Effect of Solvent Composition on Ultrasound-Generated Intensity and Its Influence on the Ultrasonically Assisted Extraction of Bioactives from Agave Bagasse (Agave salmiana)

Agave bagasse is a waste material generated during agave sap collection for pulque production. This residue is a potential feedstock for steroidal saponins and other phytochemicals. Ultrasonically assisted extraction (UAE) allows the use of green solvents such as water or ethanol for phytochemicals recovery. The influence of solvent composition and its effect on the intensity of the ultrasonic field during the UAE of agave bagasse saponins were evaluated. The best extraction conditions were a temperature of 60 degrees C (T) and a solvent-to-mass ratio of 20 (S/M), for conventional and UAE. In contrast to conventional extraction, where mixtures of ethanol-water were more efficient, water was the best extraction solvent in UAE. The amount of saponins obtained without ultrasound in 58% ethanol (22.48 +/- 1.34 mg PE/g dw) was similar to the amount obtained by UAE in water (24.41 +/- 0.84 mg PE/g dw). When only water was used, the ultrasound intensity was higher (271.40 +/- 11.91 W/L) than in ethanol mixtures (144.81-202.30 W/L) due to cavitation intensity, demonstrated in a test on aluminum foil and SEM images of exhausted bagasse. Despite lower chemical affinity of water for saponins, its lower vapor pressure and viscosity, as well as higher surface tension, compared with ethanol, provided a greater cavitation intensity. Therefore, UAE using water is an excellent alternative to recover bioactive compounds from agave bagasse.

Automated summary

Agave bagasse, a waste material in pulque production, can be extracted for steroidal saponins using ultrasonically assisted extraction (UAE). Water was found to be the most effective solvent for UAE due to its ability to create higher cavitation intensity in the extraction process. Research also demonstrated that despite lower chemical affinity, water's lower vapor pressure, viscosity, and higher surface tension compared to ethanol contribute to its better performance in UAE.