Barberry contains berberine, a quaternary ammonium salt from the group of isoquinoline alkaloids. It is strongly yellow colored, which is why in earlier times berberis species were used to dye wool, leather and wood. Wool is still today dyed with berberine in Northern India. Under ultraviolet light, berberine shows a strong yellow fluorescence. Because of this it is used in histology for staining heparin in mast cells. Berberine has showed some activity against fungal infections, candida, yeast, parasites, and bacterial/viral infections. Some research has been undertaken into possible use against MRSA infection. Although berberine has been tested and used in diabetes, prostate cancer cell lines, liver and leukaemia cancers, cardiac arrhythmia,and leukemia, it has not been researched thoroughly with humans. Berberine is considered an ineffective antibiotic, but a minority claim that when not tested in isolation but in conjunction with the other biochemical substances from the barberry plant, berberine might then be effective.