Highly Brominated Mono- and Bis-phenols from the Marine Red Alga Symphyocladia latiuscula with Radical-Scavenging Activity

Abstract

Four new highly brominated and fully substituted mono- and bis-phenols, 1-(2,3,6-tribromo-4,5-dihydroxybenzyl)pyrrolidin-2-one (1), 1,2-bis(2,3,6-tribromo-4,5-dihydroxyphenyl)ethane (2), 6-(2,3,6-tribromo-4,5-dihydroxybenzyl)-2,5-dibromo-3,4-dihydroxybenzyl methyl ether (3), and 2,3,6-tribromo-4,5-dihydroxybenzyl methyl sulfone (4), were characterized from the marine red alga Symphyocladia latiuscula. In addition, five known bromophenols, bis(2,3,6-tribromo-4,5-dihydroxyphenyl)methane (5), bis(2,3,6-tribromo-4,5-dihydroxybenzyl) ether (6), 2,3,6-tribromo-4,5-dihydroxybenzyl methyl ether (7), 2,3,6-tribromo-4,5-dihydroxymethylbenzene (8), and 2,3,6-tribromo-4,5-dihydroxybenzaldehyde (9), were also isolated and identified. The structures of these compounds were elucidated by spectroscopic methods including 1D and 2D NMR as well as by low- and high-resolution mass spectrometric analysis. Structurally, all of these compounds are highly brominated and fully substituted, and contain one or two 2,3,6-tribromo-4,5-dihydroxyphenyl unit(s) in each of the molecules. In addition, compound 4 possesses a unique sulfone structural feature. Each of the isolated compounds was evaluated for alpha,alpha-diphenyl-beta-picrylhydrazyl (DPPH) radical-scavenging activity and all were found to be potent, with IC50 values ranging from 8.1 to 24.7 microM, compared to the known positive control butylated hydroxytoluene (BHT), with an IC50 of 81.8 microM.

Synthesis and carbonic anhydrase inhibitory properties of novel bromophenols including natural products

“…Additionally, it was reported that bromophenol 1 is an inhibitor of protein tyrosine phosphatase 9 . Antioxidant activities of 1 and 4 have also been reported 10,11 . Recently, we have achieved an alternative synthesis of 1 10 , first total synthesis of 2, 3, 4 12,13 , and a series of diphenylmethanone like bromophenols 5 10 .…”

Halogenated Organic Molecules of Rhodomelaceae Origin: Chemistry and Biology

“…366 Generally, the DPPH radical-scavenging effects of the bisphenols are stronger than those of the monophenols, suggesting that the free-radical-scavenging activities of these phenolic compounds are correlated with the number of hydroxyl groups in the molecules. 380 Replacement of an OH group with an OMe group on the aromatic ring significantly decreased the activity. 366 Meanwhile, the number and position of the bromine atoms are also important factors contributing to the variation in DPPH scavenging activity observed for the compounds in this class.…”

“…Recently, the relative configuration of laurenmariannol (aplysiol B, 368) was revised with the aid of a 1D gradient selective NOESY experiment. 245 .0]undecane unit thereby affording a 7/7/6-ring system, which further connects via single bonds either to an oxolane ring (380) 240 or to an oxepane ring (381−386). 249 In contrast, two other triterpenes, enshuol (387) well as in the sea hare Dolabella auricularia, 252,253 which is known to feed on marine algae like Laurencia species.…”

Total Synthesis of the Biologically Active, Naturally Occurring 3,4‐Dibromo‐5‐[2‐bromo‐3,4‐dihydroxy‐6‐(methoxymethyl)benzyl]benzene‐1,2‐diol and Regioselective O‐Demethylation of Aryl Methyl Ethers

“…On the other hand, 3,4,6-tribromo-5-(2,5-dibromo-3,4-dihydroxybenzyl)benzene-1,2-diol (3) and 5,5'-methylenebis(3,4,6-tribromobenzene-1,2-diol) (4) show aldose reductase inhibitory activity [13]. Furthermore, it is known that 4 exhibits antioxidant activity [14].…”