Abstract
This study evaluates the enzyme inhibitory and immunomodulatory activities of the lichen specific depsidone, lobaric acid. Lobaric acid was extracted with methanol from Heterodermia sp. found in Labukelle, Sri Lanka with a yield of 0.67%. It was subjected to enzyme inhibition assays using acetyl and butyryl-cholinesterase, phosphodiesterase, beta-glucuronidase, a-glucosidase and urease. In the beta - glucuronidase inhibitory activity it showed an IC50 value of 3.28 +/- 0.05 mu M, which was significantly lower than that of the standard, D-saccharic acid 1, 4-lactone (IC50 = 48.4 +/- 1.2 mu M). Lobaric acid showed a significant inhibition of phosphodiesterase enzyme with an IC50 = 313.7 +/- 2.2, when compared with the two standards EDTA (IC50 = 274.0 +/- 0.1 mu M) and cysteine (IC50 = 748.0 +/- 0.1 mu M). Lobaric acid showed a moderate actyl and butyryl -cholinesterase inhibitory activity while it showed no activity against the enzymes alpha-glucosidase and urease.
In the immunomodulatory assay, lobaric acid exhibited a potent oxidative burst inhibitory activity in human polymorphonuclear (PMN) cells. It suppressed both the myloperozidase dependant and myloperozidase independent reactive oxygen species (ROS) production of PMNs. The results indicate the pharmacological potential of lobaric acid as a lead compound for further studies.