Minor labdane diterpenes from Marrubium thessalum

Area of Science:

• Natural Product Chemistry
• Phytochemistry
• Organic Chemistry

Background:

• Marrubium thessalum is a plant species known for its diverse secondary metabolites.
• Labdane diterpenes and flavones are classes of natural products with various biological activities.
• Understanding the chemical constituents of medicinal plants is crucial for drug discovery and chemotaxonomy.

Purpose of the Study:

• To isolate and characterize new labdane diterpenes from Marrubium thessalum.
• To investigate the structural diversity of diterpenoids in this plant species.
• To explore the potential chemotaxonomic significance of isolated compounds.

Main Methods:

• Isolation of compounds using chromatographic techniques.
• Structure elucidation using comprehensive spectroscopic methods including 1D and 2D Nuclear Magnetic Resonance (NMR) and Mass Spectrometry (MS).
• Analysis of Nuclear Overhauser Effect (NOE) correlations via NOESY and ROESY experiments.

Main Results:

• Five new labdane diterpenes, thessalines A, B, and D, 14β-hydroxythessaline A, and 14β-hydroxythessaline B, were identified.
• The known labdane diterpene deacetylvitexilactone and methoxylated flavones (4',7-dimethylapigenin and salvigenin) were also isolated.
• (3S,5R)-Loliolide was identified as an additional constituent.

Conclusions:

• The aerial parts of Marrubium thessalum are a rich source of structurally diverse labdane diterpenes.
• The identified compounds, particularly the variations in the side chain functionalities, may hold chemotaxonomic significance for the Marrubium genus.
• Further investigation into the biological activities of these novel compounds is warranted.