TULIPOSIDES AND TULIPALINS IN TULIP GUM

Abstract

Gummosis in tulip bulbs is one of the negative effects of ethylene gas that is produced during storage by Fusarium-infected bulbs on the healthy bulbs. Several aspects of the gummosis process, like the factors inducing it, the underlying carbohydrate metabolism and the composition of the gum have been described in detail in a review by Saniewski et al. (2007). The composition of tulip gum has mostly been studied in terms of large macromolecules. The gum polysaccharides have been analyzed to determine sugar composition and molecular mass. Up to now relatively little was known about the gum in terms of small (low molecular weight) metabolite content. Gummosis was induced in tulip bulbs of the cultivar ‘Apeldoorn’ by exposing the bulbs to air containing 30 ppm ethylene for 24, 48 or 72 h. Gum was collected after 3 to 4 days. A maximum amount of approximately 5 g per 100 g bulbs was obtained. Extracts of the gum were analyzed by 1H Nuclear Magnetic Resonance (1H NMR) and were found to contain tuliposides, in concentrations up to around 25% (DW). Tuliposides are glycosides consisting of glucose with one or more a-methylene-?-butyrolactone side chains. The side chains, when separated from the glucose, form ring structures known as tulipalins. Six different tuliposides and two tulipalins have been reported in various parts of the tulip plant. However, this is the first time they are reported in the gum from tulip bulbs. Isolated tulipalins and tuliposides have previously been tested for various bioactivities, and have been reported to possess antibacterial, antifungal and insecticidal properties. The presence of these bioactive molecules in tulip gum may suggest a protective role for this physiological response