Enzymatic synthesis of two isoxazolylalanine isomers by cysteine synthases in Lathyrus species

Two isoxazolylalanine isomers, beta-(isoxazolin-5-on-2-yl)-L-alanine (BIA, 1) and beta-(isoxazolin-5-on-4-yl)-L- alanine (TAN-950A, 2) were confirmed to be derived from O-acetyl-L-serine (OAS) and isoxazolin-5-one by cysteine synthases (CSases) with a different ratio in different plant parts. Some properties of this enzyme in the biosynthesis of both isomers are described.

Celahinine A, a new sesquiterpene pyridine alkaloid from Celastrus hindsii

A new sesquiterpene pyridine alkaloid, celahinine A [1], and the related known polyester celahin A, as well as the known cytotoxic sesquiterpene pyridine alkaloid emarginatine A [2], were isolated from Celastrus hindsii. The structure of 1 was determined by 2D nmr techniques and was also confirmed by spectral comparison with the related 2.

Antioxidant properties of demethyldiisoeugenol

The antioxidant properties of demethyldiisoeugenol were investigated in this study using various models. Demethyldiisoeugenol inhibited Fe(2+)-induced lipid peroxidation in rat brain homogenate in a concentration-dependent manner with an IC50 1.8 +/- 0.1 microM. Demethyldiisoeugenol was more effective than alpha-tocopherol and BHT in reducing the stable free radical diphenyl-2-picrylhydrazyl (DPPH). It also scavenged superoxide anion generated by xanthine/xanthine oxidase and peroxyl radical (ROO.) derived from 2,2'-azobis(2-amidinopropane)dihydrochloride (AAPH) in aqueous system with a stoichiometric factor of 1.3 +/- 0.2. Furthermore, it prevented conjugated-diene formation and apolipoprotein B (apo B) oxidation of LDL. However, demethyldiisoeugenol did not scavenge 2,2'-azobis(2,4-dimethylvaleronitrile) (AMVN)-derived peroxyl radical in hexane. It also did not chelate Fe2+, did not inhibit xanthine oxidase activity or possessed hydroxyl radical (.OH) scavenging activity. Experimental results indicate that demethyldiisoeugenol is a potentially effective antioxidant and can protect rat brain homogenate and LDL against oxidation.

A novel L23-related gene 40 kb downstream of the imprinted H19 gene is biallelically expressed in mid-fetal and adult human tissues

The closely linked IGF2 and H19 genes on human chromosome 11p15.5 are monoallelically expressed as a result of genomic imprinting and show altered expression in Wilms' tumors (WTs). To map regional imprinting we have sought to isolate additional human genes close to IGF2/H19 and to characterize their allelic expression patterns. Here we report a novel gene, provisionally named L23MRP [L23 (mitochondrial)-related protein], which is oriented 'tail-to-tail' with H19 and is transcribed to within 40 kb of the last H19 exon. L23MRP is expressed biallelically in many mid-fetal and adult human tissues. This gene is also expressed at normal levels in WTs which have lost expression of H19 either via loss of the maternal chromosome 11p15.5 or via an epigenetic pathway involving site-specific DNA hypermethylation. These data indicate that, at least in post-embryonic stages, L23MRP is functionally insulated from the IGF2/H19 imprinted domain.

Five new pregnane glycosides from Cynanchum taiwanianum

Five new pregnane glycosides, taiwanosides A [1], B [2], C [3], D [4], and E [5], together with wilfosides C1N [6], C2N [7], M1N [8], and K1N [9], were isolated from the roots of Cynanchum taiwanianum. Their structures were determined on the basis of spectroscopic and chemical evidence.

Inhibitory and excitatory amino acids in cerebrospinal fluid of neurolathyrism patients, a highly prevalent motorneurone disease

Neurolathyrism is caused by overconsumption of seeds containing 3-N-oxalyl-L-2,3-diaminopropanoic acid (beta-ODAP). Amino acids levels of cerebrospinal fluid (CSF) were studied in 50 patients with neurolathyrism and 12 healthy volunteers. The levels of excitatory amino acids glutamate and aspartate were 281% and 71% respectively of control values. The concentration of inhibitory amino acids glycine and taurine were 277% and 198% respectively of the levels in CSF from control individuals. There was a significant correlation between the level of glycine and the duration of the disease. We also found increased levels of threonine, serine and alanine. In contrast to reports on other motor neurone diseases where an increase of isoleucine was observed we found a significant decrease of isoleucine. The results suggest a disturbance of amino acid metabolism due to excitotoxic damages caused by beta-ODAP, a dietary excitatory amino acid.

