Elsevier

Food Chemistry

Volume 120, Issue 4, 15 June 2010, Pages 1076-1082
Food Chemistry

Acetylcholinesterase inhibition and antioxidant activity of the water extracts of several Hypericum species

https://doi.org/10.1016/j.foodchem.2009.11.055Get rights and content

Abstract

Many Hypericum species are widely used in Portugal, as well as in many other countries. In order to define the main components present in the water extracts, three Hypericum species, H. androsaemum and H. perforatum, obtained in the local supermarket, and H. undulatum, collected in an interior region of Portugal, were analysed for their inhibition of acetylcholinesterase and antioxidant activity. H. perforatum from five different suppliers was tested. All species were active, with IC50 values between 0.62 ± 0.06 and 1.79 ± 0.37 mg dry extract/ml. HPLC–diode array analysis indicated that chlorogenic acid, rutin, hyperoside, isoquercitrin, and quercitrin were the main compounds present in the water extracts. Their inhibitory activities, determined as IC50 values, were 196, 86, 66, 63 and 62 μg/ml, respectively. The highest inhibitory activity was found with H. androsaemum and H. undulatum. All the species showed high antioxidant activity (DPPHradical dot test). Values of EC50 between 9.0 ± 0.2 and 18.4 ± 0.8 μg of dry extract/ml were obtained.

Introduction

Hypericum perforatum, also known as St. John’s wort, has been used in the treatment of mild depression (Eggelkraut-Gottanka et al., 2002, Kasper et al., 2008, Pilkington et al., 2006, Wurglics and Schubert-Zsilavecz, 2006) all over the world. Portugal is no exception (Cunha, Silva, & Roque, 2003). Several studies refer to hypericin (Eggelkraut-Gottanka et al., 2002, Sauviat et al., 2007) and hyperforin (Eggelkraut-Gottanka et al., 2002, Leuner et al., 2007, Menegazzi et al., 2008, Zhou et al., 2004) as the compounds in Hypericum perforatum that may explain its biological activity. Most of the studies carried out with this plant refer to polar organic extracts (Brolis et al., 1998, Gioti et al., 2005, Liu et al., 2005, Silva et al., 2008, Tatsis et al., 2007, Williams et al., 2006). Very few studies deal with the water extracts, e.g. infusions or decoctions.

Depression is also a condition found in people suffering from Alzheimer disease (AD) and one of the processes to alleviate the symptoms is to inhibit acetylcholinesterase (AChE) (Heinrich & Teoh, 2004), the enzyme that catalyses the hydrolysis of the neurotransmitter, acetylcholine. This way to tackle the problem involves the use of drugs that have been the objective of much research. One of the active compounds in use, for instance galantamine, was isolated from the plant genus Galanthus (Latvala et al., 1995). If H. perforatum could show this double action, alleviate depression and simultaneously inhibit AChE, it might be interesting for AD treatment.

The action of Hypericum, on the central nervous system, was previously attributed to the presence hypericin and hyperforin (Verotta, 2003). Although the amounts of hypericin and hyperforin depend on the plant analysed, and also on the extraction procedure, they are usually not the main components of H. perforatum. They are found in smaller concentrations than the flavonoids rutin, hyperoside, isoquercitrin, quercetin and the caffeic acid derivative, cholorogenic acid (Brolis et al., 1998, Williams et al., 2006). These molecules may also participate in the biological activity of H. perforatum (Paulke, Noldner, Scubert-Zsilavecz, & Wurglics, 2008).

The antioxidant activity is also relevant in the treatment of Alzheimer’s disease (Frank and Gupta, 2005, Resende et al., 2008). It was demonstrated that the absence of the natural antioxidant, vitamin E, enhanced AD in a mouse model (Nishida et al., 2006). The endogenous formation of free radicals can contribute to the inflammatory processes (Gomes, Fernandes, Lima, Mira, & Corvo, 2008). It is known that inflammation can also contribute to the development of the disease (Cunningham et al., 2008, Teeling and Perry, 2008).

With the objective of finding whether the Hypericum species, commercially available, drunk as a hot beverage, could contribute to the inhibition of acetylcholinesterase, water extracts of this plant were analysed for their AChE inhibition and antioxidant activity. H. androsaemum and H. perforatum, from different suppliers, and H. undulatum, collected in the east of Portugal, Beira Baixa, were the targets of this study. The main compounds responsible for the enzyme inhibition were determined by HPLC–DAD, comparatively to standards.

Section snippets

Chemicals

All chemicals were of analytical grade. Acetylcholinesterase (AChE) type VI-S, from electric eel, 349 U/mg of solid, 411 U/mg of protein, 5,5′-dithiobis[2-nitrobenzoic acid] (DTNB), acetylthiocholine iodide (AChI), tris[hydroxymethyl]aminomethane (tris buffer), 2,2-diphenyl-1-picrylhydrazyl (DPPH), 2,6-di-tert-butyl-4-hydroxytoluene (BHT), pyrogallol, chlorogenic acid, rutin, hyperoside, isoquercitrin, quercitrin, quercetin and Folin–Ciocalteau reagent were obtained from Sigma.

Plant material

H. androsaemum and

Results

Previous results have demonstrated that, among several plants analysed, H. undulatum was the one giving the highest inhibition activity towards AChE (Ferreira, Proença, Serralheiro, & Araújo, 2006). This provoked a more detailed study on the effect of different Hypericum species on this enzyme activity, together with the identification of the main compounds responsible for this inhibitory activity. As the origin of the plant is also thought to be responsible for different activities in the

Conclusions

Most literature reports concern the chemical and bio-activity investigation of polar organic extracts, e.g. methanol, ethanol or hydro–alcoholic mixtures. The present work describes the results carried out with decoctions that are usually consumed as herbal tea of Hypericum species. These decoctions contain mainly chlorogenic acid, rutin, hyperoside, isoquercitrin and quercitrin, in different percentages. The samples did not contain either hypericin or hyperforin. Decoctions have antioxidant

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