Extraction of (Poly)phenolic Compounds of Cactus (Opuntia ficus-indica (L.) Mill.) Cladodes

Research in cactus (Opuntia ficus-indica (L.) Mill.) cladodes as a functional food increases because of their (poly)phenolic compounds and health-promoting ability. Extraction conditions are the basis to obtain the highest amount of bioactive compounds with antioxidant properties. Therefore, several individual and combination of extraction solvents and conditions were carried out. Even a great amount of (poly)phenols was extracted using 80% ethanol; the combination of solvents with different polarities (methanol, acetone and water) favored the extraction of flavonoids and antioxidant capacity (DPPH and ABTS radicals). The extract with the highest flavonoid content was that obtained by successive extractions. Additionally, in order to quantify (poly)phenols by HPLC-DAD, aglycones were released from glycosides by acid hydrolysis (0.6, 1.2, 1.5, and 1.7 M HCl) through reflux at 90 °C at different times (2 h and 3 h). Flavonoid aglycones (isorhamnetin, quercetin, and kaempferol) and phenolic acids (ferulic and 4-hydroxybenzoic acids) were identified and quantified. Acid hydrolysis with 1.5 M HCl during 2 h was the best for the release of flavonoid aglycones, without phenolic acid degradation. Likewise, less acidity (0.6 M HCl) does not completely release the aglycones whereas a higher acidity (1.7 M) and a longer time of reflux (3 h) resulted in the degradation of flavonoid aglycones.