xanthine

/ˈzænθiːn/
noun
  1. A crystalline compound found in blood, urine, and certain plants, which is a precursor to uric acid and a breakdown product of nucleic acids.
    • The lab detected elevated xanthine in the patient's urine sample.
    • Doctors measure xanthine levels in the blood to diagnose certain metabolic disorders.
    • Xanthine is formed when the body breaks down caffeine and other purines.
  2. Any of a group of related compounds (such as caffeine, theobromine, and theophylline) that are stimulants and found in coffee, tea, and chocolate.
    • Theobromine, a xanthine in chocolate, gives it a mild stimulant effect.
    • Caffeine is the most well-known xanthine found in coffee beans.
    • Some asthma medications contain theophylline, a xanthine that relaxes airways.