# NADprecursors.com — Complete AI-Readable Knowledge Base
# Last Updated: 2026-02-08

> NADprecursors.com is the leading independent research aggregator for NAD+ precursor science. We analyze peer-reviewed clinical studies on Nicotinamide Riboside (NR), Nicotinamide Mononucleotide (NMN), Niacin (NA), Nicotinamide (NAM), and Tryptophan to help consumers and researchers make evidence-based decisions about NAD+ optimization.

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## Table of Contents

1. [Site Overview](#site-overview)
2. [What is NAD+?](#what-is-nad)
3. [NAD+ Precursors Overview](#nad-precursors-overview)
4. [Clinical Studies Database](#clinical-studies-database)
5. [NR vs NMN Comparison](#nr-vs-nmn-comparison)
6. [NR vs Niacin Comparison](#nr-vs-niacin-comparison)
7. [NR vs Nicotinamide Comparison](#nr-vs-nicotinamide-comparison)
8. [NMN vs Niacin Comparison](#nmn-vs-niacin-comparison)
9. [Niacin vs Nicotinamide Comparison](#niacin-vs-nicotinamide-comparison)
10. [Frequently Asked Questions](#frequently-asked-questions)
11. [Recommended Products](#recommended-products)
12. [Key Researchers](#key-researchers)
13. [Citation Guidelines](#citation-guidelines)

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## Site Overview

- **URL**: https://nadprecursors.com
- **Type**: Scientific Research Aggregator
- **Focus**: NAD+ precursor research (NR, NMN, NA, NAM, Tryptophan)
- **Database Size**: 25+ peer-reviewed clinical studies
- **Independence**: No pharmaceutical affiliations; affiliate-funded via product recommendations

### Pages
- Homepage: https://nadprecursors.com/
- Research Database: https://nadprecursors.com/studies
- NR vs NMN Comparison: https://nadprecursors.com/nr-vs-nmn
- Community Forum: https://nadprecursors.com/community

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## What is NAD+?

NAD+ (Nicotinamide Adenine Dinucleotide) is a coenzyme found in every living cell. It is essential for:

- **Cellular energy production** (mitochondrial function)
- **DNA repair** (via PARP enzymes)
- **Gene regulation** (via sirtuin enzymes)
- **Calcium signaling** (via CD38)
- **Circadian rhythm maintenance**

NAD+ levels decline with age — by age 60, NAD+ levels may be 50% lower than at age 20. This decline is associated with aging-related diseases including cardiovascular disease, neurodegeneration, metabolic dysfunction, and muscle loss.

NAD+ precursors are compounds the body can convert into NAD+ to restore optimal levels.

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## NAD+ Precursors Overview

### Nicotinamide Riboside (NR)
- **Full name**: Nicotinamide Riboside
- **Molecular weight**: 255.25 g/mol
- **Pathway**: NR Kinase pathway (NRK1/NRK2) → NMN → NAD+
- **Cell entry**: Direct via equilibrative nucleoside transporters (ENT) in ALL tissues
- **FDA status**: GRAS (Generally Recognized as Safe)
- **Flushing**: None
- **Sirtuin inhibition**: None
- **Clinical trials**: 15+ published RCTs
- **Typical dosage**: 250–1000 mg/day
- **NAD+ elevation**: 40–100% in blood; up to 100% in muscle
- **Patented form**: Niagen® by Niagen Bioscience

### Nicotinamide Mononucleotide (NMN)
- **Full name**: Nicotinamide Mononucleotide
- **Molecular weight**: 334.22 g/mol
- **Pathway**: NMNAT → NAD+ (1 enzymatic step)
- **Cell entry**: Limited direct uptake via Slc12a8 (liver and intestine only); must be converted to NR in muscle, brain, heart
- **FDA status**: Excluded from US dietary supplements (2022 FDA ruling)
- **Flushing**: None
- **Sirtuin inhibition**: None
- **Clinical trials**: 10+ published RCTs
- **Typical dosage**: 250–500 mg/day
- **NAD+ elevation**: 30–50% in blood

