Celastramycin A is an antibiotic that inhibits the growth of bacteria and mycobacteria and is also a potent innate immune suppressor [1][2].

Celastramycin A is a benzoyl pyrrole-type compound isolated from endophytic bacteria Streptomyces MaB-QuH-8 living in plants of the Celastraceae family. Celastramycin A exhibited high activity against a series of multiresistent bacteria and mycobacteria [1]. Celastramycin A inhibited the growth of Gram-positive bacteria and mycobacteria with minimal inhibitory concentration (MIC) as low as 0.05 μg/ml [1]. In the ex vivo Drosophila culture system, Celastramycin A showed a potent immunosuppressive effect with IC50 value of 0.008 μg/mL. In human umbilical vein endothelial cells (HUVECs), Celastramycin A potently inhibited the production of IL-8 with IC50 value of 0.06 μg/mL. So Celastramycin A could be used as a lead compound for novel immunosuppressive agents [2].

References:
[1].  Pullen C, Schmitz P, Meurer K, et al. New and bioactive compounds from Streptomyces strains residing in the wood of Celastraceae. Planta. 2002 Nov;216(1):162-7.
[2].  Kikuchi H, Sekiya M, Katou Y, et al. Revised structure and synthesis of celastramycin a, a potent innate immune suppressor. Org Lett. 2009 Apr 16;11(8):1693-5.