Activity of antioxidants in solution and in irradiated heterogeneous system

The efficiency of some common antioxidants, α-tocopherol, butylated hydroxyanisole (BHA) and butylated hydroxytoluene (BHT), was studied relative to β-carotene in a homogeneous solution and in a model system of an irradiated solid food. Relative reactivities in homogeneous solution covered a range of three orders of magnitude, α-tocopherol being the best and BHT the poorest antioxidant of the three. In irradiated systems consisting of oleic acid coated on a solid support (egg white), the range of reactivities was much narrower within one order of magnitude. In solution, there was a parallelism of the relative reactivities with oxidizing alkoxyl radicals derived from oleic acid hydroperoxides andtert-butyl hydroperoxide. On the solid support the relative reactivities of α-tocopherol and BHA with oleic acid radiation-induced oxidizing radicals were reversed, BHA appearing the best. Efficient antioxidants do not retain their great antioxidant activity in comparison with the moderate ones on transition from a homogeneous solution to a heterogeneous system. Relative efficiencies of antioxidants do not critically depend on the nature of oxidizing radicals in heterogeneous media.     

疲劳对腰部稳定肌前馈控制的影响

目的采用经典落球试验研究范式和sEMG信号分析方法,研究急性运动性腰部肌肉疲劳和主观心理预期对腰部多裂肌前馈控制的影响。方法选取10名18～26岁健康男性被试,采用双因素(预期因素2×疲劳因素2)实验设计,分别于"间歇性腰部肌肉等长疲劳负荷试验"前后完成落球试验,采集被试肱二头肌和L5～S1腰部多裂肌sEMG信号,计算sEMG信号距离落球刺激的起始时间和平均反应强度,观察急性腰部肌肉疲劳和主观心理预期对被检肌肉快速反应时间和反应强度的影响。结果本研究所采用的疲劳负荷试验造成被试腰部多裂肌MPF平均下降18%;主观心理预期能够明显加快腰部多裂肌快速反应时间;疲劳具有加快腰部多裂肌快速反应时间的趋势,但无明显统计学意义;主观心理预期能够明显降低腰部多裂肌反应强度,而疲劳对腰部多裂肌快速反应强度均无明显影响。结论主观心理预期能够明显加快腰部多裂肌的快速反应时间,从而为腰部稳定性提供代偿性保护;急性运动性肌肉疲劳不能改变腰部多裂肌的快速反应时间和快速反应强度,证明中枢神经系统对腰椎稳定肌活动的前馈控制具有较好的稳定性。     

BHT与TBHQ对煎炸油稳定效果的比较研究

BHT和TBHQ是最为常用的煎炸油抗氧化剂。通过实验对比BHT和TBHQ对煎炸油及煎炸后食品中油的稳定效果,结果表明在抑制过氧化值方面,TBHQ的效果要明显优于BHT,但在酸值方面,二者都有不同程度的促进作用。     

气质联用法测定EVA材料中BHT含量的测量不确定度

介绍了气相色谱-质谱联用法测定EVA材料中2,6-二叔丁基-4-甲苯酚(BHT)测量不确定度的评定方法。对测量不确定度的来源进行了分析,建立了各不确定度分量的数学模型,并对各不确定度分量进行了量化。当EVA材料中BHT含量为2.85mg/kg时,其扩展不确定度为0.88mg/kg(k=2)。     

PG、TBHQ、BHA和BHT4种常见抗氧化剂部分稳定性的研究

研究PG、TBHQ、BHA和BHT 4种常见抗氧化剂在不同溶荆、酸碱中稳定性为检测工作者及科研工作者在试验过程中储存或者提取时提供参考依据。采用高效液相色谱法(HPLc),以4种抗氧化剂的保留率为指标,考察4种抗氧化剂的稳定性。从试验结果来看:PG、TBHQ、BHA和BHT在甲醇以及酸性条件下具有较好的稳定性。     

Mycoflora and ochratoxin a control in wheat grain using natural extracts obtained from wine industry by-products

The aim of this study was to evaluate the effect of some natural extracts obtained from grape pomace (GPE) and grape seeds (GSE) as compared to a synthetic food, antioxidant-butylated hydroxytoluene (BHT), in order to control fungal population and ochratoxin A (OTA) production in naturally contaminated wheat. The results showed that the addition of these extracts was efficient with OTA content decreasing. On treatment with these extracts the loss of OTA content after 14 days was in the range 7.8-28.3% relative to the control sample, but increased up to 26.48-37% after 28 days. The highest loss in OTA content was recorded for treatment with GPE at the 500 ppm level. Regarding the fungal development, the obtained results show that the total fungal populations were significantly reduced by using natural extracts. The most efficient extract was GPE. Both BHT and GPE inhibit the growth of Penicillium verrrucosum, for all doses, but less with Aspergillus genera. GPE affects the growth of other types of moulds such as Rhizopus microsporus, Fusarium graminearum, Alternaria infectoria and Cladosporium herbarum. Our data suggested that GPE and GSE are able to provide fungicidal and fungistatic protection and to control the OTA accumulation in wheat, at least in a similar manner to BHT.     

