Goyangamins A-C, Three Pairs of Enantiomeric 2(1H)-Quinolinone Alkaloid Dimers with Antisenescent Activity from Tetradium daniellii

Goyangamins A-C (1-3), three 2(1H)-quinolinone alkaloid dimers, were isolated from the roots of Tetradium daniellii. The structures of these dimers were elucidated by HRESIMS, 1D and 2D NMR spectroscopy, and ECD analysis. Compounds 1 and 2 feature an sp³-sp² chiral axis, whereas compound 3 contains an sp²-sp² chiral axis, giving rise to a pair of interconverting atropisomers. Variable-temperature NMR (VT NMR), in conjunction with computational potential energy surface (PES) scans, indicated that compounds 1-3 belong to class I atropisomers that can readily interconvert at room temperature. Compound 3 exhibited the most potent antisenescence activity, with an IC₅₀ value of 7.8 ± 2.2 μM and showed a dual mode of action involving inhibition of senescence-associated secretory phenotype (SASP) markers (IL-6, IL-8, IL-1α, and IL-1β) and suppression of senescence-associated β-galactosidase (SA-β-gal) activity.