Bromine In Red Algae Research On Synthesis Of Phenolic Compounds And Antioxidant Activity

Firstly, after the review of the distributing, structure studies, biological activities and synthetic status of bromophenols, three bromophenol intermediates were synthesized. The yield of3-Bromo-4,5-dihydroxy benzaldehyde32,2,3-dibromo-4,5-dihydroxy benzaldehyde33and2,5-dibromo-3,4-Dihydroxybenzal dehyde34were69.8%,26%, and29%respectively.Secondly,3-bromo-4-hydroxy-5-methoxy-benzoic acid methyl ester38, which was isolated formerly from red algae Polysiphonia urceolata, were synthesized using vanillin as raw material through bromination by bromide, oxidation over silver oxide and esterification with methanol in sequent, giving a total yield of66.4%.In addition,(E)-4-(3-bromo-4-hydroxy-5-methoxy-phenyl)-but-3-en-2-one31, which was firstly found in red algae Polysiphonia urceolata, was synthesized. The route consisted of three parts:bromination, aldol condensation and demethylation. Meanwhile a new bromophenol compound,(E)-4-(3-bromo-4-hydroxy-5-methoxyphenyl)-but-3-en-2-one44, was obtained in the synthesis procedures. Among these three steps aldol condensation played a key role that involves the conformation of E-configuratin olefinic bond and stereoisomers. The mechanism and reaction conditions including temperature and pH were mainly studied.At last, the radical scavenging activities of the bromophenol products were determined using DPPH method. It was found that3-Bromo-4,5-dihydroxybenzaldehyde and (E)-4-(3-bromo-4-hydroxy-5-methoxy-phenyl)-but-3-en-2-one showed significant radical scavenging activities with IC507.5μg/ml and47.87μg/ml respectively.3-bromo-4-hydroxyl-5-methoxy-benzoic acid methyl ester didn’t show obvious radical scavenging activity. The structures of the bromophenols were identified by IR or1HNMR.