bulksupplements.com rehmannia root extract powder - kidney support supplement - herbal rest - renal vitamins - colon support supplements (100 grams - 3.5 oz) bulksupplements rehmannia root extract comes from a flowering plant that is native to china. it has been used for thousands of years in china for its purported benefits. while different parts of the plant can be used, this extract comes from the rehmannia root, specifically. rehmannia root extract has a wide range of purported health benefits ranging from supporting urinary system to promoting brain function.* it may help aid metabolic function and sexual wellness, support the bones, and promote the skin and hair.* in addition, it may help support cardiovascular system, liver, and prostate.* this extract is the powder form.