CONTENTS & ABSTRACTS

In English. Summaries in Estonian

Proceedings of the Estonian Academy of Sciences.

Chemistry

Volume 52 No. 4 December 2003

Composition of the essential oil of dill, celery, and parsley from Estonia; 147–154

Anne Orav, Tiiu Kailas, and Anna Jegorova

Abstract. The qualitative and quantitative composition of the essential oil of dill, celery, and parsley growing in Estonia was studied using the simultaneous distillation/extraction micro-method for oil isolation and capillary gas chromatography for analysing the extracts. The yields of the oils from dried aromatic plants after two hours distillation were 2.9–4.3 mg/g. Forty-eight compounds were identified representing over 96% of the total oil. α-Phellandrene (75.1–75.8%), β-phellandrene (7.4–7.9%), dill ether (2.2–3.9%), and limonene (2.8–2.9%) were the principal components of dill oil. p-1,3,8-Menthatriene (40.0–44.6%), β-phellandrene (15.1–16.9%), myristicin (13.0–13.1%), and myrcene (6.5–7.0%) were characteristic constituents in oil from parsley leaves, but apiole (34.5%), myristicin (28.8%), and terpinolene (13.2%) predominated in parsley root oil. Celery oil contained in high quantities limonene (62.4–70.3%), (Z)-β-ocimene (10.1–10.5%), and phthalide isomers (total 13.4–16.6%). Drying of aromatic plants for four weeks at room temperature did not significantly change the chemical composition of their essential oil.

Key words: Anethum graveolens, Petroselinum crispum, Apium graveolens, Apiaceae, essential oil composition, effect of drying.

Purification of resveratrol from vine stems; 155–164

Aavo Aaviksaar, Mati Haga, Tõnu Püssa, Mati Roasto, and George Tsoupras

Abstract. A modified method for preparative purification of trans-resveratrol (trans-3,4¢,5-trihydroxystilbene) from vine stems is presented. It includes two new procedures added to the known scheme of resveratrol separation from ligneous organs of vine by ethanol–water extraction: (1) treatment of ethanolic solution of vine stem stilbenoid extract with diethyl ether for precipitation of a dark brown matter from the extract; (2) preparative column chromatography on polyamide carrier for separation of resveratrol from the crude ethanolic extract. As a result, 93.8% resveratrol concentrate with 0.7% of its dimer viniferin impurity was obtained. Resveratrol and viniferin contents in the stems of various frost-hardy hybride cultivars of Vitis vinifera grown open air in Estonia (‘Hasaine Sladki’, ‘Jubilei Novgoroda’, Vitis vinifera cv., ‘ES 12-7-98’, ‘Marechal Joffre’, ‘Zilga’) were determined for the plant material collected in July and in October. Lignified stems collected in October turned out to be an excellent source for producing vine stem stilbenoid (resveratrol and viniferin) concentrates for use as healthy ingredients in functional food for preventing heart diseases and atherosclerosis.

Key words: resveratrol, stilbenoids, viniferin, vine stems, Vitis vinifera.

Steady-state kinetic analysis of protein kinase A interaction with peptide and ATP; 165–177

Aleksei Kuznetsov, Nikita Oskolkov, Mats Hansen, and Jaak Järv

Abstract. Kinetics of Kemptide (LRRASLG) phosphorylation by protein kinase A (E.C.2.7.1.37) was studied in a wide ATP and peptide concentration interval and a simple procedure was proposed to characterize the interaction of these two substrates with the enzyme active centre. The kinetic analysis was made under steady-state conditions and was based on the assumption of the random-order mechanism of binding of the two substrates. Inhibition of the reaction by excess of ATP was observed and considered in data processing. A procedure was designed for analysis of the interaction mechanism of protein kinase reversible inhibitors with the enzyme proceeding from the steady-state kinetic data.

Key words: protein kinase A, peptide phosphorylation, kinetic mechanism, bi-substrate reaction.

Kinetic model for protein kinase simultaneous interaction with peptide, ATP, and bi-functional inhibitor; 178–187

Aleksei Kuznetsov, Heli Väärtnõu-Järv, and Jaak Järv

Abstract. A kinetic model for protein kinase inhibition by bi-functional inhibitors, resembling the bi-substrate–enzyme complex and interacting with both ATP and peptide binding sites in the enzyme active centre, was analysed. The model provides a possibility for analysis of the enzyme–ligand interactions on the basis of the second-order rate constants, calculated from the steady-state kinetic data of the protein kinase catalysed phosphorylation reaction. The experimental data should be obtained at a wide range of peptide, ATP, and the bi-functional inhibitor concentration. The kinetic equations allow characterization of the enzyme–substrate–inhibitor ternary complexes as well as the enzyme–inhibitor binary complex by the appropriate kinetic parameters. A data processing algorithm is proposed for their calculation. The results can be useful for understanding the inhibition mechanism, including the possibilities of simultaneous interaction of substrates and inhibitor in the active centre. This information is important for designing new inhibitors.

Key words: protein kinase A, peptide phosphorylation, bi-functional inhibitor, kinetic mechanism, steady-state kinetics.

Instructions to authors; 188–190

Contents of volume 52; 191–192