SUPPLEMENTARY MATERIALS 

 

Autoxidation of melatonin at excited state: mechanism proposal for formation of N1-acetyl-N2-formyl-5-methoxykynuramine

Matheus Ruffo Peres1, Vanessa Regina Miranda2, Aguinaldo Robinson de Souza1, Nelson Henrique Morgon2 and Valdecir Farias Ximenes1,*

 1Department of Chemistry, Faculty of Sciences, UNESP - São Paulo State University, 17033-360, Bauru, São Paulo, Brazil. 2Department of Physical Chemistry, Institute of Chemistry, Campinas State University (UNICAMP), 13083-861, Campinas, São Paulo, Brazil.

*Correspondence: valdecir.ximenes@unesp.br, Tel: +55 14 31036088

S1.png

Fig. S1. Chromatograms before and after autoxidation of melatonin.

     (A) pH 7.0 and (B) pH 10.0. The reaction conditions were: Melatonin 100 mM, UVC (12 W) irradiation for 60 minutes. Peaks (1) melatonin, (2) AFMK, and (3) hydroxy-melatonin.

S2.png

Fig. 2. LC-MS chromatograms of melatonin before and after autoxidation.

     The monitored molecular ion (M+H)+ were 233 (melatonin), 249 (hydroxylated melatonin), and 265 (AFMK). (A) reaction conducted at pH 7.0, (B) reaction conducted at pH 10.0, and (C) Peaks of the molecular ions.

Table S1. Electronic energies and ZPE (in Hartree) of Melatonin (Ground and 1st Excited States).

 





Molecular   System

GS/GS

EE/GS

EE/EE

ZPE





I

-764.40903

-764.25057

-764.26052

0.2747

II

-764.21167

-764.18203

-764.18059

0.2750

III

-763.91312

-763.77386

-763.78498

0.2687

IV

-763.75844

-763.71560

-763.71550

0.2612

















​      Molecular systems obtained at [PBE0 / TD-PBE0-GD3(BJ)/6-311++G(3df,2p) level of theory using IEFPCM(water) to describe the solvent effect

S3.png

Fig S3. Frontier molecular orbitals of the studied species.

    (I)Ground state melatonin, (I*) electronically excited melatonin, (II) ground state melatonin cation radical, (III) ground state deprotonated melatonin, (III*) electronically excited deprotonated melatonin, (IV) ground state melatonin radical.

Table S2. Cartesian Coordinates (in Å) of the ground state of the molecular system (I).

 




Atom

x

y

z







C

-2.095

-0.497

-0.276

C

-0.757

-0.220

-0.624

C

-0.248

1.024

-0.323

C

-1.049

2.008

0.304

C

-2.354

1.734

0.638

C

-2.880

0.465

0.346

C

1.037

1.639

-0.510

C

0.885

2.951

0.020

N

-0.324

3.188

0.501

C

2.263

1.012

-1.047

H

1.658

3.711

0.046

H

-0.174

-0.988

-1.120

H

-2.976

2.479

1.122

H

-3.907

0.251

0.611

H

2.006

0.256

-1.793

H

2.892

1.763

-1.533

C

3.111

0.339

0.049

O

-2.518

-1.739

-0.593

C

-3.852

-2.085

-0.266

H

-3.987

-3.111

-0.600

H

-4.020

-2.027

0.812

H

-4.565

-1.435

-0.783

H

3.976

-0.128

-0.422

H

3.469

1.090

0.754

N

2.397

-0.664

0.799

H

1.957

-0.396

1.664

C

2.158

-1.898

0.318

O

2.590

-2.268

-0.770

C

1.324

-2.798

1.188

H

1.098

-2.366

2.163

H

0.386

-3.011

0.671

H

1.851

-3.744

1.325










      Obtained at PBE0-GD3(BJ)/6-311++G(2d,p) using IEFPCM(water) to describe the solvent effect.

