Cucurbitane Glucosides from the Root of Machilus yaoshansis

Seven new cucurbitane triterpene glucosides (1–5, 8, and 9) and five known analogues (6, 7, 10, cucurbitacin I 2-O-β-d-glucopyranoside, and khekadaengoside K) have been isolated from an ethanol extract of roots of Machilus yaoshansis. Compounds 1 and 2 have an unusual 16,23:22,25-diepoxy unit, 4 is an uncommon cucurbitane 25-carbamate with the carbamoyl amino group attached at C-24 to form an oxazolidinone ring in the side chain, and 8 is the first example of a trinorcucurbitane derivative. The configurations in several pairs of C-24 epimeric cucurbitacins with 24,25-dihydroxy-22-one side chains were assigned, and the validity of J23a,24 and J23b,24 values to differentiate the configuration at C-24 in these cucurbitane derivatives is discussed. Compounds 2–4 showed in vitro activity against protein tyrosine phosphatase 1B with IC50 values of 8.63, 2.81, and 4.26 μM, respectively. Cucurbitacin E 2-O-β-d-glucopyranoside (10) showed selective cytotoxicity against BGC-823 and A549 cancer cells with IC50 values of 4.98 and 3.20 μM, respectively.