Deficiency in phylloquinone (vitamin K1) methylation affects prenyl quinone distribution, photosystem I abundance, and anthocyanin accumulation in the Arabidopsis AtmenG mutant.

Phylloquinone (vitamin K(1)) is synthesized in cyanobacteria and in chloroplasts of plants, where it serves as electron carrier of photosystem I. The last step of phylloquinone synthesis in cyanobacteria is the methylation of 2-phytyl-1,4-naphthoquinone by the menG gene product. Here, we report that the uncharacterized Arabidopsis gene At1g23360, which shows sequence similarity to menG, functionally complements the Synechocystis menG mutant. An Arabidopsis mutant, AtmenG, carrying a T-DNA insertion in the gene At1g23360 is devoid of phylloquinone, but contains an increased amount of 2-phytyl-1,4-naphthoquinone. Phylloquinone and 2-phytyl-1,4-naphthoquinone in thylakoid membranes of wild type and AtmenG, respectively, predominantly localize to photosystem I, whereas excess amounts of prenyl quinones are stored in plastoglobules. Photosystem I reaction centers are decreased in AtmenG plants under high light, as revealed by immunoblot and spectroscopic measurements. Anthocyanin accumulation and chalcone synthase (CHS1) transcription are affected during high light exposure, indicating that alterations in photosynthesis in AtmenG affect gene expression in the nucleus. Photosystem II quantum yield is decreased under high light. Therefore, the loss of phylloquinone methylation affects photosystem I stability or turnover, and the limitation in functional photosystem I complexes results in overreduction of photosystem II under high light.

New cytotoxic-antineoplastic prenyl-1,2-naphthohydroquinone derivatives.

Several new prenylnaphthohydroquinone derivatives have been prepared through the Diels-Alder condensation between alpha-myrcene and 1,2-benzoquinone and evaluated for their cytotoxic activity against A-549, HT-29 and MB-231 cultured cell lines. All of them have shown GI50 values in the microM level.

Effect of a prenylamine analog (MG8926) on spontaneous action potentials in isolated rabbit sinoatrial node.

Effects of verapamil, prenylamine and a prenylamine analog, MG8926 on the intracellular spontaneous action potentials recorded from the isolated rabbit sinoatrial (SA) node were studied. Verapamil (1 microM), a selective inhibitor for slow Ca2+ channels, prolonged the cycle length, decreased the rate of diastolic depolarization, the rate of rise of action potential, the amplitude of action potential and the maximal diastolic potential, and usually arrested showing subthreshold fluctuation of the membrane potential within several ten min. Prenylamine (10 microM), a nonselective inhibitor for slow Ca2+ channels, tended to prolong the cycle length to decrease the diastolic depolarization, the rate of rise of action potential, the amplitude of action potential. However, these changes were statistically insignificant. Prenylamine at the concentration of 10 microM had no effect on the maximal diastolic potential. MG8926 (10 microM) prolonged the cycle length, decreased the rate of diastolic depolarization, the rate of rise of action potential and tended to decrease the amplitude of action potential. MG8926 at the concentration of 10 microM had almost no effect on the maximal diastolic potential. The present findings may indicate that replacement of phenyl residue of prenylamine by cyclohexyl residue increases the inhibitory action on the slow Ca2+ channels in rabbit SA node.

[Clinical evaluation of a new antianginal drug: droprenylamine]. / Valutazione clinica di un nuovo farmaco antianginoso: la droprenilamina.

In this study the antianginal action of droprenylamine, a cycloaliphatic derivative of prenylamine, was evaluated. Forty patients were included in three groups: in the first group a double blind study was carried out, while in the other two groups, both treated with droprenylamine for a 12 weeks period, were evaluated the effects on workload tolerance or the efficacy in reducing the number of angina pectoris episodes per week and the assumption of nitroglycerine. The double blind study shows that droprenylamine is able to reduce significantly the nitroglycerine assumption. Furthermore, during the 12 week treatment with droprenylamine we can observe a significant reduction of the ST segment depression, at comparable workloads, a significantly increased tolerance to stress test and an early and significant reduction of the angina attacks and, subsequently, of the assumption of nitroglycerine. In conclusion, this drug, which appears free of side effects, may be useful in the treatment of angina pectoris; in particular, the possible association with other antianginal drugs should be evaluated.

Synthesis and pharmacological study of diphenylalkylamines with cycloaliphatic residues. New coronary vasodilators.

The paper describes the synthesis and the pharmacological evaluation of some derivatives of prenylamine, all with a cycloaliphatic ring within or instead of the isopropylamine moiety. Their general formulas are: (C6H5)2CH-CH2-CH2-NH-CH-CH2-R CH2 (I) (C6H5)2CH-CH2-CH2-NH-R' (II) where R contains and R' is a cycloaliphatic ring. Several compounds and particularly those of formula (I), and of formula (II), where the alicyclic ring had a bulky substituent in para were more active than prenylamine as coronary vasodilators on isolated guinea-pig heart (Langendorff). The most interesting derivative was M.G. 8926 [N-(3,3-diphenylpropyl)-alpha-methyl-beta-cyclohexylethylamine], which was more active than prenylamine on Langendorff's heart and in enhancing the pressor response to catecholamines and inhibiting the isoprenaline induced hypotension. Moreover, it had almost the same effects as prenylamine as spasmolytic, local and general anesthetic, on heart rate and arterial pressure and against coronary spasm from pitressin.