Resveratrol's Hidden Hand: A Route to the Optical Detection of Biomolecular Binding

Towards resolving the enigma of the dichotomy of resveratrol: cis- and trans-resveratrol have opposite effects on TyrRS-regulated PARP1 activation

Unlike widely perceived, resveratrol (RSV) decreased the average lifespan and extended only the replicative lifespan in yeast. Similarly, although not widely discussed, RSV is also known to evoke neurite degeneration, kidney toxicity, atherosclerosis, premature senescence, and genotoxicity through yet unknown mechanisms. Nevertheless, in vivo animal models of diseases and human clinical trials demonstrate inconsistent protective and beneficial effects. Therefore, the mechanism of action of RSV that elicits beneficial effects remains an enigma. In a previously published work, we demonstrated structural similarities between RSV and tyrosine amino acid. RSV acts as a tyrosine antagonist and competes with it to bind to human tyrosyl-tRNA synthetase (TyrRS). Interestingly, although both isomers of RSV bind to TyrRS, only the cis-isomer evokes a unique structural change at the active site to promote its interaction with poly-ADP-ribose polymerase 1 (PARP1), a major determinant of cellular NAD+-dependent stress response. However, retention of trans-RSV in the active site of TyrRS mimics its tyrosine-bound conformation that inhibits the auto-poly-ADP-ribos(PAR)ylation of PARP1. Therefore, we proposed that cis-RSV-induced TyrRS-regulated auto-PARylation of PARP1 would contribute, at least in part, to the reported health benefits of RSV through the induction of protective stress response. This observation suggested that trans-RSV would inhibit TyrRS/PARP1-mediated protective stress response and would instead elicit an opposite effect compared to cis-RSV. Interestingly, most recent studies also confirmed the conversion of trans-RSV and its metabolites to cis-RSV in the physiological context. Therefore, the finding that cis-RSV and trans-RSV induce two distinct conformations of TyrRS with opposite effects on the auto-PARylation of PARP1 provides a potential molecular basis for the observed dichotomic effects of RSV under different experimental paradigms. However, the fact that natural RSV exists as a diastereomeric mixture of its cis and trans isomers and cis-RSV is also a physiologically relevant isoform has not yet gained much scientific attention.

Resveratrol isomeric switching during bioreduction of gold nanoparticles: a gateway for cis-resveratrolArchita

Resveratrol, a polyphenolic and biocompatible molecule, exhibits significant pharmacological effects but has poor bioavailability and metabolic stability. It appears in two isomeric forms trans-(E)-resveratrol (tRes) and cis-(Z)-resveratrol (cRes). Many pharmacological activities studied so far are of tRes and is the most stable, predominant, and natural form. cRes is not commercially available due to difficulty in its purification and hence not explored much for its biological activities. Therefore, our study focuses on investigating the stability and therapeutic potential of cRes through its bio-conjugation to nanomaterial. In this study, tRes reduces gold ions to gold nanoparticles (GNPs) and itself gets oxidized to its isomeric form cRes. The isomeric switching was evidenced through cRes characteristic spectral differences and chromatographic elution pattern. The monodispersed GNPs of 25.6 ± 0.4 nm size was formed having zeta potential of -19 ± 3.82 mV confirming it to be a stable formulation. The stability studies were further extended to be tested under different physiological fluids. The cRes loaded GNPs (cRGNPs) reflecting the biological activity of cRes presented equivalent antioxidant property to that of tRes even at low concentrations. Also, cRGNPs showed the hemocompatibility by presenting no hemotoxicity and simultaneous in vitro anti-hemolytic activity. Therefore, the stability provided to cRes upon conjugating to GNPs can further be exploited to study the biological activities of cRes through its nano-conjugated delivery.

Vibrational optical activity for structural characterization of natural products

This review presents the recent progress towards elucidating the structures of chiral natural products and applications using vibrational optical activity (VOA) spectroscopy.