As the world is looking for high life expectancy, a new shocking form of diabetes, that is, Type 3 Diabetes which has recently come into picture, has become a major issue. In short, Type 3 is diabetes in brain leading to Alzheimer's disease, a main cause of death among elderly. This book focuses on the best fit model to induce Type 3 Diabetes in Wistar rats. It also focuses on suitable extraction method, solvent and time to obtain maximum phytochemical constituents with high efficacy from both leaves and twigs of Camellia sinensis. A comparative study was also carried on Citrus reticulata (Mandarin), Citrus sinensis (Sweet Orange) and Camellia sinensis (Green Tea) for their protection against Type 3 Diabetes, also known as Diabetes Associated Cognitive Decline. The book gives information on various in vitro and in vivo studies along with molecular based mechanisms to understand the ameliorating effects of the extracts. Various fractions of Camellia sinensis were isolated and best fractions were identified from spectral and chromatographic studies. Studies on twigs of Camellia sinensis adds interest to the book.