Glucoside

“ Sulphuric acid decomposes it into d-glucose, benzaldehyde and prussic acid; while hydrochloric acid gives mandelic acid, d-glucose and ammonia. The decomposition induced by enzymes may occur in two ways. Maltase partially decomposes it, giving d-glucose and mandelic nitrile glucoside, C6H5CH (CN) O·C6H11O5; this compound is isomeric with sambunigrin, a glucoside found by E. E. Bourquelot and Danjou in the berries of the common elder, Sambucus nigra. Emulsin, on the other hand, decomposes it into benzaldehyde, prussic acid, and two molecules of glucose ”

“ Normally, glucose is oxidized in the body to its final oxidation products, carbon dioxide and water. But when many difficultly oxidizable substances, such as chloral, camphor, turpentine oil, aniline, etc., are introduced into the body, the organism has the power of combining these with glucose to form glucosides. These so-called "paired" compounds are then oxidized to the corresponding glucuronic acid derivatives and eliminated from the body in the urine. No phenomenon similar to this occurs in plants, however, and glucuronic acid has never been found in plant tissues. ”

“ Hence, the [Pg 56] biochemical properties of the glucosides, so far as their hydrolysis by the enzymes which are present in many biological agents is concerned, depends wholly upon the molecular configuration of the glucose itself. Furthermore, neither the mannosides, which differ from glucosides only in the arrangement of the H and OH groups attached to one of the asymmetric carbon atoms in the hexose, nor galactosides in which two such arrangements are different (see configuration formulas on page 57) , are attacked by either maltase or emulsin. ”

“ Much attention has been given to the non-sugar parts of the molecules; the constitutions of many have been determined, and the compounds synthesized; and in some cases the preparation of the synthetic glucoside effected. ”

“ The hexoses so obtained are not necessarily identical: thus cane sugar yields d-glucose and d-fructose (invert sugar) ; milk sugar and melibiose give d-glucose and d-galactose, whilst maltose yields only glucose. Chemically they appear to be ether anhydrides of the hexoses, the union being effected by the aldehyde or alcohol groups, and in consequence they are related to the ethers of glucose and other hexoses, i.e. to the alkyl glucosides. Cane sugar has no reducing power and does not form an hydrazone or osazone ”

“ It is scarcely conceivable that substances which vary so widely in composition as do the different types of glucosides can possibly all have similar physiological uses in plants. The cyanophoric glucosides, the pigment glucosides, the mustard oil glucosides, and the saponins, for example, can hardly be assumed to have the same definite relationships to the metabolism and growth of the plant. ”

“ Many gaseous anæsthetics are known to have a marked effect in stimulating plant growth. In a number of cases, it has been shown that the contact of plant tissues with these anæsthetics brings about an interaction of the enzyme and glucoside which are present in the tissue, with the consequent hydrolysis of the latter, setting free its characteristic components. This observation has led to the supposition that many of the organic constituents of glucosides are definite plant stimulants, to which the name "hormones" has been applied. ”

“ Maltose, isomaltose, gentiobiose, and cellobiose, are all glucose-glucosides, the difference between them being undoubtedly due to linkage being between different alcoholic groups in the glucose molecules.
The disaccharide lactose is a glucose-galactoside. It is the sugar which is present in the milk of all mammals. It has never been found in plants. Melibiose, which is the corresponding vegetable glucose-galactoside, may be obtained by the partial hydrolysis of the trisaccharide raffinose (see below) . It is a reducing sugar; forms a characteristic osazone; and exhibits mutarotation. ”

“ Further, the very general occurrence of these protective glucosides in many of the vegetative parts of plants during the early stages of growth, followed by their disappearance after the seeds of the plant have been formed, certainly serves to protect these plants from consumption as forage by animals before they have been able to develop their reproductive bodies. The lack of palatability, and even the production of digestive disorders resulting from the eating of unripe fruit may be due, in part at least, to the presence of protective glucosides in unripe fruits and vegetables. ”

