The bioassay-guided fractionation of H. oblongifolium has led to the isolation of potent urease inhibitors 1-3. The structures were elucidated by NMR and mass spectroscopic techniques. Compound 2 showed a potent enzyme inhibition activity (IC(50) 20.96 +/- 0.93), which is comparatively higher than that for the standard thiourea (IC(50) 21.01 +/- 0.51 microM). Compounds 1 and 3 also showed a significant activity, with IC(50) 37.95 +/- 1.93 and 138.43 +/- 1.23 microM, respectively. The sub crude fractions (F1, F2, F3, and F4) were tested in vitro for their urease inhibition activity. Fractions F2 and F4 showed significant activity with IC(50) 140.37 +/- 1.93 and 167.43 +/- 3.03 microM, respectively.