- Email: [email protected]
1205. Sour sweetness
NATURAL PRODUCTS
125
Large single doses exercised a depressant effect. The oral LDs0s of the chlorides varied from 6200 to 7650 mg/kg, and death was due to respiratory paralysis and cardiovascular collapse. When applied to the rabbit eye, all the chlorides caused transient conjunctivitis and ulceration. They had no effect upon unbroken skin, but caused necrosis and extensive scar formation when the skin was abraded. Intradermal injections of the chlorides into guineapigs brought about nodule formation with giant cells and crystalline deposits which were probably combinations of the metals with protein. Local irritation is probably the greatest problem to be encountered in the industrial handling of compounds formed from these elements.
NATURAL PRODUCTS 1203. A goitrogen in cassava Ekpechi, O. L., Dimitriadou, A. & Fraser, R. (1966). Goitrogenic activity of cassava (a staple Nigerian food). Nature, Lond. 210, 1137. When a population whose diet is deficient in iodine adopts a staple diet which intensifies the hormonal effects of the deficiency, there is trouble in store. It has already arrived among the Lebanese, in whose favourite onions n-propyl disulphide has been assigned the villain's role (see next abstract). Visible goitre in towns of Eastern Nigeria varies in incidence from 1.4 to 41 ~o, and not unexpectedly the staple diet of cassava has come under suspicion. Thyroid function measurements in rats have now revealed that dry, unfermented cassava is rapidly goitrogenic, depleting the iodine stores of the thyroid gland more rapidly than does an iodine deficiency alone. Depletion is not arrested by iodine supplements given with cassava; nor is the impaired transfer of iodine from mono- to diiodotyro~ine in the gland corrected. These findings suggest that cassava contains a weak goitrogen, so far of unestablished nature, which is capable of acting in the same manner as the thioamide group in known antithyroid drugs. 1204. Steady with those onions Saghir, A. R., Cowan, J. W. & Salji, J. P. (1966). Goitrogenic activity of onion volatiles. Nature, Lond. 211, 87. Every day more and more articles of diet are being incriminated as inhibitors of thyroid function and, in the long run, goitrogenic. The observation that goitre is common among Lebanese communities where iodine consumption is inadequate and onion consumption excessive has focused attention upon the major volatile constituent of edible Allium species, n-propyl disulphide (I). Preliminary experiments revealed that 5-10/A doses of I slightly inhibited thyroid function in rats. Following this work, iodine-deficient rats received corn oil, the known goitrogen propylthiouracil (II) or I, followed 1 hr later by sodium iodide labelled with iodine-131. After 3 ha"it was found that at all levels of dosage (60 to 240/A) I inhibited thyroid function and depressed the radioiodine uptake in the same way as did II. It is therefore evident that a high consumption of onions rich in I may intensify the incidence and degree of goitre in regions where the regular intake of iodine is low. 1205. Sour sweetness Cs~iky, T. Z. (1965). Relation between the chemical structure and cariogenic activity of common sugars. Ann. N. Y. Acad. Sci. 131, 868. Simple sugars are fermented by the bacteria of the mouth and the resultant lowering of pH suffices to soften tooth enamel which in turn may lead to the development of dental caries. In a search for non-cariogenic dietary substitutes for fermentable sugars, 3-methyl-
126
NATURAL PRODUCTS
glucose (I) and 3-methylfructose (II) have been synthesized. Neither I nor II when incubated with normal oral washings, lactobacilli or Streptococcusfaecalis produced acid, and neither affected the hardness of tooth enamel in vitro. I and II were therefore concluded to be noncariogenic. Unlike other sugar-like compounds, I was rapidly absorbed from the gut and therefore did not induce diarrhoea. Although this sugar is not metabolized in the animal or human body, 5-19.6 g of I induced in man mild toxic symptoms which took the form of pressure in the head, facial flushing, headache and nausea during the 5 hr following ingestion. Three subjects vomited. The sole objective sign was tremor of the outstretched hands, which was proportional to the dose. Although all these effects were mild and transient, they were considered to be indicative of central nervous system (CNS) toxicity, probably as a result of interference with sugar transport within the CNS. Convulsive effects in mice, sometimes fatal, have been described by other workers. I is recommended to be used only as a diagnostic tool for the clinical study of intestinal absorption and malabsorption but not as a food sweetener. 