The UV vis and fluorescence spectra have

The UV–vis and fluorescence spectra have been used to study the interaction between small chemical molecules and biomolecules (Punith and Seetharamappa, 2012). The UV Seliciclib peak of the protein changes with the microenvironment of the chromophore. That is, the peaks may show a certain degree of red shift or blue shift, and the absorbance and band may also change. According to the UV absorption spectrum of the characteristic absorption peak intensity, displacement and peak width, the changes in the proteins and small molecules could be determined before and after the interaction of small molecules and proteins. The spectra can also be used for studying the quenching and binding mechanism of the interaction between small molecules and proteins. The interaction between the proteins and small molecules generally includes the fluorescence quenching phenomenon and the fluorescence sensitization phenomenon, of which the fluorescence quenching phenomenon is more common. The interaction types (e.g. static quenching, dynamic quenching) can be confirmed by determining some relevant parameters (such as binding constant, number of binding sites, and thermodynamic constants) (Nan et al., 2016). Chaves et al. studied the binding of lophirone B with bovine serum albumin (BSA) based on the spectroscopic and molecular docking techniques (Chaves et al., 2017). Bayraktutan et al. reported the biophysical influence of coumarin 35 on BSA and confirmed the binding mechanism between them (Bayraktutan and Onganer, 2017).
Materials and methods
Results and discussion
Conclusions
Conflict of interest
Acknowledgements
Introduction Alzheimer's disease (AD), is a neurodegenerative disorder with memory losing, language skill declining or cognitive impairment, and it is commonly found among elderly people, especially in the Western countries [1], [2]. It is reported that AD affect more than 36 million people worldwide, and the number will up to more than 115 million in 2050. Therefore, it is urgent to find new drugs for AD treatment. In the past few years, several drugs approved by FDA to treat AD are tacrine, donepezil, rivastigmine and galantamine, but tacrine is not used by now because of its side-effects [3]. Although the identified factors of AD are associated with acetylcholine deficiency, β-amyloid (Aβ) deposits, oxidative stress, neurofibrillary tangles accumulation, hormone imbalance, mitotic dysfunction and calcium mishandling, we don't know the specific etiopathogenesis [4]. Recently, most studies have concentrate on Acetylcholinesterase (AChE) inhibition, and the drugs that we mentioned above are all AChE inhibitors. AChE is a substrate-specific enzyme which plays a virtual role in the hydrolysis prevention to acetylcholine (ACh) [5], [6]. AChE inhibitors have worked by blocking the breakdown of AChE, and then slowing down neurodegeneration of patients [7], [8]. Flavonoids are widely spread in fruit, vegetables, tea or other plants, and they possess a lot of biological and pharmacological activities about Alzheimer's disease, including antioxidant, neuro-protective effect, Acetylcholinesterase inhibitory activities, anti-inflammatory, antimutagenic effect, antiviral and so on [9], [10], [11]. Hence, Flavonoids can be promising compounds not only spread widely, but also they have the feature of low toxicity [12]. Computer aided drug design (CADD) mainly includes virtual screening and pharmacophore design [13], and it has been an important method in the new drugs discovery, because it saved a great deal of money and it accomplished something that could not be done in experiment [14]. There are a few successful drugs with the aid of CADD technology, like donepezil which has been used in AD treatment [15], [16], Inviraser that has been used in HIV treatment [17]. These successful cases indicate that CADD plays an increasingly important role in the future research and development of new drugs. As we all know, Traditional Chinese Medicine (TCM) is very remarkable in medicinal field today. With little or none side effects, various researchers pay attention on studying Chinese herbal medicine [18], [19]. In this study, we aimed to construct new AChE inhibitors using CADD techniques based on the know flavonoid AChE inhibitors. The guide in the design of new AChE inhibitors is pharmacophore model, and there is no information in relation to pharmacophore for such kind of flavonoid derivatives. It is possible to find potent AChE inhibitors from Traditional Chinese Medicine Database, Druglike Database and MiniMaybridge Database.