Preparation and characterization of immobilized 5-HT1A receptor stationary phase for high throughput screening of the receptor-binding ligands from complex systems like Curcuma wenyujin Y. H. Chen et C. Ling extract

The incidence of depression has increased significantly during the COVID-19 pandemic. This disease is closely associated with serotonin _1A (5-HT_1A) receptor and often treated by complex prescription containing Curcuma wenyujin Y. H. Chen et C. Ling. Therefore, we hypothesized that this herb contains bioactive compounds specially binding to the receptor. However, the rapid discovery of new ligands of 5-HT_1A receptor is still challenging due to the lack of efficient screening methods. To address this problem, we developed and characterized a novel approach for the rapid screening of ligands by using immobilized 5-HT_1A receptor as the chromatographic stationary phase. Briefly, haloalkane dehalogenase was fused at the C-terminal of 5-HT_1A receptor, and the modified 5-HT_1A receptor was immobilized on amino-microspheres by the reaction between haloalkane dehalogenase and 6-chlorohexanoic acid linker. Scanning electron microscope and X-ray photo-electron were used to characterize the morphology and element of the immobilized receptor. The binding of three specific ligands to 5-HT_1A receptor was investigated by two different methods. Moreover, we examined the feasibility of 5-HT_1A receptor colume in high throughput screening of new ligands from complex systems as exemplified by Curcuma wenyujin Y. H. Chen et C. Ling. Gweicurculactone, 2-hydroxy-1-(3,4-dihydroxybenzene)-7-(4′-hydroxybezene)-heptane and curcuminol F were identified as the ligands of 5-HT_1A receptor with the binding energies of −7.06 kcal/mol, −7.77 kcal/mol and −5.26 kcal/mol, respectively. Collectively, these results indicated that the immobilized 5-HT_1A receptor was capable of screening bioactive compound from complex system, providing an effective methodology for high throughput screening.

Development and characterization of a selective chromatographic approach to the rapid discovery of ligands binding to muscarinic-3 acetylcholine receptor

The pursuit of new ligands binding to muscarinic-3 acetylcholine receptor (M₃R) is viewed as challenging due to the lack of screening methods with high efficiency. To address such challenges, this work developed and characterized an approach to the rapid discovery of M₃R ligands using the immobilized receptor as the chromatographic stationary phase. We fused haloalkane dehalogenase (Halo) as a tag at the C-terminus of M₃R. The fusion M₃R was immobilized on 6-chlorocaproic acid-activated ammino-microspheres by the specific covalent reaction between the Halo-tag and the linker. Comprehensive characterizations of the immobilized M₃R were performed by scanning electron microscope, X-ray photoelectron spectroscopy, and the investigation on the binding of three specific ligands to the receptor. The feasibility of the immobilized M₃R in complex matrices was tested by screening the bioactive compounds in Zhisou oral liquid, assessing the interaction between the screened compounds and the receptor using zonal elution, and evaluating the in vivo activity of the targeted compounds. The results evidenced that the immobilized M₃R has high specificity, good stability, and the capacity to separate M₃R ligands from complex matrices. These allowed us to identify naringin, hesperidin, liquiritigenin, platycodin D, and glycyrrhizic acid as the potential ligands of M₃R. The association constants of the five compounds to M₃R were 4.44 × 10⁴, 1.11 × 10⁴, 7.20 × 10⁴, 4.15 × 10⁴, and 3.36 × 10⁴ M^-1. The synergistic application of the five compounds exhibited an equivalent expectorant activity to the original formula. We reasoned that the current method is possible to provide a highly efficient strategy for the discovery of receptor ligands.

Rapidly identifying bioactive compounds from Zhisou oral liquid by immobilized receptor-based high-performance affinity chromatography

The identification of bioactive compounds in complex matrices remains a major challenge due to the lack of highly efficient and specific methods. This work developed an approach based on high-performance affinity chromatography to identify the potential antitussive compounds from Zhisou oral liquid . The main methods include the synthesis of immobilized beta2-adrenoceptor by a one-step method, the screening and identification of the potential bioactive compounds by the receptor column coupled with mass spectrometry, and the binding mechanism analysis of the compounds to the receptor by the in vivo experiment, injection amount dependent method and molecular simulation. We identified the potential bioactive compounds of Zhisou oral liquid as glycyrrhizic acid, platycodin D, tuberostemonine, and hesperidin. In vivo experiment showed that the combinational utilization of the four compounds was possible to present an equivalent antitussive effect to the formula. The docking results demonstrated that hydrogen bonds and Van der Waals forces were the main forces to drive the binding of the four compounds to beta2-adrenoceptor. We concluded that the four compounds are the effective components in Zhisou oral liquid. The proposed strategy is possible to provide an alternative for the development of highly efficient methods to pursue the bioactive compounds of complex matrices.