1206. In vino veritas Rib~reau-Gayon, P. & Sapis, J.-C. (1965). Sur la presence dans le vin de tyrosol, de tryptophol, d'alcool ph~nyl~thylique et de ~,-butyrolactone, produits secondaires de la fermentation alcoolique. C.r. hebd. S~anc. Acad. Sci., Paris 261, 1915. Wines contain a fine array of constituents, including histamine (Cited in F.C.T. 1964, 2, 512 & 761; Marquadt, Fd Cosmet. Toxicol. 1965, 3, 803). Here we shed more light on vintage mysteries. Paper chromatographic studies of a previously unidentified phenolic compound present in wine but not in grape skins have now shown that this is tyrosol (p-hydroxyphenylethanol), which is formed from tyrosine during fermentation. Red wines contain 20-45 ppm and white wines 15-25 ppm of tyrosol. It is also evident that tryptophan might yield tryptophol (indolethanol) by fermentation. An ether extract of wine subjected to chromatography showed small quantities of tryptophol and other unidentified compounds. Red wines sometimes contain up to 0.8 ppm, which tends to disappear during maturing. White wines rarely contain any tryptophol. Up to 5 ppm of'¢-butyrolactone and 10-75 ppm of phenylethanol occur in both types of wine. For the characteristic bouquet we have to thank phenylethanol and tyrosol in the main. 1207. Coffee composition: Everything but the kitchen sink Gianturco, M. A., Giammarino, A. S. & Friedel, P. (1966). Volatile constituents of coffee-V. Nature, Lond. 210, 1358. These authors give a list of 54 volatile compounds newly isolated and characterized from roasted coffee, in addition to 31 others previously described by them. The compounds were isolated by vapour phase chromatography and identified by comparison with authentic samples by their retention times on columns and by their infrared and occasionally mass spectra. The chemical range is impressive and includes aliphatic alcohols, aldehydes, ketones and acids (e.g. ethanol, formaldehyde, acetone, formic acid), acetoin, thiophene, crotonolactone, isoprene, toluene, phenol, and derivatives of furan, furfural, pyrrole, pyridine, guaiacol etc. The aroma of coffee is a many-splendoured thing.
1208. Urinary ethylam|ne: It's that cup of char Asatoor, A. M. (1966). Tea as a source of urinary ethylamine. Nature, Lond. 210, 1358. We have seen that rabbits given tea lack certain phenolic acids derived or possibly derived from 3,4-dihydroxyphenylalanine (dopa) which occur in the urine of control
125
Large single doses exercised a depressant effect. The oral LDs0s of the chlorides varied from 6200 to 7650 mg/kg, and death was due to respiratory paralysis and cardiovascular collapse. When applied to the rabbit eye, all the chlorides caused transient conjunctivitis and ulceration. They had no effect upon unbroken skin, but caused necrosis and extensive scar formation when the skin was abraded. Intradermal injections of the chlorides into guineapigs brought about nodule formation with giant cells and crystalline deposits which were probably combinations of the metals with protein. Local irritation is probably the greatest problem to be encountered in the industrial handling of compounds formed from these elements.
NATURAL PRODUCTS 1203. A goitrogen in cassava Ekpechi, O. L., Dimitriadou, A. & Fraser, R. (1966). Goitrogenic activity of cassava (a staple Nigerian food). Nature, Lond. 210, 1137. When a population whose diet is deficient in iodine adopts a staple diet which intensifies the hormonal effects of the deficiency, there is trouble in store. It has already arrived among the Lebanese, in whose favourite onions n-propyl disulphide has been assigned the villain's role (see next abstract). Visible goitre in towns of Eastern Nigeria varies in incidence from 1.4 to 41 ~o, and not unexpectedly the staple diet of cassava has come under suspicion. Thyroid function measurements in rats have now revealed that dry, unfermented cassava is rapidly goitrogenic, depleting the iodine stores of the thyroid gland more rapidly than does an iodine deficiency alone. Depletion is not arrested by iodine supplements given with cassava; nor is the impaired transfer of iodine from mono- to diiodotyro~ine in the gland corrected. These findings suggest that cassava contains a weak goitrogen, so far of unestablished nature, which is capable of acting in the same manner as the thioamide group in known antithyroid drugs. 