Gracilarioside A, New Glycolipid and other cytotoxic constituents from red algae Gracilaria edulis

A comprehensive investigation of chemical constituents from red algae Gracilaria edulis led to the isolation and identification of 12 compounds, which include a new MGDG (Mono Galactosyl Diacyl Glycerol) glycolipid, Gracilarioside A (1) alongside with two known cerebrosides (2, 3), sterols (4-7), nitrogen bases (8, 9) and nucleosides (10-12). The structures of isolated compounds were elucidated by extensive spectroscopic techniques, (IR, MS, and 2D NMR) and single crystal X-ray diffraction studies. The crystal structure of 4 was reported for the first time. Further, anticancer activities of the extract and isolated compounds were assessed against a panel of cancer cell lines including DU145 (prostate), B16F10 (melanoma), HeLa (cervical), and MDA-MB 231 (breast) using MTT assay. Among the tested compounds, compounds 1, 3, 4, 7 and 8 displayed significant activities against MDA MB 231 [IC₅₀, 7.47 ± 0.05, 7.64 ± 0.34, 6.59 ± 0.21, 6.38 ± 0.49 and 7.19 ± 0.03 µM] while compounds 4, 5, 6 and 7 manifested moderate activities against B16F10 [7.0 ± 0.35, 7.20 ± 0.25, 7.26 ± 0.18 and 5.33 ± 0.04 µM] cell lines, respectively. Given their notable activity, compounds 1, 3 and 4 were chosen for further investigation through detailed fluorescence assays, DCDFA assay and scratch assays against MDA MB-231 cell lines which suggested the induced cell death by apoptosis. Overall, the significant findings suggest that these compounds could be promising lead molecules in the development of new anticancer drug candidates.