Compounds with elastase inhibition and free radical scavenging activities from Callistemon lanceolatus

Abstract

Bioassay-guided investigation of the stems of Callistemon lanceolatus led to the isolation of five compounds such as betulinic acid (1), pyracrenic acid (2), arjunolic acid (3), catechin (4), and piceatannol (5). Their structures were elucidated on the basis of spectral studies as well as by comparison with literature data. Elastase inhibition and DPPH radical scavenging activities wereinvestigated for the isolated compounds. Among these, pyracrenic acid (2) was identified as a potent elastase inhibitor with an IC50 value of 1.5 mg/mL, more active than the control compound, oleanolic acid (IC50 = 3.0 mg/mL). With regard to antioxidative studies, strong to moderate DPPH radical scavenging activities were observed with pyracrenic acid (2), catechin (4) and piceatanol (5). Key words: Callistemon lanceolatus, elastase inhibition, radical scavenging, triterpenoids.