Phytochemical screening of the heartwood extractives of ten Congo Basin tree species

Content and type of extractives vary considerably among woody species in the Congo Basin tropical forest. They influence the natural durability of wood with respect to fungal and insect degradation. Species containing higher amounts of extractives and Klason lignin were generally less susceptible to fungal colonization. Phenolic extractives with large anti-fungal and high antioxidant activities were the main chemical family of compounds extracted from the tested species, which suggests a potential chemical valorization of these extractives.

Abstract

Several woody species from the Congo Basin are known for their natural durability, but the causes of this natural durability are not always fully elucidated. This is particularly the case for the resistance to white rotting fungi decay. The chemical composition as well as the antioxidant activity of the heartwood extractives of several species were quantified and correlated to the ability of different fungi to colonize wood sawdusts in order to better understand their decay resistance. The chemical screening of extracts was conducted using colorimetric methods. The quantity of lignin, extracts and total phenolic compounds, as well as antioxidant activities were determined. Extracted and unextracted heartwood sawdusts were exposed to two white rot fungi to assess the effect of extractives on their colonization. Extractives and lignin contents ranged from 2.7 to 16.0 % and from 26.5 to 35.9 %, respectively. Antioxidant activity was directly connected to total phenolic contents. The phytochemical screening revealed the presence of different chemical groups in all extracts. Resistance to fungi was correlated to the amount of extractives and in most cases to the lignin content. Phenolic compounds associated with antioxidant activities influenced the natural resistance of heartwood.