Myxochelin A is a microbial metabolite that has been found in A. disciformis and has diverse biological activities.1 It is active against Gram-positive bacteria, including B. cereus, S. aureus, and M. luteus, but not Gram-negative bacteria or fungi in an agar diffusion assay when used at a concentration of 80 μg/disc. Myxochelin A inhibits 5-lipoxygenase (5-LO) activity with an IC50 value of 1.9 μM for the recombinant human enzyme.2 It is cytotoxic to 26-L5 colon cancer cells when used at a concentration of 3 μg/ml.3

1.Kunze, B., Bedorf, N., Kohl, W., et al.Myxochelin A, a new iron-chelating compound from Angiococcus disciformis (Myxobacterales). Production, isolation, physico-chemical and biological propertiesJ. Antibiot. (Tokyo)42(1)14-17(1989) 2.Schieferdecker, S., K?nig, S., Koeberle, A., et al.Myxochelins target human 5-lipoxygenaseJ. Nat. Prod.78(2)335-338(2015) 3.Miyanaga, S., Obata, T., Onaka, H., et al.Absolute configuration and antitumor activity of myxochelin A produced by Nonomuraea pusilla TP-A0861J. Antibiot. (Tokyo)59(11)698-703(2006)