“ These juices, together with those of the pear, the peach, the plum, and other such fruits, if taken without adding cane sugar, diminish acidity in the stomach rather than provoke it: they become converted chemically into alkaline carbonates, which correct sour fermentation. It is said in Devonshire that apples shrump up if picked when the moon is on the wane. From the bark of the stem and root of the apple, pear and plum trees, a glucoside is to be obtained in small crystals, which possesses the peculiar property of producing artificial diabetes in animals to whom it is given. ”

“ Excessive drinking is said to lead to skin and other diseases, but per contra many medicinal virtues are ascribed to the preparation. There appears to be little doubt that the active principle in this beverage is a poison of an alkaloidal nature. It seems likely that this substance is not present as such (i.e. as a free alkaloid) in the plant, but that it exists in the form of a glucoside, and that by the process of chewing this glucoside is split up by one of the ferments in the saliva into the free alkaloid and sugar. ”

“ The crude glucoside was purified by dissolving it in water, treating the solution with animal charcoal, and evaporating under diminished pressure to a syrup, which set to a hard cake of colourless crystals which were dried on porous earthenware. ”

“ The presence of a glucoside was proved, but the glucoside was not isolated. Objection has been taken to the evidence of the uses of violet leaves having been unfortunately collected chiefly by unskilled persons, and that it has therefore been lacking in definiteness, and consequently in value. After the definite expression of the opinions mentioned in the above reference, it is disappointing to find in a paper read before the Therapeutical Society, October 30th, 1906, and reported in the Lancet, '06, ii. 1318, that all attempts to isolate and identify a glucoside from violet leaves have failed ”

“ THE PIGMENT GLUCOSIDES
Many, if not all, of the red, yellow, violet, and blue pigments of plants either exist as, or are derived from, glucosides. These are of three types: the madder, or alizarin, reds are derivatives of various oxy-anthraquinones; most of the soluble yellow pigments are glucosides derived from flavones or xanthones; and the soluble red, blue, and violet pigments of the cell-sap of plants are mostly anthocyan derivatives. ”

“ It seems much more probable that the physiological uses of glucosides depend upon their ability to form temporarily inactive "pairs" with a great variety of different types of organic compounds which are elaborated by plants for a variety of purposes. ”

“ In fact, it is easily conceivable that at least one of the reasons for the failure of the processes of decay of plant tissues to set in until after the death of the cells, is that during living, respiratory activity these antiseptic glucosides are so generally present in the tissues. ”

“ Glucosides having either a strong bitter taste, or pronouncedly poisonous properties, likewise undoubtedly serve to protect such important organs of plants as the seeds and fruits from being prematurely eaten by birds and animals. ”

“ In fact, it is the form in which carbohydrate material is supplied to the tissues as needed. Normally, much of the sugar is used up by the blood and its cells in metabolism, giving rise to heat and energy. In muscles glycogen is probably digested as lactic acid, as before action muscle is neutral or slightly alkaline and after action acid.
When the liver is deranged and allows the glycogen to pass out into the blood too freely, or when the glycogen is not held as such but turned to sugar and passed out in large quantities, sugar in the urine or diabetes mellitus results. ”

“ The power of storing and using sugar in the tissues is strictly limited, and varies considerably in healthy individuals. Normally, when about 200 grms. of glucose are taken at one time, some of it appears in the urine within one hour. In some individuals the taking of even 100 grms. leads to a transient glycosuria, while others can take 250 grms. or more and use it all. But even in the same healthy individual the power of using sugar varies at different times and in different conditions, muscular exercise markedly increasing the combustion. ”

