Moscatilin from Dendrobium nobile, a naturally occurring bibenzyl compoundwith potential antimutagenic activity

A bibenzyl compound that possesses antimutagenic activity was isolated from the storage stem of Dendrobium nobile. The isolated compound suppressed th e expression of the umu gene following the induction of SOS response in Sal monella typhimurium TA1535/pSK1002 that have been treated with various muta gens. The suppressive compound was mainly localized in the n-hexane extract fraction of the processed D. nobile. This n-hexane fraction was further fr actionated by silica gel column chromatography, which resulted in the purif ication and subsequent identification of the suppressive compound. EI-MS an d H-1 and C-13 NMR spectroscopy were then used to delineate the structure o f the compound that confers the observed antimutagenic activity. Comparison of the obtained spectrum with that found in the literature indicated that moscatilin is the secondary suppressive compound. When using 2-(2-furyl)-3- (5-nitro-2-furyl)acrylamide (furylfuramide) as the mutagen, moscatilin supp ressed 85% of the umu gene expression compared to the controls at <0.73 mu mol/mL, with an ID50 value of 0.41 mu mol/mL. Additionally, moscatilin was tested for its ability to suppress the mutagenic activity of other well-kno wn mutagens such as 4-nitroquinoline-1-oxide (4NQO), N-methyl-N'-nitro-N-ni trosoguanidine (MNNG), UV irradiation, 3-amino-1,4-climethy1-5H-pyrido[4,3b ]indole (Trp-P-1), benzo[a]pyrene (B[a]P), and aflatoxin B-1 (AFB(1)). With all of the aforementioned chemicals or treatments, moscatilin showed a dra matic reduction in their mutagenic potential. Interestingly, moscatilin alm ost completely suppressed (97%) the AFB(1)-induced SOS response at concentr ations <0.73 mu mol/mL, with an ID50 of 0.08 mu mol/mL. Finally, the antimu tagenic activities of moscatilin against furylfuramide and Trp-P-1 were ass ayed by the Ames test using the S. typhimurium TA100 strain. The results th ose experiments indicated that moscatilin demonstrated a dramatic suppressi on of the mutagenicity of only Trp-P-1 but not furylfuramide.