Background:
Plant in Rhododendron genus that contains phenolic compounds has been
used in traditional medicine and revealed considerable biological activities.
Objective:
Isolation and identification of antioxidant natural products from Rhododendron ungernii.
Methods:
Rhododendron ungernii Trautv. flowers were collected and dried in shade. The dried
flowers were extracted with methanol for 3 days. The solvent was removed by reduced pressure to
yield the extract which was subjected to column chromatography (Sephadex LH-20, C18 reversed
phase column) to isolate catechin-7-O-glucoside (1), quercetin-3-O-β-galactoside (2), quercetin-3-O-
β-xyloside (3), farrerol (4), myricetin (5), and quercetin (6). The structures of isolated compounds
were elucidated by spectroscopic methods such as 1D-NMR, 2D-NMR, and LC-TOF/MS. DPPH
scavenging effect, ABTS+ scavenging activity, and reducing power (FRAP) were performed for antioxidant
assays of isolated natural compounds.
Results:
Isolated flavonoids displayed the outstanding antioxidant activities. Catechin-7-O-glucoside
(1) and quercetin-3-O-β-galactoside (2) (IC50, 3.66 µg/mL) had the most DPPH• scavenging
effect among the compounds. The highest ABTS•+ scavenging activity (IC50, 1.41 µg/mL) and reducing
power effect (6.05 mmol TE/g comp) were observed for myricetin (5).
Conclusion:
R. ungernii extract and isolated compounds could be a promising antioxidant for food
and pharmaceutical industries.
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