Table 2.

phytochemicals depicting their diverse role in the prevention of AD.

Compounds	Class	Mechanism of action	Reference
Ginkgolides	Terpenoid	It enhances the cognitive parameters by enhancing the cholinergic transmission in AD model. Moreover, it substantially diminishing the neurotoxicity, level of proinflammatory cytokines by inhibiting the neuronal MAPK pathway. Further it also decreases the excitotoxic damage caused by glutamate and has antioxidant and antiapoptotic properties	(Kavitha et al., 2020)
Rosmarinic acid	Polyphenol	It decreases the hyperphosphorylation of the tau protein, prevents fibrilization in vitro and reduces β-sheet assembly in tau protein linked to AD	(Alkam et al., 2007)
Resveratrol	Polyphenol	It reduces the aggregation of Aβ and its toxicity and neuroinflammation in brain, thereby substantially play a substantial neuroprotective role in the progression and treatment of moderate to mild AD. It reduces the action mechanism of free radicals and pro-inflammatory proteins by inhibiting the expression of glutathione and COX-2. Moreover, it diminishes the activity and secretion of TNF-alpha and IL-1, thus reducing the pathophysiology of AD.	(Komorowska et al., 2020),(Gu et al., 2021).
Curcumin	Polyphenol	It inhibited the phosphorylation and degradation of IϏB and the nuclear translocation of NF-B p65	(Ahmed et al., 2021)
Docosahexaenoic acids	Polyunsaturated fatty acid	Reduce the oxidative stress and lipid peroxide, also downregulate the β- and γ-secretase activity and enhance the cleaving activity of α-secretase	(Grimm et al., 2016).
Punicalagin	Ellagitannin	Reduces the level of β-secretase, thus decreases the level of β-amyloid plaques.	(Andrade et al., 2019)
Rhodosin	Flavanol	Increases the learning and cognitive behavior mainly due to their antioxidant activities	(Andrade et al., 2019)
Morin	Flavonoid	Inhibit the secretion of β-amyloid plaques in vitro and downregulates Tau protein's hyperphosphorylation in vivo.	(Choudhury et al., 2017)
1,2,3,4,6-Penta-O-galloyl-β-d-glucopyranose	Polyphenol	Inhibit the oligomerisation of Aβ, thus prevent and destabilize the formation of Aβ fibrils. Therefore, reduce the Aβ plaques and enhance the cognitive behaviors.	(Li et al., 2022)
Pterostilbene	Polyphenolic compound	Pterostilbene inhibit the secretion of IL-1β, IL-6, IL-3 and TNF-α, thus reduce the cytotoxicity in cells. Moreover, it also reduces and inactivates the NLRP3/caspase-1 inflammasome.	(Li et al., 2018a)
Salidroside	Glucoside	Salidroside substantially enhance the cognitive behavior in vivo model by regulating the expressions of thioredoxin, thioredoxin associating protein and proteins of NF-ϏB pathway such as p65, NF-ϏB, IKKα, IkB- α, and IKKβ.	(Gao et al., 2015)
Paeoniflorin	Terpene	Paeoniflorin improved memory impairments and lowered A-β accumulation by inhibiting the expression of glycogen synthase kinase-3 (GSK-3), NLRP3 inflammasome, and several cytokines for instance, IL-1β and TNF-α along with the activation of NF-ϏB.	(H.-R.Zhang et al., 2015)
1,8-Cineole	Terpene	It downregulates the mitochondrial membrane dysfunction, NO and ROS levels. It also reduces the expression of several pro-inflammatory cytokines such as IL-1, TNF-α, NF-ϏB and IL-6, COX-2, and NOS-2.	(Khan et al., 2014)
L-Theanine	Amino acid in nature	It substantially diminished the level of A1–42 in brain and also reduce the memory disorders in mice, thus reducing the neuronal death in the hippocampus and cortex regions. In addition, it also dysregulates the expression of some extracellular signal-regulated kinase (ERK), MAPK, p38, and NF-ϏB along with the expression of oxidative biomarkers, glutathione and lipid damage in the brain.	(Kim et al., 2009)