AbstractLantadene A (22 β‐angeloyloxy‐3‐oxoolean‐12‐en‐28‐oic acid), a pentacyclic triterpenoid compound from lantana (Lantana camara) leaves has been obtained in two polymorphic forms I and II. Form I had white, fluffy, and rod‐shaped uniform crystals. Form II particles were irregular, shining, and polyhedral. The two forms differed in melting behavior. The powder x‐ray diffraction of form I showed sharp peaks whereas form II did not contain distinct peaks. From single‐crystal three‐dimensional x‐ray structure determination, the molecular structure of form I has been established. A/B and B/C rings of the molecule are trans fused while D/E rings are cis fused. The packing of the molecule is stabilized by hydrogen bonding. Form I of lantadene A was nontoxic to guinea pigs on oral administration. Form II induced ictericity and toxicity associated with decrease in feed intake and fecal output, hepatomegaly, increase in plasma bilirubin, and a