Jung K, Everson R J C, Joshi B, Bulsara P A, Upasani R, Clarke M J
Gematria Test Lab GmbH, Parkstraße 23, Berlin, D-13187, Germany.
Skin Health, GlaxoSmithKline Consumer Healthcare, 184 Liberty Corner Road, Warren, NJ, 07059, USA.
Int J Cosmet Sci. 2017 Apr;39(2):217-223. doi: 10.1111/ics.12367. Epub 2016 Oct 18.
The present work analysed the antioxidative activity of phenol-based antioxidants using an electron spin resonance method to predict the activity and stability of these antioxidants in cosmetic products.
The antioxidative power (AP) method was chosen to measure both the capacity and kinetics of an antioxidative reaction by detecting the DPPH (diphenylpicrylhydrazyl) radical. The antioxidative capacity (w ) relates to the amount of free radicals that can be reduced, whereas the antioxidative reactivity (t ) relates to the reaction speed and offers a fingerprinting of the redox state of the antioxidant molecules. Fifteen phenolic molecules have been analysed. They differed in the position of the hydroxyl groups and substituents on the aromatic ring. The AP of two distinct formulations containing hydroxytyrosol is presented as well as three phenol-based antioxidants within the same formulation vehicle.
The rate at which phenol (ArOH) reacts with DPPH radicals, defined by the term reactivity (t ) in this paper, was dependent upon the bond dissociation enthalpy (BDE) of the OH bond. Molecules having weak OH bonds and consequently low BDE values showed high antioxidant reactivity. On the other hand, the capacity factor (w ), which is the concentration of phenol required to reduce a fixed concentration of DPPH radical, depends on the number and position of hydroxyl groups. The results showed that ortho and para positions of the two hydroxyl groups are important for higher capacity. If one of the two hydroxyl groups is blocked by methylation, both the antioxidative capacity and reactivity are reduced, mainly for ortho disubstituted compounds. The presence of a vinylic side chain improved reactivity and capacity tremendously. AP values may be useful in formulation design when identifying antioxidants that are likely to be physically and chemically stable. The importance of optimization of the formulation vehicle itself for a given antioxidant is also illustrated.
Based on the presented findings, it is possible to predict the antioxidative performance of a phenol-based molecule and its stability and oxidation resistance within a cosmetic formulation. This is essential for antioxidant containing dermal formulations designed to combat skin ageing.
本研究采用电子自旋共振方法分析了酚类抗氧化剂的抗氧化活性，以预测这些抗氧化剂在化妆品中的活性和稳定性。
选择抗氧化能力（AP）法，通过检测二苯基苦味酰基自由基（DPPH）来测量抗氧化反应的能力和动力学。抗氧化能力（w）与可被还原的自由基数量有关，而抗氧化反应性（t）与反应速度有关，并提供了抗氧化剂分子氧化还原状态的指纹图谱。分析了15种酚类分子。它们在芳香环上羟基和取代基的位置不同。给出了两种含羟基酪醇的不同配方以及同一配方载体中的三种酚类抗氧化剂的AP值。
本文中由反应性（t）定义的苯酚（ArOH）与DPPH自由基反应的速率取决于OH键的键解离焓（BDE）。具有弱OH键且因此BDE值较低的分子表现出高抗氧化反应性。另一方面，容量因子（w），即还原固定浓度DPPH自由基所需的苯酚浓度，取决于羟基的数量和位置。结果表明，两个羟基的邻位和对位对于更高的容量很重要。如果两个羟基之一被甲基化阻断，则抗氧化能力和反应性都会降低，主要是对于邻位二取代化合物。乙烯基侧链的存在极大地提高了反应性和容量。当识别可能在物理和化学上稳定的抗氧化剂时，AP值可能有助于配方设计。还说明了针对给定抗氧化剂优化配方载体本身的重要性。
基于所呈现的研究结果，可以预测酚类分子的抗氧化性能及其在化妆品配方中的稳定性和抗氧化性。这对于旨在对抗皮肤衰老的含抗氧化剂的皮肤配方至关重要。
