Methylxanthines are a group of chemical compounds that include caffeine, theobromine, and theophylline. These substances are naturally found in various plants, such as coffee beans, tea leaves, and cocoa beans. Methylxanthines are known for their stimulant effects on the central nervous system, which can enhance alertness and reduce fatigue. In addition to their stimulating properties, methylxanthines have other effects on the body, such as relaxing smooth muscles and improving airflow in the lungs. This makes compounds like theophylline useful in treating respiratory conditions, such as asthma. Overall, methylxanthines play a significant role in both dietary sources and medicinal applications.