Abstract 2324: Translational Stroke Research: Identification Of A Novel Family Of Natural Product Derived Flavonoid-Based Polyphenols With Potent Pleiotropic Neuroprotective Activity.
Multiple plant (fruits, vegetables) and spice (turmeric)-derived natural products, which have pleiotropic activities (anti-inflammatory, antioxidant, anti-apoptotic, neurogenic) are also neuroprotective in vitro against numerous chemical insults and promote behavioral recovery in vivo following embolic strokes. We have focused on 2 types of natural products: 1) curcumin-based compounds such as CNB-001 and 2) flavone-based compounds such as fisetin and baicalein. We have synthesized a new library of flavonoid molecules to improve their pharmacological characteristics and have selected candidates using a battery of vitro screening assays with stringent criteria: 1) HT22 hippocampal cell survival (in vitro ischemia model using 20µM iodoacetic acid); 2) primary mouse cortical neurons cell survival (in vitro excitotoxicity assay using 10µM glutamate); 3) HT22 hippocampal cell survival assay (oxytosis using 5 mM glutamate to induce non-NMDA mediated cell death due to the absence of NMDA receptors on HT22 cells). EC50 ≤ 100 nM and survival ≥80% in the IAA assay, ≥35% survival in the cortical neuron assay and EC50 ≤ 300 nM and ≥50% survival in the oxytosis assay. All compounds were screened in triplicate using concentrations up to 10 µM. We chemically modified fisetin to improve its potency, increase blood brain barrier penetration (CLogP, an indicator of blood brain barrier penetration) and reduce tPSA (topographical polar surface area). We have developed a structure activity relationship (SAR) indicating that the absence of a hydroxyl group on the A ring of fisetin enhances its potency. Two compounds PM-001 and PM-004) are 6 fold more potent than fisetin. Altering a hydroxyl group at the 3-position of the B ring has no impact on activity. The addition of multiple hydrophobic groups to various positions on the A ring, such as the addition of methyl groups at the 6 and/or 7 position improved potency ∼10-100 fold over fisetin (e.g. compound PM-010) while the addition of a more hydrophobic naphthalene group (PM-002) and (PM-003) improved the potency ∼40 fold over fisetin and increased the ClogP and reduced the tPSA. SAR studies on the C ring suggested that hydrogen bond accepting groups such as a methoxy at the 4' position and a hydrogen bond donating group such as a hydroxyl at the 3' position further enhanced potency. For example compound CMS-064, CMS-069 and CMS-092 are some of the most potent compounds, with EC50s below 40 nM. These compounds also have CLogPs and tPSAs consistent with enhanced brain penetration. In conclusion, we have used a rational medicinal chemistry approach in combination with in vitro screening analysis to identify new flavonoid molecules to optimally promote neuroprotection. The molecules which will be discussed in detail are being further characterized and de-risked to treat stroke.
- © 2012 by American Heart Association, Inc.