COX-2 inhibitory activity of homoisoflavanones and xanthones from the bulbs of the Southern African Ledebouria socialis and Ledebouria ovatifolia (Hyacinthaceae: Hyacinthoideae) - Waller, C P; Thumser, A E; Langat, M K; Crouch, N R; Mulholland, D A (Phytochemistry, 2013)