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Tannic acid and vitamin B12 absorption
Natural products
585
patients reacting to garlic gave a positive reaction to tulip extract, while one who had previously shown contact dermatitis attributed to tulip failed to react when tested with garlic extracts. Gas chromatography showed that tuliposide-A (the glucose ester of ~t-methylene-),butyrolactone), the allergenic component of tulip bulbs, was absent from extracts of garlic and onion, so that the possibility of cross-reactivity due to this factor was excluded. Garlic extracts contained tuliposide-B (the glucose ester of :t-methylene-/3-hydroxy-?-butyrolactone), a compound which readily reacts with thiol groups (e.g. in cysteine), but since incubation of garlic with cysteine did not reduce skin reactivity, this compound was unlikely to be involved in epicutaneous reactions to garlic. The active compound in garlic allergy was concluded to be a low-molecular-weight, hydrophilic, heat- and acid-labile substance, which could be expected to be inactivated during normal cooking processes. Many persons who reacted to garlic reacted positively to some or all of the common allergens, coal tar, wood tar, Peruvian balsam, wool alcohols and colophony, and the presence of some cross-reacting substance common to these materials cannot bc ruled out.
2734. Gossypol locks up the iron Herman, D. L. & Smith, F. H. (1973). Effect of bound gossypol on the absorption of iron by rats. J. Nutr. 103, 882. It has becn reported that diets containing 10% cottonseed protein containing bound gossypol at levels up to 0681~/ohad little effect on the growth of weanling rats, but higher concentrations of bound gossypol impaired weight gain, probably by reducing the availability of essential amino acids (Cited in F.C.T. 1973, I 1,695). The toxic effects of gossypol have been reduced or eliminated by the addition of divalent iron to the diet of nonruminant animals, and the finding that iron would form a complex with gossypol in vitro prompted an investigation into the importance of this reaction in the gastro-intestinal tract. In rats fed 0.005 (control), 0.12, 0-24 or 0"35~o bound gossypol in the diet, the absorption of divalent iron. added to the feed at levels of 400 and 1600 ppm, decreased linearly with increasing gossypol concentration. When dietary iron (as ferrous sulphate) was increased, the absolute quantity of iron absorbed increased, although there was a reduction in absorption expressed as a proportion of the total ingested. The levels of free and bound gossypol in the animals' livers rose as the feed content was increased, but diminished with any increase in iron intake. It is suggested that if a gossypol-iron complex is formed in the liver rather than in the gut, biliary excretion of this complex and its consequent loss in the faeces could explain the apparent reduction in iron absorption in gossypol-fed rats. This study indicates, however, that bound gossypol in thc diet complexes with iron in the intestinal tract with a consequent reduction in the absorption of both components.
2735. Tannic acid and vitamin Bt2 absorption Carrera, G., Mitjavila, S. et Derache, R. (1973). Influence de l'acide tannique sur la disponibilit6 digestive de la vitamine B12 chez le rat. Ann. Nutr. Alim. 27, 73. I(T
124
J
586
Natural products
Previous studies by these authors (Cited hi F.C.T. 1973, 1 I, 1156) have shown that tannic acid (TA) depresses the absorption of dietary nitrogenous material, such as methionine, and of vitamin B~2. This paper describes a study of the bioavailability of vitamin B~2 after its interaction with glycoprotein-TA complexes in the gastro-intestinal tract. The excretion of an intragastric dose of 0"5 pg of radiolabelled B12 (specific activity, 0.25/~Ci) was investigated in groups of four Sprague Dawlcy rats dosed 2 hr previously by gavage with either normal saline or 250 or 500 mg TA/kg body weight. Faeces werc collected every 24 hr for 3 days and on day 3 the animals were killed and the gut contents of each was added to the faeces collection for that day. The results of this work are expressed in terms of the 'digestive utilization coefficient' of vitamin Bl2, which was utilized more effectively by the saline-treated controls than by the TA-treated groups, although no significant difference was found between the two TA levels of treatment. Verzar's in situ technique was used to examine the effect of TA-glycoprotein complexes on vitamin B t2 absorption, 30 anaesthetized rats being catheterized near the pylorus and the ileocaecal junction, with ligation of this section of the gut. Either 6 ml Ringer-Locke solution or 2 ml TA (125 mg/ml) plus 4 ml gastric juice, or the latter mixture centrifuged to remove the TA-glycoprotein complex was introduced into the ligatcd part of the gut. Labelled vitamin B~2 was added to all three solutions, before their introduction. After perfusion for 1"5 hr the rats were killed for removal of the ligated gut, the contents and washings were centrifuged and the complexed B~2 was measured by scintillation counter. The highest level of B12 complcx was found in the group given TA and gastric juice, withot, t centrifugation. Initial remowll of the TA glycoprotcin complex by centrifugation of the other TA mixture reduced the formation of a B~2 complex by half and accordingly increased B~2 availability. It is also possible for TA to complex with vitamin B~2 directly under certain conditions of pH and concentration (Carrera et al. Tray. Soc. Pharm. Montpellier, in press). TA- B12 dissociates above pH 5, the initial pH of the gut section used, and as the pH rises to 7 (the pH of the distal section) a complex containing increasing quantities of mucin is produced to give a stable TA-B~2-glycoprotein complex, which reduces the bioavailability of vitamin B~2.
