The Hyptis genus, comprising about 400 species, has been reported to have a diverse range of biological activities, being widely used in Brasilien folk medicine. The aim of this study is to evaluate, compare and discuss the anti-acetylcholinesterase activity of three methanolics extracts from Hyptis leaves’: Hyptis marrubioides (Hm), Hyptis pectinate (Hp) and Hyptis suaveolens (Hs). Among these species, Hs has been the most studied, mainly regarding its antioxidant activity, there being no studies addressing Hm extracts. Inhibition of AChE, the key enzyme in the breakdown of acetylcholine, may be considered as one of the treatment approaches against several neurological disorders including Alzheimer’s. To our knowledge, no studies have been reported regarding anti-AChE activity of Hyptis species.

AChE activity was measured using a modified 96-well microplate assay based on Ellman’s method. IC50 values were calculated for Hm, Hp and Hs methanolic extracts using physostigmine as a positive control. % AChE inhibition = [(Ac – Abc) – (As -Abs)]/ (Ac – Abc) x 100 (Ac = absorbance of the control; Abc = absorbance of the control blank; As = absorbance of the sample; Abs = absorbance of the sample blank). IC50 values were obtained from the graphical curves % AChE inhibition versus Hyptis extracts concentration, via non-linear regression analysis.

The extracts exhibited a dose-dependent AChE % inhibition with IC50 values lower for Hm (45,21 ± 1,672 µg/mL) than the other extracts:IC50 (Hp) = 66,30 ± 3,560 µg/mL and IC50 (Hs) = 68,05 ± 2,994 µg/mL. IC50 (physostigmine) = 6,480x10^-11 ± 7,586x10^-12 mg/mL. One-way ANOVA statistics revealed a significant difference between Hm and the other extracts (p < 0,0001) and no significant difference between Hp and Hs methanolic extracts.

Flavonoids has been considered a prominent source of anti-AD compounds, because of their potential AChE inhibitory activity allied to the well-known antioxidant activity and low toxicity. Accordingly, we have recently reported the phenolic profile and antioxidant activity of Hm, Hp and Hs species, containing mainly quercetin, luteolin, and rosmarinic acid derivatives. Given the present results, studies regarding the role of these Hyptis extracts in neurological disorders progression are warranted.

This work is financed by INTERACT - ISAC project, no. NORTE-01-0145-FEDER-000017, co-financed by the European Regional Development Fund (ERDF) through NORTE 2020 (North Regional Operational Program 2014/2020).