Introduction

Resveratrol (3,5,4’-trihydroxystibene) is a bioactive polyphenol found in grapes and other plants. Many recent studies reported that resveratrol performs multi biological and pharmacological functionalities, which include but are not limited to anti-oxidation, anti-aging and antiinflammatory, etc. These multi functionalities give it a bright future in the cosmetic field. [1-4]

Although Resveratrol offers numerous benefits to many aspects of human health in, the low solubility (about 0.003 wt% at 25 ºC) in water, as well as in most oils, photoinduced instability and high reactivity with other chemicals limit its application, particularly in cosmetics. [5] To date,many efforts have been made to improve its performance by using liposome encapsulation or by cyclodextrin coating method. However, most approaches are still in the early stages of research. [6,7] There was no better approach to enhance its photo-induced instability in cosmetic application except using opaque packaging or adding UV filters in the formulation.

In this work, a new microcapsule system was developed by using the optimal combination of nonionic surfactants to enhance solubilization of resveratrol and protective actives to reduce its reactivity with other chemicals and degradation under UV exposure in the formulation. It was found that the solubility and stability of resveratrol was significantly improved.

Materials and experimental methods

Resveratrol was kindly provided by Symrise. All other components used were of analytical grade and used as received. Double-distilled water was used throughout.

2.3.2 第2轮专家咨询结果。3名专家对1级、2级指标未提出异议。在3级指标中，1名专家提出胎儿情况中胎心异常，羊水有污染与无污染的处理方式不同，建议增加“胎心异常、羊水无污染”;2名专家提出“腹压的使用”和“宫缩强度”中共6项3级指标表述不清，存在歧义。通过课题组的讨论，增加“胎心异常、羊水无污染”，修改6项存在歧义的3级指标，分别为“在助产士指令下，不能有效地使用腹压”、“在助产士指令下，较好地使用腹压”、“在助产士指令下，有效地使用腹压”、“过弱”、“过强”和“适中”。

Resveratrol solubility determination in different solvents

The sample was stored in the dark at different temperature (4 ºC, 25 ºC, 40 ºC and 48 ºC) for one month.The resveratrol concentration was measured by HPLC and the color of the samples was recorded by digital photo.

Table 1. Resveratrol dissolved state in different solvents

Note: O means dissolved state;X means crystallization

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Optimization design for resveratrol solubilizing experiment

Optimal experiments were designed to select the solvents and surfactant composition and analyze the effect of preparation parameters on the improvement of solubility and stability. First, the solubilizing solvent and resveratrol were mixed together, then certain surfactant where added with different concentrations in the system.The mixtures were magnetically stirred for 2 hours, and water was added to the system to suspend the micelles.The samples were stored in darkness at 25 ºC for further investigation.

The stability test for the solubilizing system

At 25 ºC, a certain concentration of resveratrol indifferent solvents were prepared, mixed sufficiently, and allowed to equilibrate in the dark for one week. An optical microscope was used to detect if any crystal precipitated out of solution to determine Resveratrol solubility.

Protective agent selection to improve resveratrol light stability

As known, the chain length of PEG groups decides the HLB value of surfactants (hydrogenated castor oil)directly. An increase in the chain length of the PEG portion of the surfactant generally results in increased solubilization capacity for resveratrol in the interior of the micelle in aqueous media. The appearance of the solutions for resveratrol in different chain lengths of PEG hydrogenated castor oil changes from opaque to transparent as shown in Figure 2. With PEG length increasing, resveratrol solubility shows a trend of rising first and then down listed in Table 3.

不文明现象总让媒体揪着批，恐怕没完没了，时间长了，会给大众带来“审丑疲劳”。其实，一次法律行动胜过一万次舆论谴责，相关执法者、管理者，应走在媒体前面，该出手时就出手，积极捍卫法律规则，弥平社会争议。以高铁霸座问题为例，每次舆论曝光之后，相关部门都会在舆论压力下追加执法，给予霸座者治安处罚，以及列入黑名单等。而如果每一次高铁霸座都逃不过第一时间的处罚，恐怕霸座者也不至于这么嚣张，权益受侵害的乘客也不至于如此无助，人们更不至于要一次次呼吁执法部门的介入。

Results and discussion

Resveratrol solubility determination in different solvents

The solubilizing agent played an important role in resveratrol microcapsule systems. Although resveratrol can solubilize in PEG-40 Hydrogenated castor oil instantly, one week later the resveratrol crystalized from the sample. If polyols, such as glycerin and butylene glycol, worked as the solubilizing solvent, the resveratrol crystalized from the PEG-40 hydrogenated castor oil solution instantly. But if the solubilizing solvent with the PEG group was used, the resveratrol solubilized in the systems very well and the systems were stable for more than one week.

