Isolation and Characterization of Bioactive Compounds from Marine Macroalgae Kappaphycus alvarezii and Gracilaria opuntia

Abstract

Marine macroalgae can be considered as a major resource of bioactive leads. Species of the red marine macroalgae (class Rhodophyceae) were proven to be rich sources of structurally unique and biologically active secondary metabolites endowed with antioxidant, anti-bacterial, anti-inflammatory and anti-carcinogenic activities for applications in functional food and pharmaceuticals. In recent days, macroalgae emerge as a subject area of interest in the biomedical applications owing to the presence of pharmacologically active substances with potential health benefits. Antioxidant compounds exhibit a predominant functional role in attenuating the overproduction of free radicals formed during the regular metabolic processes. Therefore, antioxidant compounds play a vital role in the pathogenesis of oxidative stress induced diseases, such as inflammation, hypertension and diabetics. The present study demonstrated the potential of red marine macroalgae as a source of bioactive leads. Kappaphycus alvarezii and Gracilaria opuntia registered significant antioxidant potential along with in vitro enzyme inhibitory potential with respect to anti-diabetics, anti-hypertension and anti-inflammation. The organic ethylacetate-methanol (EtOAc: MeOH) extracts of the studied marine macroalgae K. alvarezii and G. opuntia from the Gulf of Mannar region of Mandapam were screened for various pharmacological activities by using different in vitro model assays. The organic extracts obtained from K. alvarezii and G. opuntia was found to possess bioactivities against different disease targets, namely hypertension, type-2 diabetes and inflammation. The ethylacetate-methanol extract of the thalli of K. alvarezii and G. opuntia was fractionated by repeated column chromatography to afford a number of previously undescribed compounds. The structures of these compounds were established by exhaustive spectroscopic experiments, including mass and two-dimensional nuclear magnetic resonance. The antioxidative and anti-inflammatory activities of the ne