Table S3. Cartesian Coordinates (in Å) of the ground state of the molecular system (II).




Atom

x

y

z







C

-2.024

-0.712

-0.284

C

-0.740

-0.298

-0.596

C

-0.359

1.012

-0.305

C

-1.297

1.891

0.288

C

-2.585

1.477

0.599

C

-2.943

0.169

0.311

C

0.857

1.752

-0.488

C

0.608

3.014

-0.014

N

-0.674

3.103

0.453

C

2.146

1.231

-1.031

H

1.264

3.871

0.022

H

-1.095

3.932

0.835

H

-0.056

-1.000

-1.060

H

-3.301

2.151

1.057

H

-3.944

-0.161

0.553

H

1.949

0.488

-1.810

H

2.711

2.040

-1.503

C

3.040

0.596

0.036

O

-2.324

-2.007

-0.592

C

-3.618

-2.476

-0.279

H

-3.648

-3.517

-0.594

H

-3.816

-2.419

0.795

H

-4.389

-1.915

-0.818

H

3.945

0.196

-0.423

H

3.334

1.352

0.768

N

2.396

-0.483

0.748

H

1.737

-0.243

1.471

C

2.436

-1.762

0.332

O

3.114

-2.126

-0.625

C

1.603

-2.737

1.120

H

1.064

-2.274

1.947

H

0.882

-3.204

0.445

H

2.252

-3.523

1.508











     Obtaimed at PBE0-GD3(BJ)/6-311++G(2d,p) using IEFPCM(water) to describe the solvent effect.

 Table S4. Cartesian Coordinates (in Å) of the ground state of the molecular system (III). 




Atom

x

y

z







C

-2.027

-0.713

-0.245

C

-0.699

-0.290

-0.557

C

-0.346

1.009

-0.295

C

-1.309

1.890

0.248

C

-2.606

1.486

0.548

C

-2.962

0.170

0.300

C

0.875

1.760

-0.467

C

0.588

3.040

-0.031

N

-0.702

3.099

0.386

C

2.177

1.244

-0.942

H

1.222

3.912

0.006

H

-1.146

3.934

0.743

H

-0.020

-1.007

-1.003

H

-3.326

2.177

0.969

H

-3.964

-0.160

0.532

H

2.024

0.496

-1.723

H

2.767

2.057

-1.370

C

3.014

0.603

0.182

O

-2.262

-1.984

-0.522

C

-3.553

-2.525

-0.246

H

-3.502

-3.568

-0.545

H

-3.775

-2.451

0.819

H

-4.315

-2.005

-0.830

H

3.960

0.274

-0.251

H

3.227

1.343

0.953

N

2.380

-0.527

0.810

H

1.913

-0.396

1.692

C

2.382

-1.757

0.256

O

2.913

-1.977

-0.828

C

1.696

-2.839

1.042

H

1.211

-2.473

1.947

H

0.953

-3.321

0.405

H

2.436

-3.594

1.315











     Obtained at PBE0-GD3(BJ)/6-311++G(2d,p) using IEFPCM(water) to describe the solvent effect.

 Table S5. Cartesian Coordinates (in Å of the ground state of the molecular system (IV).




