Nornicotine
The forgotten tobacco alkaloid — and a suspected contributor to the Alzheimer link.
At a glance
- Also known as
- Demethyl-Nikotin
- CAS number
- 494-97-3
- Toxicity
High
- Carcinogenic
- Not classified for cancer
- In cigarette smoke
- 10-60 μg per cigarette (DKFZ)
What is Nornicotine?
Nornicotine is a tobacco alkaloid chemically containing one methyl group less than nicotine. It occurs naturally in tobacco leaves and is also formed in the human body as a metabolite of nicotine. Unlike nicotine, nornicotine is biologically far less researched — most studies have focused on the prominent main alkaloid.
Why is Nornicotine in cigarettes?
Nornicotine occurs in tobacco leaves in smaller quantities than nicotine and stems mostly from the plant itself, with a smaller share from enzymatic nicotine breakdown. Each cigarette delivers 10 to 60 micrograms of nornicotine into the mainstream smoke (source: DKFZ). The toxicologically central function of nornicotine is its role as a precursor to tobacco-specific nitrosamines (TSNAs) — particularly NNN.
What Nornicotine does to your body — short term
Acute effects of nornicotine in normal tobacco use aren't specifically distinguishable from those of nicotine — nornicotine contributes to the general addictive and cardiovascular effect, but is roughly 10× weaker than nicotine at activating the reward system.
What Nornicotine does long term
Studies from the Scripps Research Institute (Dickerson & Janda, PNAS 2002 and 2003) showed that nornicotine covalently modifies proteins in the body — a reaction usually associated with high blood-sugar levels in diabetes. The 2003 follow-up specifically identified the amyloid-beta peptide (the central plaque building block in Alzheimer's) as a target. What this chemical modification means biologically — increased risk, altered plaque assembly, or even protection — is subject of ongoing research; the studies provide the molecular hook, not an established risk amplification.
Where else do you know Nornicotine from?
Nornicotine is found practically exclusively in the tobacco plant and a few related Solanaceae (nightshade family, e.g. aubergine in trace amounts). Unlike nicotine, there's no commercial use — nornicotine is neither a pesticide nor a pharmaceutical component.
How it compares
There's no workplace exposure limit for nornicotine, because as a tobacco-specific alkaloid it doesn't occur occupationally outside tobacco processing. Its toxicological importance lies not in the free substance itself but in its function as precursor to the highly carcinogenic tobacco-specific nitrosamines NNN and NNK.
Workplace exposure limit: kein AGW (tabakspezifisches Alkaloid)
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