The hydroperoxyl radical scavenging activity of sulfuretin: insights from theory

Abstract

Sulfuretin (SFR), which is isolated from Rhus verniciflua , Toxicodendron vernicifluum, Dahlia, Bidens tripartite and Dipterx lacunifera , is one of the most important natural flavonoids. This compound is known to have numerous biological activities; among these, the antioxidant activity has not been thoroughly studied yet. In this study, the hydroperoxyl scavenging activity of SFR was examined by using density functional theory calculations. SFR is predicted to be an excellent HOO • scavenger in water at pH = 7.40 with k overall = 4.75 × 10 7 M −1 s −1 , principally due to an increase in the activity of the anionic form following the single-electron transfer mechanism. Consistently, the activity of the neutral form is more prominent in the non-polar environment with k overall = 1.79 × 10 4 M −1 s −1 following the formal hydrogen transfer mechanism. Thus, it is predicted that SFR exhibits better HOO • antiradical activity than typical antioxidants such as resveratrol, ascorbic acid or Trolox in the lipid medium. The hydroperoxyl radical scavenging of SFR in the aqueous solution is approximately 530 times faster than that of Trolox and similar to ascorbic acid or resveratrol. This suggests that SFR is a promising radical scavenger in physiological environments.

7-O-Galloyltricetifavan: a promising natural radical scavenger

“…According to this data, 7OGT has lower BDE(O−H) values than e.g. vanillic acid (85.2 kcal mol −1 ), [16] puerarin (87.3 kcal mol −1 ), [54] resveratrol (83.9 kcal mol −1 ), [55] or viniferifuran (82.7 kcal mol −1 ) [56]. This suggests that 7OGT could exhibit faster antiradical activity (following the FHT mechanism) than these natural antioxidants.…”

“…Thermodynamic evaluation in pentyl ethanoate and water (electronic supplementary material, table S2) did not differ at the most likely site of activity (BDE = 74.6 and 78.9 kcal mol −1 and Δ G ° = −10.7 and −9.6 kcal mol −1 in the lipid and water media, respectively) for the neutral state (H 2 A), however, the PL and SET pathways of this state are not spontaneous in either media (Δ G ° > 0). Previous studies showed that for a compound containing acidic moieties the SET reaction of the dissociated states should be also considered in the aqueous solution [16,18,21,37,54,57]. Thus, the kinetics of the radical scavenging activity of 7OGT against HOO • radical in physiological media were carried out following equations (3.1) and (3.2) below, and the results are presented in table 3.…”

“…Previous research has shown that the antiradical activity of phenolic compounds in aqueous solutions is dominated by anion states [37,38]. The protonation states of 7OGT were investigated at physiological pH to discover potential radical scavenging mechanisms [16,38,57]. Based on the calculated data [58], p K a1 and pK a2 values were 6.87 and 8.29, respectively (figure 3).…”

“…The density functional theory-based quantum chemical calculations used here had been outlined in a range of former works for modelling antioxidant activities of various compounds [16][17][18][19][20]. In brief, the M06-2X/6-311 ++ G(d,p)//M06-2X/6-31 + G(d) method was used to calculate thermodynamic parameters in the gas phase [21].…”

On the Pro-oxidant Activity of Curcumin in Lipid Media: A Theoretical Study

“…The geometry optimization and frequency calculation were carried out with the package of programs Gaussian 09, [36] employing the functional M06-2X and the basis-set 6-31G(d,p), employing the solvent model of continuum density (SDM) [37] with pentyl ethanoate as a solvent to mimic the lipid media. [38][39][40] The M06-2X is among the best performing functionals for calculating reaction energies involving free radicals and for kinetic calculations in solutions. [41,42] The geometry optimization and frequency calculations from the first singlet excited-state ( 1 CUR*) employed TD-DFT calculations, including the solvent effects, in the TD-M06-2X/6-31G(d,p) level.…”