Barbara J. W. Cole

Betulin and lupeol in bark from four white-barked birches

Abstract Levels of betulin in the outer bark of four species of white-barked birch range from 5.0 to 22.0%. This variation in the level of betulin is taxonomically useful. The percentage of betulin in chloroform extracts is significantly different between two taxa, Betula cordifolia and B. papyrifera , that are often considered conspecific. In B. X caerulea , a putative hybrid of B. cordifolia and B. populifolia , betulin levels are intermediate between and significantly different from those of the parents. Levels of the codominant triterpenoid, lupeol, are less than 1.3% and are significantly different only between B. populifolia and B. X caerulea .

Triterpenoid extractives in the outer bark of Betula lenta (black birch)

Birch bark represents an abundant, and currently unutilized, natural resource. In this study, the triterpenoid composition of the outer bark of the darkbarked birch species, Betula lenta, was investigated. Lupeol was the most abundant triterpene. Betulin, lupenone, betulone, betulinic acid, betulin-3-caffeate, Iup-20(29)-ene-3ß,30-diol, lup-20(29)-ene-3ß-ol-30-al, lup-20(29)-ene-3ß,28-diol-30-al, and lupan-3ß,20diol were also isolated and identified.To our knowledge, betulone (lup-20(29)-ene-28-ol-3-one) and lup20(29)-ene-3ß,28-diol-30-al, previously prepared synthetically, are new natural products.

Mechanisms of oxidative degradation of carbohydrates during oxygen delignification. I. Reaction of methyl β-D-glucopyranoside with photochemically generated hydroxyl radicals.

Abstract Hydroxyl radical is considered to be the major species causing degradation of carbohydrates during oxygen delignification. In this study, reactions involving a carbohydrate model compound and either photochemically generated hydroxyl radical or superoxide from potassium superoxide were carried out to investigate the cleavage of glycosidic linkages. Experiments show that hydroxyl radicals are responsible for the degradation of glycosidic linkages in methyl β-D-glucopyranoside by a substitution reaction displacing D-glucose. Once the glycosidic linkage is broken, reducing carbohydrates undergo a series of reactions forming aldonic acids and lower order aldoses. Control experiments established that no reaction occurs in the absence of UV light under otherwise identical conditions.

Triterpenoid Constituents in the Outer Bark of Betula alleghaniensis (Yellow Birch)

Abstract Yellow birch, Betula alleghaniensis, is a dark-barked birch species that is widely utilized in the northeastern region of the United States for pulp and solid wood products. Currently, the bark is used only as a low value fuel source. In this study, the triterpenoid composition of the outer bark of B. alleghaniensis was investigated in order to evaluate potential for use as a resource for specialty chemicals. Seventeen triterpenoids, including four new compounds, were isolated and identified. Previously known compounds included lupeol, lupenone, betulone, betulin, betulonic acid, lupenyl formate, lup-20(29)-ene-30-ol-3-one, lup-20(29)-ene-3β,30-diol, lup-20(29)-ene-28-ol-30-al, 29-norlupan-3β-ol-20-one, lupan-20-ol-3-one, lupan-3β,20-diol, and lupan-3β-ol-29-oic acid. The four new compounds isolated from yellow birch were lup-20(29)-ene-28-ol-3-one-30-al, 29-norlupan-3,20-dione, 29-norlupan-28-ol-3,20-dione, and lupan-20,28-diol-3-one.

