Sesquiterpene Acids and Lactones from Inula Confertiflora with their Antibacterial Activities

Area of Science:

• Phytochemistry
• Natural Products Chemistry
• Medicinal Plant Research

Background:

• Inula confertiflora is a medicinal plant endemic to Ethiopia.
• Terpenoids are a diverse class of natural products with various biological activities.
• Understanding the chemical constituents of medicinal plants is crucial for drug discovery.

Purpose of the Study:

• To isolate and characterize terpenoids from Inula confertiflora leaves.
• To elucidate the structures of novel and known compounds using spectroscopic methods.
• To evaluate the antibacterial potential of the isolated compounds.

Main Methods:

• Phytochemical investigation involving isolation and purification techniques.
• Structural elucidation using Nuclear Magnetic Resonance (NMR) spectroscopy and High-Resolution Electrospray Ionization Mass Spectrometry (HRESIMS).
• Determination of relative configurations via NOESY correlations and single-crystal X-ray crystallography.
• Antibacterial assays against Escherichia coli and Staphylococcus aureus.

Main Results:

• Fifteen terpenoids were isolated from Inula confertiflora.
• The structure and full NMR data for 1β-hydroxy-α-costic acid (1) were reported for the first time.
• Crystallography data for carpesioline (6) and graveolide (7) were reported for the first time.
• Compounds 1, 3, 6, 7, and 8 demonstrated moderate antibacterial activity against the tested bacterial strains.

Conclusions:

• The study successfully characterized terpenoids from Inula confertiflora, including novel structural information.
• Several isolated terpenoids possess moderate antibacterial properties, suggesting potential therapeutic applications.
• The findings contribute to the chemotaxonomic understanding of the Inula genus.