Berberine 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. As a natural dye, berberine has a Colour Index (CI) of 75160.
Berberine is a quaternary ammonium salt from the protoberberine group of isoquinoline alkaloids. It is found in such plants as Berberis (e.g. Berberis aquifolium (Oregon grape), Berberis vulgaris (Barberry), and Berberis aristata (Tree Turmeric)) and Coptis chinensis (Chinese Goldthread, Huang-Lian, Huang-Lien), and to a smaller extent in Eschscholzia californica (Californian Poppy). Berberine is usually found in the roots, rhizomes, stems, and bark.
Recent progress in metagenomcs (databases, mathematical algorithms, modeling approaches, and software packages for the study of the gut microbiome) has lead to the suspicion that one cause for obesity might be the lack of sufficient Coptis chinensis in the diet. Are you fat? Check your yellowness.