Extractable and macromolecular antioxidants of Opuntia ficus-indica cladodes: Phytochemical profiling, antioxidant and antibacterial activities

Abstract

Macromolecular antioxidant (MA) fractions and their antioxidant and antimicrobial activities are largely ignored from most conventional extractive processes compared to the well-known extractable polyphenol fractions. This study investigated subtropical spineless cladode MA extracts in comparison with their extractable fractions; as well as the effect of freeze and oven drying methods on extract yields and bioactivities. Cladode extractable phenol (EP) and MA fractions antioxidant capacities, antimicrobial potential against multi-drug resistant bacterial cultures, and phenolic content were evaluated. LC/MS was used to analyse/profile extract components. Freeze-dried samples from all the extracts showed better antioxidant and antimicrobial activities than the oven-dried samples. Antibacterial and antioxidant activities were generally higher in hydrolysed (MA) than in unhydrolysed (extractable) fractions. DPPH radical scavenging activity (RSA) EC50 values correlated with phenol contents (R2 = 0.9609). LC/MS extract profiles showed the presence of phenolic acids, flavonoid derivatives and other unidentified compounds. Isovitexin 7-O-xyloside-2″-O-glucoside, polyhydroxypregnane glycoside and neohancoside C were identified for the first time in Opuntia cladode extracts. This study showed that cladode EP and MA extracts have potential as rich antioxidant sources and can be key to the discovery of new antimicrobials.