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Promsuk G, Chuawong P, Songjanthuek P, Thaisri S, Yongsmith B, Wattana-Amorn P. Absolute configuration of azaphilones from Monascus kaoliang KB9 and solvent effects on their keto and enol forms. Nat Prod Res 2022:1-8. [PMID: 35142570 DOI: 10.1080/14786419.2022.2034812] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/19/2022]
Abstract
Monascus fermented rice, also known as red yeast rice, exhibits a broad spectrum of biological activities due to its chemical constituents, such as monacolins and azaphilone pigments. Here, we cultured Monascus kaoliang KB9 in a liquid malt medium instead of on rice as a carbon source. Eleven known compounds (1-11) containing azaphilones and their early intermediate were isolated and identified. However, this was the first time that angular tricyclic azaphilones, monasfluols A (4) and B (7), acetyl-monasfluol A (5) and monasfluore A (6), were isolated from this species. Interestingly, all isolated tricyclic azaphilones existed exclusively in enol form in CD3OD, as evidenced by NMR spectroscopy. The absolute configuration of compounds 4-7 was also first experimentally identified based on ECD spectroscopy combined with conformational analyses using computational techniques. The assigned stereochemistry of Monascus azaphilones in this work provides essential structural information that will benefit future biological and pharmaceutical investigations.
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Affiliation(s)
- Gunlatida Promsuk
- Interdisciplinary Graduate Program in Bioscience, Faculty of Science, Kasetsart University, Bangkok, Thailand
| | - Pitak Chuawong
- Department of Chemistry, Special Research Unit for Advanced Magnetic Resonance and Center of Excellence for Innovation in Chemistry, Faculty of Science, Kasetsart University, Bangkok, Thailand
| | - Pacharaphan Songjanthuek
- Department of Chemistry, Special Research Unit for Advanced Magnetic Resonance and Center of Excellence for Innovation in Chemistry, Faculty of Science, Kasetsart University, Bangkok, Thailand
| | - Supunnee Thaisri
- Department of Chemistry, Special Research Unit for Advanced Magnetic Resonance and Center of Excellence for Innovation in Chemistry, Faculty of Science, Kasetsart University, Bangkok, Thailand
| | - Busaba Yongsmith
- Department of Microbiology and Center for Advanced Studies in Tropical Natural Resources (CASTNAR), National Research University-Kasetsart University (NRU-KU), Faculty of Science, Kasetsart University, Bangkok, Thailand
| | - Pakorn Wattana-Amorn
- Interdisciplinary Graduate Program in Bioscience, Faculty of Science, Kasetsart University, Bangkok, Thailand.,Department of Chemistry, Special Research Unit for Advanced Magnetic Resonance and Center of Excellence for Innovation in Chemistry, Faculty of Science, Kasetsart University, Bangkok, Thailand
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