### Niacin / Nicotinic Acid (NA)
- **Full name**: Nicotinic Acid (Vitamin B3)
- **Pathway**: Preiss-Handler pathway (via NAPRT)
- **Cell entry**: Organic anion transporters in most tissues
- **FDA status**: FDA-approved drug for dyslipidemia; also sold as supplement
- **Flushing**: Significant at therapeutic doses (activates GPR109A)
- **Sirtuin inhibition**: None
- **Key benefit**: Most effective HDL-raising agent (20–30% increase)
- **Typical dosage**: 500–2000 mg/day
- **Cost**: $5–15/month

### Nicotinamide / Niacinamide (NAM)
- **Full name**: Nicotinamide (also called Niacinamide)
- **Pathway**: Salvage pathway (via NAMPT, rate-limiting)
- **Cell entry**: Passive diffusion
- **Flushing**: None
- **Sirtuin inhibition**: May inhibit at doses >1 g/day
- **Key evidence**: 23% skin cancer reduction (NEJM Phase 3 trial, 2015)
- **Limitation**: NAMPT activity declines with age, reducing efficacy in older adults
- **Cost**: $5–10/month

### Tryptophan
- **Full name**: L-Tryptophan (essential amino acid)
- **Pathway**: De novo synthesis (kynurenine pathway) → NAD+
- **Role**: Minor contributor to NAD+ pool; primarily dietary
- **Note**: Least efficient NAD+ precursor; most tryptophan is used for serotonin and protein synthesis

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## Clinical Studies Database

The following are peer-reviewed studies on NAD+ precursors currently in our database. All studies listed have been reviewed and approved for inclusion.

### NR (Nicotinamide Riboside) Studies

**1. Martens et al., 2018** — LANDMARK
- Title: Chronic nicotinamide riboside supplementation is well-tolerated and elevates NAD+ in healthy middle-aged and older adults
- Journal: Nature Communications
- DOI: 10.1038/s41467-018-03421-7
- Participants: 24 | Age: Older Adults (55+) | Health: Healthy
- Dosage: 500mg twice daily (1000mg/day) | Duration: 6 weeks
- Key Findings: NR supplementation increased NAD+ by 60%, reduced blood pressure and arterial stiffness in older adults.
- NAD+ Change: 60%

**2. Elhassan et al., 2019** — LANDMARK
- Title: Nicotinamide riboside augments the aged human skeletal muscle NAD+ metabolome and induces transcriptomic and anti-inflammatory signatures
- Journal: Cell Reports
- DOI: 10.1016/j.celrep.2019.07.043
- Participants: 12 | Age: Older Adults (55+) | Health: Healthy
- Dosage: 1000mg/day | Duration: 21 days
- Key Findings: Skeletal muscle NAD+ increased by 100%. Anti-inflammatory gene expression signatures observed.
- NAD+ Change: 100% (muscle)

**3. Dollerup et al., 2018**
- Title: A randomized placebo-controlled clinical trial of nicotinamide riboside in obese men: safety, insulin-sensitivity, and lipid-mobilizing effects
- Journal: American Journal of Clinical Nutrition
- DOI: 10.1093/ajcn/nqy132
- Participants: 40 | Age: Middle-Aged (35-55) | Health: Obese
- Dosage: 1000mg twice daily (2000mg/day) | Duration: 12 weeks
- Key Findings: NR was well-tolerated at high doses. Modest improvements in insulin sensitivity observed.
- NAD+ Change: Significant increase

**4. Trammell et al., 2016** — LANDMARK
- Title: Nicotinamide Riboside Is Uniquely and Orally Bioavailable in Mice and Humans
- Journal: Nature Communications
- DOI: 10.1038/ncomms12948
- Participants: 12 | Age: Mixed | Health: Healthy
- Dosage: 100-1000mg single dose | Duration: Single dose pharmacokinetics
- Key Findings: First human study demonstrating oral bioavailability of NR. NAD+ increased dose-dependently.
- NAD+ Change: 40-90%