2,6‐Di‐Tert‐Butyl‐Hydroxytoluene and Its Metabolites in Foods

2,6‐Di‐tert‐butyl‐hydroxytoluene (BHT, E‐321) is a synthetic phenolic antioxidant which has been widely used as an additive in the food, cosmetic, and plastic industries for the last 70 y. Although it is considered safe for human health at authorized levels, its ubiquitous presence and the controversial toxicological data reported are of great concern for consumers. In recent years, special attention has been paid to these 14 metabolites or degradation products: BHT‐CH₂OH, BHT‐CHO, BHT‐COOH, BHT‐Q, BHT‐QM, DBP, BHT‐OH, BHT‐OOH, TBP, BHQ, BHT‐OH(t), BHT‐OH(t)QM, 2‐BHT, and 2‐BHT‐QM. These derived compounds could pose a human health risk from a food safety point of view, but they have been little studied. In this context, this review deals with the occurrence, origin, and fate of BHT in foodstuffs, its biotransformation into metabolites, their toxicological implications, their antioxidant and prooxidant properties, the analytical determination of metabolites in foods, and human dietary exposure. Moreover, noncontrolled additional sources of exposure to BHT and its metabolites are highlighted. These include their carryover from feed to fish, poultry and eggs, their presence in smoke flavorings, their migration from plastic pipelines and packaging to water and food, and their presence in natural environments, from which they can reach the food chain.     

Rhus verniciflua Stokes flavonoid extracts have anti-oxidant,anti-microbial and α-glucosidase inhibitory effect

We isolated four compounds, fustin, gallic acid, 3′,4′,7-trihydroxyflavone, and fisetin from Rhus verniciflua. These compounds showed electron donation ability (87–94%) that was stronger than butylated hydroxyanisole (52%). Gallic acid (OD₇₀₀ = 1.98) showed the highest reducing power, and the other isolated compounds (OD₇₀₀ = 0.66–1.31) showed stronger activity than α-tocopherol (OD₇₀₀ = 0.21). The ethyl-acetate fraction had the highest phenolic content (723 mg GAE/g), followed by the 80% ethanolic extract (597 mg GAE/g). For Gram-negative bacteria, fisetin had the most potent anti-bacterial activity (MIC = 8 μg/ml) against Escherichia coli. 3′,4′,7-Trihydroxyflavone (106%), the 80% ethanolic extract (101%), and ethyl-acetate (98%) had the most powerful α-glucosidase inhibitory effect at 50 μg/ml. R. verniciflua extracts have potential as functional food additives.     

Direct Spectroscopic Observation of Singlet Oxygen Quenching and Kinetic Studies of Physical and Chemical Singlet Oxygen Quenching Rate Constants of Synthetic Antioxidants (BHA,BHT, and TBHQ) in Methanol

Abstract: Singlet oxygen quenching by synthetic antioxidants (BHA, BHT, and TBHQ) was directly observed by spectroscopic monitoring of luminescence at 1268 nm. The luminescence data showed unambiguous evidence of singlet oxygen quenching by synthetic phenolic antioxidants with the highest activity for TBHQ, followed by BHA and BHT. The protective activities of these synthetic antioxidants on α-terpinene oxidation with chemically-induced singlet oxygen under dark further confirmed their singlet oxygen quenching abilities. Total singlet oxygen quenching rate constants (k_r + k_q) of BHA, BHT, and TBHQ were determined in a system containing α-terpinene (as a singlet oxygen trap) and methylene blue (as a sensitizer) during light irradiation, and the values were 5.14 × 10⁷, 3.41 × 10⁶, and 1.99 × 10⁸ M⁻¹s⁻¹, respectively. After the k_r value of α-terpinene was first determined, the k_r values of the synthetic antioxidants were calculated by measuring their relative reaction rates with singlet oxygen to that of α-terpinene under the identical conditions. The k_r values of the BHA, BHT, and TBHQ were 3.90 × 10⁵, 1.23 × 10⁵, and 2.93 × 10⁶, M⁻¹s⁻¹. The percent partition of chemical quenching over total singlet oxygen quenching (k_r × 100)/(k_r + k_q) for BHA, BHT, and TBHQ were 0.76%, 3.61%, and 1.47%, respectively. The results showed that the synthetic antioxidants quench singlet oxygen almost exclusively through the mechanism of physical quenching. This represents the first report on the singlet oxygen quenching mechanism of these synthetic antioxidants. Practical Application: The synthetic antioxidants, especially TBHQ, have been found to have a strong singlet oxygen quenching ability. This article also clearly showed that singlet oxygen quenching by synthetic antioxidants was mainly by the physical quenching mechanism. The results suggested that these synthetic antioxidants, especially TBHQ, could be used practically for the protection of the food components such as edible oils and vitamins against singlet oxygen induced oxidations without significant losses of antioxidant activity during storage under light.