroblast cells, a primary skin cell type. The anti‐QS activity of the extracts was assessed through elastase and pyocyanin production assays and qRT‐PCR analysis. Cell viability and calcium deposition were evaluated using MTT, Alamar Blue, and Alizarin Red staining assays. Results showed that P. nigra and P. brutia extracts inhibited pyocyanin production by 73% and 72%, respectively, and elastase production by 23%–26%. Additionally, a significant reduction was observed in the expression levels of the lasI, lasR, rhlI, and rhlR QS genes in P. aeruginosa . Both extracts showed minimal cytotoxic effects on fibroblasts and only slightly reduced cell viability and calcium deposits at high doses (100–400 μg/mL). These findings suggest that while the extracts have minimal cytotoxicity on fibroblasts, they exhibit significant QS inhibitory activity against P. aeruginosa PAO1, indicating potential use in treating skin‐related infectious diseases. Further characterization of these extracts may lead to new therapeutic agents derived from Pinus species.