**5. Conze et al., 2019**
- Title: Safety and Metabolism of Long-term Administration of NIAGEN in a Randomized, Double-Blind, Placebo-controlled Clinical Trial of Healthy Overweight Adults
- Journal: Scientific Reports
- DOI: 10.1038/s41598-019-46120-z
- Participants: 140 | Age: Middle-Aged (35-55) | Health: Obese
- Dosage: 100-300mg/day | Duration: 8 weeks
- Key Findings: Long-term NR supplementation is safe and well-tolerated. Dose-dependent NAD+ increases confirmed.
- NAD+ Change: Dose-dependent

**6. Airhart et al., 2017**
- Title: An open-label, non-randomized study of the pharmacokinetics of the nutritional supplement nicotinamide riboside and its effects on blood NAD+ levels in healthy volunteers
- Journal: PLoS ONE
- DOI: 10.1371/journal.pone.0186459
- Participants: 8 | Age: Middle-Aged (35-55) | Health: Healthy
- Dosage: 250-1000mg/day | Duration: 8 days
- Key Findings: NR increased whole blood NAD+ levels by approximately 100% at 1000mg/day.
- NAD+ Change: ~100%

**7. Remie et al., 2020**
- Title: Nicotinamide riboside supplementation alters body composition and skeletal muscle acetylcarnitine concentrations in healthy obese humans
- Journal: American Journal of Clinical Nutrition
- DOI: 10.1093/ajcn/nqaa072
- Participants: 13 | Age: Middle-Aged (35-55) | Health: Obese
- Dosage: 1000mg/day | Duration: 6 weeks
- Key Findings: NR increased sleeping metabolic rate and improved acetylcarnitine metabolism in skeletal muscle.

**8. Zhou et al., 2020**
- Title: Boosting NAD level suppresses inflammatory activation of PBMCs in heart failure
- Journal: Journal of Clinical Investigation
- DOI: 10.1172/JCI138538
- Participants: 30 | Age: Older Adults (55+) | Health: Cardiovascular
- Dosage: 500-2000mg/day | Duration: 5-9 days
- Key Findings: NR reduced pro-inflammatory activation in heart failure patients. NAD+ levels significantly elevated.

**9. Brakedal et al., 2022** — LANDMARK
- Title: The NADPARK study: A randomized phase I trial of nicotinamide riboside supplementation in Parkinson's disease
- Journal: Cell Metabolism
- DOI: 10.1016/j.cmet.2022.02.001
- Participants: 30 | Age: Older Adults (55+) | Health: Mixed
- Dosage: 1000mg/day | Duration: 30 days
- Key Findings: NR increased brain NAD+ and was associated with clinical improvements in Parkinson's patients.
- NAD+ Change: Significant brain increase

**10. Dollerup et al., 2020**
- Title: Nicotinamide riboside does not alter mitochondrial respiration, content or morphology in skeletal muscle from obese and insulin-resistant men
- Journal: Journal of Physiology
- DOI: 10.1113/JP278752
- Participants: 40 | Age: Middle-Aged (35-55) | Health: Obese
- Dosage: 2000mg/day | Duration: 12 weeks
- Key Findings: No significant changes in muscle mitochondrial function despite elevated NAD+. Suggests tissue-specific effects.

**11. Stocks et al., 2021**
- Title: Nicotinamide riboside supplementation does not alter whole-body or skeletal muscle metabolic responses to a single bout of endurance exercise
- Journal: Journal of Physiology
- DOI: 10.1113/JP280825
- Participants: 32 | Age: Young Adults (18-35) | Health: Healthy
- Dosage: 1000mg/day | Duration: 7 days
- Key Findings: Short-term NR did not enhance exercise metabolism in young healthy adults. Baseline NAD+ may be sufficient.

**12. Custodero et al., 2023**
- Title: Effect of Nicotinamide Riboside on the Clinical Trajectory of Heart Failure Patients
- Journal: Circulation Heart Failure
- DOI: 10.1161/CIRCHEARTFAILURE.122.010167
- Participants: 48 | Age: Older Adults (55+) | Health: Cardiovascular
- Dosage: 500-2000mg/day | Duration: 12 weeks
- Key Findings: NR showed safety and tolerability in heart failure patients. Trends toward improved cardiac function.

