New Materials, Compounds and Applications

The hybridization of Eucalyptus species, known for improved growth rates, wood quality and fibre yield, has attracted interest from the pulp and paper industry. After harvesting for pulp, the leaves are often discarded but can be repurposed for extracting essential oils of pharmaceutical, cosmetic and food value. This study evaluates ultrasound-assisted hydrodistillation (UAHD) for extracting essential oils from Eucalyptus hybrid (E. pellita × E. grandis) leaves, compared with microwave-assisted hydrodistillation (MAHD) and conventional hydrodistillation (HD). UAHD achieved the highest yield (8.0 ± 0.19%), followed by MAHD (4.0 ± 0.21%) and HD (3.2 ± 0.21%). Scanning electron microscopy confirmed greater cell disruption after ultrasonic pre-treatment, explaining the enhanced extraction. Gas chromatography–mass spectrometry (GC–MS) identified isopulegol (90.9%) as the dominant component, distinct from typical non-hybrid Eucalyptus oils. Isopulegol, a monoterpene alcohol with reported antioxidant, anti-inflammatory and gastroprotective properties, has broad industrial potential. These findings demonstrate UAHD as a more efficient and scalable technique for essential oil production, offering additional economic value to forestry by-products while contributing to sustainable industrial practices.