Berberine is a quaternary ammonium salt that belongs to the protoberberine group of benzylisoquinoline alkaloids. Chemically, berberine is classified as an isoquinoline alkaloid. More specifically, berberine is a plant alkaloid derived from tyrosine through a complex 8 step biosynthetic process. Berberine is found in plants such as Berberis vulgaris (barberry), Berberis aristata (tree turmeric), Mahonia aquifolium (Oregon grape) and Hydrastis canadensis (goldenseal). Two other known berberine-containing plants are Phellodendron chinense and Phellodendron amurense. Berberine is usually found in the roots, rhizomes, stems, and bark of Berberis plants. Due to berberine's intense yellow color, plants that contain berberine were traditionally used to dye wool, leather, and wood. Under ultraviolet light, berberine shows a strong yellow fluorescence, making it useful in histology for staining heparin in mast cells. Berberine is a bioactive plant compound that has been frequently used in traditional medicine. Among the known physiological effects or bioactivities are: 1) Antimicrobial action against bacteria, fungi, protozoa, viruses, helminthes, and Chlamydia; 2) Antagonism against the effects of cholera and E coli heat-stable enterotoxin; 3) Inhibition of intestinal ion secretion and of smooth muscle contraction; 4) Reduction of inflammation and 5) Stimulation of bile secretion and bilirubin discharge (PMID:32335802). Berberine can inhibit bacterial growth in the gut, including Helicobacter pylori, protect the intestinal epithelial barrier from injury, and ameliorate liver injury. Currently, berberine is sold as an Over-the-Counter (OTC) drug for treating gastrointestinal infections in China (PMID:18442638). Berberine also inhibits the proliferation of various types of cancer cells and impedes invasion and metastasis (PMID:32335802). Recent evidence has also confirmed that berberine improves the efficacy and safety of both chemo and radiotherapies for cancer treatment (PMID:32335802). Berberine has also been shown to regulate glucose and lipid metabolism in vitro and in vivo (PMID:18442638). In fact, berberine is the main active component of an ancient Chinese herb Coptis chinensis French, which has been used to treat diabetes for thousands of years.  As an anti-diabetic, berberine increases glucose uptake by muscle fibers independent of insulin levels. It triggers AMPK activation and increases glycolysis, leading to decreased insulin resistance and decreased oxygen respiration. The same mechanism leads to a reduction in gluconeogenesis in the liver. AMPK activation by berberine also leads to an antiatherosclerotic effect in mice. Berberine's AMPK activation may also underlie berberines' anti-obesity effects and favorable influence on weight loss (PMID:18442638). While its use as a medication is widely touted, it is important to remember that berberine inhibits CYP2D6 and CYP3A4 enzymes, both of which are involved in the metabolism of many endogenous substances and xenobiotics, including a number of prescription drugs.