Flavan-3-ols from the Leaves of Malaysian Uncaria longiflora var

A novel flavonoid, (-)-2R,3R-3,5,4’-trihydoxyflavan-[6,7:5”,6”]-2”-pyranone, named uncariechin (1), was isolated from the methanolic extract of the leaves of Uncaria longiflora var. pteropoda (Miq.) Ridsd. along with the known (-)-epiafzelechin (2) and (-)-epicatechin (3), methyl 4-hydroxybenzoate and 4-hydroxybenzaldehyde, four pentacyclic oxindole alkaloids, isopteropodine, pteropodine, uncarine F and isopteropodic acid, previously found in the stems, and two coumarins, scopoletin and 3,4-dihydroxy-7-methoxycoumarin. Structures of the compounds were elucidated by 1D and 2D NMR, FTIR, UV, MS, and experimental as well as calculated electronic circular dichroism (ECD) data. Compounds 2 and 3 were evaluated for their neurotoxic and neuroprotective properties against differentiated SH-SY5Y neuroblastoma cell lines using the MTS assay. Compounds 2 and 3 did not show any neurotoxic effects but showed strong protective potential against hydrogen peroxideinduced neurotoxicity with maximum cell viability at a concentration of 1 μM. Corresponding author. Tel.: +603-55445592 Email address: [email protected] Salim et al Phytochemistry Letters