Abstract
Crocosmia x crocovniiflora (montbretia) flowers yielded four esters (montbresides A-D) of a new sucrose-based tetrasaccharide, 3-O-beta-alpha-glucopyranosy1-4'-O-alpha-D-rhamnopyranosyl-sucrose [beta-D-Glc-(1 3)-alpha-D-Glc-(1 -> 2)-beta-D-Fru-(4 <- 1)-alpha-D-Rha]. All four possess O-p-coumaroyl residues on C-3 of fructose and C-4 of alpha-glucose, plus O-acetyl residues on C-2 and C-3 of rhamnose and C-6 of fructose. Montbresides A and B are additionally 0acetylated on C-1 of fructose. The p-coumaroyls are trans- in montbresides A and C and cis- in B and D. Elemental compositions were determined from MS data, and structures from 1D and 21) NMR spectra. Monosaccharide residues were identified from selective 1D TOCSY spectra and TLC, and acylation sites from 21) HMBC spectra. Enantiomers were distinguished by enzymic digestion. Montbretia flower extracts were cytotoxic against six human cancerous cell-lines, but purified montbresides lacked cytotoxicity. Each montbreside displayed antibacterial activity against Staphylococcus aureus (minimal inhibitory concentration similar to 6 mu g/ml). Montbretia is a potential source of new cytotoxins and antibacterial agents.