Structure-activity relationships for flavone interactions with amyloid β reveal a novel anti-aggregatory and neuroprotective effect of 2′,3′,4′-trihydroxyflavone (2-D08)

[Display omitted] •Five flavones were screened for neuroprotective and anti-aggregatory effects against amyloid β (Aβ1–42).•Quercetin, transilitin, jaceosidin and nobiletin were compared with novel sumoylation inhibitor 2′,3′,4′-trihydroxyflavone (2-D08).•2-D08 was the most effective anti-aggregatory and neuroprotective flavone of the five, with nobiletin the least effective.•Flavonoid B ring hydroxylation is the most important determinant of the Aβ1–42 anti-aggregatory and neuroprotective effect.•2-D08 may offer pleiotropic mechanisms of neuroprotection in Alzheimer’s disease. Naturally-occurring flavonoids have well documented anti-aggregatory and neuroprotective properties against the hallmark toxic protein in Alzheimer’s disease, amyloid β (Aβ). However the extensive diversity of flavonoids has limited the insight into the precise structure-activity relationships that confer such bioactive properties against the Aβ protein. In the present study we have characterised the Aβ binding properties, anti-aggregatory and neuroprotective effects of a discreet set of flavones, including the recently described novel protein sumoylation inhibitor 2′,3′,4′-trihydroxyflavone (2-D08). Quercetin, transilitin, jaceosidin, nobiletin and 2-D08 were incubated with human Aβ1–42 for 48h in vitro and effects on Aβ fibrillisation kinetics and morphology measured using Thioflavin T (ThT) and electron microscopy respectively, in addition to effects on neuronal PC12 cell viability. Of the flavones studied, only quercetin, transilitin and 2-D08 significantly inhibited Aβ1–42 aggregation and toxicity in PC12 cells. Of those, 2-D08 was the most effective inhibitor. The strong anti-amyloid activity of 2-D08 indicates that extensive hydroxylation in the B ring is the most important determinant of activity against β amyloid within the flavone scaffold. The lack of efficacy of jaceosidin and nobiletin indicate that extension of B ring hydroxylation with methoxyl groups result in an incremental loss of anti-fibrillar and neuroprotective activity, highlighting the constraint to vicinal hydroxyl groups in the B ring for effective inhibition of aggregation. These findings reveal further structural insights into anti-amyloid bioactivity of flavonoids in addition to a novel and efficacious anti-aggregatory and neuroprotective effect of the semi-synthetic flavone and sumoylation inhibitor 2′,3′,4′-trihydroxyflavone (2-D08). Such modified flavones may facilitate drug development targeting mult