Antifouling evaluation of extracts from Red Sea soft corals against primary biofilm and biofouling

Objectives: To evaluate antifouling property of extracts from Red Sea soft corals against primary biofilm and biofouling. Methods: Seven species of soft corals Sarcophyton glaucum (a), Sinularia compressa, Sinularia cruciata (a), Heteroxenia fuscescens (a), Sarcophyton glaucum (b), Heteroxenia fuscescens (b) and Sinularia cruciata (b) were chosen to test their extracts as antibacterial and antifouling agents in Eastern Harbour of Alexandria, Mediterranean Sea. Bioactive compounds of soft corals were extracted by using methanol and concentrated under vacuum. The residues of extracts were mixed in formulation of inert paint which consisted of rosin, chlorinated rubber and ferrous oxide against micro and macro fouling organisms. The formulated paints were then applied on PVC panels twice by brush, hanged in a steel frame and immersed in Eastern Harbour of Alexandria Mediterranean Sea followed by visual inspection and photographic recordings. Results: After 185 days of immersion in seawater, the antifouling results agreed with the antibacterial results where extracts of Sinularia compressa and Heteroxenia fuscescens (b) gave the best activity against marine fouling tubeworms and barnacles. The inhibition activity was correlated with the major functional groups (hydroxyl, amino, carbonyl, aliphatic (fatty acids), C=C of alkene or aromatic rings and CeCl of aryl halides) of the extracts. Conclusions: The strong antifouling activity makes them promising candidates for new antifouling additives. After the screening and application of natural organic compounds from soft corals, marine organisms show activity against micro and macro fouling organisms.