A methanol extract from
Dendrobium nobile showed asuppressive effect on
umu gene expressionof the SOS response in
Salmonella typhimurium TA1535/pSK1002against the mutagen 2-(2-furyl)-3-(5-nitro-2-furyl)acrylamide (furylfuramide). The methanolextract from
D. nobile was re-extractedwith
n-hexane, dichloromethane, 1-butanol, and water,respectively. A suppressive compound inthe
n-hexane extract fraction was isolated bySiO
2 column chromatography and chemicalfractionation and was identified as gigantol by EI-MS and
1H and
13C NMR spectroscopy.Gigantolsuppressed the SOS-inducing activity of furylfuramide in the
umu test. Gene expression wassuppressed 90% at <0.73
![](/images/entities/mgr.gif)
mol/mL, and the ID
50 value was0.35
![](/images/entities/mgr.gif)
mol/mL. Gigantol was also assayedwith the mutagen3-amino-1,4-dimethyl-5
H-pyrido[4,3
b]indole(Trp-P-1), which requires livermetabolizing enzymes, and it suppressed the SOS-inducing activity ofTrp-P-1 in the
umu test.Gene expression was suppressed 91% at <0.73
![](/images/entities/mgr.gif)
mol/mL, and theID
50 value was 0.32
![](/images/entities/mgr.gif)
mol/mL. Inaddition, gigantol was assayed for suppressive effect on UV irradiationin the
umu test, where itshowed suppression of the SOS-inducing activity caused by UVirradiation. Gene expression wassuppressed 84% at <0.36
![](/images/entities/mgr.gif)
mol/mL, and the ID
50 value was0.17
![](/images/entities/mgr.gif)
mol/mL. The antimutagenicactivities of gigantol against furylfuramide and Trp-P-1 were assayedby an Ames test using
S.typhimurium TA100, which indicated that gigantol suppressed eachof the mutagens.Keywords: Dendrobium nobile; gigantol; Orchidaceae; antimutagenic activity;umu test; Ames test