In vitro study and structure-activity relationship analysis of stilbenoid derivatives as powerful vasorelaxants: Discovery of new lead compound

Discovery of a 4-Hydroxy-3'-Trifluoromethoxy-Substituted Resveratrol Derivative as an Anti-Aging Agent

With the intensification of population aging, aging-related diseases are attracting more and more attention, thus, the study of aging mechanisms and anti-aging drugs is becoming increasingly urgent. Resveratrol is a potential candidate as an anti-aging agent, but its low bioavailability limits its application in vivo. In this work, a 4-hydroxy-3'-trifluoromethoxy-substituted resveratrol derivative (4-6), owing to its superior cell accumulation, could inhibit NO production in an inflammatory cell model, inhibit oxidative cytotoxicity, and reduce ROS accumulation and the population of apoptotic cells in an oxidative stress cell model. In D-galactose (D-gal)-stimulated aging mice, 4-6 could reverse liver and kidney damage; protect the serum, brain, and liver against oxidative stress; and increase the body's immunity in the spleen. Further D-gal-induced brain aging studies showed that 4-6 could improve the pathological changes in the hippocampus and the dysfunction of the cholinergic system. Moreover, protein expression related to aging, oxidative stress, and apoptosis in the brain tissue homogenate measured via Western blotting also showed that 4-6 could ameliorate brain aging by protecting against oxidative stress and reducing apoptosis. This work revealed that meta-trifluoromethoxy substituted 4-6 deserved to be further investigated as an effective anti-aging candidate drug.

The predominance of endothelium-derived relaxing factors and beta-adrenergic receptor pathways in strong vasorelaxation induced by 4-hydroxybenzaldehyde in the rat aorta

4-hydroxybenzaldehyde (4HB), known as ρ-hydroxybenzaldehyde, is commonly present in traditional Chinese medicine herb, most frequently used for hypertension treatment. This research aims to determine the potency of 4HB's vasorelaxant action. In the study, the vasodilation effect of 4HB was evaluated using in vitro isolated rat aortic rings assay. The aortic rings were pre-incubated with respective antagonists before being pre-contracted with phenylephrine (PE) and challenged with various concentrations of 4HB for mechanistic action studies. R_max (maximal vasodilation) and pEC₅₀ (negative logarithm of half-maximal effective concentration) values of each experiment were determined for comparison purposes. 4HB caused vasodilation on endothelium-intact aortic rings which pre-contracted with PE (pEC₅₀ = 3.53 ± 0.05, R_max = 100.95 ± 4.25%) or potassium chloride (pEC₅₀ = 2.96 ± 0.13, R_max = 72.13 ± 4.93%). The vasodilation effect of 4HB was significantly decreased in the absence of an endothelium (pEC₅₀ = 2.21 ± 0.25, R_max = 47.96 ± 4.16%). The atropine, 4-aminopyridine, Nω-nitro-L-arginine methyl ester, glibenclamide, and propranolol significantly reduced the vasorelaxation effect of 4HB. Besides that, 4HB blocked the voltage-operated calcium channel (VOCC) and regulated the intracellular Ca²⁺ release from the sarcoplasmic reticulum (SR) in the aortic ring. Thus, the results indicated that 4HB exerted its vasodilatory effect via cGMP and β₂ pathways, M₃-dependent PLC/IP₃ pathways, and potassium and calcium channels.

Discovery of trans-3,4,4'-trihydroxystilbene as new lead vasorelaxant agent for antihypertensive drug development

AIMS

The structure-vasorelaxant activity relationships (SARs) assessment in previous study has found that trans-3,4,4'-trihydroxystilbene (344OH) could potentially act as a vasorelaxing agent with demonstration of over 2-fold maximal relaxation (Rmax) compared to its analogue, resveratrol. The present study focuses on the mechanism of actions and pathways employed by 344OH and compared to its analogue to further speculate the SAR of stilbenoids towards vasorelaxation.

MATERIALS AND METHODS

The 344OH employed in present study was synthesized based on the protocol in previous study. The vascular responses towards the cumulative addition of 344OH were evaluated using in vitro rat aortic rings assays.

KEY FINDINGS

The pEC50 and Rmax values were found to be 4.33 ± 0.05 and 106 ± 3.99%, respectively. Results showed that the vasorelaxation of 344OH were predominated by G-protein-coupled muscarinic- (M3) and β2-adrenergic receptors, followed by PGI2/AC/cAMP- and NO/sGC/cGMP-dependent pathways. It was also identified that 344OH employed voltage-activated- (Kv), calcium-activated- (Kca) and inwardly-rectifying (Kir) potassium channels and act as an antagonist for both VOCC and IP3R while regulating the action potential in the vasculature.

SIGNIFICANCE

The different position of hydroxyl substituent located in A-ring of the stilbenoid backbone in 344OH compared to resveratrol resulted in a significant difference in mechanistic actions that lead to 344OH's fast-acting and less time-dependent vasorelaxation behaviour. This has substantially increased the potential of 344OH to be developed as an effective antihypertensive drug in future. Present findings further strengthen our inferences where the SARs study approach should be carried out as the mainstream methodology in future drug development research.