Correction: Agbadua et al. Oxidized Resveratrol Metabolites as Potent Antioxidants and Xanthine Oxidase Inhibitors. Antioxidants 2022, 11, 1832

Text Correction

There was an error in the original publication (Section 2.6) [1]: Dry residue of the combined organic layers was purified by preparative HLPC on a biphenyl column with an isocratic elution of CH₃CN-H₂O (31:69, v/v) to produce compounds 7 (24.80 mg), 8 (13.30 mg), and 9 (33.98 mg) (13.30 mg). Further purification was carried out on the compounds on the same column but using an elution of CH₃OH-H₂O (52:48, v/v) to obtain compounds 7 (11.93 mg) and 9 (22.62 mg). Compound 8 was further purified by HPLC on a Luna Silica column (250 × 4.6 mm, 5 µm, 100 Å) using an elution of cyclohexane-isopropanol (85:15, v/v) to obtain 8.38 mg of pure compound.

A correction has been made to Section 2.6, Reaction with PIFA in Ethanol (Ox4):

The dry residue of the combined organic layers was purified by preparative HLPC on a biphenyl column with an isocratic elution of CH₃CN-H₂O (31:69, v/v) to produce compounds 7 (24.80 mg), 8 (33.98 mg), and 9 (13.30 mg). Further purification was carried out on the compounds on the same column but using an elution of CH₃OH-H₂O (52:48, v/v) to obtain compounds 7 (11.93 mg) and 8 (22.62 mg). Compound 9 was further purified by HPLC on a Luna Silica column (250 × 4.6 mm, 5 µm, 100 Å) using an elution of cyclohexane-isopropanol (85:15, v/v) to obtain 8.38 mg of pure compound.

There was an error in the original publication (Section 2.7) [1]: 2.7. Reaction of Resveratrol with FeCl₃ and Oxone in Ethanol (Ox5).

A correction has been made to the title of Section 2.7, Reaction of Resveratrol with FeCl₃ and Oxone in Ethanol (Ox5):

2.7. Reaction of Resveratrol with Periodic Acid and Oxone in Ethanol (Ox5).

There was an error in the original publication (Section 3.2) [1]: Compound 5, i.e., (E)-(±)-2,3-cis-δ-viniferin, is structurally (±)-(E)-5-(3,5-dihydroxystyryl)-3-(3,5-dihydroxyphenyl)-2-(4-hydroxyphenyl)-cis-dihydrobenzofuran.

A correction has been made to Section 3.2, Structure Elucidation of the Isolated Compounds, Paragraph Number 5:

Compound 5, i.e., (E)-(±)-2,3-trans-δ-viniferin, is structurally (±)-(E)-5-(3,5-dihydroxystyryl)-3-(3,5-dihydroxyphenyl)-2-(4-hydroxyphenyl)-trans-dihydrobenzofuran.

There was an error in the original publication (Section 3.2) [1]: Considering the approximately planar structure of the five-membered ring of dihydrobenzofurans, in the cis isomer (compound 5), a dihedral angle close to zero degrees is consistent with a J(H-2,H-3) = 8 Hz coupling. On the other hand, in the case of trans substituents, the detected J(H-2,H-3) = 5 Hz coupling is in accordance with a ≈ 120° dihedral angle (see compound 6).

A correction has been made to Section 3.2, Structure Elucidation of the Isolated Compounds, Paragraph Number 5:

Even though both compounds 5 and 6 are trans-substituted at the 2,3 positions of the nearly planar dihydrobenzofuran ring, the peri-effect, caused by the 4 substituent of compound 6, alters the geometry of the dominant conformer as compared to that of compound 5. This manifests in differences in the J(H-2,H-3) coupling constants, i.e., 8 Hz and 5 Hz for compounds 5 and 6, respectively.

Error in Figure (in the Main Text)

In the original publication [1], there was a mistake in “Figure 1. Structures of resveratrol (1) and its metabolites obtained by chemical oxidation (2–9). Each optically active compound (5, 6, 8, 9) is racemate; for simplicity, only one enantiomer is presented. For compounds 7 and 9, the relative configuration could not be determined” as published.

