Neuroprotective potential and phytochemical composition of acorn fruits
Graphical abstract
Introduction
Cancer and neurodegenerative disorders have become major health problems almost all over the world. Cancer is known to be the second most common disease, for this reason, it is a major health problem that leading cause of death worldwide (Siegel et al., 2018; Stewart and Wild, 2014). Alzheimer’s diseases (AD) is a progressive neurodegenerative disorder that are increasing particularly among elderly population and responsible for about 60–70% dementia cases (Rathore et al., 2017).
Although, there are so many methods for combatting the cancer and AD, they cannot always provide effective treatments and mediations. Hence, an extensive research on developing new treatment strategies against these disorders are still needed to cure nowadays. Since ancient times, natural products (NPs), originated from natural sources such as plants, have been used for the cure and treatment of many diseases in Anatolian folk medicine ‘herbal therapies’ (Awasthi et al., 2016; Godyń et al., 2016).
Plants are known to possess various pharmacological activities and extraordinary therapeutic possibilities, have afforded more potent, more selective and less toxic compounds as anti-cancer, -tumor and -proliferation agents. The plant-derived compounds can be used for not only their anticancer activities, but also for their enzyme inhibition activities. Therefore, the scientists have focused on finding alternative treatment strategies such as novel inhibitors derived from natural products with less or no side effects (Gezici and Sekeroglu, 2017; Donadu et al., 2017; Safarzadeh et al., 2014; Cragg and Newman, 2005).
The genus Quercus (Fagaceae) is represented by 32 taxa, and almost 300 species that are distributed almost all over the world, five of the taxa and some of the species are endemic to Turkey. Quercus species are known as ‘meşe’ in Turkish, and mostly used for production of furniture and buildings. Among Quercus species, Quercus coccifera L., known as kermes oak, is an evergreen shrub that is well adapted to the Mediterranean climate, and especially distributed in the Mediterranean phytogeographic region (Şenol et al., 2018; Ozcan and Bayçu, 2005). Acorns are the fruits of oak species that have also been recorded to be used against hemorrhoids, diabetes, and kidney stones as remedy in the Anatolian folk medicine, due to their several biological activities such as antimicrobial, antiulcerogenic, antihelmintic, antiinflammatory, and antioxidant activities (Akcan et al., 2017; Söhretoglu et al., (2007). Besides their therapeutic uses, acorns have been consumed as an herbal coffee due to their distinguished aroma. In our previous study, we analyzed mineral compositions of the acorn coffees which were processed by two ways; boiled-roasted-ground and roasted-ground, and processed herbal coffees were also compared with their raw material in terms of mineral compositions. According to this analysis, we found that raw peeled acorns and acorn coffees prepared by different ways had different mineral compositions. On the other hand, processing affected their mineral composition as well as heavy metal concentrations were found by Sekeroglu et al. (2017a, 2017b).
Neuroprotective effects of the ethyl acetate and methanol extracts of four terebinth coffee brands and the fruits of Pistacia terebinthus L., consumed in Turkey were explored through enzyme inhibition tests against acetylcholinesterase, butyrylcholinesterase, and tyrosinase as well as antioxidant test systems in our previous research (Orhan et al., 2012). In our another previous research proved that herbal coffees prepared from date coffee samples (Phoenix dactylifera L.) showed the highest enzyme inhibitory effects among the tested coffees obtained from Gundelia tournefortii L. (tumble thistle), Nigella sativa L. (black cumin), Phoenix dactylifera L. (date), and Ceratonia siliqua L. (carob) as well as a sample of instant coffee (Nescafe®, green blend) (Sekeroglu et al., 2012).
Taking our previous results on herbal coffees, the present study aimed to investigate total polyphenolic contents, in vitro antioxidant effects, neuroprotective and enzyme inhibitory activities of the ethanol and water extracts from the shell, cup and shelled acorn parts of acorn (Q. coccifera L.). Since oxidative damage is one of the major factors contributing to both cancer and neurodegeneration, in vitro antioxidant activity was analyzed by using 2,2-diphenyl-1-picrylhydrazyl (DPPH) free radical scavenging and ferric reducing antioxidant power (FRAP) assays. Neuroprotective activity of the extracts was assessed through enzyme inhibition assays on acetylcholinesterase (AChE) and butyrylcholinsterase (BChE), which are linked to AD. Enzyme inhibitory activity, radical scavenging and ferric reducing antioxidant power activities of different parts from acorn (Q. coccifera L.) have not previously been reported elsewhere. This assessment may help us to find new potential sources of natural agents against treatment of Alzheimer's disease and cancer.
Section snippets
Chemicals
Ferric chloride, Folin–Ciocalteu’s reagent, ethanol-EtOH, methanol-MeOH, 2,2-diphenyl-1-picrylhydrazyl (DPPH), 5,5-dithio-bis(2-nitrobenzoic acid) (DTNB), AChE (Electric ell acetylcholinesterase, Type-VI-S, EC 3.1.1.7), BChE (horse serum butyrylcholinesterase, EC 3.1.1.8), 3,4-dihydroxy-l-phenylalanine (L-DOPA), acetylthiocholine iodide (ATCI), butyrylthiocholine chloride (BTCl), all phenolic and flavonoid standards were purchased from Sigma (St. Louis, MO, USA), and the others from Merck
Total phenol and flavonoid contents of the extracts
Total phenol and the flavonoid quantities of the extracts were determined spectrophotometrically. Equations for total phenol contents of the extracts were determined in accordance with the equation (y = 0.9144x-0.643, r2 = 0.9905) as gallic acid equivalent (mg/g extract), while their total flavonoid contents were calculated according to the equation (y = 0.9344x-0.703, r2 = 0.9967) as quercetin equivalent (mg/g extract).
As given in Table 1, Ethanol extract prepared from the shelled acorn parts
Discussion
Many biological activities including anticarcinogenity, antimurtagenity, antiaging and others are originated from antioxidant properties of phytochemicals that are of great importance and fundamental for pathological pathways. Decreasing the adverse effects of free radical reactions and eliminating the hazardous effects of reactive oxygen species are strongly associated with the efficient treatment strategies of cancer and Alzheimer disease. As the main treatment strategy, the scientists have
Conclusion
In conclusion, these results suggest that different parts of Acorn could be used as novel herbal products’ raw material in the treatment of Alzheimer's disease for their inhibitory activity on the AChE and BChE enzymes, as well as cancer for their rich antioxidant capacity. As far as our literature survey, there has been no study so far examining neuroprotective and antioxidants effects of the extracts using different parts of kermes oak acorn. Therefore, the results presented in this research
Conflict of interests
The authors declare that they have no conflicts of interest with the contents of this article.
Acknowledgments
The authors would like to thank to Kilis 7 Aralık University, Central Laboratory for their technical support. The abstract of our manuscript, had been presented as an oral presentation in The Fourth International Congress on Applied Biological Sciences (ICABs-2018) in Eskisehir-Turkey in 2018.
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