Maximization of the recovery of phenolic compounds from sugar maple leaves

A maceration process was optimized using a full factorial design coupled to a response surface model for the extraction of phenolic compounds (PCs) from sugar maple leaves (SML). As part of the extraction process, high-speed homogenization (HSH) as a pre-treatment condition was investigated to promote the efficiency of maceration. Finally, characterization of SML was performed using colorimeter, SEM, FTIR spectroscopy, and LC-ESI-Q-TOF–MS/MS. The antioxidant activity of the extract was investigated as well using standard methods. Results showed that ethanol concentration and solid-to-solvent ratio had significant effects (p < 0.05) on the extraction of PCs and HSH can be considered as an effective pre-treatment towards maximizing phenolic compounds recovery from SML. Under the optimal conditions (ethanol concentration of 61.63% at a solid-to-solvent ratio of 1:38.22 g/mL), the experimental %total yield (28.57%), total phenolics (110.87 mg GAE/g DM), and total flavonoids (18.95 mg CTE/g DM) were in close agreement with the predicted values. A total of 81 PCs were tentatively identified including mostly phenolic acids and flavonoids and their derivatives from SML using LC-ESI-Q-TOF–MS/MS. What is more, a gallotannins pathway existing in SML from gallic acid to tetragalloyl-D-glucopyranose was proposed. The study suggested SML as a promising source of PCs which can be effectively extracted through maceration and be further used as natural antioxidants in the formulation of functional food systems.