Spiranthenones A and B, tetraprenylated phloroglucinol derivatives from the leaves of Spiranthera odoratissima

Two new polyprenylated acylphloroglucinols, spiranthenones A (1) and B (2), a sesquiterpenoid, 6 α-acetoxy,1 β-hydroxyeudesm-4(15)-ene (3), along with sesamin and β-sitosterol, were isolated from the EtOAc extract of the leaves of Spiranthera odoratissima, and shown to display antiprotozoal activity. Their structures and relative stereochemistry were elucidated by NMR and mass spectrometry. These compounds exhibited moderate antiprotozoal activity, but without significant cytotoxicity against fibroblasts cell line NIH-3T3. Compound 3 was the most selective towards parasites.