Stéphane Dumarçay

The current study focused on extract content, phytochemical screening, GC-MS analysis, infrared analysis and antioxidant activity evaluation of bark, sapwood and heartwood of Letestua durissima, commonly called Kong Afane in Gabon, using DPPH and ABTS methods. The highest extract contents, reaching 37.3%, were observed in the bark. Phytochemical tests revealed the presence of alkaloids, polyphenols, sterols, terpenes, flavonoids and saponins in the extracts. The quantitative results highlighted high concentrations of polyphenols (95.56 mg GAE g−1 of dry extract in the acetone extract), condensed tannins (113.45 mg CE g−1 of dry extract in the extract toluene–ethanol) and flavonoids (20.26 mg CE g−1 of dry extract in the toluene–ethanol extract) in the bark. Regarding the evaluation of antioxidant activity, the results showed a significant capacity of the extracts to scavenge free radicals. This activity was more pronounced in the toluene–ethanol extracts, with an IC50 of 0.66 for the ABTS method and 2.39 for that of DPPH. The GC-MS identification of phenolic compounds such as hydroxybenzoic acid, protocatechuic acid, gallic acid, catechin and triterpenes could explain the high reactivity of our extracts as antioxidants.

Intraspecific macromolecule variation in stemwood, knotwood, and branchwood was studied using analytical pyrolysis with the intention of introducing a rapid working method to assess the variance in lignin content using analytical pyrolysis and highlight variability markers. The study was performed on Picea abies, Abies alba, and Pseudotsuga menziesii. Lignin determined via analytical pyrolysis–GC/MS (Py-lignin) can be used to identify variations in lignin content, compared to using classical Klason lignin values as a reference method for lignin determination, which requires a correction factor. Principal component analysis (PCA) was performed to identify biopolymer pyrolysis product markers for different species, tissues, or heights that could help highlight structural differences. Douglas fir was differentiated from spruce and silver fir in the levoglucosan amount. Guaiacol was more present in spruce wood, and creosol was more present in Douglas fir. Knotwood was structurally close to stemwood in spruce and silver fir, but there was a clear transition between stemwood and branchwood tissue in Douglas fir. Knotwood was differentiated by higher furan compounds. Branchwood was clearly separate from stemwood and knotwood and presented the same markers as compression wood in the form of phenylpropanoid lignins (H-lignin) as well as isoeugenol and vinyl guaiacol, the two most produced lignin pyrolysis products.