Photostability assessment of sunscreens. Benzylidene camphor and dibenzoylmethane derivatives

A rapid method has been developed in order to compare the photostability of several sunscreen agents incorporated in the same type of emulsion. Thin films of the different preparations were spread on quartz plates and irradiated with a solar simulator. Differences in energy distribution according to wavelengths observed with solar simulator and sun radiation were taken into account. A kinetic study of absorption properties was carried out under solar simulator irradiation. A simple calculation gave the results which would be obtained under sunlight.
This technique differentiated the reversible transformations of photoisomerizable compounds from an irreversible disappearance which resulted in a significant loss of protective power.
Applied to benzylidene camphor derivatives, this technique showed the excellent photostability of these sunscreen agents.     

樟树籽仁油及长碳链食用油脂对大鼠血脂及动脉硬化的影响

为探讨樟树籽仁油与长碳链食用油脂对大鼠血脂及动脉硬化的影响。实验分为6组:4%樟树籽仁油+8%大豆油组（A-1）、8%樟树籽仁油+4%大豆油组（A-2）、12%樟树籽仁油组（B）、12%大豆油组（C）、12%猪油组（D）、空白对照组（E）。饲喂7w后,测定大鼠血清TC、TG、HDL-C、LDL-C、SOD、AST、ALT指标。结果表明,A-1、A-2各组大鼠血清中TC、TG含量极显著低于C、D组（p<0.01）,且与D组比较,AAI指数极显著升高（p<0.01）,AI指数显著降低（p<0.05）;B组在降低TC、TG方面与D组比较有极显著性差异（p<0.01）,在降低AI以及升高AAI、HDL-C方面与D组相比差异显著（p<0.05）,且HDL-C显著高于E组（p<0.05）。在ALT、AST指标上,A-1、A-2、B各组与E组无显著性差异（p>0.05）。长期食用樟树籽仁油特别是樟树籽仁油与大豆油的混合油脂对预防大鼠血脂的升高及动脉硬化的形成明显优于猪油组,也优于大豆油组。      

Pitfalls in the in vitro determination of sunscreen protection factors using broad band ultraviolet radiation detectors and solar simulating radiation

Reliable in vitro techniques for assessing sunscreen protection factors have relied upon obtaining the forward scattering transmission spectrum of the test compound applied to a suitable substrate such as mouse or human epidermis. A theoretical analysis of alternative techniques using broad-band ultraviolet radiation detectors in conjunction with a source of simulated sunlight shows that the method is likely to yield unreliable values of sun protection factors and the reasons for this are discussed.     

Substantivity of sunscreens—preparation and evaluation of some quaternary ammonium benzophenone derivatives

In continuation of previous studies on keratin-substantive sunscreens, two series of quaternary ammonium compounds, derived from 2,4-dihydroxy and from 4-hydroxybenzophenone and containing O-alkyl and N-alkyl chains of different length were prepared and submitted to substantivity tests on wool, to microbiological tests on two bacterial and two fungal species, and to tests for allergenicity/irritation on human skin. All compounds were rapidly adsorbed by wool in aqueous solution: as expected, the maximum amounts adsorbed at equilibrium (S_max), indicative of the skin substantivity, were greatest for the C12 N-alkyl derivatives, and showed a progressive decrease with increasing length of the N-alkyl substituent. No substantial substantivity differences were detected in four C12 quaternary derivatives, differing by the presence (or absence) of a 2-OH group in the benzophenone moiety and by the length of the O-alkyl ( n = 2 or 3) side chain. When tested for antimicrobial activity, however, only the 4-hydroxybenzophenone C12 quaternary derivatives showed an order of activity comparable with that of two reference compounds. The conditions leading to a maximal antibacterial activity in the present compounds appeared to be the absence of the 2-OH group, and a shorter O-alkyl side chain. None of the new quaternary derivatives showed skin-irritant properties. The results of this investigation, while confirming the peak substantivity of C12 quaternary derivatives, indicate the possibility of dissociating, in a quaternary ammonium sunscreen, the skin substantivity from other unwanted side-effects, and offer some guidelines for the development of safer agents of this type.     

Substantivity of sunscreens —in vitro evaluation of the transdermal permeation characteristics of some benzophenone derivatives

The in vitro permeation through excised hairless mouse skin of a series of 4-O-(N, N-dimethylaminoalkyl)-benzophenones, non-quaternarized and quaternarized, and of two commercial benzophenone sunscreens, taken as reference compounds, was investigated. The aim of the study was to verify the skin penetration of the highly skin-substantive quaternary ammonium derivatives, in comparison with their parent, non-quaternarized compounds. While the quaternary derivatives proved unable to permeate the skin during the period of observation (45 h), their parent amine hydrochlorides and the reference sunscreens (2-hydroxy-4-methoxy-benzophenone-5-sulphonic acid and 2,2'-dihydroxy-4,4'-dimethoxy-benzophenone 5,5'-sodium disulphonate), showed appreciable transdermal fluxes.
These data indicate that the presence of a quaternary ammonium group in a molecule, besides inducing a high affinity for cutaneous keratin, may result in hindered or reduced transdermal (and possibly systemic) absorption. Both features may contribute in improving the safety of a cosmetic sunscreen.     

