GC/MS identification and applications of bioactive seaweed extracts from Mediterranean coast of Egypt

Abstract

The antibacterial activity of different seaweed species against five fishpathogens (A. hydrophila, V. parahaemolyticus, V. alginolyticus, V. damsela andVibrio sp.) has been evaluated. The ethanolic extract of C. sinuosa (CSE1) anddichloromethane extract of C. officinalis (COM) exhibited the highest antibacterialactivity with activity index (AI) = 1.4 ±0.74 and 1.2 ±0.71, respectively. When theextracts were encapsulated into calcium alginate beads their antibacterial activityagainst the most susceptible bacterial pathogens showed that the significant growthinhibition was against V. parahaemolyticus after 5 min post addition of the beadsrecording 1.4 and 2 fold decrease in the growth, respectively. Recycling of the(CA/COM) beads was carried out for 7 successive cycles with success inelimination of V. parahaemolyticus. The potential applications of encapsulatedextracts for elimination of microbial load in fish rearing water and antifoulingactivity were proved in the current investigation. The chemical composition of thebioactive extracts (CSE1) and (COM) was determined using GC/MS analysiswhich revealed the presence of several constituents that have been reported toexhibit antimicrobial activity. Additionally, the dichloromethane extract (COM)produced six major components including n-nonadecane, 1,2,3-propanetricarboxylic acid, 2-(acetyloxy)-, tributyl ester, 2-methylhexadecan-1-ol,1-docosene, 1-eicosanol and chloroacetic acid, octadecyl ester. However, theethanolic extract (CSE1) was characterized by the presence of fatty acids, fattyacids ethyl esters and aromatic hydrocarbon where the most abundant compoundwas n-tridecanoic acid ethyl ester.