2736. New mycotoxins characterized Eppley, R. M. & Bailey, W. J. (1973). 12,13-Epoxy-A'~-trichothecenes as the probable mycotoxins responsible for stachybotryotoxicosis. Science, N.Y. 181,758. Although first associated with horses, stachybotryotoxicosis has since been shown to affect a wide variety of domestic and farm animals. This mycotoxicosis results from the ingestion of feed contaminated with certain strains of Stachybotry.s atra (also known as S. alternans) and occurs in two fairly distinct forms. The acute or 'shock' form is characterized principally by nervous disorders, which may terminate in death, while the other 'typical' form develops through three stages, of which the main signs are stomatitis and necrosis of oral fissures, thrombocytopaenia and an increase in clotting time, and finally an increase in thrombocytopaenia and leucopaenia, total failure of the clotting mechanism, an increase in body temperature and development of further areas of necrosis, frequently accompanied by bacterial infection. In these cases, death usually ensues within 1-6 days.
585
patients reacting to garlic gave a positive reaction to tulip extract, while one who had previously shown contact dermatitis attributed to tulip failed to react when tested with garlic extracts. Gas chromatography showed that tuliposide-A (the glucose ester of ~t-methylene-),butyrolactone), the allergenic component of tulip bulbs, was absent from extracts of garlic and onion, so that the possibility of cross-reactivity due to this factor was excluded. Garlic extracts contained tuliposide-B (the glucose ester of :t-methylene-/3-hydroxy-?-butyrolactone), a compound which readily reacts with thiol groups (e.g. in cysteine), but since incubation of garlic with cysteine did not reduce skin reactivity, this compound was unlikely to be involved in epicutaneous reactions to garlic. The active compound in garlic allergy was concluded to be a low-molecular-weight, hydrophilic, heat- and acid-labile substance, which could be expected to be inactivated during normal cooking processes. Many persons who reacted to garlic reacted positively to some or all of the common allergens, coal tar, wood tar, Peruvian balsam, wool alcohols and colophony, and the presence of some cross-reacting substance common to these materials cannot bc ruled out.
2734. Gossypol locks up the iron Herman, D. L. & Smith, F. H. (1973). Effect of bound gossypol on the absorption of iron by rats. J. Nutr. 103, 882. It has becn reported that diets containing 10% cottonseed protein containing bound gossypol at levels up to 0681~/ohad little effect on the growth of weanling rats, but higher concentrations of bound gossypol impaired weight gain, probably by reducing the availability of essential amino acids (Cited in F.C.T. 1973, I 1,695). The toxic effects of gossypol have been reduced or eliminated by the addition of divalent iron to the diet of nonruminant animals, and the finding that iron would form a complex with gossypol in vitro prompted an investigation into the importance of this reaction in the gastro-intestinal tract. In rats fed 0.005 (control), 0.12, 0-24 or 0"35~o bound gossypol in the diet, the absorption of divalent iron. added to the feed at levels of 400 and 1600 ppm, decreased linearly with increasing gossypol concentration. When dietary iron (as ferrous sulphate) was increased, the absolute quantity of iron absorbed increased, although there was a reduction in absorption expressed as a proportion of the total ingested. The levels of free and bound gossypol in the animals' livers rose as the feed content was increased, but diminished with any increase in iron intake. It is suggested that if a gossypol-iron complex is formed in the liver rather than in the gut, biliary excretion of this complex and its consequent loss in the faeces could explain the apparent reduction in iron absorption in gossypol-fed rats. This study indicates, however, that bound gossypol in thc diet complexes with iron in the intestinal tract with a consequent reduction in the absorption of both components.
