ABSTRACT
Marine algae are potential sources of biologically active compounds with antiviral, antimicrobial and anticancer activities. Two species of marine algae, Padina boryana Thivy and Enteromorpha sp were collected from the Red Sea. Both species were extracted with ethanol, acetone, and hexane. The extracts of each sample were examined for, total phenolic, total flavonoid contents and antimicrobial activities. The results showed that solvents with different polarities have various effects on phenolic and flavonoid contents. Among the tested solvents, ethanolic extract of Padina boryana Thivy and Enteromorpha sp showed the highest phenolic content. Results also indicated that the extracts of Padina boryana Thivy showed higher antimicrobial activity compared to Enteromorpha sp. The present study demonstrates that both algae species exhibited excellent antimicrobial properties which may use as natural food preservative for possible application in food for health promotion.