From the resveratrol solubility experiment, alcohol and the ingredients containing PEG group are good solvents for resveratrol, and we speculate that the solubilizer-solvent interaction(s) through the hydrogen bond which the hydrogen atom of the OH group in resveratrol can associate with -O- groups in PEG groups, which could be the driving force to solubilize the resveratrol around the solvent structure as shown in Figure 1. In addition, PEG-8 and PEG-12 also were known as excellent moisturizers in cosmetic application,alcohol could be used as a coolant and solvent but it has the potential risk to make human skin sensitive or irritated.

From the solubilization features and mechanism, the solubilizing system was optimized and works as below. When the surfactant containing PEG group worked as the solubilizing system, the PEG chain organized toward the outside of the micelles where resveratrol associated with the PEG chain and makes the solubilization possible. With PEG-8 or EPG-12 as the solubilizing solvent, they make the higher concentration of PEG chain on the surface of the micelles, so the difference of concentration can be driving force to solubilize the resveratrol at the sites around the micelle surface and anchor them tightly. When the PEG chain length is short, the HLB value of surfactant is low, which leads to a bigger micelle, so that the solubilization system was not transparent. When PEG chain became longer, the HLB value of the surfactant became higher, the smaller micelle can be formed to obtain transparent resveratrol solution. Thus the higher the PEG chain number,the higher the density of PEG for resveratrol dissolution.Once the PEG chain number is longer than 60, the resveratrol solubility decreased. The possible reason is that longer PEG chain made the micelle solid, the flexibility of micelle decreases,which make less space for resveratrol solubilization. The schematic of solubilization system is shown as Figure 3.

跨境电商师资培训还应该注重培训内容的层次性和递进性，做到投其所好而非一锅烩。对于没有跨境电商授课经验和培训经历的参训教师，培训单位和基地应该提供基础性的培训课程，通过讲练结合的方式教会教师如何操作和运用速卖通、阿里国际、敦煌网和Ebay等常用电商平台进行线上和线下交易。对于已经对跨境电商有初步了解并能够操作电商平台的受训教师，培训的重点应倾向于教学研究方面，比如重点讲授跨境电商的教材开发，课程设置，人才培养方案制定，微课和慕课的制作等。分层次的和递进性的培训既能够解决他们当下知识储备不够，实践技能缺乏的急迫问题又能满足他们对跨境电商开展深入研究，进一步提升教学科研能力和水平的未来需求。

Figure 1. The mechanism of PEG group dissolving resveratrol

Optimization design for Resveratrol solubilizing experiment

Based on the knowledge obtained from the solubility experiments, at the 5.0% concentration of solubilizing agents, nonionic surfactants with polyglycerol ester,glycolipid, PEG group at the concentration of 1.0%were screened to build microcapsule systems to further enhance resveratrol solubility. The results in Table 2 show that the polyglycerol ester surfactant and glycolipid surfactant do not solubilize the resveratrol, no matter what the hydrophobic groups; however, the surfactant with the PEG group can solubilize resveratrol dramatically.

孤岛采油厂加强“班组舆情疏导员”的培训和管理，不断提升他们的心理学应用、人际沟通技巧、形势政策解读等综合素质能力，确保他们能够找准切入点，把握着力点，抓好落脚点，确保自我教育法的作用得到有效发挥。

Eight representative solvents were selected for study based on the physical-chemical properties of resveratrol and the results listed in Table 1. The outcome indicated that resveratrol has low solubility in polyols including glycerin and butylene glycol, and limited solubility in propylene glycol, propanediol and pentylene glycol. It has good solubility in the ingredients containing the PEG group,such as PEG-8 and PEG-12. More than 15% resveratrol can dissolve in PEG-8 and PEG-12 at room temperature as shown in Table 1.

A certain protective agent with different concentrations was added to the resveratrol solubilizing system and mixed well. The stability test under UV beams and at different temperatures (4 ºC, 25 ºC, 40 ºC and 48 ºC) were carried out to select the suitable protective agent to enhance resveratrol’s light stability. The resveratrol concentration was monitored by HPLC, and the color was recorded by digital photo and colorimeter.

