Figure 2.

Phlorotannins inhibit the biosynthesis and oligomerization of amyloid beta fragments. (A) Aβ is produced via the proteolytic cleavage of APP protein by β-secretase and then γ-secretase. Phlorotannins inhibit β-secretase (BACE1) and γ-secretase activity and promote APP processing by α-secretase, suppressing Aβ production. (B) Aβ monomers aggregate into soluble oligomers, fibrils, and plaques. Phlorotannins inhibit the oligomerization into soluble oligomers as well as fibrilization into fibrils. Ultimately, plaque formation is reduced. Red flat-ended arrows indicate inhibition, red upward arrows indicate upregulation, and red downward arrows indicate downregulation. Aβ, amyloid beta; APP, amyloid precursor protein; BACE1, beta secretase 1; sAPPα, soluble amyloid protein precursor alpha; sAPPβ, soluble amyloid protein precursor beta; CTFα, C-terminal fragment alpha; CTFβ, C-terminal fragment beta. Adapted from Kang et al. (2011) and Yang et al. (2018).