2735. Tannic acid and vitamin Bt2 absorption Carrera, G., Mitjavila, S. et Derache, R. (1973). Influence de l'acide tannique sur la disponibilit6 digestive de la vitamine B12 chez le rat. Ann. Nutr. Alim. 27, 73. I(T
124
J
586
Natural products
Previous studies by these authors (Cited hi F.C.T. 1973, 1 I, 1156) have shown that tannic acid (TA) depresses the absorption of dietary nitrogenous material, such as methionine, and of vitamin B~2. This paper describes a study of the bioavailability of vitamin B~2 after its interaction with glycoprotein-TA complexes in the gastro-intestinal tract. The excretion of an intragastric dose of 0"5 pg of radiolabelled B12 (specific activity, 0.25/~Ci) was investigated in groups of four Sprague Dawlcy rats dosed 2 hr previously by gavage with either normal saline or 250 or 500 mg TA/kg body weight. Faeces werc collected every 24 hr for 3 days and on day 3 the animals were killed and the gut contents of each was added to the faeces collection for that day. The results of this work are expressed in terms of the 'digestive utilization coefficient' of vitamin Bl2, which was utilized more effectively by the saline-treated controls than by the TA-treated groups, although no significant difference was found between the two TA levels of treatment. Verzar's in situ technique was used to examine the effect of TA-glycoprotein complexes on vitamin B t2 absorption, 30 anaesthetized rats being catheterized near the pylorus and the ileocaecal junction, with ligation of this section of the gut. Either 6 ml Ringer-Locke solution or 2 ml TA (125 mg/ml) plus 4 ml gastric juice, or the latter mixture centrifuged to remove the TA-glycoprotein complex was introduced into the ligatcd part of the gut. Labelled vitamin B~2 was added to all three solutions, before their introduction. After perfusion for 1"5 hr the rats were killed for removal of the ligated gut, the contents and washings were centrifuged and the complexed B~2 was measured by scintillation counter. The highest level of B12 complcx was found in the group given TA and gastric juice, withot, t centrifugation. Initial remowll of the TA glycoprotcin complex by centrifugation of the other TA mixture reduced the formation of a B~2 complex by half and accordingly increased B~2 availability. It is also possible for TA to complex with vitamin B~2 directly under certain conditions of pH and concentration (Carrera et al. Tray. Soc. Pharm. Montpellier, in press). TA- B12 dissociates above pH 5, the initial pH of the gut section used, and as the pH rises to 7 (the pH of the distal section) a complex containing increasing quantities of mucin is produced to give a stable TA-B~2-glycoprotein complex, which reduces the bioavailability of vitamin B~2.
2736. New mycotoxins characterized Eppley, R. M. & Bailey, W. J. (1973). 12,13-Epoxy-A'~-trichothecenes as the probable mycotoxins responsible for stachybotryotoxicosis. Science, N.Y. 181,758. Although first associated with horses, stachybotryotoxicosis has since been shown to affect a wide variety of domestic and farm animals. This mycotoxicosis results from the ingestion of feed contaminated with certain strains of Stachybotry.s atra (also known as S. alternans) and occurs in two fairly distinct forms. The acute or 'shock' form is characterized principally by nervous disorders, which may terminate in death, while the other 'typical' form develops through three stages, of which the main signs are stomatitis and necrosis of oral fissures, thrombocytopaenia and an increase in clotting time, and finally an increase in thrombocytopaenia and leucopaenia, total failure of the clotting mechanism, an increase in body temperature and development of further areas of necrosis, frequently accompanied by bacterial infection. In these cases, death usually ensues within 1-6 days.