In vitro DPPH Radical Scavenging Activity of α-Pyrones from Odontonema strictum (Acanthaceae)

Area of Science:

• Phytochemistry
• Pharmacology
• Natural Products Chemistry

Background:

• Odontonema strictum ethyl acetate leaf extract exhibits potent antihypertensive activity.
• The specific phytochemicals responsible for this activity were previously unidentified.
• This study focuses on the isolation and characterization of active compounds and their antioxidant properties.

Purpose of the Study:

• To isolate and characterize phytochemicals from the active fraction of Odontonema strictum.
• To evaluate the in vitro antioxidant activity of the isolated compounds.
• To explore the potential of Odontonema strictum as an herbal medicine based on its chemical constituents.

Main Methods:

• Isolation of four known alpha-pyrones from the ethyl acetate leaf extract.
• Characterization of the isolated alpha-pyrones.
• In vitro antioxidant activity evaluation using the 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging assay.
• Comparison with ascorbic acid as a positive control.

Main Results:

• Four known alpha-pyrones were successfully isolated and characterized: umuravumbolide, deacetylumuravumbolide, dideacetylboronolide, and deacetylboronolide.
• Deacetylumuravumbolide demonstrated the most potent antioxidant activity (IC50 = 0.24±0.0002 µg/mL), followed by deacetylboronolide (IC50 = 24±0 µg/mL).
• The study suggests that 6-substituted 5,6-dihydro-α-pyrones and phenylpropanoid glucosides in the extract contribute to its antihypertensive effects.

Conclusions:

• This research is the first to report the isolation and antioxidant evaluation of these specific alpha-pyrones from Odontonema strictum.
• The identified compounds possess significant antioxidant potential, supporting the traditional use of O. strictum.
• Further chemotaxonomic investigations are recommended to understand the distribution of alpha-pyrones in related genera.