Elsevier

Food and Chemical Toxicology

Volume 49, Issue 9, September 2011, Pages 2305-2312
Food and Chemical Toxicology

Insights into cholinesterase inhibitory and antioxidant activities of five Juniperus species

https://doi.org/10.1016/j.fct.2011.06.031Get rights and content

Abstract

In vitro acetylcholinesterase (AChE) and butyrylcholinesterase (BChE) inhibitory and antioxidant activities of the aqueous and ethanol extracts of the leaves, ripe fruits, and unripe fruits of Juniperus communis ssp. nana, Juniperus oxycedrus ssp. oxycedrus, Juniperus sabina, Juniperus foetidissima, and Juniperus excelsa were investigated in the present study. Cholinesterase inhibition of the extracts was screened using ELISA microplate reader. Antioxidant activity of the extracts was tested by 2,2-diphenyl-1-picrylhydrazyl (DPPH) and superoxide radical scavenging, ferrous ion-chelating, and ferric-reducing antioxidant power (FRAP) assays. Total phenol and flavonoid contents of the extracts were determined spectrophotometrically. The extracts had low or no inhibition towards AChE, whereas the leaf aqueous extract of J. foetidissima showed the highest BChE inhibition (93.94 ± 0.01%). The leaf extracts usually exerted higher antioxidant activity. We herein describe the first study on anticholinesterase and antioxidant activity by the methods of ferrous ion-chelating, superoxide radical scavenging, and ferric-reducing antioxidant power (FRAP) assays of the mentioned Juniperus species.

Highlights

Anticholinesterase and antioxidant activities of five Juniperus species were investigated. ► The leaf aqueous extract of Juniperus foetidissima showed the highest BChE inhibition (93.94 ± 0.01%). ► The leaf extracts usually exerted higher antioxidant activity. ► This is the first study on anticholinesterase and antioxidant activity on Juniperus species.

Introduction

Juniperus species (Cupressaceae) are evergreen shrubs or trees that favor dry rocky or sandy soils. The genus consists of approximately 67 species all native to the northern hemisphere, although Juniperus procera Hochst. ex Endl. grows southward along the rift mountains in East Africa into the southern hemisphere. In Turkey, the genus is represented by 10 taxa, from coastal foredunes of the Mediterranean up to altitudes of 1500 m on the Taurus Mountains and also in central and northern parts of Anatolia (Adams, 1998, Davis, 1997).

The essential oils, leaves, and berries of Juniperus species have been used for cosmetic and medicinal purposes for several centuries. The oils obtained by either steam distillation of berries and wood or by dry distillation of heartwood (cade oil and juniper tar oil) are applied for treatment of many diseases from leprosy, typhoid to tape worm. Juniper berries and leaves are used for diuretic, antiseptic, carminative, stomachic, antirheumatic, antifungal, and disinfectant properties in many folk medicines. Juniper berries are used as a spice, particularly in European cuisine, which are the only spice derived from conifers. The berries are used in northern European and particularly Scandinavian cuisine to ‘‘impart a sharp, clear flavor” to meat dishes, especially wild bird and game meats. It is also used to season pork, cabbage, and sauerkraut dishes. Traditional recipes for “choucroute garnie”, an Alsatian dish of sauerkraut and meats, universally include juniper berries (Loizzo et al., 2007).

Alzheimer’s disease (AD) is a deadly neurodegenerative disease with progressive character and has become a major health problem especially in industrialized countries in which the life standards are higher. The pathogenesis of AD has not been totally elucidated, yet, and, therefore, no cure is available to seize the disease except for only symptomatic treatment against mild to moderate types of AD (Orhan et al., 2007). Acetylcholinesterase (AChE) inhibitors have lately become the most prescribed drug class in AD treatment since acetylcholine deficit has been diagnosed in the brains of AD patients (Nordberg and Svensson, 1998). However, AD is also known to be associated with oxidative stress and metal accumulation in senile plaques formed in the patients. In this regard, it is important for any drug candidate, which can be used for AD treatment, to possess both cholinesterase inhibitory potential besides antioxidant activity (Senol et al., 2010).

In Turkey, nearly all Juniperus (Cupressaceae) species are used commonly as tea in traditional medicine. In our endeavoring research on finding new cholinesterase inhibitors from medicinal plants since the year of 2000, we have now targeted to investigate AChE and butyrylcholineesterase (BChE) inhibitory activities of the aqueous and ethanol extracts of the leaves and ripe fruits and the ethanol extracts of the unripe fruits of Juniperus communis ssp. nana, Juniperus oxycedrus ssp. oxycedrus, Juniperus excelsa, Juniperus foetidissima, and Juniperus sabina by spectrophotometric method of Ellman using ELISA microplate reader at 50, 100, and 200 μg/ml concentrations. Antioxidant activity of the extracts was assayed by four in vitro methods namely; 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical and superoxide anion radical scavenging, ferrous ion-chelating, and ferric-reducing antioxidant power (FRAP) tests. In addition, total phenol and flavonoid contents of the extracts were determined spectrophotometrically.

Section snippets

Plant materials

The plant species were collected during October and June in 2007 from the vicinities of Yozgat province (Turkey) and were identified by one of us (N.O.). The voucher specimens have been stored in the Herbarium of Faculty of Pharmacy (GUEF), Gazi University, Ankara, Turkey. The herbarium (GUEF) numbers of the plants are given as follows; J. oxycedrus ssp. oxycedrus (GUEF 2616), J. communis ssp. nana (GUEF 2617), J. sabina (GUEF 2618), J. foetidissima (GUEF 2619), J. excelsa (GUEF 2754).

Preparation of the extracts

Total phenol and flavonoid contents

Calibration equation for total phenol determination was found as y = 0.0606x + 0.1016 (r2 = 0.9828). On the other hand, it was calculated as y = 0.0055x + 0.0635 (r2 = 0.9991) for total flavonoid contents. Results of total phenol and flavonoid amounts of the extracts were listed in Table 2. The extracts appeared to be richer in total phenol, where as their total flavonoid contents were quite low as compared to their total phenol amounts. The richest extract regarding total flavonoid content was found to be

Discussion

Inhibition of cholinesterase is an important target in the fight against AD. Since several adverse effects have been reported with the currently available anticholinesterase agents, by which only symptomatic therapy can be achieved, it is necessary to explore new drug candidates for AD. Many aromatic plants containing remarkable amount of essential oil have been reported to have inhibitory effects against cholinesterase enzymes (AChE and BChE) in various studies (Perry et al., 2000, Orhan et

Conclusion

In the current study, we have screened the EtOH and H2O extracts prepared from the leaves and berries of five Juniperus species (J. communis ssp. nana, J. oxycedrus ssp. oxycedrus, J. sabina, J. foetidissima, and J. excelsa) for their cholinesterase inhibitory and antioxidant activities. Although the extracts were not much effective against AChE, the unripe fruit EtOH and the leaf H2O extracts of J. foetidissima (63.45 ± 4.32% and 93.94 ± 0.01%, respectively) displayed remarkable inhibition against

Conflict of Interest

The authors declare that there are no conflicts of interest.

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