Bioactive Compounds and Antioxidant Activity of Tropical Red Algae Gracilaria sp. from Bintan Island, Indonesia

Abstract

Macroalgae that grow in the tropics are continuously exposed to ultraviolet radiation and sunlight. Macroalgae have self-defense to avoid damage caused by ultraviolet radiation by carrying out secondary metabolism and producing several bioactive compounds. The bioactive compounds produced have the potential to be utilized to inhibit free radicals that can cause degenerative diseases in humans. This research aims to identify bioactive compounds and determine the antioxidant activity, total phenolic compound, total flavonoid compound, and pigment content of red algae Gracilaria sp. from Bintan island. This research has the novelty of the sampling location to be later developed into a sustainable resource in the pharmaceutical field. Gracilaria sp. found in Bintan island was taken, dried in indirect sunlight, and macerated using universal solvent methanol. Phytochemical testing was conducted to determine the presence of flavonoids, steroids, triterpenoids, saponins, and tannins. Antioxidant activity was determined using DPPH as a free radical at the maximum wavelength of DPPH (515 nm) with an incubation time of 55 minutes. Total phenolic and flavonoid compounds were determined using standard solutions of gallic acid and quercetin, respectively. The results showed that the methanol extract of Gracilaria sp. contains flavonoid and tannin compounds, has a chlorophyll-a content of 0.43 mg/g, a carotenoid content of 0.91 µmol/g, the total phenolic compound of 4.67 mg/GAE g, total flavonoid compound of 2.26 mg/QE g and has antioxidant activity with IC50 value of 982.25 ppm. Utilization of Gracilaria sp extract from Bintan waters as a pharmaceutical ingredient is expected to increase prospects and sustainable use in the pharmaceutical and health fields.