Anti-inflammatory, antioxidant, and antitermite valorization of extractable substances from the heartwood of four major species of the Gabonese forest-timber sectors

The aim of this study was to focus on the chemical characterization and the anti-inflammatory, antioxidant, and anti-termite properties of extractable substances from the heartwood of Tieghemella africana, Testulea gabonensis, Staudtia kamerunensis, Entandrophragma utile in Gabon with a view to their valorization. The results of cold maceration extractions revealed that the extractable content varies with wood species and solvent. The high extract contents were obtained with acetone and ethanol, except for S. kamerunensis where the levels of dichloromethane and water extracts were high, respectively, 3.40 and 6.35%. E. useful showed a high content with dichloromethane (4.15%). Phytochemical screening indicated the presence in the acetonic, ethanolic, and water extracts of the wood species several groups of bioactive molecules, such as polyphenols, flavonoids, free quinones, sterols and triterpenes, and saponins. The results of the total phenols assay corroborated those obtained during the phytochemical screening. The results of anti-inflammatory, antioxidant, and anti-termite activities revealed that they vary with wood species, solvent, and concentration in terms of anti-termite activity. The strong anti-inflammatory activities were recorded with the ethanolic, acetonic, and water extracts where the EC50 values of all the essences were the lowest and close to that of our control, diclofenac (555.25 μg/mL). The ethanol extracts of the wood species showed strong activities, particularly those of S. kamerunensis and E. useful where we obtained low EC50 values of 604.13 and 602.38 μg/mL, respectively. The strong antioxidant activities were recorded with the acetonic, ethanolic extracts of S. kamerunensis and E. useful whose respective EC50 values (6.50 and 4.50 μg/mL) for S. kamerunensis and (4.50 and 3.01 μg/mL) for the E. useful. Similarly, the water extract of E. useful whose value is close to that of gallic acid (0.40 μg/mL) our control. The antitermite activity revealed that the acetone and ethanol extracts of the wood species and the water extract of E. useful at 20 mg/mL showed interesting antitermite activities. The strongest activities were recorded with the dichloromethane extracts of the wood species, where the survival rates of the termites were the lowest. Particularly with the dichloromethane extract of E. useful with a survival rate of 30% at 10 mg/mL and 1.70% at 20 mg/mL.