“ Commercial Glucose.—The glucose of commerce, which may be regarded as a mixture of grape sugar, maltose and dextrins, is prepared by hydrolysing starch by boiling with a dilute mineral acid. In Europe, potato starch is generally employed; in America, corn starch. The acid employed may be hydrochloric, which gives the best results, or sulphuric, which is used in Germany; sulphuric acid is more readily separated from the product than hydrochloric, since the addition of powdered chalk precipitates it as calcium sulphate, which may be removed by a filter press. ”

“ Glucinum, glōō-sī′num, n. a white metal prepared from beryl—its oxide, Glucī′na, white, tasteless, insoluble in water.—adj. Glū′cic, pertaining to sugar.—ns. Glucide′—Saccharin (q.v.) ; Glucohæ′mia, the presence of an excessive quantity of glucose in the blood; Glucōse′, the peculiar kind of sugar in the juice of fruits: the sugar-syrup obtained by the conversion of starch into sugar by sulphuric acid—grape-sugar, &c.; Glu′coside, any of those vegetable products which, on treatment with acids or alkalies, yield a sugar or some closely allied carbohydrate ”

“ Glucose, which is abundant in the juice of plants and fruits, and to a more or less degree in the blood of all animals (usually about 0.1%) occurs free in nature. This sugar is likewise obtained from many carbohydrates, either through the action of acids, or as the result of the digestive enzymes, and as such becomes the principal form in which the animal body utilizes the carbohydrates ingested. Under normal conditions the glucose in the blood is constantly being burned and replaced ”

“ The principal carbohydrates are starch, dextrine, cane-sugar or common table sugar, grape-sugar, the principal sugar in fruits, and milk-sugar, the natural sugar in milk. They are substances made up, as before stated, of carbon, hydrogen, and oxygen, but no nitrogen. They are important food substances, but are of themselves incapable of sustaining life.
The carbohydrates, both starch and sugar, in the process of digestion are converted into glucose. This is stored in the liver in the form of glycogen, which the liver has the power of manufacturing ”

“ The water is then evaporated in vacuum-pans, so as to boil at about 74 degrees and to prevent conversion into grape sugar. By this process much glucose or syrup is formed, which is separated from the crystalline sucrose by rapidly revolving centrifugal machines. Great quantities of sucrose are used for food by all civilized nations. A single refinery in New York purifies 2,000,000 pounds per day.
321. Glucose, or invert sugar, the principal member of the second class, consists of two distinct kinds of sugar, —dextrose and levulose. These differ in certain properties, but have the same symbol. ”

“ It is found naturally in many fruits, and is here called grape sugar. It is the normal sugar of human blood, and in this connection, is usually called dextrose. Glucose is made commercially by boiling starch, most frequently cornstarch, in water, to which sulphuric acid has been added up to one to one and one half per cent. After sufficient boiling, the acid is neutralized with lime, and the sugar separated by chemical methods. If the process is carried out carefully, and reasonably pure reagents are used in the process, the result will be a sirup of fair purity and one of value as a food. ”

“ Many of the impurities which have been imputed to glucose, really belong to the cane-sirups with which they have been mixed. These largely adulterated glucoses should always be looked upon with suspicion. The cane-sirups, which are used for this purpose, yield from three to five per cent. of ash, while the ash from a genuine glucose is so little as to be almost unweighable.
There is no reason to believe that a glucose or grape-sugar properly manufactured is any less wholesome than cane or maple-sugar. ”

“ Glucose, if free from sulphuric acid or other chemicals, is as harmless as any other form of sugar. Most of our candies contain more or less of it, and are in every way as satisfactory as when manufactured wholly from other sugars. ”

“ More exact methods of determining the amount of acidosis are the determination of the ratio between the total urinary nitrogen and the ammonia, the quantitation of the acetone, diacetic acid and oxy-butyric acid excreted, and the carbon dioxide tension of the alveolar air. These are rather complicated for average clinical use, however.
When the patient is sugar-free he is put upon a diet of so-called "5% vegetables," i.e. vegetables containing approximately 5% carbohydrate. It is best to boil these vegetables three times, with changes of water. ”