ARGINASE INHIBITORY PROPERTIES OF PHENOLIC COMPOUNDS FROM RHODIOLA TANGUTICA

Rhodiola tangutica (Maxim.) S. H. Fu is a traditional Tibetan herb growing on the Tibetan plateau at an altitude of 3000-4500 meters. The medicinal value of this plant is mainly concentrated in the roots and rhizomes containing its bioactive compounds, which have important developmental value. In course of the study of plant bioactivity, we conducted a screening of arginase inhibitors. The results showed that the alcoholic extract of R. tangutica with vasodilatory effect inhibited arginase at the highest rate of 48.22 +/- 6.69%, and that 14 of the 22 main chemical components of the active site inhibited arginase at a rate greater than 20%, while the positive control group inhibited caffeic acid by 61.68 +/- 6.65%. Based on this, we screened five new arginase inhibitors from the active site of R. tangutica, including salidroside, p-coumaric acid, rhodiosin, eriodictyol, and ethyl gallate, with IC50 values of 15.34, 127.5, 21.98, 62.45 mu M and > 200 mu M, respectively. In the enzyme kinetic experiments, the Ki'/Ki of the five compounds p-coumaric acid, salidroside, rhodiosin, ethyl gallate, and eriodictyol were 0.64, 10.08, 18.50, 0.72, and 1.46, respectively, indicating that their mechanisms of action on arginase were all mixed competitive inhibition type.