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568. More on coumarin biosynthesis
FLAVOURINGS, SOLVENTS AND SWEETENERS
405
mg/kg. The animals were killed after 20.5 days, when the uteri were examined for resorption sites and the foetuses for malformations. A dose of 50 mg AB/kg produced 30 % resorption of embryos and 90 ~o of abnormal foetuses, whereas at the same dose NB produced only 5.8% resorptions and 1.2% of abnormal foetuses. At the highest level of NB, however, the foetuses were invariably resorbed before them. 567. Whirling around the whorls
Timme, A. H. & Fowle, L. G. (1963). Effects of p-dimethylaminoazobenzene on the fine structure of rat liver cells. Nature, Lond. 200, 694. More arid more evidence accumulates of a primary attack of hepatotoxic agents on the endoplasmic reticulum of liver cells. First the retieulum undergoes hypertrophy, and becomes transformed into a mass of vesicles surrounded by smooth membranes. Then the paired membranes seem to be 'whisked up' into whorls, so that up to ten paired membranes appeared wrapped around a single space but at the periphery of the whorl the membranes are continuous with those lining adjacent vesicles. This electron-microscopic picture has been described after administration of DDT to rats ,(Cited in F.C.T. 1963, 1, 127). It is reported here in the livers of rats given p-dimethyl.aminoazobenzene. The cells studied were situated periportally. The changes described are also seen following the administration of any one of three other hepatocarcinogens--thioacetamide, dimethylnitrosamine and ethionine.
FLAVOURINGS, SOLVENTS AND SWEETENERS 568. More on coumarin biosynthesis
Stoker, J. R. (1964). The biosynthesis of colamarin in Melilotus alba. Biochem. biophys. Res. Commun. 14, 17. Reference has been made to the mechanism of plant biosynthesis of coumarin (I) (Cited .in F.C.T. 1963, 1, 271). Starting from trans-cinnamic acid Stoker & Bellis (J. biol. Chem. 1962, 237, 2303) and Kosuge & C o n n (ibid 1961, 236, 1617) followed the synthesis of I in the plant Melilotus alba through the intermediary stages involving o-coumaric acid (II) and its cis-isomer o-coumarinic acid (III). The present authors have shown that a heat-lalile extract of M. alba catalyses the isomerization of II to III while the biosynthesis of trans.cinnamic acid to I was not dependent oil light. Both observations point to the presence of an isomerase enzyme system. The course of these events is represented as follows: COOH COOH
/
Irons-
Isomerase enzyme
/
Cinnamic acid
[/~C ~"-OH
H--------"C~ COOH
n-Coumartnic acid (lID
o- Coumaric acid. {II)
~
0 Coumarin (I)
405
mg/kg. The animals were killed after 20.5 days, when the uteri were examined for resorption sites and the foetuses for malformations. A dose of 50 mg AB/kg produced 30 % resorption of embryos and 90 ~o of abnormal foetuses, whereas at the same dose NB produced only 5.8% resorptions and 1.2% of abnormal foetuses. At the highest level of NB, however, the foetuses were invariably resorbed before them. 567. Whirling around the whorls
Timme, A. H. & Fowle, L. G. (1963). Effects of p-dimethylaminoazobenzene on the fine structure of rat liver cells. Nature, Lond. 200, 694. More arid more evidence accumulates of a primary attack of hepatotoxic agents on the endoplasmic reticulum of liver cells. First the retieulum undergoes hypertrophy, and becomes transformed into a mass of vesicles surrounded by smooth membranes. Then the paired membranes seem to be 'whisked up' into whorls, so that up to ten paired membranes appeared wrapped around a single space but at the periphery of the whorl the membranes are continuous with those lining adjacent vesicles. This electron-microscopic picture has been described after administration of DDT to rats ,(Cited in F.C.T. 1963, 1, 127). It is reported here in the livers of rats given p-dimethyl.aminoazobenzene. The cells studied were situated periportally. The changes described are also seen following the administration of any one of three other hepatocarcinogens--thioacetamide, dimethylnitrosamine and ethionine.
FLAVOURINGS, SOLVENTS AND SWEETENERS 568. More on coumarin biosynthesis
Stoker, J. R. (1964). The biosynthesis of colamarin in Melilotus alba. Biochem. biophys. Res. Commun. 14, 17. Reference has been made to the mechanism of plant biosynthesis of coumarin (I) (Cited .in F.C.T. 1963, 1, 271). Starting from trans-cinnamic acid Stoker & Bellis (J. biol. Chem. 1962, 237, 2303) and Kosuge & C o n n (ibid 1961, 236, 1617) followed the synthesis of I in the plant Melilotus alba through the intermediary stages involving o-coumaric acid (II) and its cis-isomer o-coumarinic acid (III). The present authors have shown that a heat-lalile extract of M. alba catalyses the isomerization of II to III while the biosynthesis of trans.cinnamic acid to I was not dependent oil light. Both observations point to the presence of an isomerase enzyme system. The course of these events is represented as follows: COOH COOH
/
Irons-
Isomerase enzyme
/
Cinnamic acid
[/~C ~"-OH
H--------"C~ COOH
n-Coumartnic acid (lID
o- Coumaric acid. {II)
~
0 Coumarin (I)