Phytochemical and in vitro antimicrobial and genotoxic activity in the brown algae Dictyopteris membranacea

The emergence and increase of microbial resistance towards many conventional therapeutics necessitate the investigation and discovery of new natural sources of antimicrobial agents. In this study the Mediterranean brown alga, Dictyopteris membranacea, was investigated. The total phenolic, flavonoid and tannin contents were quantified and antibacterial, antifungal and antitubercular activities of the crude extract and semi-purified ethanol, acetone and methanol/CH2Cl2 fractions were determined. The antimicrobial activity was determined by the agar diffusion method against six strains of Gram-positive, two strains of Gram-negative bacteria and one yeast strain. The MIC and MBC or MFC values served to identify the bactericidal and bacteriostatic effects of all prepared fractions against the different strains. The acetone fraction presented a source of phenolic (112 mg GAE/g of sample) and tannin (130 mg CAE/g sample) compounds whereas the ethanol fraction showed the highest concentration of flavonoids (120 mg QE/g). Ethanol and acetone fractions exhibited considerable antibacterial, antifungal and antitubercular activities with a good correlation between the phytochemical composition of all prepared fractions and the different biological activities. This study on the phytochemical and in vitro antimicrobial activity of this brown alga was supplemented by an in vitro investigation of the potential genotoxicity of the extract and fractions using the bacterial Vitotox test and micronucleus test on human C3A cells. The results show that all prepared fractions were not genotoxic in the presence or absence of S9. Overall, the results are therefore encouraging and justify further investigations on the therapeutic and other values of this alga. (C) 2016 SAAB. Published by Elsevier B.V. All rights reserved.