Phenolic Constituents and Inhibitory Effects of Hibiscus sabdariffa L. (Sorrel) Calyx on Cholinergic, Monoaminergic, and Purinergic Enzyme Activities.

This study revealed the effect of phenolic extract from Hibiscus sabdariffa L. (sorrel) calyx on acetylcholinesterase (AChE), butyrylcholinesterase (BChE), monoamine oxidase (MAO), and ecto-5' nucleotidase (E-NTDase) activities as well as pro-oxidant-induced oxidative damage in rat brain in vitro. Sorrel extract inhibited AChE (EC50 = 46.96 µg/mL), BChE (EC50 = 40.38 µg/mL), MAO (EC50 = 43.69 µg/mL), and E-NTDase (EC50 = 40.52 µg/mL) and stimulated Na+/K+-ATPase (EC50 = 22.01 µg/mL) activities. The phenolic extract also reduced Fe2+- (EC50 = 22.37 µg/mL) and sodium nitroprusside- (SNP-) (21.46 µg/mL) induced malondialdehyde (MDA) production in rat brain homogenates. Catechin (53.12 mg/g), chlorogenic (67.12 mg/g), rutin (16.25 mg/g), and caffeic acid (15.38 mg/g) were the most abundant phenolic compounds in the extract. The synergistic effects of the phenolic compounds may contribute to the enzyme inhibitory and stimulatory activities of the extract. Our findings suggest that sorrel extract shows promising potential for the treatment and/or management of some neurodegenerative diseases such as Alzheimer's disease and Parkinson's disease.