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No.20 (1973/12) >

 
Title :甘蔗の赤変に関する生化学的研究(農芸化学科)
Title alternative :Biochemical studies on sugar cane reddening (Department of Agricultural Chemistry)
Authors :外間, 宏一
Authors alternative :Hokama, Koichi
Issue Date :1-Dec-1973
Abstract :甘蔗赤腐病は糸状菌Physalospora tucumanensisの不完全時代であるColletotrichum falcatum wentによる汚染が主原因であるとされているが,その他の微生物,昆虫の食傷,生育中の裂傷などが原因でも,類似の現象が起こるといわれているように,赤変機構そのものについては,不明な点が多い。殊に生化学的立場から検討を加えた報告は皆無である。筆者は甘蔗赤変現象の発現に関して化学的並びに生化学的研究を行ない,次の様な結果を得た。即ち1章では,赤変甘蔗抽出物のペーパークロマトグラムから色素A, B, C, Dを分離し,それぞれ分子式と官能基を元素分析,MS, IRスペクトルおよび定性試験の結果から検討した結果を述べたものである。すなわち,1)色素A (C_<18>H_<24>O)はbutenyl基を有するphenol化合物,2)色素B (B-1 C_<22>H_<22>O_<10>, B-2 C_<22>H_<22>O_9)はflavonol誘導体,3)色素C (C_9H_8O_3), D (C_6H_8O_4)はともにエーテル型酸素あるいはmethylendioxide型酸素を有するphenol化合物であろうと推察された。何れも前掲文献に挙げたものとは一致しなかった。2章では,甘蔗赤変の発現は糖類の存在と密接な関係があるが,その濃度の影響をほとんど受けないこと,酸素の存否にも関係ないことを明らかにした。3章では,赤変甘蔗からphoma sp菌とC. pulcherima菌の分離同定について述べた。またこの両菌ともP. tuoumanensis同様赤変については間接的に関与していることを明らかにした。4章では,甘蔗peroxidaseについて論述した。即ち,自然赤変区においては甘蔗peroxidase活性はほとんど一定しているために,色素の生成とperoxidaseとの関係は不明であったが,人為赤変区においては,赤変が僅かに認められる頃の培養初期に最高の酵素活性を示した。甘蔗梢頭部から根茎に至る各茎の酵素活性はほとんど一定であった。また含有糖分とも無関係であった。5章では,phenol性化合物の同定と,その生化学的反応をin vitroで実施したものである。即ち,甘蔗中にはphenol性化合物として,phenol, ferulic acid, p-coumaric acidのほかに痕跡程度の3未確認化合物が存在すること,およびこれらのうち生体内赤変反応に関与するものは,phenolとferulic acid(あるいは,これに極めて近縁なもの)だけであることを明らかにした。phenolと甘蔗peroxidase, phenolとHMF, ferulic acidとperoxidaseはそれぞれ反応して異なる褐変色素を生じるが,前二者の反応は甘蔗赤変に関与していることが推論された。第6章では,赤変色素の抗菌活性等を検討した。その結果,何れも若干の抗菌力,魚毒性をもっていた。従って赤変色素は甘蔗における1種のphytoalexinではないかと推察される。
1) Pigments A (C_<18>H_<24>O), B (C_<22>H_<22>O_9 or C_<22>H_<22>O_<10>), D (C_9H_8O_4) and E (molecular formula unknown) were isolatated from the paperchromatograms of naturally reddened sugar cane and pigment C was from the artificially reddened sugarcane and they were purified by recrystallization from ethylacetate. 2) Any of pigments A, B, C and D was aromatic compounds, of which A was phenol compond containing butenyl group, B flavonol derivative, C and D were spposed to have not only one phenolic oxygen, but also ether or methyledioxide type oxygen. 3) Sugar cane reddening needed sufficient amount of water and little amount of sugar, but not oxygen. 4) The pigments interested in sugar cane reddening were brought about not only by the infection with P. tucumanensis into the sugar cane tissues, but also mixed with the pigments occurring from other various cases. 5) As a result of the investigations of the ealy stage of red rot diseases of sugar cane, as well as the tolerably developing one, it was found that the concentrations of sugar were slightly reduced in spite of an increase in pigment concentration and a decrease in pH. 6) In the reddening sugar cane slice formed by an acid treament, the pignemt concentration increaed with time and reached finally after 11 days about twice as much as that after 4 days. 7) The sugar cane juice treated with acids changed from pink-brown to brown with an increase in concentration, of which hydrochloric acid contributed to form pignemt extremly much more than other acids. 8) However, the pigments formed according to the above mentioned paragraphs (4) and (5) were different from those of the naturally reddened sugar cane. 9) The fungus B which produced red pigments and pinkish yeast A were separated from the sugar cane infected with red rot disease and the former was supposed to be Phoma sp., and the latter to be Candida pulcherrma. 10) The fact that sugar cane of dead tissue didn't redden but rotted indicates that the appearance of red rot disease was closely related with the condition of the sugar cane tissue, i.e. living and dead.
11) Judging from the facts that the pigments of red rot disease fungi themselves were completely different from those formed in sugar cane tissue by them and that the sugar cane slices inoculated with them reddened more rapidly than those not inoculated, it was found that they didn't take direct part in the formation of pigments and only contribute to promote it. 12) The optimum pH and temperature of sugar cane peroxidase were 7.8 and 50℃ respectively. EDTA, ammonium oxalate and potassium cyanide were used as inhibitor against the emzyme activity. The unexpected activiation by the former two agents seemed to be due to the removal of metals acting as inhiditors. The latter inhibitted the activity completely. The effects of Ag^+, K^+, Mg^<2+>, Na^+ on the enzyme activity were found slighty, Ca^<2+>, Fe^<3+>, Zn^<2+> moderately, and Cu^<2+>, Fe^<2+>, Pb^<2+> remarkably. 13) The enzyme activity of each part of sugar cane was almost unchanged and not affected by the existing sugars. 14) The enzyme activities in naturally reddend sugar cane formed small peaks even after 4 days, whereas the artificially reddened a giant maximum peak after 2 days from the cultiavation. 15) Phenol, ferulic acid, p-coumaric acid and other three phenolcarboxylic acid were found as phenolic compounds in the sugar cane tissue, of which phenol and ferulic acid were found to be related in forming the pigments. 16) The paperchromatograms of pigments formed by the autooxidation of phenol were much the same as ones formed by the action of peroxidase on phenol, of which some were identified as the components of artificially or naturally reddened sugar cane. 17) The direct relationship among pigments formed by the action of peroxidae on ferulic acid and red sugar cane pigments was not observed. 18) The main com
Type Local :紀要論文
ISSN :0370-4246
Publisher :琉球大学農学部
URI :http://hdl.handle.net/20.500.12000/4424
Citation :琉球大学農学部学術報告 = The Science Bulletin of the Faculty of Agriculture. University of the Ryukyus no.20 p.37 -93
Appears in Collections:No.20 (1973/12)

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