Microbial transformation of some triterpenoids of Guayule resin by Chaetomium sp

• Published in: Phytochemistry letters 2023-06, Vol.55, p.124-130
• Main Authors: Inacio, Marielle C., Zhong, Weimao, Xu, Ya-Ming, Wijeratne, E.M. Kithsiri, Madasu, Chandrashekhar, Molnár, István, Gunatilaka, A.A. Leslie
• Format: Article
• Language: English
• Subjects: Argentatins; Biotransformation; Chaetomium sp.PA001; Enzymatic Baeyer-Villiger oxidation; Guayule; Parthenium argentatum
• ISSN: 1874-3900; 1876-7486
• DOI: 10.1016/j.phytol.2023.05.001

Microbial biotransformation of argentatin A (1), isoargentatin A (2) and argentatin C (3), the triterpenoid constituents of guayule (Parthenium argentatum) resin was conducted with Chaetomium sp. PA001, an endophytic fungus of the same plant. The experiments yielded six new products (4–9) formed by: (i) nucleophilic oxygenation of the 3-ketone moiety resulting in Baeyer-Villiger oxidation; (ii) lactone ring opening of these oxidation products; (iii) rearrangement of the 9(10)-cyclopropane ring; and (iv) reduction of the 3-ketone moiety. The structures of all new biotransformation products were established by detailed analysis of their spectroscopic data. None of the products exhibited any antimicrobial activity. However, the hydroxy-carboxylic acid derivative 5 of argentatin A showed weak cytotoxic activity, but improved selectivity against human breast cancer cell line MCF-7 compared to the parent compound. This constitutes the first report of microbial biotransformation of isoargentatin A and argentatin C. [Display omitted] •Biotransformation of guayule resin triterpenes was studied for value-added products.•Chaetomium sp. PA001 was selected for biotransformation after screening 16 fungi.•Six new biotransformation products were isolated and characterized.•One of the products had weak cytotoxicity with selectivity for breast cancer cells.