1204. Steady with those onions Saghir, A. R., Cowan, J. W. & Salji, J. P. (1966). Goitrogenic activity of onion volatiles. Nature, Lond. 211, 87. Every day more and more articles of diet are being incriminated as inhibitors of thyroid function and, in the long run, goitrogenic. The observation that goitre is common among Lebanese communities where iodine consumption is inadequate and onion consumption excessive has focused attention upon the major volatile constituent of edible Allium species, n-propyl disulphide (I). Preliminary experiments revealed that 5-10/A doses of I slightly inhibited thyroid function in rats. Following this work, iodine-deficient rats received corn oil, the known goitrogen propylthiouracil (II) or I, followed 1 hr later by sodium iodide labelled with iodine-131. After 3 ha"it was found that at all levels of dosage (60 to 240/A) I inhibited thyroid function and depressed the radioiodine uptake in the same way as did II. It is therefore evident that a high consumption of onions rich in I may intensify the incidence and degree of goitre in regions where the regular intake of iodine is low. 1205. Sour sweetness Cs~iky, T. Z. (1965). Relation between the chemical structure and cariogenic activity of common sugars. Ann. N. Y. Acad. Sci. 131, 868. Simple sugars are fermented by the bacteria of the mouth and the resultant lowering of pH suffices to soften tooth enamel which in turn may lead to the development of dental caries. In a search for non-cariogenic dietary substitutes for fermentable sugars, 3-methyl-
126
NATURAL PRODUCTS
glucose (I) and 3-methylfructose (II) have been synthesized. Neither I nor II when incubated with normal oral washings, lactobacilli or Streptococcusfaecalis produced acid, and neither affected the hardness of tooth enamel in vitro. I and II were therefore concluded to be noncariogenic. Unlike other sugar-like compounds, I was rapidly absorbed from the gut and therefore did not induce diarrhoea. Although this sugar is not metabolized in the animal or human body, 5-19.6 g of I induced in man mild toxic symptoms which took the form of pressure in the head, facial flushing, headache and nausea during the 5 hr following ingestion. Three subjects vomited. The sole objective sign was tremor of the outstretched hands, which was proportional to the dose. Although all these effects were mild and transient, they were considered to be indicative of central nervous system (CNS) toxicity, probably as a result of interference with sugar transport within the CNS. Convulsive effects in mice, sometimes fatal, have been described by other workers. I is recommended to be used only as a diagnostic tool for the clinical study of intestinal absorption and malabsorption but not as a food sweetener. 1206. In vino veritas Rib~reau-Gayon, P. & Sapis, J.-C. (1965). Sur la presence dans le vin de tyrosol, de tryptophol, d'alcool ph~nyl~thylique et de ~,-butyrolactone, produits secondaires de la fermentation alcoolique. C.r. hebd. S~anc. Acad. Sci., Paris 261, 1915. Wines contain a fine array of constituents, including histamine (Cited in F.C.T. 1964, 2, 512 & 761; Marquadt, Fd Cosmet. Toxicol. 1965, 3, 803). Here we shed more light on vintage mysteries. Paper chromatographic studies of a previously unidentified phenolic compound present in wine but not in grape skins have now shown that this is tyrosol (p-hydroxyphenylethanol), which is formed from tyrosine during fermentation. Red wines contain 20-45 ppm and white wines 15-25 ppm of tyrosol. It is also evident that tryptophan might yield tryptophol (indolethanol) by fermentation. An ether extract of wine subjected to chromatography showed small quantities of tryptophol and other unidentified compounds. Red wines sometimes contain up to 0.8 ppm, which tends to disappear during maturing. White wines rarely contain any tryptophol. Up to 5 ppm of'¢-butyrolactone and 10-75 ppm of phenylethanol occur in both types of wine. For the characteristic bouquet we have to thank phenylethanol and tyrosol in the main. 1207. Coffee composition: Everything but the kitchen sink Gianturco, M. A., Giammarino, A. S. & Friedel, P. (1966). Volatile constituents of coffee-V. Nature, Lond. 210, 1358. These authors give a list of 54 volatile compounds newly isolated and characterized from roasted coffee, in addition to 31 others previously described by them. The compounds were isolated by vapour phase chromatography and identified by comparison with authentic samples by their retention times on columns and by their infrared and occasionally mass spectra. The chemical range is impressive and includes aliphatic alcohols, aldehydes, ketones and acids (e.g. ethanol, formaldehyde, acetone, formic acid), acetoin, thiophene, crotonolactone, isoprene, toluene, phenol, and derivatives of furan, furfural, pyrrole, pyridine, guaiacol etc. The aroma of coffee is a many-splendoured thing.
1208. Urinary ethylam|ne: It's that cup of char Asatoor, A. M. (1966). Tea as a source of urinary ethylamine. Nature, Lond. 210, 1358. We have seen that rabbits given tea lack certain phenolic acids derived or possibly derived from 3,4-dihydroxyphenylalanine (dopa) which occur in the urine of control