Monarubins A-C from the Marine Shellfish-Associated Fungus Monascus ruber BB5

Area of Science:

• Marine natural products chemistry
• Chemical biology
• Mycology

Background:

• Marine-derived fungi are a rich source of bioactive secondary metabolites.
• The fungus Monascus ruber BB5, isolated from shellfish, has not been extensively studied for its chemical constituents.

Purpose of the Study:

• To isolate and characterize new and known compounds from Monascus ruber BB5.
• To evaluate the cytotoxic activities of these compounds against human cancer cell lines.

Main Methods:

• Isolation and purification of compounds using chromatographic techniques.
• Structure elucidation using 1D and 2D NMR, MS, UV, and IR spectroscopy.
• Determination of absolute configurations using ECD calculations.
• Cytotoxicity assays against nasopharyngeal and hepatocellular carcinoma cell lines.

Main Results:

• Three new compounds, monarubins A-C (1, 6, 13), were identified, along with ten known compounds (four alkaloids, two isocoumarins, four polyketides).
• The NMR data for deoxyhydroxyaspergillic acid (3) and 2-hydroxy-6-(1-hydroxy-1-methylpropyl)-3-sec-buthylpyrazine (4) were reported for the first time.
• Monarubin B (6) exhibited potent cytotoxicity against HepG2 and QGY7701 cells (IC50 values of 1.72 and 0.71 μM).
• Lunatinin (7) demonstrated moderate cytotoxicity against HepG2, QGY7701, and SUNE1 cells (IC50 values of 9.60, 7.12, and 28.12 μM).

Conclusions:

• Monascus ruber BB5 is a source of structurally diverse secondary metabolites.
• Monarubin B and lunatinin possess significant cytotoxic potential against specific human cancer cell lines, warranting further investigation.