Uncovering the Power of HSCCC: Separation of Diastereomeric and Regioisomeric Styrylpyrones from the Stem Bark of Goniothalamus leiocarpus

Abstract

The plant Goniothalamus leiocarpus of the Annonaceae family is used as an alternative medicine in tropical regions. Applying high-speed counter current chromatography (HSCCC), eight new bioactive styrylpyrone isomers, including 6R,7S,8R,2′S-goniolactone B (1), 6S,7S,8S,2′S-goniolactone B (2), 6R,7R,8R,2′S-goniolactone B (3), 6R,7S,8S,2′S-goniolactone C (4), 6R,7S,8R,2′S-goniolactone C (5), 6S,7R,8S,2′S-goniolactone C (6), and two positional isomers, 6R,7R,8R,2′S-goniolactone G (7) and 6S,7R,8R,2′S-goniolactone G (8), were isolated from a chloroform fraction (2.1 g) of G. leiocarpus, which had a prominent spot by TLC analysis. The structures of the new compounds were elucidated by MS, NMR, IR, and UV spectra, and their absolute configurations were determined by Mosher’s method, ECD, and X-ray diffraction analysis. The isolates are characteristic components found in plants of the genus Goniothalamus and consist of two structural moieties: a styrylpyrone and a dihydroflavone unit. The isolation of the eight new compounds demonstrates the effectiveness of HSCCC in separating the isomers of natural styrylpyrone. In a bioactivity assessment, compounds 1 and 6 exhibited cytotoxic effects against the human colon carcinoma cell lines LS513 and SW620 with IC50 values ranging from 1.6 to 3.9 μM. Compounds 1, 2, 7, and 8 showed significant synergistic activity against antibiotic-resistant Staphylococcus aureus strains.