Barclay L R, Antunes F, Egawa Y, McAllister K L, Mukai K, Nishi T, Vinqvist M R
Department of Chemistry, Mount Allison University, Sackville, Canada.
Biochim Biophys Acta. 1997 Aug 14;1328(1):1-12. doi: 10.1016/s0005-2736(97)00057-6.
Phenolic antioxidants of the hydroxychroman class, alpha-tocopherol (alpha-TOC) and 2,2,5,6,7-pentamethyl-6-hydroxychroman (PMHC), and the hindered phenols 2,3-dihydro-5-hydroxy-2,2,4-trimethylnaphtho[1,2-b]furan (NFUR), 2,6-di-tert-butyl-4-methoxyphenol (DBHA), and 2,6-di-tert-butyl-4-methyl phenol (BHT), were delivered into oxidizable (ACCEPTOR) liposomes of dilinoleoylphosphatidylcholine (DLPC) or 1-palmitoyl-2-linoleoyl-phosphatidylcholine (PLPC) from saturated DONOR liposomes of dimyristoylphosphatidylcholine (DMPC) by liposomal transfer. The antioxidant activities, k(inh), by the inhibited oxygen uptake method were compared with the k(inh)s determined when the antioxidants were introduced into the liposomes by coevaporation from organic solvents. The peroxidations were initiated using either thermal initiators, water-soluble azo-bis-amidinopropane hydrochloride (ABAP), lipid-soluble azo-bis-2,4-dimethylvaleronitrile (ADVN) and di-tert-butylhyponitrite (DBHN), or the photoinitiator benzophenone. The antioxidants PMHC, NFUR, DBHA, and BHT transferred rapidly between liposomes, but several hours of incubation were needed to transfer alpha-TOC. The average k(inh)s in liposomes, in the relative order NFUR approximately DBHA > PMHC > BHT approximately alpha-TOC, were markedly lower than known values in organic solvent. k(inh) values in liposomes appear to be controlled by effects of hydrogen bonding with water and by restricted diffusion of antioxidants, especially in the case of alpha-TOC. Product studies of the hydroperoxides formed during inhibited oxygen consumption were carried out. The cis,trans/trans,trans (c,t/t,t) product ratios of the 9- and 13-hydroperoxides formed from PLPC during inhibited peroxidation by PMHC were similar for both the coevaporated and liposomal transfer procedures. The c,t/t,t ratio for the same concentration of alpha-TOC, 1.52, compares to a value of 1.69 for PMHC at the start of the inhibition period. The higher c,t/t,t ratio observed for NFUR in DLPC, which varied between values of 7.0 at the start of the inhibition to about 1.8 after the break in the induction period, is a reflection of the increased hydrogen atom donating ability of the antioxidant plus the increased concentration of oxidizable lipid provided by DLPC.
通过脂质体转移，将羟基色满类酚类抗氧化剂α-生育酚（α-TOC）、2,2,5,6,7-五甲基-6-羟基色满（PMHC）以及受阻酚类2,3-二氢-5-羟基-2,2,4-三甲基萘并[1,2-b]呋喃（NFUR）、2,6-二叔丁基-4-甲氧基苯酚（DBHA）和2,6-二叔丁基-4-甲基苯酚（BHT）从二肉豆蔻酰磷脂酰胆碱（DMPC）的饱和供体脂质体递送至二亚油酰磷脂酰胆碱（DLPC）或1-棕榈酰-2-亚油酰磷脂酰胆碱（PLPC）的可氧化（受体）脂质体中。通过抑制吸氧法测定抗氧化活性k(inh)，并与抗氧化剂通过从有机溶剂中共蒸发引入脂质体时测定的k(inh)进行比较。使用热引发剂（水溶性偶氮双脒丙烷盐酸盐（ABAP）、脂溶性偶氮双-2,4-二甲基戊腈（ADVN）和二叔丁基亚硝酸盐（DBHN））或光引发剂二苯甲酮引发过氧化反应。抗氧化剂PMHC、NFUR、DBHA和BHT在脂质体之间快速转移，但转移α-TOC需要数小时的孵育。脂质体中的平均k(inh)值，相对顺序为NFUR≈DBHA＞PMHC＞BHT≈α-TOC，明显低于有机溶剂中的已知值。脂质体中的k(inh)值似乎受与水的氢键作用以及抗氧化剂受限扩散的影响，尤其是α-TOC的情况。对抑制耗氧过程中形成的氢过氧化物进行了产物研究。在PMHC抑制PLPC过氧化过程中形成的9-和13-氢过氧化物的顺式，反式/反式，反式（c,t/t,t）产物比率，对于共蒸发和脂质体转移过程来说是相似的。相同浓度的α-TOC的c,t/t,t比率为1.52，与抑制期开始时PMHC的1.69值相比。在DLPC中观察到NFUR的较高c,t/t,t比率，在抑制开始时为7.0，在诱导期中断后约为1.8，这反映了抗氧化剂供氢能力的增加以及DLPC提供的可氧化脂质浓度的增加。