Influence of irradiation time and solution concentration on the photochemical degradation of EDDHA/Fe3+: effect of its photodecomposition products on soybean growth

BACKGROUND: Ethylenediamine‐N, N′‐bis(2‐hydroxyphenylacetic acid (EDDHA) is one of the most efficient iron‐chelating agents employed to relieve iron chlorosis in plants. It has been well known for decades that this compound is photosensitive, but in spite of this fact its degradation pathways are virtually unknown. The aim of this work was to evaluate how the length of sunlight exposure and the concentration of irradiated EDDHA/Fe³⁺ solutions influence the photostability of the chelate at constant pH. Moreover, the possible toxic effect of the chelate photodegradation products, elsewhere proposed, on soybean growth has been tested. RESULTS: The photodecomposition of the chelate increased as the time of sunlight exposure increased, and resulted in a partial decomposition of the organic ligand. Moreover, EDDHA/Fe³⁺ photodecomposition was highly correlated with the concentration of solution exposed. Plants did not present differences in recovery from chlorosis among treatments with and without decomposition products. CONCLUSIONS: EDDHA/Fe³⁺ undergoes photodegradation, like other aminopolycarboxylic acids, being more degraded as solution concentration decreases and exposure time increases. The photodecomposition products salicylic acid, salicylaldehide and Salicylaldehyde ethylenediamine diimine tested did not have negative effects on soybean growth, at least in the short‐term hydroponic experimental design tested. Copyright © 2011 Society of Chemical Industry     

ESR Study of the Singlet Oxygen Quenching and Protective Activity of Trolox on the Photodecomposition of Riboflavin and Lumiflavin in Aqueous Buffer Solutions

ABSTRACT:  Singlet oxygen quenching activity of Trolox, a water-soluble derivative of tocopherol, was studied by electron spin resonance (ESR) spectroscopy in a buffer solution (pH 7.4) containing methylene blue (MB), 2,2,6,6-tetramethyl-4-piperidone (TMPD) after light illumination for 30 min. Trolox at the concentration of 125 μM quenched 89.1% singlet oxygen in the system. Trolox showed significantly higher singlet oxygen quenching activity than ascorbic acid in the buffer solution ( P  < 0.05). Riboflavin in phosphate buffer solutions was degraded very fast under fluorescent light illumination. The photodegradation rate of riboflavin at pH 8.5 was significantly higher than pHs 4.5 and 6.5 ( P  < 0.05). Lumiflavin was also degraded under the fluorescent light illumination, but its degradation rate was much lower than that of riboflavin under the same light intensity. Unlike riboflavin, the rate of lumiflavin photodegradation was the greatest at pH 4.5 and followed by pHs 6.5 and 8.5, in a decreasing order. Trolox greatly protected the photodegradation of riboflavin and lumiflavin. The protective activities of Trolox against the photodegradation of riboflavin and lumiflavin were also pH dependent. The treatments of 5 mM Trolox in the buffer solutions of pHs 8.5 and 6.5 exhibited 56.1% and 31.7% protection of riboflavin against degradation during 120 min light illumination, respectively. The treatments of Trolox at the concentrations of 1, 3, and 5 mM in the buffer of 6.5 exhibited 14.8%, 58.4%, and 81.4% protection of lumiflavin against degradation during 24 h light illumination, respectively.     

尕里巴小牛皱胃酶的制备及其部分性质的探讨

介绍了小牛皱胃酶的制备及其部分性质的探讨。采用超滤技术对粗制酶液进行浓缩、脱盐、去杂蛋白，还同时应用鼓风干燥和真空冷冻干燥两种方法制备出了小牛皱胃酶粉状制剂。实验结果表明，用此法制备的皱胃酶分子量是40800u，最适温度为39-47℃，最适pH值为5．8。超滤技术和真空冷冻干燥技术适用于小牛皱胃酶的制备。     

海篷子籽油制备共轭亚油酸及其组分分析

研究海篷子籽油中亚油酸转化制备共轭亚油酸的工艺条件。以海篷子籽油为原料,KOH为催化剂,乙二醇为溶剂,碱异构法转化共轭亚油酸。采用Box-Behnken试验设计,优选海篷子籽油共轭亚油酸的最佳制备技术条件。结果表明海篷子籽油是制备共轭亚油酸的良好原料,所得产品中共轭亚油酸质量分数达87%以上,共轭亚油酸两种活性异构体9c,11t-CLA和10t,12c-CLA质量分数达68%以上。用海篷子籽油制备共轭亚油酸最适条件为:反应温度在180℃,反应时间3.9 h,溶剂用量为油质量的2倍,催化剂用量为籽油质量的25%。本研究所优选的工艺条件可使籽油中亚油酸转化率高达94.6%,所制得的海篷子共轭亚油酸产品的各项理化指标接近食用油标准,工艺条件实际可行,制备的共轭亚油酸产品安全无毒,有望开发成一种高附加值的保健食用油。     

