Plants represent a vast source of potentially useful dietary supplements for improving blood glucose control and preventing long-term complications in type 2 diabetes mellitus. Ten aqueous plant extracts with proven antihyperglycemic properties were examined at a concentration of 50g plant extract/l using an in vitro method to assess their possible effects on glucose diffusion across the gastrointestinal tract. Agrimony eupatoria (agrimony) and Persea americana (avocado) decreased glucose movement in vitro more than 50%. Aqueous extracts of Agaricus campestris (mushroom), Coriandrum sativum (coriander), Eucalyptus globulus (eucalyptus), Juniperus communis (juniper), Medicago sativa (lucerne), and Viscum album (mistletoe) decreased significantly glucose movement but were less effective than agrimony and avocado. Urtica diocia (nettle) and Sambucus nigra (elder) extracts did not significantly decrease glucose diffusion. The effects of agrimony. avocado, coriander and mushroom extracts were found to be concentration-dependent. These results suggest that part of the antihyperalycemic actions of these plants may be by decreasing glucose absorption in vivo. (C) 2003 Elsevier Science Inc. All rights reserved.