In vitro Evaluation of Antiproliferative and Antioxidant Activities of Methanolic Extracts of Gracilaria corticata and Gracilaria foliifera Against Breast Cancer Cells

The present study was aimed to assess the methanolic extracts of Gracilaria corticata and G. foliifera for anti-proliferative and anti-oxidant potency against breast cancer cell line MDA-MB-231. The antitumor activity of G. corticata methanolic extract (GCME) and G. foliifera methanolic extract (GFME) against MDA-MB-231 cells was assessed by 3-(4,5-dimethylthiazol-2-cyl)-2,5-diphenyltetrazolium bromide (MTT) assay. The extracts decreased cell viability of MDA-MB-231 cells with an estimated half-maximal inhibitory concentration (IC₅₀) of 0.18 ± 1 and 0.078 ± 1 for GFMEs; and 0.116 ± 1 and 0.107 ± 1 for GCMEs. GCME significantly increased ROS level after 48 h of treatment and decreased glutathione (GSH) level (p<0.01) in a dose-and time-response manner. Intracellular ROS in MDA-MB-231 cells was determined by staining with fluorogenic agent 2',7'-dichloro-dihydrofluorescein diacetate (H₂DCFDA). The mitochondrial membrane potential (Δψm)) disruption of GFME and GCME treated cells were maximum at 0.078 and 0.107 μg μL^-1 (p<0.005). G. foliifera showed significantly higher 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging activity (78.6%) as compared to G. corticata(68.3%). This study also explored the phytochemical constituents of GFME and GCME such as hexadecanoic acid, methyl ester and cholesta-4,6-dien-3-ol, (3 beta), through GC-MS analysis.