A Comparative Study of the Chemical Compositions of Heartwood and Sapwood in Erythrophleum fordii

The chemical composition, lignin structure, and extractive profiles of sapwood and heartwood were studied for 18-year-old Erythrophleum fordii trees to elucidate their chemical disparities and potential for high-value utilization. The cellulose, hemicellulose, and lignin contents were higher in sapwood than in heartwood. In contrast, heartwood exhibited significantly higher ash content, moisture content, and yields of various extractives, along with greater acidity. FTIR spectroscopy revealed SG-type lignin in both sapwood and heartwood, dominated by syringyl units. Heartwood formation did not alter the fundamental lignin structure but increased its condensation degree and reduced the characteristic hemicellulose absorbance. Notably, the heartwood was the primary site for bioactive constituent enrichment, with total phenolic and flavonoid contents (19.9 mg GAE/g DW and 36.5 mg RE/g DW, respectively) 4.3 and 5.6 times higher than those in sapwood. GC-MS analysis further showed that heartwood extractives were rich in terpenoids and sterols (e.g., vitamin E, stigmasterol, and β-sitosterol), compounds known for their antioxidant, cholesterol-lowering, and pharmaceutical properties. These findings underscore the potential of E. fordii heartwood for developing functional natural products and as a source of pharmaceutical raw materials.