Understanding the structure of industrial Eucalyptus cloeziana extracts: An analytical multi-technical approach

Due to its rapid growth and valuable wood, Eucalyptus is one of the most widely planted tree species worldwide. This has led to a decline in mimosa (Acacia mearnsii) plantations, resulting in a reduced availability of mimosa wood and bark and an increase in prices throughout the supply chain. Therefore, finding viable alternatives to mimosa tannins has become essential, and Eucalyptus cloeziana could represent a suitable candidate. In this study, we characterized both extracts by determining the total phenolic and condensed tannin contents using wet-chemistry methods, the carbohydrate content by HRSEC, and by analyzing FT-IR and NMR spectra using advanced techniques such as HSQC and 31P NMR. The results showed that the Eucalyptus extract is also mainly composed of condensed tannins, with procyanidin as the predominant flavonoids, although some hydrolysable ones are also present. However, this extract contains a high amount of high-molecular-weight carbohydrates, which reduces its antioxidant activity and its solubility in ethanol/water.