Hydrogen donation is the key to supercritical water upgrading of heavy oil, because it benefits light distillate production and inhibits condensation , but the mechanism is still unclear. In this work, an isotope tracing method, combined with Fourier transform infrared spectroscopy and nuclear magnetic resonance spectroscopy analyses, was used to elucidate the hydrogen donation mechanism in supercritical water upgrading of asphaltenes . In asphaltenes upgrading, it was found that the aliphatic carbon at the end of the side chain of asphaltene macromolecules could capture deuterium from supercritical heavy water via free radical reactions , and the deuteration ratio at this position was 11 %. For supercritical water upgrading of vacuum residue which is generally considered as a system of asphaltenes dissolved in maltenes, the existing maltenes enhanced hydrogen donation to asphaltenes. Further, a possible hydrogen donation pathway was proposed. This work provides an in-depth understanding of the hydrogen donation mechanism for supercritical water upgrading.
Erastin-treated bone marrow-derived mesenchymal stem cells (bmMSCs) were prepared and used to compare the ferroptosis inhibitory bioactivities of four monostilbenes, including rhapontigenin (1a), isorhapontigenin (1b), piceatannol-3′-O-glucoside (1c), and rhapontin (1d). Their relative levels were 1c ≈ 1b > 1a ≈ 1d in 4,4-difluoro-5-(4-phenyl-1,3-butadienyl)-4-bora-3a,4a-diaza-s-indacene-3-undecanoic acid (C11-BODIPY), 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT), and flow cytometric assays. The comparison highlighted two 4′-OH-containing monostilbenes (1c and 1b) in ferroptosis inhibitory bioactivity. Similar structure–activity relationships were also observed in antioxidant assays, including 1,1-diphenyl-2-picryl-hydrazl radical (DPPH˙)-trapping, 2-phenyl-4,4,5,5-tetramethylimidazoline-1-oxyl 3-oxide radical (PTIO˙)-trapping, and Fe3+-reducing assays. UPLC-ESI-Q-TOF-MS analysis of the DPPH˙-trapping reaction of the monostilbenes revealed that they can inhibit ferroptosis in erastin-treated bmMSCs through a hydrogen donation-based antioxidant pathway. After hydrogen donation, these monostilbenes usually produce the corresponding stable dimers; additionally, the hydrogen donation potential was enhanced by the 4′-OH. The enhancement by 4′-OH can be attributed to the transannular resonance effect. This effect can be used to predict the inhibition potential of other π–π conjugative phenolics.
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