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

Authors: ZAFAR ALI SHAH, ALMAS JABEEN, SAMREEN SOOMRO, M.AHMED MESAIK, M.IQBAL CHOUDHARY, FARZANA SHAHEEN

Abstract: Brachystemin A (\textbf{1}) is a biologically active peptide from a Chinese traditional plant \textit{Brachystemma calycinum} D. Don. (Caryophyllaceae). The current study describes the complete solid-phase total synthesis of peptide \textbf{1} by using Kenner's sulfonamide safety-catch linker strategy. It was identified by QTOF/MS data and NMR studies. Synthetic peptide \textbf{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$^{.})$. The synthetic peptide \textbf{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.

Keywords: \textit{Brachystemma calycinum}, cyclic peptide, brachystemin A, safety-catch linker, immunomodulatory effect, cytokines

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