No abstract

The photoinduced exchange reactions of cytosine (la) and 5‐methylcytosine (IIa) with two primary amines have been studied. The reactions of Ia and IIa with methylamine lead, respectively, to 1‐methylcytosine (Ib) and 1,5‐dimethylcytosine (IIb) as final products; the reactions of the same two starting materials with n‐butylamine gives the corresponding n‐butyl compounds. The reactions of IIa with the two amines also gave small amounts of 1‐methylthymine and 1‐n‐butylthymine. An opened ring intermediate, N‐(N'‐methylcarbamoyl)‐3‐arnino‐2‐methylacrylamidine (IVa), was isolated from the IIa‐methylamine system irradiated at pH 7 and shown to be a precursor of both IIb and 1‐methylthymine. The pH profiles for rate of production of IIb, 1‐methylthymine and IVa in the reaction of IIa with methylamine were determined and found to be similar in shape. All three profiles show a maximum in reactivity at about pH 8.7 with some reactivity being detectable at pH values as low as 5.

The hypoglycaemic activities of Opuntia ficus-indica, 0. lindheimeri and 0. robusta were investigated in streptozotocin-induced diabetic rats using enteral (oral) and parenteral (intraperitoneal and intravenous) routes of administration. When the aqueous extracts of the three Opunfriz species were administred intraveneously, they produced a hypoglycaemic effect. However, when the extracts were administered orally, only 0. lindheimeri produced a hypoglycaemic effect. A dilute aqueous (ammonium sulphate) solution of 0. lindheimeri dialysate also produced a hypoglycaemic effect when administered intravenously. Intraperitoneal administations of all Opuntia species extracts including 0. lindheimeri dialysate failed to produce hypoglycaemic effects. It appears that the concentration andor potency of the active hypoglycaemic principle in Opuntiu cacti is species-specific.

Determination of reactivity ratios for the system acrylic acid / methyl methacrylate in dimethylsulfoxide.