Innovative approach for obtaining phenolic compounds from guava (Psidium guajava L.) coproduct using ionic liquid ultrasound-assisted extraction (IL-UAE)

An innovative ionic liquid ultrasound-assisted extraction (IL-UAE) approach using 1-Butyl-3-methylimidazolium tetrafluoroborate [BMIM][BF₄] and 1-Butyl-3-methylimidazolium chloride [BMIM][Cl] for obtaining extracts rich in phenolic compounds (PC) from guava coproduct was investigated. A screening design 2⁴, followed by a central composite design 2² with response surface methodology and desirability function were used to optimize the extraction condition of PC with antioxidant activity (AA). The results showed that 20 g L^-1 of sample, during 25 min of ultrasound-assisted extraction at 45 °C, using 2.5 mol L^-1 of [BMIM][BF₄] was the optimal condition for the extraction of the PC from guava coproduct (1.18 eq. mg g^-1 gallic ac.). The IL-UAE extracts showed a higher recovery for condensed tannins and ortho-diphenols and high AA by DPPH (2,2-Diphenyl-1-picrylhydrazyl), FRAP (ferric reducing antioxidant power), ABTS (2,2-azinobis-(3-ethylbenzothiazoline-6-sulfonate)) and Cu²⁺ chelating methods compared to volatile organic solvents (VOS). IL-UAE represents an innovative, fast and straightforward approach for obtaining high-value PC with antioxidant activity from guava coproduct.