Diterpenoids from Haplopappus rigidus

Area of Science:

• Phytochemistry
• Natural Products Chemistry
• Organic Chemistry

Background:

• Haplopappus rigidus Phil. is a plant species with potential medicinal properties.
• Natural products are a source of novel therapeutic agents.
• Bioassay-guided fractionation is a common strategy for isolating active compounds.

Purpose of the Study:

• To isolate and characterize new diterpenoids from Haplopappus rigidus Phil.
• To evaluate the cytotoxic activity of the isolated compounds.

Main Methods:

• Phytochemical analysis of Haplopappus rigidus aerial parts.
• Brine shrimp lethality test (BST) for bioassay-guided fractionation.
• Structure elucidation using 2D Nuclear Magnetic Resonance (NMR) spectroscopy (DEPT, DQF-COSY, HMQC, HMBC).

Main Results:

• Isolation of two new cis-cleroda-3,14-diene diterpenoids: rigidusol and deacetylrigidusol.
• Rigidusol's structure: 13-hydroxy-18-acetoxy-cis-cleroda-3,14-diene (8βH, 10βH, 19β, 20α form).
• Deacetylrigidusol's structure: 13,18-dihydroxy-cis-cleroda-3,14-diene (8βH, 10βH, 19β, 20α form).
• Rigidusol demonstrated moderate cytotoxic activity against the MCF-7 human breast adenocarcinoma cell line.

Conclusions:

• The study successfully isolated and characterized two novel diterpenoids from Haplopappus rigidus.
• Rigidusol exhibits potential as an anticancer agent, warranting further investigation.
• The findings contribute to the understanding of the chemical constituents of Haplopappus rigidus and their biological activities.