Anti-Allergic Compounds from the Deep-Sea-Derived Actinomycete Nesterenkonia flava MCCC 1K00610

A novel cyclic ether, nesterenkoniane (1), was isolated from the deep-sea-derived actinomycete Nesterenkonia flava MCCC 1K00610, together with 12 known compounds, including two macrolides (2, 3), two diketopiperazines (4, 5), two nucleosides (6, 7), two indoles (8, 9), three phenolics (10-12), and one butanol derivate (13). Their structures were established mainly on detailed analysis of the NMR and MS spectroscopic data. All 13 compounds were tested for anti-allergic activities using immunoglobulin E (IgE) mediated rat mast RBL-2H3 cell model. Under the concentration of 20 μg/mL, 1 exhibited moderate anti-allergic activity with inhibition rate of 9.86%, compared to that of 37.41% of the positive control, loratadine. While cyclo(d)-Pro-(d)-Leu (4) and indol-3-carbaldehyde (8) showed the most potent effects with the IC50 values of 69.95 and 57.12 μg/mL, respectively, which was comparable to that of loratadine (IC50 = 35.01 μg/mL). To the best of our knowledge, it is the first report on secondary metabolites from the genus of Nesterenkonia.