复合诱变选育细菌纤维素耐酸性高产菌株的研究

首先用紫外线对出发菌株的菌体进行诱变,然后再用硫酸二乙酯对突变株进行诱变,最后经筛选获得耐酸突变株。该突变株在pH值为3.1以下生长时,产纤维素水平为9.2 g/L,比突变株U31提高了12.2%,比出发菌株提高了31.43%。对突变株UE26进行传代和稳定性试验,结果表明该菌株具有遗传稳定性,适宜作为研究细菌纤维素的高产菌株。     

ESR study of hair and melanin–keratin mixtures – the effects of temperature and light

The ESR spectrum of hair presents a symmetrical absorption band with the same characteristics as pure melanin ( g = 2.0030; δ H = 5 G). Between 250°K and 490°K, the intensity of the signal increases as for pure melanin. This variation may be explained by a change in the moisture content of hair as function of the temperature. Below 250° K, in a frozen medium, melanin-water interactions remain constant and the number of radicals is no longer a function of temperature.
Under exposure to light of hair, melanin-derived radicals were formed. Stable and short-lived radicals were observed at λ > 345 nm; only unstable radicals were formed at λ > 450 nm. At shorter wavelengths (λ > 280 nm), a new asymmetric signal ( g = 2.0065 H = 20 G) appeared on UV exposure of black, grey or white hair; this signal was attributed to radicals formed in the direct excitation of keratin amino acids.
Le spectre RPE des cheveux     

Study of the drying behaviour in peeled and unpeeled whole figs

Aim of this study was to estimate the effect of peeling on drying kinetics and effective diffusivity D_eff of figs (Ficus carica L. var. tsapela) during air-drying. For this purpose three temperatures (45, 55 and 65 °C) were tested. The Logarithmic model was chosen to describe the drying curves among seven drying models. The estimated drying constants were associated with the drying temperature by an Arrhenius type equation. The ratio of peeled to unpeeled relaxation times was found to be 0.54 ± 0.16. The D_eff of figs (peeled and unpeeled) was estimated by the method of slopes. The D_eff of the peeled figs was higher than this of the unpeeled figs presenting smaller differences as drying temperature was increased. This behaviour was attributed to the case hardening effect which is faster developed as the drying rate increases during high temperature drying.     

紫甘薯色素的提取工艺及其稳定性研究

试验以95％乙醇为溶剂，研究了不同料液比、温度、pH值、时间对紫甘薯色素提取产率的影响，确定了紫甘薯色素提取的最佳工艺条件：料液比1：5、pH=4、温度60℃、时间lh，并对其色素的稳定性进行了研究。     

真鳕鱼骨明胶的提取工艺及性质研究

以真鳕鱼骨为原料对其明胶的提取工艺进行了研究。在单因素实验基础上,通过正交实验探讨HCl浓度、酸处理时间、提取温度和提取时间对鱼骨明胶得率的影响。结果表明:HCl浓度4%,酸处理时间18 h,提取温度70℃,提取时间8 h,明胶提取率最高,达98.02%。明胶在235 nm处有最大吸收。在上述提取条件下,得到的明胶经红外光谱检测失去三螺旋结构,在扫描电镜观察下明胶具有多孔的网状结构。     

全溶大豆蛋白对鸡胸肉蒸煮出品率的影响

研究鸡胸肉中添加全溶大豆蛋白(60%)来提高鸡胸肉的保水性.鸡胸肉中通过滚揉加入大豆蛋白和亲水胶体,蒸煮后测定失水情况.全溶大豆蛋白(60%)的效果明显,当添加量为7%的时候有最好蒸煮出品率102.01%.大豆蛋白在提高鸡胸肉的保水性有着积极的意义.     

Existing and potential applications of ultraviolet light in the food industry – a critical review

Short‐wave ultraviolet light (UVC, 254 nm) can reduce dramatically the microbial load in air or on hard surfaces free from food residues, and can eliminate pathogens from potable water filtered to remove organic residues and ‘clumps’ of bacteria. More recently, approval of the Food and Drug Administration (USA) has been sought for a system for the destruction of pathogenic bacteria in fruit juices using UVC, and the same approach could perhaps be applied to remove spoilage organisms from cider or wines. In contrast, long‐wave UV light (UVA, >320 nm) has limited microbiocidal properties, and for practical applications its effectiveness has to be enhanced by the presence of photosensitive compounds (eg furocoumarins) that will diffuse into a microbial cell prior to irradiation. The penetration of UVA into water is better than that of UVC, and its bacteriocidal action in the presence of photosensitisers can be rapid. However, pure furocoumarins are expensive and their addition to foodstuffs might be questioned on safety grounds. © 2000 Society of Chemical Industry