Flavones from Heavenly Blue as modulators of Alzheimer’s amyloid-beta peptide (Aβ) production

Phenolic constituents are the principle bioactive compounds exist in Heavenly Blue (Ipomoea). Little was found in the literature concerning the previous phytochemical and biological studies of Ipomoea tricolor. From leaves of this plant, six compounds were identified: rhoifoloside (1), luteolin-7-O-β-D-glucoside (2), 5,7,4′-trihydroxy-6-methoxyflavone-7-O-β- d -glucoside (3), apigenin (4), 5,7-dihydroxy-3,3′,4′-trimethoxyflavone (5), and 2-hydroxymethylhydroquinone-6-carbaldehyde (6). Their structures were elucidated on the basis of chromatographic, chemical, and spectroscopic methods. All metabolites were reported for the first time in the genus Ipomoea. In vitro and in vivo investigations of the flavones 1, 3, and 5 were assessed as modulators of Alzheimer’s amyloid-beta peptide (Aβ) production. The results indicated that all the three flavones were able to modulate the Aβ concentration both in vitro and in vivo without any cytotoxic effect. A dose-dependent inhibition of Aβ42 secretion was observed. The results showed no inhibition activity of these flavones against cyclooxygenase (COX)-1 and COX-2 up to 500 nM concentration and concomitant reduction in prostaglandin synthesis, indicating that the reduction in Aβ42 levels may be independent of COX activity.