Red yeast rice is derived from the fermentation of rice with the yeast Monascus purpureus, yielding a series of cholesterol-lowering monacolins. The monacolin in highest concentration in red yeast rice is monacolin K, also known as lovastatin, the first FDA-approved HMG-CoA reductase inhibitor. Red yeast that is not fermented correctly may contain the nephrotoxin, citrinin.