Influence of factors and interactions in ultrasound-assisted extraction and conventional maceration on aqueous extract of Psidium guajava leaves

Background: Extraction techniques of phenolic compounds (PC), such as conventional maceration (CM) has been associated with high consumption of organic solvents and time. Objective: The objective of this study was to evaluate the effects and interactions of the variables involved in the aqueous extraction of phenolic compounds from Psidium guajava leaves by CM and ultrasound-assisted extraction (UAE). Methods: A split-plot design was developed according to the extraction variables of interest. For CM was time, temperature, and dilution were considered and for UAE the wave amplitude was included.  Response variables were considered the following parameters: yield, total phenolic compounds, total flavonoid compounds, antioxidant capacity measured as radical uptake by ABTS and DPPH.Results: The results show that for UAE, the treatment of 1 g/ 50 mL, 50ºC temperature, 30% amplitude, and 20 min of extraction was associated with a higher extraction yield, reporting 125.84 mg of acid gallic equivalents/ g for PC, 381.18 mg quercetin equivalents/g for total flavonoids and 85.28% ABTS and DPPH 40.2% expressed as radical scavenging activity. On the other hand, the maceration method reported best extraction yield, using the treatment of 1 g/ 50 mL of dilution, 50ºC temperature and 10h of extraction time, achieving a total of 62.04 mg of gallic equivalents/ g for PC, 289 mg quercetin equivalents/g for total flavonoids, and 95.9% ABTS and DPPH 48% regarding radical scavenging activity.Conclusion: The ultrasound process was more effective in extracting phenolic compounds, flavonoid compounds, and their extracts had the highest antioxidant capacity. Keywords: Psidium guajava, phenolic compounds, extraction, ultrasound.