小檗碱，又称为黄连素，是一种生物碱，主要存在于小檗属与黄连属植物中。在应用上，有抗菌、止泻、消炎等效果。

小檗碱的分子式为C20H18NO4。小檗碱为一种季铵生物碱。从乙醚中可析出黄色针状晶体；熔点145°C；能缓慢溶解于冷水（1∶20）或冷乙醇（1∶100），在热水或热乙醇中溶解度比较大，难溶于苯、乙醚和氯仿。其盐类在水中的溶解度都比较小，例如盐酸盐为1∶500，硫酸盐为1:30。它存在于中药黄连、黄柏、三颗针等许多植物中。它的提取方法有酸水法、石灰乳法的几种，网络上均有报道.

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), Berberis aristata (tree turmeric)), Hydrastis canadensis (goldenseal), Xanthorhiza simplicissima (yellowroot), Phellodendron amurense (Amur cork tree), Coptis chinensis (Chinese goldthread), Tinospora cordifolia, Argemone mexicana (prickly poppy), and Eschscholzia californica (Californian poppy). Berberine is usually found in the roots, rhizomes, stems, and bark.