Extracts of several Chinese plant species used traditionally to treat cancer were
tested for cytotoxicity using the SRB assay [1] with three cancer cell lines (COR-L23,
C32 and MCF-7) and a mammalian non-cancer cell line Hep G2. A chloroform extract of
the rhizomes of Iris tectorum Maxim. gave the greatest cytotoxicity with 100µg/ml giving less than 15% survival
with all three cancer cell lines. The SRB assay was used for bioassay-guided fractionation
of this extract and yielded two novel iridogermanal triterpenes IT4C and IT4D, two
known iridogermanal triterpenes iridobelamal 1 and isoiridogermanal and two flavonoids, 7-OMe-aromadendrin and tectorigenin, whose
structures were determined by advanced MS and NMR spectroscopy. The compounds were
tested for cytotoxicity using the SRB assay against the four cell lines with iridobelamal
1 having the greatest activity (Table).
Table: Cytotoxicity (IC50 µM±SEM) of isolated compounds n=3
|
Compound
|
Cell line
|
|
COR-L23
|
MCF-7
|
C32
|
HepG2
|
|
IT4C
|
35±1
|
18±1
|
40±2
|
29±2
|
|
IT4D
|
19±1
|
11±1
|
25±2
|
20±1
|
|
Iridobelamal 1
|
14±0
|
11±1
|
23±1
|
18±0
|
|
Isoiridogermanal
|
16±2
|
11±2
|
24±1
|
22±2
|
|
7-OMe-Aromadendrin
|
33±1
|
21±1
|
33±3
|
25±2
|
|
Tectorigenin
|
189±6
|
105±2
|
207±14
|
149±2
|
References: [1] Itharat, I. et al. (2004) J. Ethnopharmacology 90: 33–38.
