Sekikaic acid is a phenolic lichen metabolite that has been found in H. obscurata and has diverse biological activities. It scavenges superoxide and DPPH radicals in cell-free assays when used at a concentration of 0.5 µM. Sekikaic acid is active against the rg recombinant strain of respiratory syncytial virus (RSV; IC50 = 5.69 µg/ml). It inhibits the protein-protein interaction between mixed lineage leukemia 1 (MLL1) and the GACKIX domain of CREB-binding protein (CBP; IC50 = 34 µM).