Comparative study of four timber wood species in southern Mali (West Africa) by combining FTIR spectroscopy and multivariate analysis

Wood materials from tropical forests are particularly prized for their characteristics and properties. In this regard, wood from the West African forests comes up with an established reputation in the international wood market. Despite this, there has been little research on the properties of timber wood species in this geographical region. This study aims to characterize the main chemical contents and molecular structures of four timber wood species (Daniellia oliveri, Isoberlinia doka, Khaya senegalensis, and Pterocarpus erinaceus) from forests in southern Mali. The wood samples used in this study consisted of 11 wood cross-sections taken from individual planks of commercialized timber originating from three different localities (Kita, Kéniéba, and Sibi). Fourier transform infrared spectroscopy was applied to record 20 spectra per cross-section over 10 cm in the heartwood region. Next, a database made of 220 infrared spectra was analyzed using relative absorbance, FTIR ratios, and multivariate data analysis methods. The results showed that the molecular structure and functional groups in carbohydrate and lignin compounds are suitable to characterize the studied wood species. FTIR signals of polysaccharide compounds with crystalline structures are more abundant in the wood samples of D. oliveri, whereas wood samples of P. erinaceus contain the highest relative amount of lignin compounds with guaiacyl structures. Hemicellulose components are relatively more prolific in I. doka as well as in K. senegalensis. Finally, the results provide valuable details about the chemical properties of the studied wood species, which may be relevant for the assessment of the quality and for the definition of the adequate end-uses.