Diketopiperazine derivatives from  isolated from the Red Sea alga

Mohammed, Noha A.; Hassan, Hossam M.; Rateb, Mostafa E.; Ahmed, Eman F.; Hawas, Usama W.; Sameer, Somayah; Ebel, Rainer; El-Safty, Mounir M.; Hameed, Mohammed S. Abdel; Hammouda, Ola H.

doi:10.4103/1687-4315.124030

Diketopiperazine derivatives from isolated from the Red Sea alga

Authors

Abstract

Aim
This study is an attempt to explore the biological activities of isolated endophytic bacteria from marine sources that were coded A1, A2, and A3 (), A4 (), A5 (), and A6 (). The bacteria coded C1, C2, and C3 were isolated from the soft coral Nephthea mollis and S1 and S2 were isolates from the sponge spp. The primary aim of the study was the identification of active compounds.
Materials and methods
The bioactive compounds were extracted using ethyl acetate from nutrient broth media; biological activities of the extracted metabolites and 16S rDNA identification of the most promising isolate were studied. The eight major fractions of the extract showed different composition patterns when identified by liquid chromatography/mass spectrometry analyses.
Results and conclusion
Agar diffusion assay showed inhibitory activities of A4 extracts against the growth of most pathogenic microorganisms. Identification using PCR 16S rDNA and electrophoresis confirmed 98% identity to the strain GH1 (ac: JF261136.1). Eight compounds out of fifteen in the extract were identified as diketopiperazine derivatives. The maximum growth of was obtained at 30°C, pH 7, with the addition of maltose and KI to the media. The free radical scavenging activity exhibited good antioxidant activity (72.19%, IC = 1.266 mg/ml) on using 2.0 mg/ml of the crude extract. The extract showed a high antiviral activity towards Newcastle disease virus and avian influenza virus A(H5N1).

Keywords