| Abstract: | Euonymus laxiflorus Champ., a medicinal herb collected in Vietnam, has been reported
to show several potent bioactivities, including anti-NO, enzyme inhibition, hypoglycemic and
antidiabetic effects. Recently, the antioxidant activity of Euonymus laxiflorus Champ. trunk bark
(ELCTB) has also been reported. However, the active antioxidant and anti-NO constituents existing
in ELCTB have not been reported in the literature. The objective of this study was to purify the active
antioxidants from ELCTB and investigate the anti-NO effect of the major constituents. Twenty-two
phenolics isolated from ELCTB, including 12 compounds newly isolated in this study (1–12) and
10 constituents obtained from our previous work, were evaluated for their antioxidant activity.
Of these, 12 compounds (4–6, 9, 13–15, 18–22) showed a potent antioxidant capacity (FRS50 =
7.8–58.11 µg/mL), in comparison to α-tocopherol (FRS50 = 23 µg/mL). In the anti-NO activity tests,
Walterolactone A (1a) and B (1b) β-D-glucopyranoside (13) demonstrated the most effective and
comparable activity to that of quercetin with max inhibition and IC50 values of 100%, 1.3 µg/mL, and
100%, 1.21 µg/mL, respectively. The crude extract and its major compounds showed no cytotoxicity
on normal cells. Notably, three constituents (9, 11, and 12) were identified as new compounds,
another three constituents, including 1, 7, and 8, were found to be new natural products, constituents
9 and 13 were determined to be new antioxidants, and compound 13 was reported to have novel
potent anti-NO activity for the first time. The results of this study contribute to the enrichment of
new natural products and compounds, as well as the novel biological activity of constituents isolated
from Euonymus laxiflorus Champ. The current study also indicates ELCTB as a rich natural source of
active phenolics. It is suggested that ELCTB could be developed as a health food with promising
antioxidant and anti-NO effects, as well as other beneficial biological activities. |
