Didychaudianin A: a new tirucallane triterpenoid from the stem bark of Indonesian <i>Didymocheton gaudichaudianus</i> (Meliaceae)

A new tirucallane-type triterpenoid, didychaudianin A (<b>1</b>), along with two known tirucallane analogs (<b>2</b> and <b>3</b>), was isolated from the stem bark of <i>D. gaudichaudianus</i> (Meliaceae) growing in West Java, Indonesia. Their structures, including absolute configurations, were elucidated using HRESIMS, extensive 1D and 2D NMR spectroscopic analysis, ECD spectroscopy, and quantum chemical calculations based on density functional theory (DFT), supported by DP4+ statistical analysis. Cytotoxic evaluation against human cervical cancer HeLa cells revealed that <b>2</b> exhibited moderate activity, with an IC₅₀ value of 44.4 μM. Structure-activity relationship (SAR) analysis indicated that the stereochemistry at C-21 and the presence of a tetrahydrofuran ring in the side chain play a crucial role in modulating biological activity. The isolation of tirucallane-type triterpenoids (<b>1-3</b>) further enriches the chemical diversity of this compound class within the <i>Didymocheton</i> genus.