INHIBITION OF ACETYLCHOLINESTERASE AND BUTYRYLCHOLINESTERASE ACTIVITIES BY TWO TOMATO VARIETIES AND THEIR SUBSTITUTES

Abstract

This study sought to characterize the effects of Snake gourd (Tricosanthes cucumerina), Hmong red tomato (Cucumis sativus 'Hmong Red') and two varieties of common tomatoes: Lycopersicon esculentum Mill. var. esculentum (Roma tomato) and Lycopersicon esculentum Mill. var. cerasiforme (local tomato) on acetylcholinesterase (AChE) and butyrylcholinesterase (BChE) activities in vitro. Characterisation of the phenolics and carotenoids, inhibition of Fe2+ and quinolinic acid induced malondialdehyde (MDA) production in rats brain homogenate in vitro,free radicals [1,1-diphenyl–2 picrylhydrazyl (DPPH), 2,2'-azino-bis(3-ethylbenzthiazoline-6-sulphonic acid) (ABTS) and nitric oxide (NO)] scavenging abilities, Fe2+ chelation and ferric reducing antioxidant property (FRAP) were also assessed. There was no significant (P>0.05) difference in the total phenolic content of the samples [Snake gourd (3.44mg/g), Roma tomato (3.48mg/g), Local tomato (3.42mg/g), Hmong red (3.50mg/g)], while Roma tomato (0.62mg/g) had significantly (P<0.05) higher total flavonoid content than snake gourd (0.44mg/g), local tomato (0.41mg/g) and Hmong red (0.44mg/g). The GC characterization of the phenolics from the samples revealed the presence of high amounts of naringenin chalcone [Snake gourd (57.778mg/100g), Roma tomato (77.943mg/100g), Local tomato (60.141mg/100g), Hmong red (105.196mg/100g)], naringenin [Snake gourd (21.542mg/100g), Roma tomato (26.327mg/100g), Local tomato (30.267mg/100g), Hmong red (20.822mg/100g)], rutin [Snake gourd (65.354mg/100g), Roma tomato (73.692mg/100g), Local tomato (55.246mg/100g), Hmong red (134.752mg/100g)]. Also, a high amount of lycopene [Snake gourd (4.5301mg/100g), Roma tomato (4.2881mg/100g), Local tomato (4.3747mg/100g), Hmong red (5.6307mg/100g)] were detected. Hmong red had significantly (P<0.05) lower AChE inhibitory ability than the other samples [Snake gourd (EC50 = 5.20/ml), Roma tomato (EC50 = 5.83mg/ml), Local tomato (EC50 = 5.70/ml)], while Local tomato (EC50 = 3.75mg/ml), and Hmong red (EC50 = 3.58/ml) had significantly higher BChE inhibitory activity than Snake gourd (EC50 = 5.80/ml), and Roma tomato (EC50 = 7.42mg/ml). Furthermore, the samples inhibited Fe2+ and quinolinic acid induced malondialdehyde (MDA) production in rats brain homogenates in a dose-dependent manner and further exhibited antioxidant activities as typified by their reducing power, Fe2+ chelation and radicals (DPPH, ABTS, OH and NO) scavenging abilities. Therefore, inhibition of AChE and BChE activities as well as the antioxidant properties of the “tomatoes” could make them good dietary means for the management of neurodegenerative disorders