Daphnoretin-induced respiratory burst in rat neutrophils is, probably, mainly through protein kinase C activation

Daphnoretin, a dicoumarin isolated from Wikstroemia indica C.A. Mey. (Thymelaceae), induced superoxide anion (O2-) formation in rat neutrophils in a concentration-dependent manner. Addition of staurosporine reduced daphnoretin-induced respiratory burst. Removal of extracellular free Ca2+ by EGTA did not affect the respiratory burst of neutrophils in response to daphnoretin. Prior exposure of neutrophils to phorbol 12-myristate 13-acetate (PMA) or daphnoretin reduced the O2- formation caused by a subsequent challenge with PMA and daphnoretin, but potentiated the response caused by a subsequent addition of formyl-Met-Leu-Phe (fMLP). Like PMA, daphnoretin did not increase the [Ca2+]i during cell activation. In neutrophil suspension, daphnoretin increased the membrane associated protein kinase C activity. In the presence of Ca2+ and phosphatidyl-serine, daphnoretin also activated protein kinase C isolated from cytosolic fraction of resting neutrophils. Staurosporine inhibited the direct activation of protein kinase C caused by daphnoretin as well as by PMA. Daphnoretin reduced the [3H]Phorbol-12,13-dibutyrate ([3H]PDB) binding to the neutrophil cytosolic protein kinase C in a concentration-dependent manner with an IC50 value of 1.77 +/- 0.37 microM. These results indicate that daphnoretin, like PMA, may direct activation of protein kinase C which in turn activated NADPH oxidase and elicited respiratory burst.

Antiplatelet and vasorelaxing actions of the acetoxy derivative of cedranediol isolated from Juniperus squamata

The antiplatelet and vasorelaxing actions of 14-acetoxycedrol, an acetyl derivative of the sesquiterpene 8,14-cedranediol isolated from Juniperus squamata Hayata, were investigated in washed rabbit platelets and rat aorta, respectively. 14-Acetoxycedrol inhibited the aggregation and ATP release of rabbit platelets induced by ADP, arachidonic acid, platelet-activating factor (PAF), collagen, and thrombin. Prolongation of the incubation time of 14-acetoxycedrol with platelets did not cause further inhibition and the aggregability of the treated platelets could be restored after washing of the platelets. It inhibited thromboxane B2 formation of washed platelets caused by arachidonic acid, collagen, and thrombin in a concentration-dependent manner. The formation of inositol phosphate caused by collagen and PAF was inhibited by 14-acetoxycedrol, while that caused by thrombin was not affected. 14-Acetoxycedrol markedly inhibited the intracellular calcium rise caused by PAF, and slightly inhibited that caused by thrombin in quin-2/AM-load platelets. In rat thoracic aortae, 14-acetoxycedrol inhibited the high K+ (60 mM) and Ca2+ (0.03-3 mM) induced cumulative contractions in a concentration-dependent manner, while it did not affect the phasic and tonic contractions elicited by norepinephrine. The tonic contractions elicited by KCl (60 mM) and Bay K 8644 were also relaxed by 14-acetoxycedrol. It is concluded that the antiplatelet effect of 14-acetoxycedrol is due to the inhibition of thromboxane formation and phosphoinositides breakdown and the vasorelaxing action of 14-acetoxycedrol is due to inhibition of Ca2+ influx through the voltage-dependent Ca2+ channel.

From soil to brain: zinc deficiency increases the neurotoxicity of Lathyrus sativus and may affect the susceptibility for the motorneurone disease neurolathyrism

Zinc deficiency and oversupply of iron to the roots of grass pea (Lathyrus sativus) induce increases in the content of the neurotoxin beta-L-ODAP (3-oxalyl-L-2,3-diaminopropanoic acid) in the ripe seeds. The transport of zinc to the shoots is enhanced by the addition of beta-L-ODAP. The neurotoxin of L. sativus is proposed to function as a carrier molecule for zinc ions. Soils, depleted in micronutrients from flooding by monsoon rains (Indian subcontinent) or otherwise poor in available zinc and with high iron content (Ethiopian vertisols), may be responsible for higher incidence of human lathyrism, one of the oldest neurotoxic diseases known to man. A role for brain zinc deficiency in the susceptibility for lathyrism is postulated.

