Phycobiliproteins of Marine Red Alga, Kappaphycus Alvarezii Possess Potent Antioxidant and Metal Chelating Properties, and Inhibit Hepatocellular Carcinoma (HepG2) Cell Growth

Kappaphycus alvarezii is one of the economically important red alga, harvested primarily
for the production of hydrocolloids. This study aimed to identify an effective extraction
method for the isolation of phycobiliproteins (PBPs) from K. alvarezii and evaluate its
biofunctional properties. Organic solvents, inorganic acids, organic acids, phosphate buf-
fer saline (PBS), distilled water, and freeze-thawing were used to identify an effective
extraction method. The identification of PBPs was carried out by UV-Vis spectrophotom-
etry, FTIR spectroscopy, and SDS-PAGE analysis. The antioxidant potentials of PBPs was
examined by DPPH and ABTS radical scavenging assays. The metal chelating efficiency
was determined using divalent, monovalent, and trivalent metal ions. The WST-1 assay
and DAPI staining were performed to examine HepG2 cell viability and apoptosis, re-
spectively. Among the extraction methods, higher content of phycoeryhrin was recorded
in phosphate buffer saline. The results showed that extraction using PBS exhibits highest
content of phycoerythrin. The PBPs fraction contains phycoerythrin as a major pigment
molecule. The isolated PBPs exhibited increased DPPH and ABTS radical scavenging
activity in a concentration-dependent manner. It has possible quenching ability of Co2+
and Cu2+. The isolated PBPs inhibited HepG2 cell growth in a dose-dependent manner
and induced nuclear fragmentation. The data emphasize that K. alvarezii could be utilized
for the extraction of phycoerythrin which has antioxidant, metal chelation, and anticancer
properties.