This chapter describes the sources and types of alkaloids and highlights their potential health benefits besides their toxicity. Alkaloids are multi-purpose compounds active in various environmental interactions, such as defense against herbivores, bacteria, fungi, viruses or competing plants. The toxicity of many alkaloids and their pharmacological activity in humans and animals appears to be correlated with their interactions with particular molecular targets. Pyrrolizidine alkaloids (PAs) occur in several plant families as amino alcohols or as macrocyclic ring structures, such as retrorsine. Rising levels of reactive oxygen species (ROS) and systemic inflammation are often serious concerns in many disease conditions, like obesity. Therefore, compounds with both antioxidant and anti-inflammatory activities are considered beneficial in treating several chronic human diseases. Cardiovascular diseases (CVD) are a group of disorders of the heart and blood vessels. Heart attacks and strokes are typically acute events and are primarily caused by a blockage that prevents the flow of blood to the heart or brain.