Table 1.

The plant extracts and formulations providing neuroprotection in Parkinson's disease models by targeting α-synuclein.

Plant extract(s) (Plant name, family)	Experimental model system (s)	Effects and mechanisms observed	References
Acanthopanax senticosus harms (Siberian Ginseng, Araliaceae)	SH-SY5Y cells overexpressing wild-type or A53T mutant α-syn	■ Inhibits α-syn, caspase-3, Akt, and p-GSK3β ■ Reverses phospho-microtubule-associated tau in cells	Li et al., 2014
Alaria esculenta (Winged kelp, Araliaceae)	α-syn aggregation biochemical, biophysical assays	■ Reduces the melting point of α-syn ■ Inhibits aggregation and fibril formation by interacting with an unfolded form of α-syn	Giffin et al., 2017
Bacopa monnieri (Waterhyssop, Plantaginaceae)	Caenorhabditis elegans expressing human α-syn and 6-OHDA expressing GFP neurons	■ Reduces α-syn aggregation ■ Prevents dopaminergic cell death	Jadiya et al., 2011
Cinnamon zeylanicum (Cinnamon, Lauraceae)	α-syn aggregation assay and A53T α-syn expression in drosophila	■ Inhibits α-syn aggregation, stabilizes soluble oligomers of α-syn and redirects to “off-pathway” oligomers ■ Improves behavior and cognition	Shaltiel-Karyo et al., 2012
Centella asiatica (Asiatic pennywort, Apiaceae)	α-syn aggregation assay	■ Inhibits α-syn aggregation and stabilizes oligomer ■ Disintegrates preformed fibrils	Berrocal et al., 2014
Carthamus tinctorius (Safflower extract with flavonoids, Asteraceae)	6-OHDA-induced rat model of PD	■ Improves behavioral performances ■ Reduces α-syn aggregation and astrogliosis ■ Decreases tortuosity and the rate constant of clearance	Ren et al., 2016
Crocus sativus L. (Saffron, Iridaceae)	α-syn aggregation, and α-syn fibril dissociation assays	■ Prevents dissociation of fibrils and inhibit α-syn aggregation	Inoue et al., 2018
Chondrus crispus (Red seaweed or Irish Moss, Gigartinaceae)	6-OHDA-induced neurodegeneration in transgenic Caenorhabditis elegans	■ Reduces α-syn accumulation ■ Attenuates oxidatives stress and improved longevity	Liu et al., 2015
Corema album (Portuguese Crowberry, Ericaceae)	Cellular and in vitro models of α-syn toxicity and aggregation	■ Promotes non-toxic α-syn and inhibits its aggregation ■ Promotes autophagic flux and reduces oxidative stress	Macedo et al., 2015
Geum urbanum (Bennet, colewort, Rosaceae)	α-syn aggregation biochemical, biophysical assays	■ Inhibits α-syn fibrillation dose dependent ■ Disintegrates preformed α-syn fibrils	Lobbens et al., 2016
Opuntia ficus-indica (Prickly pear, Cactaceae) and Padina pavonica (Peacock's tail, brown algae, Dictyotaceae)	PD model of transgenic drosophila expressing human α-syn A53T	■ Increases lifespan and correct behavioral deficit ■ Inhibits fibrillogenesis, stabilize/remodeloligomers	Briffa et al., 2017
Panax ginseng (G115) (Asian ginseng, Araliaceae)	β-sitosterol β-d-glucoside-induced PD in rats	■ Prevents dopaminergic loss and locomotor deficits ■ Attenuates α-Syn aggregation, microgliosis, and apoptosis	Van Kampen et al., 2003
Polygala tenuifolia (Tenuigenin) (Chinese Senega, Polygalaceae)	SH-SY5Y cells transfected with wild-type or A53T mutant α-syn	■ Improves cell viability ■ Reduces α-syn phosphorylation and PLK3 levels	Zhou et al., 2013
S/B formulation (Scutellaria baicalensis Georgi; Baikal skullcap, Lamiaceae and Bupleurum scorzonerifolfium Willd)	α-syn aggregation in the infused substantia nigra of rats	■ Attenuates inflammation, apoptosis, oxidative, mitochondrial and ER stress and preserves glutathione ■ Attenuates astrocytosis/microgliosis, improve dopamine ■ Inhibits α-syn aggregation in SNc	Lin et al., 2011
Rehmannia glutinosa Libosch (Chinese foxglove, Scrophulariaceae)	Monosodium L-glutamate induced-hippocampal changes in rats	■ Polysaccharides show anxiolytic activity ■ Inhibits down-regulation of β-Syn	Cui et al., 2013
Scutellaria pinnatifida (Skullcap, Lamiaceae)	PC12 and primary dopaminergic neurons	■ Dichloromethane and n-butanol extract reduces α-SN aggregation and scavenges free radicals	Sashourpour et al., 2017
Tianma Gouteng Yin (Traditional Chinese medicine decoction)	Rotenone intoxicated and human α-syn transgenic drosophila and SH-SY5Y cells	■ Enhances fly survival and locomotion ■ Reduces the loss of dopaminergic neurons and cytotoxicity ■ Inhibits α-syn and dopaminergic neurons degeneration	Liu et al., 2015