Inhibition of Plasminogen Activator Inhibitor-1 Activity by Two Diketopiperazines, XR330 and XR334 Produced by Streptomyces sp.

Abstract

Two diketopiperazines, XR334 (1) and the novel compound XR330 (2), were isolated from the lyophilised biomass of an unidentified Streptomyces sp. Their structures were elucidated on the basis of spectroscopic studies and confirmed by chemical synthesis. Both compounds inhibited plasminogen activator inhibitor-1 activity in an amidolytic assay of tissue plasminogen activator mediated plasmin generation. Compound1 also enhanced fibrinolysis ex vivo and protected against thrombus formation in the rat. These diketopiperazines represent the first low molecular weight inhibitors of plasminogen activator inhibitor-1, a physiological regulator of fibrinolysis protein including a 23 amino acid signal peptide with a predicted, glycosylated mass of 52 kD3). PAI-1 inhibition of tPA is mediated through a "bait" residue (Arg 346-Met 347) which mimics the normal substrate40. The physiological importance of PAI-1 has been demonstrated in transgenic mice which express high levels of human PAI-1 and suffer severe venous thrombosis5). An increase in the plasma concentration of PAI-1 has been proposed as a risk factor in thrombotic disease6). During a screening programme for inhibitors of PAI-1 activity we discovered a series of low molecular weight, nonpeptidyl inhibitors of PAI-1 from fermentation of an unidentified Streptomyces sp. Twoexamples of this series, XR334 (1) and the novel compound XR330 (2) were purified from the mycelium7) (Fig. 1). A series of closely related metabolites has been isolated from Streptomyces thioluteus including 18). Several of these compounds were reported to show weak antibacterial activity. Synthetic analogues of 1 have also been reported previously9~11}. Related diketopiperazines with putative cytotoxic activity have also been isolated from Micromonospora neiheunsis12). Wereport here an important new biologi- Structures of 1 and 2 isolated from the culture biomass of Streptomyces sp. and the structure confirmed by synthesis. Structures for two additional minor metabolites, 3 and 4, are proposed.

Small molecules inhibitors of plasminogen activator inhibitor-1 – An overview

“…In 1996, research scientists from Xenovia Limited [52] isolated two molecules bearing a diketopiperazine moiety (XR334 (8) and XR330 (9), Fig. 6) from the lyophilized biomass of an unknown Streptomyces sp.…”

“…The initial bis-acetylation of 2,5-piperazinedione was followed by two successive condensations with various aromatic aldehydes using first potassium tert-butoxide in THF, then Cs 2 CO 3 in DMF [52,56].…”

Phenotype-Guided Natural Products Discovery Using Cytological Profiling

“…A query of the Antimarin database revealed one compound, diketopiperazine XR334, which possessed a matching molecular formula, as well as identical NMR and UV spectroscopic features. 18,19 Because this scaffold is synthetically accessible through a two-step condensation reaction between diacetyl-2,5-piperazinedione, benzaldehyde, and p-anisaldehyde, the structure of the isolated antimitotic agent was confirmed by total synthesis (Scheme S1, Supporting Information) and validated by NMR and HPLC-MS comparison with the original reported data ( Figure S2, Supporting Information). 19−21 In addition to the structural verification, the biological activity for the isolated natural product was confirmed through parallel CP screening for dilution series of both the natural and synthetic materials ( Figure 3A).…”

“…XR344 was synthesized from diacetyl-2,5-piperazinedione, benzaldehyde, and p-anisaldehyde following established literature procedures (Scheme S1, Supporting Information). 19 The structures of all synthetic products were confirmed by NMR and MS data and comparison with literature values. Synthetic and naturally occurring XR334 were compared by NMR spectroscopy and LCMS co-injection (Supporting Information).…”

In vitro thrombolytic potential of bioactive compounds from marine Streptomyces sp. VITJS4

“…Apart from enzymes bioactive compounds also play a vital role against thrombus formation, fibrinolytic compounds isolated from a brown algae, Sargassum fulvellum has been reported with fibrinolytic property (WU et al 2009). Diketopiperazines, XR330 and XR334 two diketopiperazines, XR334 the novel compound XR330 produced by Streptomyces sp were found with Plasminogen activator inhibitor-1 (JUSTIN et al 1996). Monamidocin from Streptomyces sp.…”