Phytochemical Composition and Antioxidant Potential of Gracilaria verrucosa and Gracilaria multipartita

Abstract

Red algae play a significant role in free radical scavenging due to their abundance of phenolics and flavonoids, which contribute to cosmeceutical benefits. Such natural compounds support the development of bio-based products while aligning sustainable goals for environmental conservation. Also, there are very limited studies on Sri Lankan red algal species. In this study, two algal species, Gracilaria verrucosa (Trincomalee) and Gracilaria multipartita (Weligama, Matara), were collected with the permission from the Department of Wildlife Conservation (Permit No: W/3/2/113/2024) to evaluate their potential as natural antioxidants. Samples were shade-dried for three days, ground, and extracted using 80% methanol. The total phenolic content (TPC) was quantified using the Folin-Ciocalteu method with a gallic acid standard curve (r²=0.9905). Antioxidant activity was determined using the 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging assay with each sample triplicated (n=3) and incubated for 30 minutes before absorbance was measured at 517 nm. The TPC of G. verrucosa and G. multipartita was found to be 4.94±0.13 and 3.43±0.23 mg GAE/g extract, respectively. G. verrucosa showed a stronger antioxidant response with 82.9±0.9% DPPH radical scavenging activity at 2 mg/mL compared to 61.5±1.3% in G. multipartita. Trolox was used as the positive control, which results in 93.44±0.45% scavenging activity. G. verrucosa demonstrated a significantly higher scavenging activity value among two algal extracts (p<0.05), reflecting higher antioxidant efficiency. The methanol extract of G. verrucosa exhibited higher phenolics than G. multipartita (p<0.05). The results revealed that both algae species contain notable levels of phenolics and bioactive constituents. This suggests that phenolic compounds may play a more dominant role in the radical scavenging capacity of these extracts. Beyond the bioactivity of these red algae, this research increases the significance of utilizing biological materials for value-enhanced, sustainable innovations.

Keywords: Red algae, Gracilaria sp., Antioxidant activity, Total phenolic content, Sustainable biological materials