Atom

x

y

z







C

-2.160

-0.777

-0.332

C

-0.946

-0.264

-0.754

C

-0.556

1.015

-0.325

C

-1.422

1.777

0.533

C

-2.639

1.231

0.938

C

-3.008

-0.037

0.511

C

0.582

1.839

-0.537

C

0.311

3.000

0.192

N

-0.876

2.994

0.838

C

1.827

1.501

-1.292

H

0.966

3.866

0.261

H

-0.323

-0.865

-1.411

H

-3.303

1.793

1.589

H

-3.955

-0.450

0.836

H

1.587

0.882

-2.165

H

2.300

2.411

-1.675

C

2.867

0.763

-0.448

O

-2.472

-2.035

-0.792

C

-3.682

-2.608

-0.357

H

-3.735

-3.596

-0.812

H

-3.710

-2.713

0.732

H

-4.549

-2.019

-0.680

H

3.716

0.439

-1.055

H

3.251

1.434

0.328

N

2.277

-0.408

0.158

H

1.297

-0.345

0.395

C

2.943

-1.535

0.437

O

4.146

-1.679

0.210

C

2.124

-2.641

1.052

H

1.065

-2.395

1.134

H

2.237

-3.541

0.445

H

2.518

-2.861

2.046











        Obtained at PBE0-GD3(BJ)/6-311++G(2d,p) using IEFPCM(water) to describe the solvent effect.

 Table S6. Cartesian Coordinates (in Å) of the ground state of O2.




Atom

x

y

z







O

0.000

0.000

0.598

O

0.000

0.000

-0.598










     Obtained at PBE0-GD3(BJ)/6-311++G(2d,p) using IEFPCM(water) to describe the solvent effect.

 Table S7. Cartesian Coordinates (in Å) of the ground state of the O2- (GS).




Atom

x

y

z







O

0.000

0.000

0.662

O

0.000

0.000

-0.662











     Obtained at PBE0-GD3(BJ)/6-311++G(2d,p) using IEFPCM(water) to describe the solvent effect.

 Table S8. Cartesian Coordinates (in Å) of the 1st EE of the molecular system (I).





Atom

x

y

z







C

-2.083

-0.488

-0.286

C

-0.762

-0.226

-0.638

C

-0.228

1.034

-0.335

C

-1.018

2.032

0.300

C

-2.324

1.769

0.639

C

-2.860

0.495

0.344

C

1.042

1.615

-0.521

C

0.917

2.952

0.021

N

-0.274

3.220

0.504

C

2.268

0.981

-1.054

H

1.715

3.689

0.040

H

-0.179

-0.994

-1.138

H

-2.945

2.514

1.128

H

-3.890

0.291

0.613

H

2.012

0.215

-1.793

H

2.904

1.726

-1.544

C

3.108

0.313

0.058

O

-2.542

-1.730

-0.594

C

-3.879

-2.053

-0.253

H

-4.030

-3.081

-0.583

H

-4.039

-1.991

0.828

H

-4.591

-1.398

-0.768

H

3.976

-0.162

-0.404

H

3.464

1.067

0.764

N

2.378

-0.683

0.806

H

1.932

-0.405

1.667

C

2.131

-1.920

0.325

O

2.573

-2.298

-0.765

C

1.277

-2.811

1.188

H

1.069

-2.390

2.174

H

0.327

-2.989

0.676

H

1.776

-3.776

1.306











     Obtained at PBE0-GD3(BJ)/6-311++G(2d,p) using IEFPCM(water) to describe the solvent effect.

 Table S9. Cartesian Coordinates (in Å)  of the 1st EE of the molecular system (II).





Atom

x

y

z







C

-2.060

-0.643

-0.256

C

-0.713

-0.291

-0.596

C

-0.301

1.022

-0.297

C

-1.214

1.931

0.257

C

-2.536

1.609

0.559

C

-2.946

0.250

0.301

C

0.938

1.717

-0.478

C

0.739

3.044

-0.034

N

-0.539

3.127

0.396

C

2.205

1.148

-0.971

H

1.417

3.879

0.014

H

-0.954

3.971

0.765

H

-0.063

-1.031

-1.045

H

-3.222

2.327

0.988

H

-3.955

-0.048

0.547

H

2.009

0.385

-1.730

H

2.824

1.928

-1.424

C

3.038

0.495

0.153

O

-2.355

-1.934

-0.540

C

-3.659

-2.390

-0.244

H

-3.691

-3.437

-0.542

H

-3.870

-2.306

0.826

H

-4.409

-1.824

-0.805

H

3.962

0.115

-0.282

H

3.292

1.243

0.905

N

2.366

-0.593

0.812

H

1.783

-0.388

1.606

C

2.305

-1.832

0.281

O

2.884

-2.122

-0.762

C

1.516

-2.848

1.060

H

0.975

-2.418

1.902

H

0.809

-3.336

0.388

H

2.204

-3.612

1.432











     Obtained at PBE0-GD3(BJ)/6-311++G(2d,p) using IEFPCM(water) to describe the solvent effect.

