Enzymatic Synthesis of Resveratrol α‑Glycosides from β‑Cyclodextrin-Resveratrol Complex in Water

Although resveratrol (3,5,4′-trihydroxy-stilbene) is one of the most studied natural product because of its biological properties such as antioxidant or anticancer, its low water solubility and stability (influenced by pH, light and increased temperature), as well as its propensity to oligomerize, limit its bioavailability and applications in nutraceutic, cosmetics or pharmaceutical industries. Besides, resveratrol production at the multigram scale through vine cell culture is limited by the tedious extraction of pure resveratrol from the bioconversion medium due to its complexation by cyclodextrins, the latter being used as elicitors in the bioproduction process. In this work, we have been able to overcome all these drawbacks by performing a single organic solvent-free enzymatic α-glycosylation directly from the β-cyclodextrin-resveratrol complex in water using β-cyclodextrin as glycoside-donor. The combined effects of five parameters (CGTase amount, cyclodextrin amount, cyclodextrin/resveratrol ratio, pH, and temperature) were studied by design of experiments (DoE) to maximize the glycosylation yield. The optimal setting point of parameters was obtained by response surface methodology (RSM). After optimization, an efficient α-glycosylation was performed being obtained 35% of molar yield. The major glycosidestwo monoglycosides: 3-<i>O</i>-α-d-glucosyl-resveratrol and 4′-<i>O</i>-α-d-glucosyl-resveratrol and two diglycosides: 3-<i>O</i>-α-d-maltosyl-resveratrol and 4′-<i>O</i>-α-d-maltosyl-resveratrolwere characterized using a hyphenated liquid chromatography-solid phase extraction-nuclear magnetic resonance system, then separated and purified using centrifugal partition chromatography (CPC). Their antiradical properties, as well as that of their crude mixture, were evaluated through DPPH analysis. Results confirmed that the position 4′–OH is the best position for the glycosylation to maintain the highest antiradical properties

¹³C NMR and LC-MS Profiling of Stilbenes from Elicited Grapevine Hairy Root Cultures

Resveratrol and related oligostilbenes are defense molecules produced by grapevine in response to stresses including various elicitors or signal molecules. Together with their prominent role <i>in planta,</i> these compounds have been the center of much attention in recent decades due to their pharmacological properties. The cost-effective production of resveratrol derivatives such as viniferins or more structurally complex stilbene oligomers remains a challenging task. In this study, the chemical diversity of stilbenes produced by <i>Vitis vinifera</i> Pinot Noir hairy roots was investigated after elicitation for 4 days with a mixture of methyl jasmonate (100 μM) and cyclodextrins (50 mM). Two crude extracts obtained from the culture medium and from the hairy roots were fractionated by centrifugal partition chromatography. The fractions were chemically investigated by two complementary identification approaches involving a ¹³C NMR-based dereplication method and liquid chromatography coupled to mass spectrometry (LC-MS). In total, groups of 21 and 18 molecules, including flavonoids and stilbenes, were detected in the culture medium and root extracts, respectively. These included resveratrol monomers, dimers, trimers, and a tetramer, thus highlighting the ability of elicited hairy root culture systems to synthesize a wide diversity of secondary metabolites of pharmaceutical significance. The main compounds were unambiguously identified as <i>trans</i>-resveratrol, ε-viniferin, <i>trans</i>-piceatannol, pallidol, scirpusin A, eriodictyol, naringenin, vitisin B, and maackin