Solid-phase total synthesis of cyclic peptide brachystemin A and its immunomodulating activity

Brachystemin A (1) is a biologically active peptide from a Chinese traditional plant Brachystemma calycinum D. Don. (Caryophyllaceae). The current study describes the complete solid-phase total synthesis of peptide 1 by using Kenner's sulfonamide safety-catch linker strategy. It was identified by QTOF/MS data and NMR studies. Synthetic peptide 1 was tested for its immunomodulatory effect on different inflammatory parameters, including production of inflammatory cytokines, interleukin 2 (IL-2), tumor necrosis factor-alpha (TNF-alpha), and interleukin-1 beta (IL-1 beta), and generation of nitric oxide (NO center dot). The synthetic peptide 1 showed a moderate to low level of inhibition on the production of IL-2 (35.2%), TNF-alpha (19.3%), and IL-1 beta (7.5%) at a concentration of 25 mu M. The effect of the compound on viability of cells was also evaluated, and it was found to be nontoxic on 3T3 cells.