<i>tert</i>.-Butylhydroperoxide 処理による赤ビート切片からのベタシアニン リーケージに及ぼす各種の添加物質の影響

Abstract

With the purpose of getting much information about the mechanism of leakage observed at the onset of plant senescence or other physiological disorders, a model system using red beet discs has been investigated in our study. The present paper describes the effects of various chemicals added to the incubation medium, in which red beet discs are exposed or pre-exposed to tert. -butylhydroperoxide (BHP), on the leakage of red betacyanin pigment from the cells. The mechanism of betacyanin leakage induced by the BHP treatment is suggested from these results.1. Under the same conditions reported in our previous paper, the treatment with BHP (10mM and 8hrs) evidently caused the abrupt increase of OD 540nm (leakage of red betacyanin pigment), and the optical density reached about 1.0 from 5hrs to 7hrs after the treatment.2. The addition of 5mM sodium diethyldithiocarba mate, 20mM thiourea, 5.0mM (+)-catechin and 1mM n-propyl gallate, separately, to the incubation medium effectively inhibited the increase in OD 540nm, when each chemical and BHP were added simultaneously.3. L-Cysteine (5mM) and D-ascorbic acid (5mM), which are well known as endogenous reducing agents, also showed the inhibitory effect on Betacyanin leakage of red beet discs.4. When (+)-catechin (5mM), cysteine (10mM) and thiourea (20mM) wereadded, separately, to the incubation medium in the absence of BHP after the BHP treatment (10mM and 8hrs), they also showed significant effects on inhibition of betacyanin leakage.5. The presence of 5mM EDTA or 2.5mM FeCl3 in the incubation medium containing 10mM BHP enhanced the increase in OD 540nm considerably.These results suggest that BHP taken into the discs of red beet, as indicated in the red cells of human blood, may be transformed by either free Fe3+, chelated Fe3+ or other endogenous unknown factors to the tert. -butoxyl radical, and consequently will attack various biomembranes in the cells to cause the lakage of red betacyanin pigment. Further biochemical investigation will be required to confirm the mechanism.