Direct proof by 13C‑nuclear magnetic resonance of semi‑purified extract and isolation of ent‑Catechin from leaves of Eucalyptus cinerea

Background: Eucalyptus cinerea F. Muell. ex Benth. is native to Australia and acclimatized to Southern Brazil. Its aromatic leaves are used for ornamental purposes and have great potential for essential oil production, although reports of its use in folk medicine are few. Objective: This study evaluated the composition of E. cinerea leaves using the solid state 13C‑nuclear magnetic resonance (NMR) and isolation of the compound from the semipurified extract (SE). Materials and Methods: The SE of E. cinerea leaves was evaluated in the solid state by 13C‑NMR spectrum, and the SE was chromatographed on a Sephadex LH‑20 column, followed by high‑speed counter‑current chromatography to isolate the compound. The SE was analyzed by 13C‑NMR and matrix‑assisted laser desorption/ionization‑time‑of‑flight spectra. Results: Flavan‑3‑ol units were present, suggesting the presence of proanthocyanidins as well as a gallic acid unit. The uncommon ent‑catechin was isolated. Conclusion: The presence of ent‑catechin is reported for the first time in this genus and species.