In Vitro Ubiquitination Platform Identifies Methyl Ellipticiniums as Ubiquitin Ligase Inhibitors

Agelasine Diterpenoids and Cbl-b Inhibitory Ageliferins from the Coralline Demosponge Astrosclera willeyana

“…The organic solvent extract of the sponge Astrosclera willeyana was separated by bioassay-guided diol flash chromatography and C 18 HPLC to yield four new metabolites named agelasines W-Y (1-3) and N(1)-methylisoageliferin (4) (Figure 1), along with six known compounds: N(1 )-methylisoageliferin (5), N(1 )-methylageliferin (6), N(1),N(1 )dimethylisoageliferin (7), N(1),N(1 )-dimethylageliferin (8), N(1 )-methyl-2-bromoageliferin (9), and N(1 )-methyl-2 -bromoageliferin (10). The calcareous demosponge Astrosclera willeyana is often referred to as a "living fossil" that is representative of late Paleozoic and Mesozoic reef sponges, and it has provided unique secondary metabolites such as N-methylated ageliferin derivatives and manzacidin D [9,10].…”

“…While the ageliferins are rather modest inhibitors of Cbl-b, the ageliferin structural scaffold could serve as a starting point for the development of more potent analogs with enhanced inhibitory properties. The known compounds 5-10 were identified as N(1′)-methylisoageliferin (5 methylageliferin (6), N(1),N(1′)-dimethylisoageliferin (7), N(1),N(1′)-dimethylag (8), N(1′)-methyl-2-bromoageliferin (9), and N(1′)-methyl-2′-bromoageliferin comparison of their spectroscopic data with the appropriate literature values [10] Compounds 1-10 were tested for their ability to inhibit the in vitro enzymatic of the Cbl-b ubiquitin ligase (Table 3). The adenine-diterpenoid metabolites agelas Y (1-3) showed weak inhibitory activities against Cbl-b (IC50 > 50 µM), while the ag derivatives (4-10) had more pronounced inhibitory effects (IC50 = 18~35 µM).…”

“…An extract of Astrosclera willeyana was identified as an active source in a screening campaign of prefractionated natural product samples for the inhibition of Cbl-b ubiquitin ligase activity [8]. The bulk extract was fractionated as described above, and the resulting fractions were evaluated for activity in the Cbl-b bioassay, the details of which have already been reported [8].…”

“…Thus, targeting Cbl-b may be an effective strategy to enhance antitumor immunity. As part of an ongoing effort to identify small molecule inhibitors of the Cbl-b function from natural products [8], an extract of the sponge Astrosclera willeyana was screened and showed a marked reduction of Cbl-b ligase activity.…”

“…The agelasines represent a family of diterpene-adenine conjugates that has only been described from sponges in the genus Agelas. In addition, a new bromopyrrole alkaloid, N(1)methylisoageliferin (4), along with six known ageliferin derivatives (5)(6)(7)(8)(9)(10) were isolated and identified. Herein, we describe the isolation, structure elucidation, and biological activities of the A. willeyana metabolites.…”