In Section 3.2, the stereochemistry of compound 5 was erroneously assigned as (E)-(±)-2,3-cis-δ-viniferin. The subsequent extensive spectroscopic analysis and high-level in silico quantum chemical calculations revealed this compound as a trans-isomer. The structure and stereochemistry of compound 5 were confirmed by comparing with the ¹H-NMR spectroscopic data of trans-δ-viniferin previously reported by Huber and colleagues [2]. Figure 1 should be corrected as follows due to an erroneous additional -OH group added to the structure of 6 in the previously published article. The corrected “Figure 1. Structures of resveratrol (1) and its metabolites obtained by chemical oxidation (2–9). Each optically active compound (5, 6, 8, 9) is racemate; for simplicity, only one enantiomer is presented. For compounds 7 and 9, the relative configuration could not be determined” appears below.

Error in Figure (in Supplementary Materials)

In the original publication [1], there was a mistake in “Figure S4. HPLC-PDA fingerprint of oxidized product mixture Ox4” as published. The numbers 8 and 9 were placed wrongly. The corrected “Figure S4. HPLC-PDA fingerprint of oxidized product mixture Ox4” appears below.

Figure S4. HPLC-PDA fingerprint of oxidized product mixture Ox4.

Figure S4. HPLC-PDA fingerprint of oxidized product mixture Ox4.

In the original publication [1], there was a mistake in “Figure S12. Compound 5, HRMS (positive mode)” as published. The structure of 5 needs to be revised. The corrected “Figure S12. Compound 5, HRMS (positive mode)” appears below.

Figure S12. Compound 5, HRMS (positive mode).

Figure S12. Compound 5, HRMS (positive mode).

In the original publication [1], there was a mistake in “Figure S28. Compound 5, ¹H NMR spectrum, and selROE on δ4.47 and δ5.45 ppm” as published. All stereostructures of compound 5 in Supplementary Figures S28–S32 should be revised. The corrected “Figure S28. Compound 5, ¹H NMR spectrum, and selROE on δ4.47 and δ5.45 ppm” appears below.

Figure S28. Compound 5, ¹H NMR spectrum, and selROE on δ4.47 and δ5.45 ppm.

Figure S28. Compound 5, ¹H NMR spectrum, and selROE on δ4.47 and δ5.45 ppm.

In the original publication [1], there was a mistake in “Figure S29. Compound 5, ¹³C, APT NMR spectrum” as published. All stereostructures of compound 5 in Supplementary Figures S28–S32 should be revised. The corrected “Figure S29. Compound 5, ¹³C, APT NMR spectrum” appears below.

Figure S29. Compound 5, ¹³C, APT NMR spectrum.

Figure S29. Compound 5, ¹³C, APT NMR spectrum.

In the original publication [1], there was a mistake in “Figure S30. Compound 5, HSQC spectrum and HSQC section” as published. All stereostructures of compound 5 in Supplementary Figures S28–S32 should be revised. The corrected “Figure S30. Compound 5, HSQC spectrum and HSQC section” appears below.

Figure S30. Compound 5, HSQC spectrum and HSQC section.

Figure S30. Compound 5, HSQC spectrum and HSQC section.

In the original publication [1], there was a mistake in “Figure S31. Compound 5, COSY spectrum” as published. All stereostructures of compound 5 in Supplementary Figures S28–S32 should be revised. The corrected “Figure S31. Compound 5, COSY spectrum” appears below.

Figure S31. Compound 5, COSY spectrum.

Figure S31. Compound 5, COSY spectrum.

In the original publication [1], there was a mistake in “Figure S32. Compound 5, HMBC spectrum” as published. All stereostructures of compound 5 in Supplementary Figures S28–S32 should be revised. The corrected “Figure S32. Compound 5, HMBC spectrum” appears below.

Figure S32. Compound 5, HMBC spectrum.

Figure S32. Compound 5, HMBC spectrum.

The authors state that the scientific conclusions are unaffected. This correction was approved by the Academic Editor. The original publication has also been updated.