Five Pairs of Meroterpenoid Enantiomers from Rhododendron capitatum

Area of Science:

• Natural Product Chemistry
• Organic Chemistry
• Pharmacognosy

Background:

• Rhododendron species are known sources of bioactive natural products.
• Meroterpenoids represent a diverse class of compounds with complex structures.
• Investigating plant secondary metabolites can lead to the discovery of novel chemical entities.

Purpose of the Study:

• To isolate and characterize new meroterpenoids from Rhododendron capitatum.
• To determine the structures and absolute configurations of the isolated compounds.
• To evaluate the biological activity of the novel compounds.

Main Methods:

• Chemical investigation using chromatographic techniques, including chiral High-Performance Liquid Chromatography (HPLC).
• Structure elucidation employing comprehensive spectroscopic data (NMR, MS).
• Determination of absolute configurations via single-crystal X-ray diffraction and Electronic Circular Dichroism (ECD) analysis.

Main Results:

• Five enantiomeric pairs of new meroterpenoids, rhodonoids C-G (1a-5b), were identified.
• Compounds 1a and 1b represent the first meromonoterpenes with a 6/6/6/5 ring system.
• Compounds 2a and 2b are novel meromonoterpenes featuring a unique 6/6/5/5 ring system.
• Rhodonoid C (1a) exhibited in vitro antiviral activity against herpes simplex virus type 1 (HSV-1).

Conclusions:

• The chemical study of Rhododendron capitatum yielded structurally unique meroterpenoids.
• The discovery of rhodonoids C-G expands the known chemical diversity of this compound class.
• Rhodonoid C (1a) shows potential as an antiviral agent, warranting further investigation.