Correlation of antioxidant and antibacterial activities of the aqueous Pinus pinaster Aiton bark extract within a cytocompatible concentration range

Abstract

This study explores the antioxidant, antibacterial, and cytocompatibility properties of aqueous Pinus pinaster bark extract (PBE). PBE was prepared using two solvent systems—100% distilled water and 1% DMSO in aqueous solution—at a solid-to-liquid ratio of 1:20 (w/v), following ISO guidelines. Extract characterization included yield determination, FTIR analysis, quantification of total phenolic (TPC) and flavonoid (TFC) contents, and assessment of antioxidant activity using four complementary methods: free radical scavenging (DPPH and ABTS), metal ion reduction (FRAP), and a competitive reaction assay (ORAC). The phenolic compound profile was further examined by HPLC-DAD. The results indicated that the two extracts exhibited comparable values across all evaluated parameters when expressed per gram of PBE. The TPC and TFC were approximately 400 mg GAE (gallic acid equivalents)/g PBE and 92 mg CE (catechin equivalents)/g PBE, respectively. Antioxidant capacity values were about 880, 1030, 3210, and 585 mg TE (Trolox equivalents)/g PBE for the DPPH, ABTS, ORAC, and FRAP assays, respectively. Furthermore, in both extracts, the phenolic and flavonoid contents exhibited strong positive correlations with antioxidant activity across all four chemical assays. The 100% aqueous extract was additionally evaluated for antibacterial activity and cytocompatibility with eukaryotic cells. Compared to the control, the extract demonstrated IC50 values of 0.304, 0.678, and 0.845 mg/mL PBE for the inhibition of Staphylococcus aureus, Escherichia coli, and fibroblast cells, respectively. Antioxidant and antibacterial activities showed a positive association within concentration ranges that remained non-cytotoxic to fibroblasts. Overall, these findings indicate that the aqueous PBE retains cytocompatibility across a wide concentration range while maintaining both antioxidant and antibacterial activities, underscoring its potential for biological applications involving direct contact with eukaryotic cells.