Abstract
Two new ecdysteroids, spectasterone A (1) and spectasterone B (2), together with four known ecdysteroids, breviflorasterone (3), ajugalactone (4), 20-hydroxyecdysone (5), and polypodine B (6) were isolated from the Korean endemic plant Ajuga spectabilis using feature-based molecular networking analysis. The chemical structures of 1 and 2 were determined based on the interpretation of NMR and mass spectrometric data. Their absolute configurations were established using 3JH, H coupling constants, NOESY interactions, Mosher's method, and ECD and DP4+ calculations. To identify their biological target, a machine learning-based prediction system was applied, and the results indicated that ecdysteroids may have 11β-hydroxysteroid dehydrogenase type 1 (11β-HSD1)-related activity, which was further supported by molecular docking results of ecdysteroids with 11β-HSD1. Following this result, all the isolated ecdysteroids were tested for their ability to affect the expression of 11β-hydroxysteroid dehydrogenase type 1 and glucocorticoid receptors (GRs) in HaCaT cells irradiated with UVB. Compounds 2-5 exhibited inhibition of 11β-HSD1 expression and increases in GR activity.