In vitro antioxidant and anti-inflammatory activities of Angelica decursiva

Abstract

Angelica decursiva is widely distributed in hillside, grass land or sparse forest throughout Japan, China and Korea. It is one of the earliest and most important edible herbs in traditional medicine which is used as antiseptic, carminative, lenitive, stomachic, tonic, analgesic, antipyretic, antispasmodic, antitussive, expectorant and stimulant. A. decursiva contains high amounts of coumarins. However, there is no report on its antioxidant and anti-inflammatory activities, especially for the whole plants of A. decursiva. Therefore, in this study, anti-inflammatory and antioxidant activity of the methanolic (MeOH) extract and its solvent soluble fractions such as the dichloromethane (CH2Cl2), ethyl acetate (EtOAc), n-butanol (n-BuOH) and water (H2O) fractions from the whole plants of A. decursiva were investigated. Antioxidant activities were evaluated by in vitro scavenging activities against 1,1-diphenyl-2-picrylhydrazyl (DPPH), 2,2’-azino-bis-3-ethylbenzothiazoline-6-sulfonic acid (ABTS), nitric oxide (NO•), and peroxynitrite (ONOO). Intracellular anti-inflammatory capacities were determined by in vitro inhibitory activities against lipopolysaccharide (LPS)-induced nitric oxide (NO) production in RAW 264.7 cells. Among these, EtOAc fraction has been found as the most potent antioxidant fraction with the IC50 values 45.50 ± 0.33, 10.07 ± 0.16, 1.29 ± 0.08 and 1.38 ± 0.09 μg/ml in DPPH, ABTS, NO and ONOO- scavenging assays, respectively while CH2Cl2 fraction has been found as the most potent anti-inflammatory fraction with IC50 value of 23.83 μg/ml. Since EtOAc fraction has been found as active fraction in both antioxidant and anti-inflammatory assays, this fraction was selected for further investigation to isolate active compounds. From the active EtOAc fraction, repeated column chromatography was accomplished to isolate five known compounds, including four coumarin derivatives nodakenin, nodakenetin, umbelliferone, umbelliferone-6-carboxylic acid and a phenolic compound, vanillic acid. Among these compounds, umbelliferone 6-carboxylic acid and vanillic acid were isolated for the first time in this plant. Both umbelliferone 6-carboxylic acid and vanillic acid exerted weak scavenging activity of DPPH with an IC50 value of 681.86 μg/ml and 725.79 μg/ml respectively compared with the positive control, L-ascorbic acid of which IC50 value 5.20 μg/ml. On the other hand, vanillic acid and umbelliferone 6-carboxylic acid displayed higher degree of scavenging activities in both ABTS and ONOO scavenging assays (IC50 values of 1.39 and 11.20 μg/ml in ABTS scavenging assay and 1.29 and 8.04 μg/ml in ONOO- scavenging assay, respectively). Furthermore, vanillic acid showed 1.6 times stronger activity than L-ascorbic acid (IC50 value of 2.55 μg/ml) and 2.5 times stronger than trolox (3.62 μg/ml), the positive control used in the assay, in the ABTS radical scavenging assay. In addition, vanillic acid was also found as the potent ONOO scavenger of which scavenging activity was just similar to the positive control L-penicillamine (IC50 value of 1.07 μg/ml). In the anti-inflammatory assay, umbelliferone 6-carboxylic acid exhibited highest inhibitory activity in a dose-dependent manner on LPS-induced NO production in RAW 264.7 cells with an IC50 value of 72.98 μg/ml and showed no toxicity up to the concentration of 125 μg/ml. Umbelliferone and nodakenetin exerted weak suppressive effect on NO production with 40.35 % and 20.72 % inhibition at the concentration at 125 μg/ml. On the other hand, vanillic acid and nodakenin showed no inhibitory effect on the cellular NO production within noncytotoxic concentrations. Taken together all these results from the present study clearly demonstrated the potential antioxidant and anti-inflammatory activities of the whole plants of A. decursiva and its constituent, mainly umbelliferone 6-carboxylic acid which could be used in the development of therapeutic and preventive agents for oxidative stress-related diseases and inflammatory diseases.