Figure 2. Photos for the Resveratrol/ Hydrogenated castor oil system with different PEG length from left to right, PEG-20, PEG-40, PEG-60, PEG-80 and PEG-100 respectively

Table 2. Resveratrol solubilizing experiments with different surfactant and solubilizing agents

Note: O means dissolved state;X means crystallization

Polysorbate 20 PEG-8 O O

Table 3. Resveratrol solubilization with different chain length of PEG hydrogenated castor oil at the concentration of 1.0%

Resveratrol/% 0.60 1.20 1.70 1.50 0.90

目标是否能够成功实现，取决于主体行动的过程，努力的态度预示着最后成功的可能性。所以，在实现目标的过程中，态度是目标成功的动力，决定了最终的效果。目标实现的动力，主要源自三个因素：主体、主动和主要。

Figure 3. The mechanism schematic of the Resveratrol solubilization

The stability test for the solubilizing system

Figure 4 is the HPLC results that showed the resveratrol concentration under different stability conditions. The optimized solubilization system was very stable for resveratrol for 4 weeks, no matter whether stored at high temperature or low temperature. Formulated with this system, 1.70% stable resveratrol solution was achieved, the solubility of resveratrol increases over 550 times compared with that in water.

Figure 4. Resveratrol concentration in the stability test

The color of the resveratrol system didn’t change during the stability test, no matter at high temperature or low temperature, which showed that resveratrol was stable in this system as well (Figure 5). Testing results further supported the assumption that resveratrol was locked at the PEG group of the micelle tightly to achieve the target of solubilization and stability enhancement with the microcapsules system.

Figure 5. The appearance of microcapsules system after different temperature of stability test

Protective agent selection to improve resveratrol light stability

As for solubilizing system, the micelle aggregation structure didn’t prevent degradation by UV light. Four common water-soluble protective agents were tested to study their effects on the improvement of resveratrol light stability. Table 4 shows the results of resveratrol concentration change with and without a protective agent at 0.5%. The resveratrol concentration dramatically dropped to 40% after 24 hours UV exposure. With ascorbic acid and niacinamide as protective agents, the resveratrol concentration also dropped significantly, which meant that ascorbic acid and niacinamide didn’t protect the resveratrol from UV exposure very well. In sharp contrast, with grape extract or disodium phenyl dibenzimidazole tetrasulfonate(DPDT), the resveratrol concentration remained more than 90% after 24 hours UV exposure. These two ingredients improved the resveratrol photo stability significantly.

Table 4. Resveratrol content change with different protective agents after 24 hrs UV exposure

Resveratrol/% 40.4 90.1 41.2 45.0 91.6

Table 5. The colorimetry changed with different protective agents before or after UV exposure

Sample Before UV exposure After UV exposure ΔL Δa Δb L a b L a b No protective agent 57.8 0.6 0.4 57.2 0.5 3.2 -0.6 -0.1 2.8 Grape extract 57.5 -1.1 5.6 57.3 -1.0 5.6 -0.2 0.1 0 Ascorbic acid 57.9 0.5 0.5 57.8 -0.8 4.2 -0.1 -1.3 3.7 Niacinamide 57.9 0.5 0.7 57.0 0.6 3.1 -0.9 0.1 2.4 DPDT 54.1 1.8 2.8 53.7 1.6 5.1 -0.4 -0.2 2.3

Furthermore, the colorimetry (L★a★b) data presented in Table 5, except for Jahwa patented technology, b value increased for all others as protective agents after UV exposure, which indicated the color of samples becomes yellow. Visible color changes of the samples before and after UV exposure showed in Figure 6, which proved the same color change direction.With DPDT, after UV exposure, the sample color changes to dark yellow eventually. Only if the system was protected by grape extract, the L,a,b value remained unchanged.

UV light can break down the structure of resveratrol significantly, [8] which made the sample change color. The DPDT is a well-known UV filter by absorbing 320 ～ 360 nm UV rays to protect the resveratrol photo stability. But the color of the sample still changes to dark yellow (Figure 6) which might be explained by the alkaline environment caused by adding DPDT accelerating the resveratrol degradation. Further studies will be conducted to prove the hypothesis, but right now, grape extract is a better choice to protect the resveratrol solubilizing system.

Figure 6. The color changed with different protective agents before and after UV exposure (1) No protective agent (2)Grape extract (3) Ascorbic acid (4) Niacinamide (5) DPDT

Conclusions

It can be concluded that by using the newly designed microcapsule the resveratrol solubility is dramatically increased to about 550 times higher than it is in pure water.This finding enables the resveratrol to deliver the required bio efficacy in cosmetic applications. Furthermore, the protective active has showed significant enhancement of resveratrol stability, which makes resveratrol applications more feasible.

各小组完成一部分项目后要以PPT形式进行展示汇报，各小组成员以不同任务分工的形式分别阐述本小组的主题思想、设计理念等。同时其他小组要对汇报小组的设计进行点评，该点评计入学生平时成绩中。这种教学方法有效锻炼了学生的语言表达能力、有效沟通能力和思考问题分析问题的能力，同时又能有效避免“一个小组在汇报、其他小组在睡觉”的尴尬现象出现。另外，由于班级规模较小，所分小组较少，教师能够在有效的常规教学时间内采用该教学方法完成教学任务，避免出现“持久战”的情况。

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