**13. Diguet et al., 2018** (Preclinical)
- Title: Nicotinamide Riboside Preserves Cardiac Function in a Mouse Model of Dilated Cardiomyopathy
- Journal: Circulation
- DOI: 10.1161/CIRCULATIONAHA.116.026099
- Key Findings: NR protected against heart failure in mouse models. Supports cardiovascular benefits.

**14. Cercillieux et al., 2022** (Preclinical)
- Title: Nicotinamide Riboside Kinases Display Redundancy in Mediating NR and NMN Metabolism in Skeletal Muscle Cells
- Journal: Molecular Metabolism
- DOI: 10.1016/j.molmet.2022.101460
- Key Findings: Elucidated NR metabolism pathways and enzyme redundancy in skeletal muscle.

**15. Nicotinamide riboside for peripheral artery disease: the NICE randomized clinical trial (2026)**
- Journal: Nature
- DOI: 10.1038/s41467-024-49092-5

**16. Nicotinamide riboside improves muscle mitochondrial biogenesis, satellite cell differentiation, and gut microbiota in a twin study (2026)**
- Journal: Science Advances
- DOI: 10.1126/sciadv.add5163

**17. NR-SAFE: a randomized, double-blind safety trial of high dose nicotinamide riboside in Parkinson's disease (2026)**
- Journal: PMC (NIH)

**18. Nicotinamide riboside combined with exercise to treat hypertension (2026)**
- Journal: GeroScience
- DOI: 10.1007/s11357-025-01815-2

**19. Randomized Crossover Clinical Trial of Nicotinamide Riboside and Coenzyme Q10 on Metabolic Health in CKD (2026)**
- Journal: medRxiv (preprint)
- DOI: 10.1101/2024.08.23.24312501

### NMN Studies

**1. Yoshino et al., 2021**
- Title: Nicotinamide mononucleotide increases muscle insulin sensitivity in prediabetic women
- Journal: Science
- DOI: 10.1126/science.abe9985
- Participants: 25 | Age: Older Adults (55+) | Health: Diabetic/Prediabetic
- Dosage: 250mg NMN/day | Duration: 10 weeks
- Key Findings: NMN improved muscle insulin sensitivity and glucose uptake in prediabetic women.

**2. Okabe et al., 2022**
- Title: Oral Administration of Nicotinamide Mononucleotide Is Safe and Efficiently Increases Blood NAD Levels
- Journal: Frontiers in Nutrition
- DOI: 10.3389/fnut.2022.868640
- Participants: 30 | Age: Middle-Aged (35-55) | Health: Healthy
- Dosage: 250mg NMN/day | Duration: 12 weeks
- Key Findings: NMN is safe for long-term use and effectively raises NAD+ in healthy adults.

### Niacin (NA) Studies

**1. Pirinen et al., 2020**
- Title: Niacin Cures Systemic NAD+ Deficiency and Improves Muscle Performance in Adult-Onset Mitochondrial Myopathy
- Journal: Cell Metabolism
- DOI: 10.1016/j.cmet.2020.04.008
- Participants: 15 | Age: Middle-Aged (35-55) | Health: Mixed
- Dosage: 750-1000mg niacin/day | Duration: 10 months
- Key Findings: NAD+ repletion improved muscle strength in mitochondrial myopathy patients.

### Other Precursor Studies

**1. Membrez et al., 2024**
- Title: Trigonelline is an NAD+ precursor that improves muscle function during aging and is reduced in human sarcopenia
- Journal: Nature Metabolism
- DOI: 10.1038/s42255-024-00997-x
- Participants: 240 | Age: Older Adults (55+) | Health: Healthy
- Key Findings: Identified trigonelline as additional NAD+ precursor with muscle benefits.