New findings and symptomatic treatment for neurolathyrism, a motor neuron disease occurring in north west Bangladesh

Neurolathyrism is a form of spastic paraparesis caused by the neuroexcitatory amino acid 3-N-oxalyl-L-2,3-diaminopropanoic acid (beta-ODAP) present in the seeds and foliage of Lathyrus sativus. The disease is irreversible and usually nonprogressive. Tolperisone HCl, a centrally acting muscle relaxant, has been shown to reduce significantly the spasticity in neurolathyrism patients. Sporadic occurrence of HTLV-1 infection (0.9%) and of osteolathyrism was found among the neurolathyrism patients. Osteolathyrism is linked to the consumption of the green shoots of Lathyrus sativus.

Two new macrolide sesquiterpene pyridine alkaloids from Maytenus emarginata: emarginatine G and the cytotoxic emarginatine F

Two new macrolide sesquiterpene pyridine alkaloids, emarginatine F [1] and emarginatine G [2], were isolated from Maytenus emarginata. The structural determinations of 1 and 2 by 2D nmr techniques and spectral comparison with a related compound, emarginatine A [3], are discussed. Biological evaluation showed that emarginatine F [1] demonstrated strong cytotoxicity against human epidermoid carcinoma of the nasopharynx (KB), ileocecal adenocarcinoma (HCT-8), melanoma (RPMI-7951) and medulloblastoma (TE-671) tumor cells, and against murine leukemia (P-388).

Inhibition of platelet thromboxane formation and phosphoinositides breakdown by diisoeugenol

Diisoeugenol inhibited the platelet aggregation and ATP release of rabbit platelets caused by ADP, arachidonic acid, platelet-activating factor (PAF), collagen and thrombin. Prolongation of the incubation time of platelets with diisoeugenol did not cause further inhibition and the aggregability of platelets could not be restored after washing. In human platelet-rich plasma, diisoeugenol inhibited the biphasic aggregation and ATP release induced by adrenaline and ADP in a concentration-dependent manner. Thromboxane B2 formation caused by arachidonic acid, collagen and thrombin was markedly inhibited by diisoeugenol in a concentration-dependent manner. Diisoeugenol also inhibited the formation of inositol monophosphate caused by collagen, PAF and thrombin. The cAMP level of washed platelets was not changed by diisoeugenol. It is concluded that the antiplatelet effect of diisoeugenol is due to the inhibition of thromboxane formation and phosphoinositides breakdown.

Daphnoretin, a new protein kinase C activator isolated from Wikstroemia indica C.A. Mey

Daphnoretin, a biologically active principle isolated from Wikstroemia indica C.A. Mey., caused platelet aggregation in washed rabbit platelets, platelet-rich plasma and whole blood. The aggregation of and ATP release from platelets induced by daphnoretin were similar to phorbol ester- and diacylglycerol-induced aggregation and release. The EC50 values of daphnoretin-, phorbol 12,13-dibutyrate (PDBu)- and 1-oleoyl-2-acetylglycerol (OAG)-induced platelet aggregation in washed rabbit platelets were 17.2 +/- 2.8 microM, 20.6 +/- 2.1 nM and 38.6 +/- 1.7 microM respectively. Platelet aggregation induced by daphnoretin and PDBu was not inhibited by indomethacin, BN52021 or sodium nitroprusside. ADP-scavenging systems, apyrase and phosphocreatine/creatine kinase, showed weak inhibition of the aggregation, and EGTA, triflavin, verapamil and prostaglandin E1 markedly inhibited the aggregation. Staurosporine, a potent protein kinase C inhibitor, suppressed daphnoretin-, PDBu- and OAG-induced aggregation and ATP release in a concentration-dependent manner. The IC50 values of staurosporine on daphnoretin (50 microM)-, PDBu (100 nM)- and OAG (50 microM)-induced aggregation were 37.7 +/- 8.3, 52.2 +/- 6.3 and 42.8 +/- 8.9 nM respectively. Daphnoretin did not cause significant thromboxane B2 formation in rabbit platelets. Neither daphnoretin nor PDBu caused [3H]inositol monophosphate formation or an increase in intracellular Ca2+ concentration in myo-[3H]inositol-labelled and Fura-2-loaded platelets. Platelet cytosolic protein kinase C was activated by daphnoretin and PDBu in a concentration-dependent manner with an EC50 of 12.4 +/- 1.2 microM and 18.7 +/- 1.4 nM respectively. Membrane-associated protein kinase C activity was increased by either daphnoretin or PDBu. [3H]PDBu binding to washed rabbit platelets was inhibited by daphnoretin in a concentration-dependent manner with an IC50 value of 45.2 +/- 5.2 microM. These results indicate that daphnoretin is a protein kinase C activator in rabbit platelets.

