What’s Actually Inside An Average Cup of Coffee — Wired Magazine

In general, coffee consists of 98% of water and 2% of other stuff.
Some interesting compounds in coffee:

• 2-Enthelphenol “has tar-like odor and is actually a cockroach pheromone that warns other cockroaches of danger.” (It makes me wonder if it could hold cocroach invasion at bay.
• Dimethyl Disulfide “smells like rotting meat.” Wiki: It penetrates the skin very readily, giving it the unusual property for many individuals of being secreted onto the surface of the tongue after contact with the skin and causing a garlic-like taste in the mouth.
• Acetylmethylcarbinel or Acetoin gives buttery odor.
• Trigonelline “has a sweet, earthy taste.” According to wiki, it may help to prevent dental caries by preventing the bacteria Streptococcus mutans from adhering to teeth.
• 3,5 Dicaffeoylquinic Acid or Chlorogenic acid is an antioxidant and may slow the release of glucose into the bloodstream after a meal.
• Finally, there is Caffeine. :)

Source: Wired