This book is completed which the author believe that it will contributed plant cultivation knowledge especially in medicinal plant. The tendency for the world community today and in the future to use medicines from natural materials is increasing. Tropical plants have better future with the global warming phenomena, since it has all the characteristics needed for it. Moreover it was equipped with metabolism that could encountered reactive oxygen species (ROS) that will be found because of the fluctuation of abiotic stresses. Guava as one of tropical plant is found distributed all around the tropical area and it is used by many nation in the world as traditional medicine or as pharmaceuticals. Almost every part of guava has medicinal uses, and phenolics and flavonoids are two of guava leaf bioactive content that can be extracted. These compounds are antioxidants that is beneficial for human health. This book can be used as a direction to manage the production of guava leaf phenolics and flavonoids production in the tropics with cultivation maneuver that can be done to increase it.