Background:Alpha-synuclein (α-syn) aggregation products may cause neural injury and
several neurodegenerative disorders (NDs) known as α-synucleinopathies. Alkaloids are secondary
metabolites present in a variety of plant species and may positively affect human health, particularly
α-synucleinopathy-associated NDs.Aim:To summarize the latest scientific data on the inhibitory properties of alkaloids in α-
synucleinopathies, especially in Parkinson’s disease.Methods:Literature search was performed using web-based databases including Web of Science,
PubMed, and Scopus up to January 2024, in the English language.Results:Harmala alkaloids, caffein, lycorine, piperin, acetylcorynoline, berberin, papaverine, squalamine,
trodusquemine and nicotin have been found to be the most active natural alkaloids against
synucleinopathy. The underlying mechanisms that contribute to this effect would be the inhibition
of α-syn aggregation; elimination of formed aggregates; improvement in autophagy activation; promotion
of the activity and expression of antioxidative enzymes; and prevention of oxidative injury
and apoptosis in dopaminergic neurons.Conclusion:The findings of the present study highlight the inhibitory activities of alkaloids against
synucleinopathy. However, no clinical data supports the reported activities in humans, which calls
attention to the need for conducting clinical trials to elucidate the efficacy, safety, proper dosage,
unwanted effects and pharmacokinetics aspects of alkaloids in humans.