MECHANISMS OF OXIDATIVE DEGRADATION OF CARBOHYDRATES DURING OXYGEN DELIGNIFICATION. II. REACTION OF PHOTOCHEMICALLY GENERATED HYDROXYL RADICALS WITH METHYL β-CELLOBIOSIDE

Reactions involving methyl β-cellobioside and several oxygen species were used to investigate cleavage of glycosidic linkages in cellulose by reaction with photochemical hydroxyl radicals. The intent is not to reproduce delignification conditions, but rather to study the specific behavior of carbohydrate models toward hydroxyl radical. Experiments show that hydroxyl radicals are responsible for the degradation of glycosidic linkages in methyl β-cellobioside by substitution reactions displacing cellobiose, D-glucose, methyl β-D-glucoside, and methanol. Once the glycosidic linkages are broken, the reducing carbohydrates undergo a series of reactions forming aldonic acids and lower order aldoses in the same manner as described previously.[1]

Triterpenes from the Outer Bark of Betula nigra

Abstract Twelve pentacyclic triterpenes were isolated from the outer bark of river birch, Betula nigra. 3β-Acetoxyolean-11-oxo-12-ene-28-oic acid was isolated for the first time from a Betula species. 3β-Caffeatoxyolean-12-ene-28-oic acid has been spectrally characterized for the first time. 3β-Acetoxyolean-12-ene-28-oic acid and 3β-acetoxyolean-11-oxo-12-ene-28-oic acid have been demonstrated to be active as antifeedants for the Colorado potato beetle, Leptinotarsa decemlineata.

Limonoids from Turraea floribunda

Abstract Extracts of the root bark of Turraea floribunda have yielded four new limonoids of the havanensin class: 28-nor-4α-carbomethoxy-11β-acetoxy-12α-(2-methylbutanoyloxy)-14,15-deoxyhavanensin-1,7-diacetate; 28-nor-4α-carbomethoxy-11β-hydroxy-12α-(2-methylbutanoyloxy)-14,15-deoxyhavanensin-1,7-diacetate; 18-nor-4α-carbomethoxy-11β-acetoxy-12α-(2-methylbutanoyloxy)-14,15-deoxyhavanensin-1-acetate; and 28-nor-4α-carbomethoxy-7-deoxy-7-oxo-11β-acetoxy-12α-(2-methylbutanoyloxy)-14,15-deoxyhavanensin-1-acetate. The structures were determined by spectroscopic methods. The structure for the first of these compounds was also confirmed by X-ray diffraction methods.

Modification of High-Yield Pulps with Polyethylene Glycols. I. Model Compound and Isolated Lignin Studies

Phenolic hydroxyl groups in three lignin model compounds, guaiacol, acetoguaiacone, and dehydrodiisoeugenol, and in organosolv lignin were blocked by etherification with polyethylene glycol (PEG). Polyethylene glycol modification, even at a low degree of substitution, greatly enhanced the hydrophilicity of the substrate, producing water-soluble substances. When etherified by reaction with PEG-mesylate, the lignin dimer model compound, dehydrodiisoeugenol, was stabilized considerably against light-induced yellowing.

The bleaching and photostabilization of high-yield pulp by sulfur compounds. II. Reaction of glycol mercaptoesters with model quinones

Abstract The reaction of ethylene glycol dimercaptoacetate and pentaerythritol tetramercaptoacetate with p-benzoquinone have been investigated, both in solution and in the presence of cellulose fibers. In either system, Michael addition is the predominant reaction, leading to decolorization of the quinone by converting it to a substituted hydroquinone. This reaction accounts for the initial bleaching of high-yield pulp produced by these compounds. Handsheets impregnated with these compounds have been irradiated for extended periods of time, and are found ultimately to become more discolored than untreated handsheets. The darkening may be the result of photoinitiated redox chemistry between the Michael adducts and quinones produced in the photodegradation of lignin.

The Bleaching and Photostabilization of High-Yield Pulp by Sulfur Compounds. I. Reaction of Thioglycerol with Model Quinones

The reaction of thioglycerol with quinones selected to model the chromophores present in high-yield pulp has been investigated. The reaction is rapid and complex, involving initial Michael addition, aromatization of the adducts to hydroquinones, and reoxidation of those hydroquinones to new chromophores. The Michael addition is responsible for the bleaching effect of thioglycerol upon pulp, and the reoxidation is responsible for the eventual development of more intense color by treated pulp. Semi-empirical and ab initio molecular orbital calculations have been used as an aid to rationalizing the experimental results.