Alteration of oxalate content in rice leaves obtained from ion beam-irradiated plants

Rice straw obtained from rice leaves and stems can be used as a livestock feed. Rice leaves accumulate soluble oxalate, which easily binds to cationic ions such as calcium, iron, and magnesium ions, then becomes insoluble. It is an important agricultural topic to reduce oxalate content in crops because excess uptake of oxalate-rich plants causes mineral racking or urinary syndrome for human and livestock, although it is a useful molecule for plants to defense themselves from predators, to reduce aluminum toxicity in the acidic soil, to regulate calcium content in their body, and to provide hydrogen peroxide which acts as a signal molecule during aging or wounding. Three pathways (isocitrate, glycolate and ascorbate pathways) have been reported for oxalate synthesis in plants. However, it has been unknown which pathway contributes the oxalate accumulation in rice leaves. For reducing oxalate content in rice leaves and understanding oxalate synthesis mechanism, we first grew rice mutagenized M2 population (Koshihikari) generated from seeds irradiated by carbon ion beams and measured oxalate contents in their leaves. The oxalate measurement using CE-MS showed that there was no difference between means of oxalate contents in the population of M2 plants and those in the control plants, but wider variation of oxalate contents was observed in M2 plants compared with control plants. Metabolomic analyses of oxalate and other metabolite in the M2 plants showed that organic acids such as 2OG and succinate were decreased in the low-oxalate rice plants, although amino acids except for alanine, glutamate, and aspartate were increased. These suggested that oxalate accumulation in rice leaves would be affected by carbon flow via isocitrate pathway, and that reduction of oxalate contents might lead to increase of amino acids contents.Plant Biology 202

Metabolome analysis of rice leaves to obtain low-oxalate strain from ion beam-mutagenised population

Rice leaves and stems, which can be used as rice straw for livestock feed, accumulate soluble oxalate. The oxalate content often reaches 5% of the dry weight leaves. Excess uptake of oxalate-rich plants causes mineral deficiencies in vertebrates, so it is important to reduce the oxalate content in rice leaves to produce high-quality rice straw. However, the mechanism of oxalate accumulation in rice has remained unknown. In this study, we performed metabolome analysis of rice M 2 population generated by ion-beam irradiation using CE-MS to understand metabolic networks relating oxalate accumulation in rice. The result showed wide variation of oxalate contents in M 2 plants compared with those of control plants. Multivariate analyses of metabolome dataset revealed that oxalate accumulation was strongly related with anionic compounds such as 2OG and succinate. For low-oxalate plants, four patterns of metabolic alterations affected oxalate contents in the M 2 leaves were observed. In M 3 plants, we found putative low-oxalate line obtained from low-oxalate M 2 mutant. These findings would lead to produce the low-oxalate rice and to understand the oxalate synthesis in plants

Screening of low oxalate rice plants from ion beam-irradiated seeds

Oxalate, which is contained in many plant species, easily combines cationic ions such as calcium, iron, and magnesium ions. It is important agricultural topic to reduce oxalate content　in crops, because excess uptake of oxalate causes mineral deficiency or urinary syndrome for human and livestock. Rice straw can be used as a livestock feed. However, rice accumulates oxalate in leaves and stems which consist mostly of rice straw. For the reduction of oxalate content in rice leaves, we performed screening of low oxalate rice plants from seeds irradiated by carbon ion beam. The CE-MS (Capillary Electrophoresis-Mass Spectrometry) measurement of oxalate contents in leaves obtained from ion beam-irradiated seeds (M2) showed that low-oxalate plants which contained less than one tenth of oxalate content in comparison with those in non-irradiated plants was obtained. Multivariate analyses in the basis of oxalate and other metabolite data sets revealed that amino acids (except for alanine, glutamate, and aspartate) were accumulated in low oxalate rice plants, although organic acids and phosphate compounds were decreased. These suggested that carbon flow via isocitrate affected oxalate accumulation. In the M3 mutants, several lines showed decreased oxalate contents (60% of non-irradiated plant) and could grow normally.16th International Symposium on Rice Functional Genomic

Pharmacokinetics of 6-shogaol, a pungent ingredient of Zingiberis Rhizoma, and the anti-inflammatory activity of its metabolite, 6-paradol

金沢大学医薬保健研究域薬学系Zingiberis Rhizoma の辛味成分である 6-shogaol およびその代謝物 6-paradol の体内動態および薬理活性について， 検討した。 6-shogaol （10 mg/kg） をラットに経口投与した際の血漿中 6-shogaol および 6-paradol 濃度を LC/MS/MSを用いて測定したところ， ともに投与 5 分後で Cmax に到達し， 投与 2 時間後までに速やかに血漿中から消失した。 代謝物である血漿中 6-paradol 濃度はいずれの採血時間においても， 6-shogaol 濃度に比べて約 4 倍高い値を示した。 次に， 6-shogaol および6-paradolの薬理活性について検討したところ， in vitro 実験において 6-paradol は 6-shogaol に比べ約 6 倍強い COX-2 阻害活性を示し， in vivo 実験においても 6-paradol が 6-shogaol より有意に強い抗炎症作用， 鎮痛作用および解熱作用を示した。 このことから， Zingiberis Rhizoma 中の 6-shogaol は体内で速やかに 6-paradol に代謝されること， また代謝物である 6-paradol が抗炎症作用を示すメイン化合物であることが示唆された。This study examined the pharmacokinetics and pharmacological activities of 6-shoganol, a pungent ingredient of Zingiberis Rhizoma, and its metabolite, 6-paradol. The concentrations of 6-shogaol and 6-paradol in rat plasma determined by LC/MS/MS reached their maximum values (Cmax) at 5 minutes after oral administration of 6-shogaol (10 mg/kg). Both 6-shogaol and 6-paradol were eliminated from the plasma within 2 hours after injection. The plasma concentration of 6-paradol, the metabolite, was about 4 times higher than that of 6-shogaol at all points during blood sampling. Next, pharmacological activities of 6-shogaol and 6-paradol were studied. In vitro experiment revealed that the cyclooxygenase-2-inhibitory activity of 6-paradol was about 6 times stronger than that of 6-shogaol. In vivo experiments, 6-paradol demonstrated significantly stronger anti-inflammatory, analgesic, and antipyretic activities compared to 6-shogaol. These results suggest that 6-shogaol in Zingiberis Rhizoma is metabolized rapidly to 6-paradol and that 6-paradol is the main compound having anti-inflammatory activity. © 2013, Medical and Pharmaceutical Society for WAKAN-YAKU. All rights reserved