Certain phytochemicals can cure several types of diseases, and may play an important role in pharmacology as natural supplements to control various diseases as fast and reliable alternatives. Many synthetic drugs cause severe side effects that are not acceptable. Natural products with therapeutic properties have been used since antiquity in folklore for the treatment of many diseases and formed one of the main sources of drugs. The majority of these compounds cannot yet be synthesized economically so they are still obtained from wild or cultivated plants. Recently, there has been rising interest in alternative-therapies and the therapeutic-use of natural products, particularly those derived from plants. This interest in drugs of plant origin is due to several reasons including, probable abusive and/or abuse of synthetic drugs, then because “natural products” are considered harmless (especially for “Generally Recognized As Safe” herbs, GRAS). Hence, isolation and characterization of novel types of plant secondary-metabolites could be a safer substitute to synthetic compounds. Several studies using different analytical techniques have examined the phytochemical composition of plants. The coupling of HPLC with Ultraviolt and mass spectrometry (MS) detectors offers a potent analytical tool, which has been widely useful in the characterization of plant matrices. In this context, the aim of this proposed project is the investigation of bio-active metabolites in anti-diabetic medicinal plants we have studied in the last decade by applying different analytical techniques such as HPLC-UV and GC-MS. Further evaluation of the novel isolated compounds/fractions by using in vitro assays will be performed.