The exact chemical nature of the tannins and the quantity depends on the species being considered, but oak and sweet chestnut that are rich in tannins are also known for the durability of their wood. Whilst the microbial toxicity of the tannins is not to be compared to commercial bacteriocides or fungicides - the sheer quantity of tannins affords protection against attack. The tannins / polyphenols may represent 10% or more of the dry mass of the heartwood.

The exact chemical nature of the tannins and the quantity depends on the species being considered, but oak and sweet chestnut that are rich in tannins are also known for the durability of their wood. Whilst the microbial toxicity of the tannins is not to be compared to commercial bacteriocides or fungicides - the sheer quantity of tannins affords protection against attack.  The tannins / polyphenols may represent 10% or more of the dry mass of the heartwood.