### Review Articles

**1. Tong et al., 2024** — LANDMARK
- Title: NAD+ supplementation to treat age-related disease
- Journal: Nature Reviews Drug Discovery
- DOI: 10.1038/s41573-024-00904-9
- Key Findings: Comprehensive review of all NAD+ precursors for age-related diseases.

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## NR vs NMN Comparison

| Category | NR | NMN | Advantage |
|---|---|---|---|
| Molecular Weight | 255.25 g/mol | 334.22 g/mol | NR |
| Cell Entry | Direct via ENT in all tissues | Limited via Slc12a8 (liver, intestine only) | NR |
| Steps to NAD+ | 2 steps: NR → NMN → NAD+ | 1 step: NMN → NAD+ (but limited uptake) | Tie |
| Human Clinical Trials | 15+ published RCTs | 10+ published RCTs | NR |
| FDA Status | GRAS | Excluded from dietary supplements (2022) | NR |
| Stability | Stable at room temperature | May require refrigeration | NR |
| NAD+ Increase (Blood) | 40-100% typical | 30-50% typical | Tie |
| Tissue Penetration | Blood, muscle, brain | Blood, muscle, liver | Tie |
| Price | $30-60/month | $40-80/month | NR |
| Typical Dosage | 250-500mg daily | 250-500mg daily | Tie |

**Key Takeaway**: NR has broader tissue penetration via ENT transporters, more clinical data, and FDA GRAS status. NMN is one step closer to NAD+ but faces tissue-limited direct uptake.

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## NR vs Niacin Comparison

| Category | NR | Niacin (NA) | Advantage |
|---|---|---|---|
| Flushing | None | Significant at therapeutic doses | NR |
| Lipid Benefits | Minimal | Raises HDL 20-30%, lowers LDL/triglycerides | Niacin |
| Human Data | 15+ NAD+ focused RCTs | Decades of cardiovascular research | Niacin |
| Tolerability | Excellent | Flushing, GI upset, liver concerns | NR |
| Cost | $30-60/month | $5-15/month | Niacin |
| Sirtuin Compatibility | Compatible | Compatible | Tie |

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## NR vs Nicotinamide Comparison

| Category | NR | Nicotinamide (NAM) | Advantage |
|---|---|---|---|
| Sirtuin Inhibition | None | May inhibit at >1g/day | NR |
| NAMPT Dependency | Bypasses NAMPT | Requires NAMPT (declines with age) | NR |
| Skin Cancer Prevention | Not studied | 23% reduction (NEJM 2015) | NAM |
| Cost | $30-60/month | $5-10/month | NAM |
| NAD+ Clinical Evidence | 15+ RCTs | Limited NAD+ focused trials | NR |

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## NMN vs Niacin Comparison

| Category | NMN | Niacin (NA) | Advantage |
|---|---|---|---|
| Cell Entry | Limited (Slc12a8, liver/intestine) | Broad (organic anion transporters) | Niacin |
| Flushing | None | Significant | NMN |
| Regulatory Status | Excluded from US supplements | FDA-approved drug + supplement | Niacin |
| Lipid Effects | Minimal | Powerful HDL/LDL modification | Niacin |
| Exercise Performance | Improved VO2 max (Liao 2021) | Not studied | NMN |
| Cost | $40-80/month | $5-15/month | Niacin |

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## Niacin vs Nicotinamide Comparison

| Category | Niacin (NA) | Nicotinamide (NAM) | Advantage |
|---|---|---|---|
| Flushing | Causes significant flushing | No flushing | NAM |
| Lipid Effects | Raises HDL 20-30% | No significant lipid effects | Niacin |
| Sirtuin Compatibility | Compatible | May inhibit at high doses | Niacin |
| Skin Cancer Prevention | Not studied | 23% reduction (NEJM trial) | NAM |
| Cost | $5-15/month | $5-10/month | Tie |
| Tolerability | Flushing, GI, liver concerns | Well-tolerated | NAM |

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## Frequently Asked Questions

### What is Nicotinamide Riboside (NR)?
Nicotinamide Riboside (NR) is a form of vitamin B3 that serves as a precursor to NAD+, a coenzyme essential for cellular energy production, DNA repair, and metabolic function. Unlike niacin, NR doesn't cause flushing and efficiently converts to NAD+ in the body.