Table S10. Cartesian Coordinates (in Å) of the 1st EE of the molecular system (III).




Atom

x

y

z







C

-2.071

-0.509

-0.271

C

-0.710

-0.235

-0.607

C

-0.208

0.996

-0.310

C

-1.058

1.964

0.299

C

-2.398

1.699

0.630

C

-2.899

0.459

0.344

C

1.089

1.626

-0.500

C

0.955

2.888

-0.021

N

-0.329

3.079

0.455

C

2.303

0.975

-1.058

H

1.672

3.692

0.025

H

-0.665

3.943

0.856

H

-0.132

-1.014

-1.091

H

-3.018

2.455

1.097

H

-3.925

0.223

0.588

H

2.013

0.249

-1.821

H

2.936

1.721

-1.545

C

3.153

0.264

0.002

O

-2.469

-1.717

-0.584

C

-3.812

-2.131

-0.308

H

-3.875

-3.153

-0.669

H

-4.000

-2.098

0.764

H

-4.517

-1.497

-0.845

H

3.980

-0.243

-0.496

H

3.571

0.998

0.691

N

2.424

-0.702

0.791

H

2.139

-0.448

1.722

C

2.084

-1.916

0.322

O

2.365

-2.274

-0.818

C

1.333

-2.810

1.270

H

1.134

-2.346

2.236

H

0.386

-3.097

0.809

H

1.914

-3.721

1.425











     Obtained at PBE0-GD3(BJ)/6-311++G(2d,p) using IEFPCM(water) to describe the solvent effect.

Table S11. Cartesian Coordinates (in Å) of the 1st EE of the molecular system (IV). 




Atom

x

y

z







C

-2.022

-0.060

-0.315

C

-0.657

-0.073

-0.731

C

0.116

1.029

-0.339

C

-0.436

2.146

0.300

C

-1.804

2.200

0.602

C

-2.577

1.023

0.329

C

1.504

1.343

-0.535

C

1.669

2.655

-0.013

N

0.534

3.134

0.496

C

2.529

0.413

-1.048

H

2.595

3.216

0.035

H

-0.244

-0.942

-1.228

H

-2.245

3.043

1.121

H

-3.624

1.013

0.606

H

2.096

-0.223

-1.825

H

3.375

0.955

-1.483

C

3.078

-0.499

0.072

O

-2.710

-1.196

-0.646

C

-4.073

-1.250

-0.296

H

-4.440

-2.219

-0.633

H

-4.209

-1.167

0.787

H

-4.644

-0.455

-0.787

H

3.708

-1.269

-0.376

H

3.695

0.092

0.751

N

2.057

-1.145

0.861

H

1.603

-0.569

1.555

C

1.322

-2.181

0.378

O

1.644

-2.787

-0.650

C

0.184

-2.625

1.252

H

-0.263

-1.794

1.801

H

-0.579

-3.100

0.637

H

0.546

-3.361

1.980










     Obtained at PBE0-GD3(BJ)/6-311++G(2d,p) using IEFPCM(water) to describe the solvent effect.

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This work is licensed under a Creative Commons Attribution 4.0 International License

Please cite this paper as:

Peres, M.R, Miranda, V.R, de Souza, A.R, Morgon, N.H and Ximenes, V.F 2022. Autoxidation of melatonin at excited state: mechanism proposal for formation of N1-acetyl-N2-formyl-5-methoxykynuramine. Melatonin Research. 5, 3 (Sep. 2022), 325-334. DOI:https://doi.org/https://doi.org/10.32794/mr112500135.