The chain length of lignan macromolecule from flaxseed hulls is determined by the incorporation of coumaric acid glucosides and ferulic acid glucosides

Lignan macromolecule from flaxseed hulls is composed of secoisolariciresinol diglucoside (SDG) and herbacetin diglucoside (HDG) moieties ester-linked by 3-hydroxy-3-methylglutaric acid (HMGA), and of p-coumaric acid glucoside (CouAG) and ferulic acid glucoside (FeAG) moieties ester-linked directly to SDG. The linker molecule HMGA was found to account for 11% (w/w) of the lignan macromolecule. Based on the extinction coefficients and RP-HPLC data, it was determined that SDG contributes for 62.0% (w/w) to the lignan macromolecule, while CouAG, FeAG, and HDG contribute for 12.2, 9.0, and 5.7% (w/w), respectively.Analysis of fractions of lignan macromolecule showed that the higher the molecular mass, the higher the proportion of SDG was. An inverse relation between the molecular mass and the proportion (%) CouAG + FeAG was found. Together with the structural information of oligomers of lignan macromolecule obtained after partial saponification, it is hypothesized that the amount of CouAG + FeAG present during biosynthesis determines the chain length of lignan macromolecule.Furthermore, the chain length was estimated from a model describing lignan macromolecule based on structural and compositional data. The average chain length of the lignan macromolceule was calculated to be three SDG moieties with CouAG or FeAG at each of the terminal positions, with a variation between one and seven SDG moieties.     

Enzymatic hydrolysis of plumieride to plumieridine

The hydrolysis of plumieride to form the aglycone plumieridine was catalysed by a commercial preparation of cellulase from Aspergillus niger.     

Biotransformation of digitoxigenin by cell suspension cultures of Digitalis purpurea

Digitoxigenin was oxidized to digitoxigenone which was reduced to epidigitoxigenin and then glucosylated to epidigitoxigenin glucoside by cell cultures of Digitalis purpurea. The epidigitoxigenin glucoside, together with digitoxigenone and epidigitoxigenin, was isolated in considerable amounts, whereas digitoxigenin glucoside could only be detected in low concentration. Furthermore, it was confirmed by TLC and HPLC that digitoxigenin was hydroxylated to periplogenin.     

New carotenoids from the thermophilic green sulfur bacterium Chlorobium tepidum: 1′,2′-dihydro-γ-carotene, 1′,2′-dihydrochlorobactene, and OH-chlorobactene glucoside ester, and the carotenoid composition of different strains

The complete carotenoid composition of the thermophilic green sulfur bacterium Chlorobium tepidum strain TNO was determined by spectroscopic methods. Major carotenoids were four kinds of carotenes: γ-carotene, chlorobactene, and their 1′,2′-dihydro derivatives (1′,2′-dihydro-γ-carotene and 1′,2′-dihydrochlorobactene). In lesser amounts, hydroxyl γ-carotene, hydroxyl chlorobactene, and their glucoside fatty acid esters were found. The only esterified fatty acid present was laurate, and OH-chlorobactene glucoside laurate is a novel carotenoid. In other strains of C. tepidum, the same carotenoids were found, but the composition varied from strain to strain. The overall pigment composition in cells of strain TNO was 4 mol carotenoids and 40 mol bacteriochlorophyll c per mol bacteriochlorophyll a. The effects of nicotine on carotenoid biosynthesis in C. tepidum differed from those in the thermophilic green nonsulfur bacterium Chloroflexus aurantiacus. Received: 3 February 1997 / Accepted: 6 June 1997