As a part of our continuing search for bioactive constituents from Korean medicinal plants, we investigated a methanol extract from the stems of Lagerstroemia indica and Firmiana simplex for cytotoxic constituents, since the extracts showed considerable cytotoxicity against tested human cancer cells in screening procedures. By column chromatography methods, seventeen phenolic derivatives and ten triterpene derivatives were isolated from the stems of L. indica, and eighteen lignan derivatives, five phenylethanoid derivatives, and three triterpene glycoside from the stems of F. simplex were isolated. The structures of compounds from L. indica were identified as stroside A-C (L-1 ? L-3), lagerindiol (L-4), pterospermin A (L-5), hovetrichoside A (L-6), hovetrichoside B (L-7), balanophonin (L-8), (7R,8S)-4-O-methyldihydrodehydrodiconiferyl alcohol (L-9), 9,9''-dihydroxy-3,4-methylenedioxy-3''-methoxy[7-O-4'',8-5'']neolignan (L-10), (7R,8S)-dihydrodehydrodiconiferyl alcohol 4-O-β-D-glucopyranoside (L-11), glochidioboside (L-12), (+)-syringaresinol (L-13), evofolin-B (L-14), ficusol (L-15), (1''S,2''R)-guaiacyl glycerol (L-16), alatusol A (L-17), lagerindiside (L-18), quadranoside I (L-19), betulinic acid (L-20), 3β-acetoxyolean-12-en-28-acid (L-21), arjunglucoside II (L-22), hederagenin (L-23), arjunolic acid (L-24), oleanolic acid (L-25), maslinic acid (L-26), and 3β,23-dihydroxy-1-oxo-olean-12-en-28-oic acid (L-27) by using spectroscopic data, including 1D and 2D NMR. The structures of compounds from F. simplex were established as firmianol A-C (F-1-F-3), firmianoside A-C (F-4-F-6), simposide A and B (F-7 and F-8), 28-O-[β-D-glucopyranosyl-(1→6)-β-D-glucopyranosyl]-2α,3α,19α-trihydroxy-12-en-28-ursolic acid (F-9), 28-O-[β-D-glucopyranosyl-(1→6)-β-D-glucopyranosyl]-2α,3α,19α,23-tetrahydroxy-12-en-28-ursolic acid (F-10), 28-O-[β-D-glucopyranosyl-(1→6)-β-D-glucopyranosyl]-2α,3β,19α-trihydroxyurs-12-ene-24,28-dioic acid (F-11), paulownin (F-12), (+)-8-hydroxypinoresinol (F-13), (+)-syringaresinol-O-β-D-glucopyranoside (F-14), pinoresinol-4-O-β-D-glucopyranoside (F-15), balanophonin 4-O-β-D-glucopyranoside (F-16), (-)-(7R,8S,7''''S,8''''R)-3,3'''',5,5''-tetramethoxy-4''''-hydroxy-4'',7-epoxy-8'',9''-dinor-4,8''''-oxy-8,3''-sesquineolignan-7'''',9,9''''-triol-7''-al (F-17), wilfordiol B (F-18), (-)-olivil (F-19), tanegool (F-20), (+)-lariciresinol (F-21), (-)-diepiolivil (F-22), (+)-isolariciresinol (F-23), jionoside C (F-24), acteoside (F-25), and isoacteoside (F-26) by using spectroscopic data, including 1D and 2D NMR. Among these isolates, compounds L-1 ? L-4, L-18, and F-1 ? F-11 were newly isolated from the nature.
Cytotoxic activities of compounds (L-1 - L-27) isolated from the stems of L. indica against A549, SK-OV-3, SK-MEL-2, and HCT15 human cancer cell lines were evaluated using the SRB assay in vitro. Compounds L-20 and L-21 showed considerable cytotoxicity against all tested tumor cell lines with IC50 values in the range of 3.38 to 17.74 mm. Compound L-4, L-5 and L-25 moderate cytotoxicity against all tested tumor cell lines with IC50 values in the range of 5.87 to 17.26 mm.
Cytotoxic activities of the isolated compounds (F-1 - F-26) were evaluated by determining their inhibitory effects on human tumor cell lines (A549, SK-OV-3, SK-MEL-2, and HCT15) in vitro using the sulforhodamine B (SRB) assay. Compounds F-25 and F-26 considerable cytotoxicity against SK-MEL-2 cell line. (IC50 (F-25): 3.79 μM and IC50 (F-26): 5.93 μM, respectively)