Impact of natural degradation on the phenolic profile of pedunculate oak stump (Quercus robur L.): Insights from HPTLC and spectrophotometric assays

The pedunculate oak (Quercus robur L.) is rich in extractives, especially in its heartwood, stumps, and bark, making it valuable to bio-based industries. Due to this reason and the increasing demand for efficient wood utilization, this study investigated the extractives of stumps remaining after freshly cut trees and Q. robur trees cut two years prior. During these two years, the stumps were exposed to various weather conditions (precipitation, UV radiation, and others) and the action of fungi, bacteria, and other pathogenic organisms. These factors contributed to the natural degradation of the wood and the disruption of the original chemical structure of the stumps. Water extracts from the xylem and bark of freshly cut and biodegraded Q. robur stumps were analyzed for total phenols, activity against H2O2, and free radical scavenging activity. Total phenol content was higher in degrading Q. robur stumps, with 71.70 and 59.17 mg gallic acid equivalents/g dry wood in bark and xylem, respectively. Degrading Q. robur stump bark and xylem showed higher antioxidant activity, with IC50 values against H2O2 of 682.39 µg/mL and 923.90 µg/mL, and free radical scavenging activity of 91.97% and 83.98%, respectively. High-performance thin-layer chromatography fingerprinting profile of xylem and bark extracts revealed different chemical profiles, while the HPTLC-DPPH scavenging assay evaluated antioxidant activity in extracts. This research showed that extracts from the bark and xylem of the degrading stump are stronger radical scavengers and have a richer phenolic profile than extracts from a freshly cut stump. Degrading Q. robur stumps may represent a valuable source of polyphenols.