Lignin is an underexploited side-stream of pulp and paper industry and biorefineries, being used for energy production at mill site or as low value material for dispersants or binding applications.However, an integrated process of reaction and separation can be implemented for the production of high added-value monomeric phenolic chemicals such as vanillin and syringaldehyde. In this review, the main research advances in the recovery of vanillin and syringaldehyde resulting from oxidation of lignin are addressed, covering various separation methodologies namely liquidliquid extraction, supercritical fluid extraction, distillation, crystallization, membrane separation, and adsorption.A c c e p t e d M a n u s c r i p t 2 Studies in this area started in the early years of the 20 th century, but in the last decades several processes have been suggested, mainly for vanillin separation. Finding the ultimate industrially feasible process is still a necessary task and this review points out the most promising technologies and sequence of processes.

The bark of Eucalyptus globulus is a promising source of polyphenolic compounds that could be extracted employing polar solvents. Extraction experiments were planned according to the Box−Behnken design to evaluate the effect of temperature and time of extraction and the ethanol/water ratio on the dependent variables total phenolic content (TPC; as gallic acid equivalents, GAE), antioxidant activity (AA; as millimoles of ascorbic acid equivalents, AAE), proanthocyanidins (Pac; as mimosa extract equivalents, MEE), Stiasny number (SN), and coextracted total carbohydrates (TC). Response surface models were developed, and statistical analysis of variance was performed. A maximum of TPC of 32% (w GAE /w extract ) was achieved for 264 min, 82.5°C, and 52% ethanol corresponding to about 2% of the bark weight. These conditions are close to those leading to maximum values of compounds with AA (2.1 mmol AAE /g extract ) and Pac 14% (w MEE /w extract ). TC in the extract and the SN predicted were 22.7% (w TC /w extract ) and 37, respectively. Preliminary studies concerning the biological activity of some extracts have demonstrated their differential capacity to reduce human breast cancer cell proliferation.

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