Investigation on the evaluation possibilities of some industrial tree barks grown in Turkey

Wood and non-wood forest products, have potential usage areas in chemical and pharmacological industries as their rich chemical components like phenolic compounds and terpenes. This kind of components can be got from wood and non-wood forest products easily by different extraction techniques with different solvents. During wood processing, because of their own characteristics, bark, trimming residues and sawdust are consumed as fuel sources in most of plants. Although chemical structures of tree barks are similar to wood content and variety, the bark extractive compounds are quite rich. Therefore, the industries have been using these compounds are interested in research findings accordingly the intensive researches increased recently. Fir (Abies nordmanniana), Beech (Fagus orientalis), pine (Pinus sylvestris), poplar (Populus alba), and Oak (Quercus robur) barks were taken from harvesting areas in Kastamonu province in Turkey. The wood barks processed separately were dried at room temperature and milled by using Wiley mill. Tree bark with high chemical diversity is important for their characterization. In this study, the basic components of five different bark samples and their solubility in different solvents were investigated. According to the results obtained, differences in extractive content were measured among bark species examined, comparisons in extractives content showed that poplar contained higher content extractive ranged from about 15 to 20 %, moreover all barks examined was found amount of holocellulose of the bark lower than wood, the highest holocellulose amount was found in Poplar and Fir tree bark with 54.93 %, 50.70 % respectively, in addition Lignin is one of the main constituent components of the bark, the maximum amount of lignin was in the oak tree bark 32.67 %. However, bark samples were extracted by hexane for analyses volatile components by GC-MS and extracted by methanol-water mixture (65-35% v/v) for flavonoid components analyses. Total phenolic content, total flavonoid content, antioxidant oxidant activities determined after lyophilization of methanol-water extracts. The highest total phenolic, total flavonoid contents and antioxidant activity were obtained from Populus alba bark extracts. It was observed that, the amount of volatile compounds and types were changed with tree species. According to HPLC results, highest value obtained from white poplar bark extract is 87.76 mg/L (at 280 nm) which is a flavonoid with rich antioxidant properties. The prodctıvıty of ethanol of bark are less than letretures that ıs because the study used the pretreatment by diluted sulfrıc acid and fermıntaıon wıthout used enzymatıc pretreatment The prodctivity of ethanol of bark was ın Fır 2.28 ml/100g, Beech 2.17 ml/100g, Oak 2.02 ml/100g, Pıne 1.95 ml/100g, whİle the Poplar bark 1.87 ml/100g. FTIR spectrum to functional groups in lignin bark samples show a broad band at 3153–3275 cm−1, attributed to the hydroxyl groups in phenolic and aliphatic structures, and the bands centered around 2920 and 2850 cm−1, predominantly arising from CH stretching in aromatic methoxyl groups and in methyl and methylene groups of side chains. The Thermo-gravimetric analysis (TGA) of bark samples decomposition in three steps at tempreture from 0 to 600C the wight loss of lignin occurs. Furthermore differential Scanning Calorimetry (DSC) of bark samples the glass transition temperatures were determined as follows: Poplar bark; 107 °C, Beech bark; 114 °C, Pine bark; 91 °C, Fir bark; 119 °C, Oak bark; 135 °C. The presence of valuable extracts suggests that barks may have uses as valuable raw materials for chemical applications such as cosmetics, perfumes, and food preservatives. Industrial wood bark can be largest source of energy and a potential feedstock for industrial production of different bio-materials, bio-chemicals, bio-fuels, and other novel products. Further research is needed on the wood barks' compositions for additional using areas.