Study on the structural modification of Pixiu alcohol and its anticoagulant factor Xa activity
Pixiu grass is an annual herbaceous plant of the Pixiu genus in the Asteraceae family. The 2020 edition of the Pharmacopoeia of the People’s Republic of China includes dried aboveground parts of three plants in the Asteraceae family, namely Siegesbeckia orientalis L., Siegesbeckia pubescens Makino, and Siegesbeckia glabrescent Makino, as traditional Chinese medicine “Siegesbeckia”. It has the effects of dispelling wind and dampness, promoting joint development, and detoxifying. It is used for rheumatism and pain, muscle and bone weakness, soreness and weakness in the waist and knees, limb paralysis, hemiplegia, rubella and wet sores. Modern pharmacological experiments have shown that the extract of Polygonatum sibiricum has anti-inflammatory, anti allergic, anti thrombotic, and anti histamine release activities. Chemical composition and pharmacological activity studies have shown that the abundant diterpenoid compounds in Polygonatum sibiricum are the material basis for its various effects, especially in anti-inflammatory, analgesic, and blood activating and stasis removing aspects.
Darutigenol is a diterpenoid compound extracted from the plant Scutellaria baicalensis. Modern pharmacological experiments have shown that Darutigenol can significantly inhibit the maximum platelet aggregation rate and adhesion rate in rats, prolong the dissolution time of euglobulin and the bleeding and coagulation time in mice, significantly reduce the whole blood viscosity and plasma viscosity in blood stasis model rats, improve abnormal blood rheology, and inhibit TXB2 synthesis in blood stasis model rats. It has obvious antithrombotic, thrombolytic, anticoagulant and hemorheological effects. The coagulation factor Xa (FXa) is located at the intersection of endogenous and exogenous coagulation pathways, and plays an important role in the coagulation pathway, making it one of the hotspots in anticoagulant drug research in recent years. Therefore, this paper conducted structural modification studies on the active compound Pixiu alcohol isolated from Pixiu grass by our research group in the early stage, and explored its effect on coagulation factor Xa, in order to discover lead compound molecules with better activity. This study will provide reference for the discovery of new small molecule antithrombotic drugs and the development of medicinal plants such as Hedyotis diffusa.

 

From the clinical efficacy of FXa inhibitors represented by iduban, it can be seen that it has good anticoagulant effect, a wide treatment window, and is not prone to causing hypercoagulable reactions, with high safety. It has become a hot topic in the research of anticoagulant drugs today. Natural products have unique advantages in anticoagulation, and discovering active ingredients from traditional Chinese medicine with precise clinical efficacy and conducting structural modification research may be an important way to discover new anticoagulants. Pixiu alcohol is an active compound isolated from the traditional Chinese medicine Pixiu grass. Previous studies have shown that it has significant anticoagulant activity. Therefore, this study conducted structural modification research on Pixiu alcohol and screened for FXa inhibitory activity, aiming to discover novel FXa inhibitors with development value.

Based on the structural characteristics of berberine, a heterocyclic ring was introduced into the original structure to improve the hydrophilicity and activity of this type of compound. Therefore, several derivatives were designed and synthesized by introducing a five membered heterocyclic ring on the A ring of berberine. By conducting in vitro FXa inhibition experiments on berberine and its derivatives, seven compounds with good activity (IC50<10 μ mol/L) were obtained. Compared with berberine, most derivatives showed a certain enhancement in the inhibitory activity of coagulation factor FXa, among which compounds 9 and 11 were the most significant, with IC50 values of 0.71 ± 0.07 and 0.22 ± 0.03 μ mol/L, respectively. Preliminary structure-activity relationship studies have shown that introducing methylene groups onto the 15,16-diols in the original structure and introducing heterocycles into the A ring can enhance the activity of compounds, and the electronic effect on the heterocyclic substituents plays an important role in improving activity. According to the analysis of ligand protein interaction patterns in computer-aided drug design, the hydroxyl group on the imidazole ring of compound 9 and the amino group on the thiophene ring of compound 11 act as hydrogen bond donors to form hydrogen bonds with FXa, thereby enhancing the affinity between the compound and the receptor. This may be the reason for its strong activity. In addition, the sulfur heterocycle in the structure of compound 11 may contribute to the improvement of compound activity, and further exploration is needed. The above will provide new ideas for further optimizing the structure of derivatives of berberine.