Biosynthesis in vitro of 2-(3-amino-3-carboxypropyl)-isoxazolin-5-one, the neurotoxic amino acid in Lathyrus odoratus

2-(3-Amino-3-carboxypropyl)-isoxazolin-5-one (ACI), a neurotoxic amino acid from Lathyrus odoratus, was confirmed to be derived enzymatically from S-adenosyl-L-methionine (SAM) and isoxazolin-5-one. Some properties of an enzyme in the biosynthesis of ACI are described.

Analysis of the neurotoxin beta-ODAP and its alpha-isomer by precolumn derivatization with phenylisothiocyanate

A method is presented for determining 3-N-oxalyl-2,3-diaminopropanoic acid (beta-ODAP), the most potent neurotoxic substance of the seeds and seedlings of Lathyrus sativus, and its much less toxic 2-isomer (alpha-ODAP). The separation of the two forms is achieved after derivatization with phenylisothiocyanate employing a HPLC system. This method was used to monitor the isomerization of beta-ODAP to alpha-ODAP at different time intervals and to quantify the toxin level in seed extracts.

Toxins in the seedlings of some varieties of grass pea (Lathyrus sativus)

The major toxin present in the dry seeds and seedlings of Lathyrus sativus is the neurotoxin 3-N-oxalyl-L-2,3-diaminopropanoic acid (beta-ODAP). The presence of one additional neurotoxin and an osteotoxin in the seedlings increases the overall toxicity. Isolation, purification, and detection of these toxins are described.

Regulation of alpha-amylase-encoding gene expression in germinating seeds and cultured cells of rice

Four alpha-amylase-encoding cDNA (alpha Amy-C) clones were isolated from a cDNA library derived from poly(A)+RNA of gibberellic acid (GA3)-treated rice aleurone layers. Nucleotide sequence analysis indicates that the four cDNAs were derived from different alpha Amy genes. Expression of the individual alpha Amy gene in germinating seeds and cultured suspension cells of rice was studied using gene-specific probes. In germinating seeds, expression of the alpha Amy genes is positively regulated by GA3 in a temporally coordinated but quantitatively distinct manner. In cultured suspension cells, in contrast, expression of the alpha Amy genes is negatively and differentially regulated by sugars present in the medium. In addition, one strong and one weak carbohydrate-starvation-responsive alpha Amy genes have been identified. Interactions between the promoter region (HS501) of a rice alpha Amy gene and GA3-inducible DNA binding proteins in rice aleurone cells were also studied. A DNA mobility-shift assay showed that the aleurone proteins interact with two specific DNA fragments within HS501. One fragment is located between nt -131 to -170 and contains two imperfect directly repeated pyrimidine elements and a putative GA3-response element. The other fragment is located between nt -92 to -130 that contains a putative enhancer sequence. The interactions between aleurone proteins and these two fragments are sequence-specific and GA-responsive.

Biosynthesis of beta-(isoxazolin-5-on-2-yl)alanine, the precursor of the neurotoxic amino acid beta-N-oxalyl-L-alpha,beta-diaminopropionic acid

beta-(Isoxazolin-5-on-2-yl)alanine (BIA), a biosynthetic precursor of the neurotoxic amino acid beta-N-oxalyl-L-alpha,beta-diaminopropionic acid (ODAP), was confirmed to be derived from O-acetyl-L-serine (OAS) and isoxazolin-5-one by cysteine synthase in higher plants. Some properties of this enzyme in the biosynthesis of BIA are described.

