By extracting the epigeal part of Nitraria sibirica collected in the environs of the settlement of Rybache (KirgSSR), in May 1976, in the budding phase we have obtained 0.25% of total alkaloids. A benzene solution of the ether-soluble nonphenolic fraction of the combined alkaloids was separated according to basicity with citrate-phosphate buffer solutions having pH values from 8 to 4 at intervals of 1 pH unit. By working up the ethereal fraction with pH 8 we isolated a white crystalline optically active base (I) with [α]D -30° (c 1.36; chloroform), mp 102-103°C, which we have called isonitramine. The molecular weight of the alkaloid (169, mass spectrometrically) and elementary analysis gave the composition C10H19ON. The UV spectrum of (I) showed no absorption, and the IR spectrum contained absorption bands of active hydrogen at 3288 and 3305 cm⁻¹. To determine the nature of the active hydrogen, we acetylated (I) with acetic anhydride in the presence of p-toluenesulfonic acid, as a result of which we obtained a O,N-diacetyl derivative of isonitramine (II) in the IR spectrum of which the bands of active hydrogen had disappeared and strong absorption bands of amide and ester carbonyl groups had appeared (1640 and 1735 cm⁻¹, respectively). In the NMR spectrum of (I) (CDCl₃) at 3.87 ppm there is a broadened two-proton singlet apparently due to the protons of the NH and OH groups. Spectral characteristics of isonitramine are close to and the empirical formula is identical with those of the alkaloid nitramine isolated previously from the plant Nitraria schoberi and having the structure of 7-hydroxy-8-methyldecahydroquinoline. Mass-spectrometric fragmentation and condensation experiments confirmed the same substituent positions (C7 and C8) as nitramine. The undoubted difference between these alkaloids is shown by their different states of aggregation and the sign and magnitudes of their optical rotations (for nitramine [α]D + 16.5°), and the opposite Cotton effects of the ketones from isonitramine and nitramine. The isolation and the quaternary structure of triacetinase - an esterase of cotton seeds - have been reported previously. It has been shown that the esterase consists of four identical polypeptide chains with mol. wt. ~ 10,000 and the amino-acid composition of a subunit has been determined (moles per mole): Asp, 13.5; Thr, 7.0; Ser, 9.8; Glu, 15; Pro, 4.2; Gly, 14; Ala, 11.1; Val, 3.2; Met, 3.8; Ileu, 3.0; Leu, 5.2; Phe, 3.8; His, 2.0; Lys, 4.2; Arg, 6.8; Tyr, 1.6; 1/2 Cys, 1.8. It has also been established that the N-terminal amino acid is methionine and the C-terminal amino acid is tyrosine. We now give the results of an investigation of the peptides from the cyanogen bromide hydrolysis of triacetinase.