D-Saccharic acid 1,4-lactone hydrate is an orally active β-glucuronidase inhibitor ( IC 50 =48.4 μM). D-Saccharic acid 1,4-lactone hydrate can be used as a standard agent compared with novel β-glucuronidase inhibitors. D-Saccharic acid 1,4-lactone hydrate possesses anticarcinogenic, detoxifying, and antioxidant properties .