Xanthines are a group of naturally occurring compounds that include substances like caffeine, theobromine, and theophylline. They are primarily found in various plants and are known for their stimulant effects on the central nervous system. Xanthines can enhance alertness and reduce fatigue, making them popular in beverages like coffee and tea. In addition to their stimulating properties, xanthines have medicinal uses. For example, theophylline is often prescribed to treat respiratory conditions such as asthma and chronic obstructive pulmonary disease (COPD) because it helps relax the airways. Overall, xanthines play a significant role in both dietary and therapeutic contexts.