A Combined NMR and UV-Vis Approach to Evaluate Radical Scavenging Activity of Rosmarinic Acid and Other Polyphenols.

Oxidative stress results from an imbalance between reactive oxygen species (ROS) production and the body's ability to neutralize them. ROS are reactive molecules generated during cellular metabolism and play a crucial role in normal physiological processes. However, excessive ROS production can lead to oxidative damage, contributing to various diseases and aging. This study is focused on rosmarinic acid (RA), a hydroxycinnamic acid (HCA) derivative well known for its antioxidant activity. In addition, RA has also demonstrated prooxidant behavior under specific conditions involving high concentrations of transition metal ions such as iron and copper, high pH, and the presence of oxygen. In this study, we aim to clarify the underlying mechanisms and factors governing the antioxidant and prooxidant activities of RA, and to compare them with other HCA derivatives. UV-Vis, NMR, and EPR techniques were used to explore copper(II)'s binding ability of RA, caffeic acid, and p-coumaric acid. At the same time, UV-Vis and NMR methods were exploited to evaluate the polyphenols' free radical scavenging abilities towards ROS generated by the ascorbic acid-copper(II) system. All the data indicate that RA is the most effective polyphenol both in copper binding abilities and ROS protection.

Vietnamese Dalbergia tonkinensis: A Promising Source of Mono- and Bifunctional Vasodilators.

Hypertension is a risk factor for cardiovascular diseases, which are the main cause of morbidity and mortality in the world. In the search for new molecules capable of targeting KCa1.1 and CaV1.2 channels, the expression of which is altered in hypertension, the in vitro vascular effects of a series of flavonoids extracted from the heartwoods, roots, and leaves of Dalbergia tonkinensis Prain, widely used in traditional medicine, were assessed. Rat aorta rings, tail artery myocytes, and docking and molecular dynamics simulations were used to analyse their effect on these channels. Formononetin, orobol, pinocembrin, and biochanin A showed a marked myorelaxant activity, particularly in rings stimulated by moderate rather than high KCl concentrations. Ba2+ currents through CaV1.2 channels (IBa1.2) were blocked in a concentration-dependent manner by sativanone, 3'-O-methylviolanone, pinocembrin, and biochanin A, while it was stimulated by ambocin. Sativanone, dalsissooside, and eriodictyol inhibited, while tectorigenin 7-O-[ß-D-apiofuranosyl-(1→6)-ß-D-glucopyranoside], ambocin, butin, and biochanin A increased IKCa1.1. In silico analyses showed that biochanin A, sativanone, and pinocembrin bound with high affinity in target-sensing regions of both channels, providing insight into their potential mechanism of action. In conclusion, Dalbergia tonkinensis is a valuable source of mono- and bifunctional, vasoactive scaffolds for the development of novel antihypertensive drugs.