Metabolic derepression of alpha-amylase gene expression in suspension-cultured cells of rice

We present evidence to show that the alpha-amylase gene family in rice is under two different modes of regulation: 1) hormonal regulation in germinating seeds, and 2) metabolic repression in cultured cells by available carbohydrate nutrients. Expression of alpha-amylase genes in deembryoed rice seeds is known to be induced by exogenous gibberellic acid. On the other hand, expression of alpha-amylase genes in suspension-cultured cells is induced by the deprivation of carbohydrate nutrient. A lag period of 2-4 h is required for the induction of alpha-amylase mRNA in sucrose-depleted medium. The induction of alpha-amylase expression is extraordinarily high and levels of alpha-amylase mRNA can be increased 8-20-folds after 24 h of sucrose starvation. The synthesis and secretion of alpha-amylase is also dependent upon the level of carbon source. The derepression or repression of alpha-amylase synthesis can be readily reversed by the deprivation or replenishment of sucrose in the medium, respectively. Glucose and fructose exert a repression on the alpha-amylase synthesis similar to that of sucrose. A hypothesis that explains the induction of alpha-amylase synthesis by carbohydrate starvation is proposed. Our data have suggested a hitherto undiscovered, potentially important control mechanism of carbohydrate metabolism in higher plants.

Antitumor agents. 113. New 4 beta-arylamino derivatives of 4'-O-demethylepipodophyllotoxin and related compounds as potent inhibitors of human DNA topoisomerase II

A number of 4'-O-demethylepipodophyllotoxin derivatives possessing various 4 beta-N-, 4 beta-O- or 4 beta-S-aromatic rings have been synthesized and evaluated for their inhibitory activity against the human DNA topoisomerase II as well as for their activity in causing cellular protein-linked DNA breakage. The results indicated, that for DNA topoisomerase II, a basic unsubstituted 4 beta-anilino moiety is structurally required for the enhanced activity. Substitution on this moiety with CN, COOCH3, COOC2H5, OH and COOCH3, OCH3, COCH3, CH2OH, OCH2O, OCH2CH2O, phenoxy, morpholino, NO2, and NH2 either at the para and/or the meta position yielded compounds which are as potent or more potent than etoposide. Substitution with COOC2H5 and OH at the ortho position afforded inactive compounds. Replacement of the aryl nitrogen with oxygen or sulfur gave compounds which are much less active or inactive. However, replacement of the phenyl ring with a pyridine nucleus furnished compounds which are as active or slightly more active than etoposide. There is a lack of correlation between the ability of these compounds in inhibiting DNA topoisomerase II and in causing protein-linked DNA breaks.

Antitumor agents. 111. New 4-hydroxylated and 4-halogenated anilino derivatives of 4'-demethylepipodophyllotoxin as potent inhibitors of human DNA topoisomerase II

A series of C-4 hydroxylated and halogenated anilino derivatives of epipodophyllotoxin or 4'-demethylepipodophyllotoxin have been synthesized and evaluated for their inhibitory activity against the human DNA topoisomerase II as well as for their activity in causing cellular protein-linked DNA breakage. Compounds 11-17 and 22 are more potent than etoposide in causing DNA breakage, while compounds 11-13, 15, 16, and 20 are as active or more active than etoposide in their inhibition of the human DNA topoisomerase II. The cytotoxicity in KB cells appears to have no direct correlation with their ability to inhibit DNA topoisomerase II and to cause protein-linked DNA breaks in cells.

Studies on several naturally occurring lignans

Form the bark of Taiwania cryptomerioides, the flower buds of Magnolia fargesii, the wood of Juniperus formosana, and the nutmeg of Myristica fragrans and Myristica cagayanensis, eleven new kinds of lignans and neoli gnans were isolated. The structures of these compounds were elucidated by physical and chemical methods.

[Natural product research in Taiwan (II)]

The results of natural product research of the field of pharmaceutics and others (other than the field of chemistry) in Taiwan were described in this review and 290 research papers (until 1985) were collected. The review introduced the studies of chemical constituents of 270 maybe species of plants, one species of animal and one species of metabolite of fungus, from which 136 kinds of new compounds were isolated and elucidated.

Isoxazolin-5-ones and Amino Acids in Root Exudates of Pea and Sweet Pea Seedlings

Seeds of Pisum sativum L. cv Finale and Lathyrus odoratus L. cv Spencer were germinated aseptically in moistened sand in the dark. At several stages, the amino acid composition of the exudate and of the corresponding roots was analyzed. A number of common amino acids, including homoserine, were exuded by the growing seedling root in an early stage and were partly reabsorbed later. A number of uncommon amino acids, including several isoxazolin-5-one derivatives, uracil alanines, l-gamma-glutamyl-d-alanine, and alpha-aminoadipic acid were exuded at different rates.