Phytochemical composition, in vitro antioxidant, antibacterial potential and GC-MS analysis of red seaweeds (Gracilaria corticata and Gracilaria edulis) from Palk Bay, India

Increasing of resistance pathogenic microorganisms to majority of antibiotics, there is an urgent need for exploring plant based drugs and bioactive compounds with least side effects. The study was aimed to determine the level of phytochemicals, antioxidant, antibacterial properties of the edible red seaweeds, Gracilaria corticata and G. edulis. The extraction with methanol yielded 7.10 ± 0.16 and 6.39 ± 0.16% extracts from G. corticata and G. edulis respectively. The G. corticata possess higher total phenol content (4.00 ± 0.35 mg GAE/g) compare to G. edulis (3.4 ± 0.21 mg GAE/g). G. corticata and G. edulis extracts significantly varied in total flavonoid content i.e 3.33 ± 0.12 and 2.6 ± 0.08 mg CE/g DW respectively. In this investigation, G. edulis presented the highest 2, 2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging activity (23.95%) when compare to G. corticata (20.32%). G. edulis showed significantly higher 2, 2′-azino-bis (3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) radical scavenging activity (40.24%) compare to G. corticata (32.65%). In addition, G. corticata exhibited higher nitric oxide (NO*) radical scavenging activity (36.78%) than G. edulis 35.25%. Antimicrobial properties of 70% methanol and DMSO extracts were found effective against Bacillus subtilis. GC-MS analysis revealed the presence of phytochemical compounds including sulfurous acid, 2-ethylhexyl isohexyl ester, pentatriacontane, eugenol and phthalic acid played a vital role in antioxidant and antibacterial activities.