Assessing the bioactivity, cytotoxicity, and rheological properties of pectin recovered from citrus peels

The recovery of pectin from citrus peel waste for application in the food, nutraceutical, pharmaceutical, and medical industries has attracted much interest. It has been postulated that the presence of polyphenols, sometimes regarded as an impurity, in extracted pectin might confer enhanced biological property. This research study aimed at investigating the physicochemical and biological properties (antioxidant, enzyme inhibitory, and cytotoxic properties) of pectin extracted from the alcohol insoluble residues of the peel waste of grapefruit, lime, and lemon as well as the pectin recovered from untreated peel waste. The rheological behavior of the pectin samples was also evaluated. High methoxyl pectin with galacturonic acid content greater that 60% was recovered from the different raw materials. Pectin obtained from untreated material possessed high phenolic content (19.83-5.94 mg gallic acid equivalent/g sample) and showed higher antioxidant activity. Inhibition against pancreatic cholesterol esterase, pancreatic lipase, and alpha-glucosidase was observed and pectin enriched with polyphenol showed higher activity. Addition of pectin samples to healthy Vero cells enhanced proliferation and did not show cytotoxic effect. Pectin solutions extracted from untreated lime and untreated grapefruit presented highest viscosity and elastic modulus, which were comparable to those obtained for commercial high-methoxyl pectin. Pectin extracted from lime, lemon, and grapefruit peels possessed interesting biological and viscoelastic properties, which can be exploited for development of novel bioproducts.