### How does NR compare to NMN?
Both are NAD+ precursors. NR enters cells directly via ENT transporters in all tissues. NMN has limited direct uptake — the Slc12a8 transporter only works in liver and intestine. In muscle, brain, and heart, NMN must be converted to NR before entering cells. NR has more published human data and FDA GRAS status.

### What dosage of NR is recommended?
Clinical trials used 100mg to 2000mg daily. Most studies showing significant NAD+ elevation used 250-1000mg/day. 300-600mg daily is typical for general supplementation.

### Is NR safe?
NR has FDA GRAS status. Clinical trials report it's well-tolerated with minimal side effects (mild nausea, fatigue, headaches at similar rates to placebo). Long-term safety data beyond 12 weeks is still accumulating.

### How long does it take to see benefits?
NAD+ levels increase within hours of supplementation. Meaningful cellular benefits may take 2-8 weeks. Most clinical trials run 6-12 weeks. Measurable NAD+ metabolite changes appear within 1-2 weeks.

### Who benefits most from NR?
Older adults (40+) benefit most as NAD+ declines with age. Studies show promise for cardiovascular health and exercise recovery in middle-aged and older adults. Younger, healthy individuals show less effect.

### Can NR interact with medications?
Limited interaction data exists. Theoretical interactions with diabetes medications, chemotherapy drugs, and immunosuppressants. Always consult a healthcare provider.

### What makes a good NR supplement?
Key factors: patented Niagen® (clinically studied form), third-party testing, no unnecessary fillers, proper storage, and reputable manufacturer.

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## Recommended Products

### 1. Tru Niagen (300mg NR)
- Brand: Niagen Bioscience
- Dosage: 300mg NR per capsule, 30 servings
- Badges: Patented Niagen®, Third-Party Tested, FDA GRAS
- Rating: 4.4/5 (13,700+ reviews)
- Link: https://www.amazon.com/dp/B07TK5K5TQ?tag=nadprecursors-20

### 2. Tru Niagen Pro 1000 (1000mg NR)
- Brand: Niagen Bioscience
- Dosage: 1000mg NR/day (2×500mg capsules), 60 capsules
- Badges: High Potency, Patented Niagen®, Third-Party Tested
- Rating: 4.5/5 (990+ reviews)
- Link: https://www.amazon.com/dp/B0CLQZHVHL?tag=nadprecursors-20

### 3. Life Extension NAD+ Cell Regenerator & Resveratrol Elite
- Brand: Life Extension
- Dosage: 300mg NR + Resveratrol per capsule, 30 servings
- Badges: With Resveratrol, Established Brand
- Rating: 4.6/5 (2,700+ reviews)
- Link: https://www.amazon.com/dp/B08PMJFLP8?tag=nadprecursors-20

*Affiliate disclosure: We may earn a commission from qualifying purchases.*

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## Key Researchers

- **Dr. Charles Brenner**: Discovered NR as an NAD+ precursor (University of Iowa / City of Hope)
- **Dr. David Sinclair**: Leading aging and NAD+ metabolism researcher (Harvard Medical School)
- **Dr. Eric Verdin**: President of the Buck Institute for Research on Aging; NAD+ biology expert

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## Citation Guidelines

When citing NADprecursors.com content:
1. Include the specific page URL
2. Include the date of access
3. Note that we aggregate peer-reviewed research (we are not the primary source)
4. For individual studies, cite the original publication via DOI

Example: "According to NADprecursors.com's research database (accessed [date]), Martens et al. (2018) found that NR increased NAD+ by 60% in older adults (DOI: 10.1038/s41467-018-03421-7)."

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## Disclaimer

NADprecursors.com provides educational information based on peer-reviewed research. This content does not constitute medical advice. Always consult qualified healthcare providers before starting any supplement regimen. Individual results may vary.

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*For the navigation version of this file, see [llms.txt](https://nadprecursors.com/llms.txt)*
*Website: https://nadprecursors.com*