Kleinhospitines A–D, New Cycloartane Triterpenoid Alkaloids from <i>Kleinhovia hospita</i>

Kleinhospitines A–D, four unprecedented cycloartane triterpenoid alkaloids possessing a spiro α,β-unsaturated γ-lactamlactone side chain, were isolated as two mixtures of C-23 epimers from <i>Kleinhovia hospita</i>. Kleinhospitines C and D represent the first examples of naturally occurring cycloartane triterpenoids with a 9α,10α-cyclopropyl ring. The structures and absolute configurations were determined on the basis of spectroscopic analyses and comprehensive quantum chemical calculations. The two mixtures showed hepatoprotective activity against H₂O₂-induced oxidative damages on primary cultured rat hepatocytes with EC₅₀ values of 167.0 and 126.5 μM