Characterisation of bark of six species from mixed Atlantic forest

Abstract

Bark is one of the most available by-product derived from the wood-base industry because of the total volume of the tree that comprised. This study aimed at evaluating the chemical composition of barks of six typical species of the mixed Atlantic forest of the Basque Country and the potential of their extractives. The used species were Northern red oak (Quercus rubra), Common oak (Quercus robur), Common ash (Fraxinus excelsior), Iberian White birch (Betula celtiberica), Sweet chestnut (Castanea sativa) and Black locust (Robinia pseudoacacia). Differences between chemical compositions of all the barks were noted. Extractive content was very high for all the barks remarking Sweet chestnut and Common ash with the highest content with 31.89 and 29.44% respectively. The suberin content was higher than 3% with a maximum value for Black locust of 16.37%. Variation of EtOH/H2O was high depending on studied species with a range of extraction yield of 3.08to15.77%. Total phenolic content of the bark extracts ranged from 178.11 to 635.08 mg GAE/g of dry bark extract and total flavonoid content from 439.19 to 1021.78 mg CE/g of dry bark extract. The antioxidant capacity of the bark extracts was measured by DPPH, ABTS and FRAP and the obtained values were ranged from 167.23 and 1912.38 mg TE/g dried bark extract, 561.92 to 1556.57 mg TE/g dried bark extract 146.11 to 640.30 mg TE/g dried bark extract, respectively. The structural differences were confirmed by GPC and FT-IR, where it was observed an average molecular weight differences and different spectra. The obtained results confirm the high interest in barks source as biomolecules for specific uses such as cosmetics or pharmaceuticals among others.