The design, synthesis, and biological evaluation of aplysinopsin analogs as potential neuromodulators
Aplysinopsins are tryptophan-derived natural products that have been isolated from a variety of marine organisms and have been shown to possess a range of biological activities. Initial synthesis of a library of 50 aplysinopsin analogs revealed that of the 12 serotonin receptor subtypes and 34 other CNS receptors, aplysinopsin analogs shoa high affinity for the 5-HT2B and 5-HT2C receptor subtypes, with selectivity for 5-HT2B over 5-HT2C. Bromination at C-4 and C-5 of the indole ring resulted in greater binding affinities, with Ki's as low as 35 nM. In addition, biological evaluation of the MAO-A and MAO-B inhibitory activities of these compounds revealed some potent and selective MAO inhibitors. The most active compound 54, which is brominated at C-6 and methylated at N-2' and N-4', shostrong inhibitory activity at MAO-A (IC50 of 0.0056 uM) and had an SI of 80.24. Compounds 31, 51, and 54 were evaluated in the chick anxiety-depression model to assess their in vivo efficacy. Compound 33 shoa modest antidepressant effect at a dose of 30 nM/kg in the animal model. In an effort to improve the in vivo efficacy of aplysinopsin analogs, we used an in silico ADME predictor (QikProp) to evaluate and design a new series of analogs with improved ADME properties. We also evaluated the metabolic stability of compound 53 and found that the aplysinopsin scaffold does not appear to be overly susceptible to phase I metabolism, with a T1/2 of 61 minutes. We synthesized a new library of 12 analogs and evaluated their affinities at 46 CNS receptors and inhibitory activity at MAO-A and B. We found that N-benzyl aplysinopsin analogs had moderate nanomolar-level affinities for 5-HT2B and 5-HT2C receptor subtypes. C-5 Substituted compounds (88 and 89) had potent and selective inhibitory activity at MAO-A. Compounds 83, 88, and 89 were evaluated in the chick-anxiety depression model to evaluate their in vivo efficacy. Compound 83 shomodest antidepressant activity at a dose of 10 mg/kg and compound 89 shopotent antidepressant activity across all doses (1-10 mg/kg).
antidepressant, aplysinopsins, MAOI, natural products, serotonin, Pharmacy and Pharmaceutical Sciences
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