Good or bad???
Other names : 1,3,7-trimetilxantine; (IUPAC) 1,3,7-trimetil-1H-purine-2,6(3H,7H)-dione; guaranine; teine.
Formula : C 8 H 10 N 4 O 2
Solubility in water :
2.17 g/100 mL (25 °C)
18.0 g/100 mL (80 °C)
67.0 g/100 mL (100 °C)
1,3,7-trimetilxantine is a bitter, white, crystalline xanthine alkaloid and a stimulant drug.
In humans, caffeine acts as a central nervous system stimulant,temporarily warding off drowsiness and restoring alertness.
Where we can find it.
Caffeine is found in varying quantities in the seeds, leaves, and fruit of some plants, where it acts as a natural pesticide.
It is most commonly consumed by humans in infusions extracted from the seed of the coffee plant and the leaves of the tea bush.
Other sources include yerba matè, guaranà berries, kola nut.
Caffeine Content in Food and Drugs.
| Product | Serving size | Content (mg) |
| Caffeine tablet | 1 tablet | 100 |
| Coffee espresso | 50 ml | 80-100 |
| Drip coffee (americano) | 200 ml | 115-175 |
| Coca-Cola | 330 ml | 35 |
| Red Bull | 250 ml | 80 |
| Tea | 200 ml | 20-70 |
| Yerba matè | 6g (leaf) | 85 |
Administration and Pharmacology.
Inside the body caffeine acts through several mechanisms. Its most important effect is to counteract a substance called adenosine , especially in the nervous system, where adenosine plays a protective role, part of which is to reduce neural activity levels.
Mechanism of action
Caffeine's primary mechanism of action is an nonselective antagonist of adenosine receptors in the brain. It readily crosses the blood-brain barrier, and 'cause its similarity to adenosine molecule, caffeine molecule acts binding to adenosine receptors on the surface of cells as a competitive inhibitor .
Caffeine also has effects on most of the other major neurotransmitters: dopamine, acetylcholine, serotonine and, in high doses, on norepinephrine.
At high doses, exceeding 500mg, caffeine inhibits GABA neurotransmission . GABA reduction explains why caffeine increases anxiety, insomnia, rapid heart and respiration rate.
Caffeine, like other xanthines, also acts as a phosphodiesterase inhibitor , raises intracellular cAMP, activates PKA, inhibits TNF-alpha and leukotriene synthesis. It can also reduces inflammation and innate immunity.
In the classic theory caffeine may increase fat utilization and decrease glycogen utilization by mobilyzing free fatty acids from fat and intramuscolar triglycerides, by increasing circulating epinephrine levels. The increased availability of free fatty acids increases fat oxidation and spares muscol glycogen, thereby enhancing endurance performance .
Metabolism
Caffeine is absorbed by the small intestine within 45 minutes of ingestion. Peak blood concentration is reached within one hour and it is eliminated by first-order kinetics.
This molecule is metabolized in the liver by the cytochrome P450 oxidase enzyme system , in particular, by the CYP1A2 isozyme, into three primary metabolites:
Paraxanthine : increases lipolysis, leading to elevated glycerol and FFA levels in the blood plasma.
Theobromine : dilates blood vessels and increases urine volume. Theobromine is also the principal alkaloid in the cocoa bean, and therefore chocolate.
Theophylline : Relaxes smooth muscles of the bronchi, and is used to treat asthma.
Each of these metabolites is further metabolized and then excreted in the urine .
Health effects
Positive effects
- High long-term consumption is associated with a lower risk of cardiovascular disease and diabetes.
- Research is beginning to suggest that caffeine minimizes the cognitive decline associated with aging, including reducing risk of Alzheimer's disease.
- Low doses of caffeine show increased alertness and decreased fatigue.
- Caffeine has been shown to increase the metabolic rate.
- Caffeine is studied as a treatment for the Parkinson’s disease motor symptoms.
- Caffeine may lower the risk of developing type 2 diabetes.
Negative effects
- Caffeine can increase blood pressure in non-habitual consumers. High blood pressure is associated with an increase in strokes, and cerebral vascular disease, which in turn increase the risk of multi-infarct dementia.
- Caffeine may reduce control of fine motor movements (e.g. producing shaky hands)
- Caffeine can contribute to increased insomnia and sleep latency.
- Caffeine withdrawal can produce headache, fatigue and decreased alertness.
- High doses of caffeine (300 mg or higher) can cause anxiety.
Toxicity
Caffeine overdose can result in a state of central nervous system over-stimulation called caffeine intoxication (DSM-IV 305.90). This syndrome typically occurs only after ingestion of large amounts of caffeine, more than 400–500 mg at a time.
The symptoms of caffeine intoxication are comparable to the symptoms of overdoses of other stimulants: they may include restlessness, anxiety, excitement, insomnia, flushing of the face, increased urination, gastrointestinal disturbance, muscle twitching, a rambling flow of thought and speech, irritability, irregular or rapid heart beat, and psychomotor agitation.
In cases of much larger overdoses, mania, depression, lapses in judgment, disorientation, disinhibition, delusions, hallucinations, or psychosis may occur, and rhabdomyolysis (breakdown of skeletal muscle tissue) can be provoked.
Extreme overdose can result in death.
The median lethal dose (LD50) given orally in humans is dependent on individual sensitivity, but is estimated to be about 150 to 200 milligrams per kilogram of body mass (80 to 100 cups of coffee for an average adult).
It is easier to reach high doses with caffeine pills, and the lethal dose can be lower in individuals whose ability to metabolize caffeine is impaired. Chronic liver disease is one factor that can slow the metabolism of caffeine.
Tesina elaborata da Naike Faienza e Roberta Danese
