Following the extraction of betulin and polysaccharides, the extraction of EFA was adapted from the protocol developed by Rüdiger et al. 5.77 g of the bark was dried overnight at 105 °C to remove any residual water from the ASE treatment before it was subjected to alkaline hydrolysis. 1.28 g of NaOH pellets were dissolved in water and the solution was added to 51 mL of ethanol in a round bottom flask. Before adding the bark, the solution was brought to a boil using an oil bath and then refluxed under magnetic stirring for 2 h. The flask was allowed to cool down to room temperature and the residual bark was removed through centrifugation. The supernatant was collected and 25 mL of ethanol was evaporated using a rotary evaporator (approximately half of the initial volume).