Antioxidant and anticancer properties of plant-based bioactive flavonoids cardamonin and alpinetin: A theoretical insight from •OOH antiradical and Cu (II) chelation mechanisms

A density functional theory (DFT) study aimed at a comparative investigation on the antioxidant mechanisms of cardamonin and alpinetin, two flavonoid bioactive components derived from plant sources with potential medicinal properties, has been performed through assessment of their (OOH)-O-center dot scavenging ability in non-polar medium and Cu (II) chelation ability in the absence and presence of explicit water molecules stabilising the metal cation. In addition, a comparison of the antioxidant properties of cardamonin with the moiety of phloroglucinol and acylated phloroglucinol has been performed to establish cardamonin's antioxidant potentiality among the phloroglucinol family of compounds. The results of the investigation reveal that alpinetin could be considered a better radical scavenger than cardamonin within the non-polar lipid bilayer medium of biological systems. However, the role of both compounds as (OOH)-O-center dot scavengers may be limited, in comparison to standard antioxidant molecules, such as alpha-tocopherol, because of the fact that the bond dissociation enthalpy for the hydrogen atom abstraction mechanism has a positive value, which signifies that the radical scavenging mechanism is not a thermodynamically preferred reaction. Cardamonin is found also to be a weaker antioxidant molecule than phloroglucinol and acylated phloroglucinol moieties. In terms of metal chelation mechanism, cardamonin is a better Cu (II) chelator than alpinetin since it has a higher metal ion affinity than alpinetin upon coordination to the Cu (II) cation. The results obtained could also imply that cardamonin is a better agent in dealing with angiogenesis, tumour growth and metastatis stages of cancer than alpinetin, since the ability of chelating metal cation shown by cardamonin ascribes it a better role as an anticancer agent than alpinetin. Therefore, although alpinetin may prove to play an important role as a promising antioxidant and antiinflamatory agent than cardamonin, by scavenging radical species, cardamonin would prove more valuable in the control of various stages of cancer growth than alpinetin.