HPLC-DAD fingerprinting analysis, antioxidant activities of Tithonia diversifolia (Hemsl.) A. Gray leaves and its inhibition of key enzymes linked to Alzheimer's disease.

Tithonia diversifolia (Hemsl.) A. Gray leaves have long been used to manage neurodegenerative diseases without scientific basis. This study characterized the phenolic constituents, evaluated the antioxidant properties of phenolic extracts from T. diversifolia leaves used as traditional medicine in Africa and its inhibition of key enzymes linked to Alzheimer's disease. The extract was rich in phenolic acids (gallic acid, chlorogenic acid, caffeic acid and p -coumaric acid) and flavonoids (apigenin) and had 1,1-diphenyl-2-picryl-hydrazil radical scavenging abilities (IC ₅₀  = 41.05 μg. mL ^-1 ), 2,2-Azino-bis3-ethylbenthiazoline-6sulphonic acid radical scavenging ability (IC ₅₀  = 33.51 μg. mL ^-1 ), iron chelation (IC ₅₀  = 38.50 μg. mL ^-1 ), reducing power (Fe ³⁺ - Fe ²⁺ ) (7.34 AAEmg/100 g), inhibited acetylcholinesterase (IC ₅₀  = 39.27 μg mL ^-1 ) and butyrylcholinesterase (IC ₅₀  = 35.01 μg mL ^-1 ) activities. These results reveal the leaf as a rich source of phenolic compounds with antioxidant and cholinesterase inhibitory activity.