Halo-phenolic metabolites and their in vitro antioxidant and cytotoxic activities from the Red Sea alga Avrainvillea amadelpha

From the green alga Avrainvillea amadelpha, two new naturally halo-benzaldehyde derivatives were isolated by various chromatographic methods along with 10 known metabolites of bromophenols, sulfonoglycolipid, and steroids. Based on the 1D and 2D NMR spectra as well as on MS data, the structures of the new compounds were identified as 5-bromo-2-(3-bromo-4-hydroxybenzyl)-3,4-dihydroxybenzaldehyde named avrainvilleal ( 1 ), and 3-iodo-4-hydroxy-benzaldehyde ( 2 ). Using SRB assay, both compounds showed mild and weak cytotoxic activity against HeLa and MCF-7 cancer cell lines, compared to the good activity of their extract (IC 50 values 3.1 and 4.3 μg/mL, respectively). However, avrainvilleal ( 1 ) displayed an effective scavenged DPPH radical activity with IC 50 value 3.5 μM, compared to the antioxidant quercetin with IC 50 value 1.5 μM.