Cytotoxic Lignan and Flavonoid Derivatives from the Branches of Beilschmiedia yunnanensis

An investigation of a cytotoxic MeOH extract of the branches of Beilschmiedia yunnanensis, collected in Vietnam, led to the isolation of four new compounds (1-4). Two of these, isolated from a CHCl₃-soluble partition, were characterized as the furofuran-type neolignans, beilschmiedianins A (1)[(7R,7'R,8S,8'S,8″R)-4',4″,9''-trihydroxy-3,5,3',3''-tetramethoxy-4,8''-oxy-7,9':7'9-diepoxy-8,8'-sesquilignan-7''-one)] and B (2) [(7R,7'R,7″R,8S,8'S,8″R)-9″-feruloyl-4',4''-dihydroxy-3,5,3',3''-tetramethoxy-4,8″-oxy-7,9':7',9-diepoxy-8,8'-dilignan-7″-ol]. In turn, the flavonoid glycosides 3 and 4 were obtained from an EtOAc-soluble partition and were assigned as (2R,3R)-dihydrokaempferol-5-O-β-l-arabinosyl-(2→1)-α-l-rhamnopyranoside and (2R,3R)-dihydrokaempferol-5-O-β-l-arabinopyranoside, respectively. The structures of these new compounds were determined using a combination of spectroscopic and spectrometric methods. Additionally, the known dilignan, (-)-9,9'-O-diferuloylsecoisolariciresinol (5), showed selective cytotoxicity against the OVCAR3 ovarian cancer cell line, with an IC₅₀ value of 0.51 μM. Mechanistic studies showed that compound 5 increased the cPARP levels and decreased the expression of BCL-2 in OVCAR3 cells.