Antioxidant and Antitumor Metabolites of Saudi Red Sea Seagrasses Halodule uninervis and Thalassia hemprichii

The present study aimed to investigate the chemical constituents, and antioxidants and antitumor activities of the seagrasses Halodule uninervis and Thalassia hemprichii. Seventeen compounds were isolated from both seagrasses, and identified as flavonoids, phenolic acids, nitrogen compound, steroids and fatty acids. Their structures were established by spectral analysis (UV, MS, and 1D- and 2D-NMR) and chemical investigation (for glycosides). The total metabolites of each seagrass and the isolated flavonoids tested in different in vitro assays (DPPH, ABTS, FRAP, Fe2+ chelating, reducing power, and Ehrlich ascites carcinoma cell line) showed significant antioxidant and antitumor activities. H. uninervis extract revealed good antioxidant activities compared to water and butanol extracts of T. hemprichii, while quercetin 3-O-β-glucoside from H. uninervis revealed potent antioxidant activity at concentration of 25µg/ml. Moreover, the seagrasses extracts were displayed mild antitumor activity against Ehrlich ascites carcinoma cells in mice with less undesirable side effects compared to vincristine as a drug control.