辻 耕治

The extract of cultured Lentinula edodes mycelia (LEM) is a medicinal food ingredient that has hepatoprotective effects. In this study, we fractionated the LEM extract to explore novel active compounds related to hepatoprotection by using primary cultures of rat hepatocytes exposed to carbon tetrachloride (CCl4). The LEM extract and the fractions markedly inhibited the release of alanine aminotransferase (ALT) from hepatocytes damaged by CCl4 into the culture medium. The strongest hepatocyte-protective activity was seen in a fraction (Fr. 2) in which a 50% ethanol extract was further eluted with 50% methanol and separated using reverse-phase HPLC. Fr. 2 had an average molecular weight of 2753, and the main components are lignin (49%) and saccharides (36%, of which xylose comprises 41%). Therefore, Fr. 2 was presumed to be a low-molecular-weight compound consisting mainly of lignin and xylan-like polysaccharides. The hepatocyte-protective activity was observed even after digestion of xylan-like polysaccharides in Fr.2 and confirmed with low-molecular-weight lignin (LM-lignin) alone. In addition, Fr. 2, the xylan-digested Fr. 2 and LM-lignin showed higher superoxide dismutase (SOD)-like activity than the LEM extract. These results suggested that the effective fraction in the LEM extract related to hepatocyte protection consisted mainly of LM-lignin, and its antioxidant activity partially contributes to the hepatocyte-protective activity of the LEM extract.

Nipa (Nypa fruticans) is one of the most widely distributed and useful palm in the mangrove forests in the South, Southeast Asia and Oceania. Its distribution area is known to be larger in ancient lime than at present, as evidenced by its fossils found in North America, South America, Egypt and Europe. Nipa has a wide diversity of use. Traditionally it is used as roof materials, cigarette wrapper, medicine and its sap is fermented to alcohol. Recently, research on nipa has focused on its potential use as a biofuel crop because it has several advantages compared with other biofuel-alcohol crops. For example it has high alcohol content, no competition with other crop for agricultural land and no bagasse disposal problem. In spite of such usefulness, scientific reports on biology of nipa are limited. Information on genetic diversity, cytogenetics and chemical composition are lacking for nipa plant. On the other hand, morphological characters of nipa have been described in many reports. This paper attempted to provide a general review of the nipa plant based on available literatures.

Six new acylated anthocyanins (1-6) were isolated along with the three known congeners (7-9) from the fresh roots of red radishes (Raphanus sativus L.) cultivated by our group. Their chemical structures were elucidated by spectroscopic properties. Among the six new anthocyanins, the five constituents (1, 2, 4-6) were shown to contain the malonyl function at 6-OH in the glucopyranosyl residue linked to C-5 in the pelargonidin nucleus.

アントシアニン高含有アカダイコン(Raphanus sativus L.)の育種研究の一環として、種子にγ線を各々200Gy、400Gy、600Gyの線量で照射した3集団とγ線無照射の集団を秋期栽培し、収穫個体のアントシアニン含量をHPLCにより定量し、放射線照射の生育およびアントシアニン産生能への影響を検討した。この結果、200Gy照射集団は、γ線無照射集団と比較して、アントシアニン含量が単位体積あたりと個体あたりどちらについても有意に増加し、個体体積もほとんど変動しなかった。さらに、種子に対するγ線照射は、いずれの強度においてもアカダイコン中のアントシアニン組成にほとんど影響を与えなかった。したがって、200Gy照射はアントシアニン高含有アカダイコンの育種に有効な手法となる可能性のあることが示された。

酵素処理イソクエルシトリン(EMI)の経口摂取後の代謝挙動を明らかにする目的で、主8成分(IQC, IG₁〜IG₇)各々について、唾液α-アミラーゼ、膵液α-アミラーゼ、人工胃液存在下での反応生成物をHPLCを用いて定量解析した。主8成分のうち、イソクエルシトリン(IQC)、IG₁およびIG₂は、いずれのα-アミラーゼによる加水分解をほとんど受けないことが判明した。一方、IG₃からIG₇については、生体内での滞留時間を考慮した場合、ほぼ完全にIQC,IG₁,IG₂へと代謝されることが明らかとなった。また、EMIのいずれの成分も、人工胃液および唾液アミラーゼ含有人工胃液処理においては、まったく代謝を受けないことが判明した。これら一連の結果から、経口摂取されたEMIは、唾液、膵液アミラーゼの作用で小腸に移行される前の段階で、IQC, IG₁, IG₂に集約されることが明らかとなった。

アカダイコンについて、中国雲南省から導入した種子と、導入後に3回の選抜を行った種子について、AFLP法による遺伝的変異の程度の検討を行った。その結果、これら2つの集団は、塩基多様度に有意差は認められず、系統樹でもひとつのグループを形成した。この結果から、この2集団は、遺伝的変異の程度ではいずれの種子も交配に用いるうえでは差異のないことが判明した。

Phylogenetic relationships among cultivated landraces and natural populations of wild subspecies of Tartary buckwheat were investigated at the individual level by constructing a phylogenetic tree based on amplified fragment length polymorphism (AFLP) markers. Seven individuals from seven cultivated landraces and 35 individuals from 21 natural populations of wild subspecies were utilized for AFLP analyses. Three groups were recognized: (1) all cultivated landraces and wild subspecies from northern Pakistan, central and eastern Tibet., and northwestern Yunnan, (2) wild subspecies from central and southern Sichuan, (3) wild subspecies from northern Sichuan and eastern Tibet. It was concluded that cultivated Tartary buckwheat probably originated in eastern Tibet or northwestern Yunnan in China.

Phylogenetic relationships among cultivated landraces and natural populations of wild subspecies of Tartary buckwheat were investigated by constructing an NJ tree based on RAPD markers focussing on east Tibetan natural populations. Ten plants from three cultivated landraces and 29 plants from five natural populations of wild subspecies in eastern Tibet were used for RAPD analyses. The wild subspecies from eastern Tibet was classified into three types; (1) same type as cultivated landraces; (2) closely related to natural populations of northwestern Yunnan; and (3) an exceptional population, Zhuka, which was closely related to Sichuan populations. Since the type (2) is considered as the wild ancestral type of cultivated Tartary buckwheat, we conclude that eastern Tibet too may be one of the center of origin of this crop.

The phylogenetic relationships among cultivated landraces and natural populations of wild subspecies of Tatary buckwheat were investigated at the individual level by constructing a phylogenetic tree based on RAPD markers. As the PCR templates, DNA of individuals rather than bulked samples, was used. Ten individuals from 10 cultivated landraces. 71 individuals from 21 natural populations of wild subspecies, and 7 individuals from 3 weedy Tatary buckwheat were provided for RAPD analyses. Three groups were recognized: (1) all cultivated landraces and wild subspecies from central Tibet and northern Pakistan (2) 10 individuals of wild subspecies from northwestern Yunnan (3) the remaining individuals of wild subspecies from northwestern Yunnan and all individuals of wild subspecies from Sichuan. Group (2) was phylogenetically closely related to group (1). The origin of cultivated Tatary buckwheat, the hybrid origin of weedy Tatary buckwheat and of the wild populations from central Tibet and northern Pakistan are discussed. We arrive at the conclusion that cultivated Tatary buckwheat probably originated in northwestern Yunnan in China.