Fennel has neuroprotective effects against Alzheimer’s disease, dementia, and multiple sclerosis, and the proposed mechanisms are as follows: acetylcholinesterase (AChE) and butyrylcholinesterase (BChE) inhibitory activity, increasing the depleted levels of oxidative stress markers (SOD1 and peroxiredoxin-6), and the three isoforms of APP (APP common, 770 and 695) expression; estrogenic function; suppression of nuclear transcription factor κB (NF-κB) pathway (by the inhibiting the inhibitory subunit of NF-kB (IκBα) degradation. Here, PRDX6 is linked to early-onset autosomal dominant Alzheimer disease.