Asperginols A and B, Diterpene Pyrones, from an Aspergillus sp. and the Structure Revision of Previously Reported Analogues

Abstract

Two new diterpene pyrones, asperginols A (1) and B (2), and four known analogues (3–6) were isolated from the endophytic fungus Aspergillus sp. HAB10R12. The structures and absolute configurations of these compounds were elucidated based on the analysis of their NMR, MS, and X-ray diffraction data. The revision of the absolute configurations at C-10, C-11, and C-14 of the known diterpene pyrones (3–6) and the determination of the configuration at the polyene side chain for compounds (4–6) were made using chemical methods and vibrational circular dichroism analysis. This group of diterpene pyrone compounds showed unique structural features including a 7/6/6 tricyclic diterpene moiety with an unusual trans–syn–trans stereochemical arrangement. Compound 6 showed moderate activity against the HT-29 colon cancer cell line.

Incorporation of 4J-HMBC and NOE Data into Computer-Assisted Structure Elucidation with WebCocon

“…The proton-rich diterpene pyrone asperginol A ( 3 ) was chosen for the application of WebCocon calculations using NOEs ( Figure 5 ), because NMR and X-ray data were available, allowing for a comparison of the results [ 52 ]. The experimental data set comprises 18 COSY and 38 HMBC correlations ( Table 1 ).…”

“…The marine natural product oxocyclostylidol ( 2 ) serves as an example for the use of -HMBC correlation data because several identified experimentally observed -HMBC correlations were available [ 51 ]. The diterpene pyrone asperginol A ( 3 ) was chosen as example for the use of NOE data in CASE because, besides good-quality NMR data, including 15 NOEs, a reference X-ray structure was available [ 52 ]. All NMR data available for the molecules 1 – 3 is summarized in Table 1 .…”

Unravelling the Secrets of α‐Pyrones from Aspergillus Fungi: A Comprehensive Review of Their Natural Sources, Biosynthesis, and Biological Activities

“…Notably, among these compounds, only asperginols F (125) demonstrated moderate activity against the HT-29 colon cancer cell line. [103] The discovery of these structurally unique diterpene pyrones from endophytic Aspergillus species opens up new avenues for research, prompting further exploration of their potential therapeutic applications An endophytic fungus, Aspergillus sp. J215, obtained from the fresh inner tissue of the bark of Garcinia smeathmannii, yielded a novel α-pyrone named, asperpyrone (126), and two previously known metabolites.…”

The endophytic Aspergillus strains: A bountiful source of natural products

“…HAB10R12, an endophyte associated with the roots of Garcinia scortechinii . According to the conducted antiproliferative assay against HT‐29, HCT‐116 and HepG2, compound ( 145 ) showed moderate activity against the colon cancer cell line (HT‐29) with IC 50 value of 7.6 μmol l −1 (Al‐Khdhairawi et al 2020).…”