Departamento de Tecnologia Farmacêutica, Faculdade de Farmácia da Universidade do Porto, Rua Aníbal Cunha 164, 4099-030 Porto, Portugal.
AAPS PharmSciTech. 2010 Mar;11(1):120-5. doi: 10.1208/s12249-009-9360-9. Epub 2010 Jan 12.
A growing body of evidence suggests that free radicals are generated by UV irradiation being responsible for skin injury. In this regard, the topical use of formulations composed of plant extracts with antioxidant activity could represent a useful strategy for the prevention of photoaging and oxidative-stress-mediated diseases. The aim of this study was to assess the reproducibility of the extraction method and the functional stability of a Castanea sativa leaf extract in view of its application as topical antioxidant. Measurements of 1,1-diphenyl-2-picryl hydrazyl (DPPH) scavenging activity, total phenols (measured by the Folin Ciocalteu assay) and phenolic composition (high-performance liquid chromatography unit coupled to a UV detector) were carried out on three different batches. The influence of pH and temperature on the extract's DPPH scavenging activity was assessed in aqueous and glyceric solutions (0.025% w/v) over a 3-month period. Minor differences were found between the three extract batches for all the evaluated parameters, and therefore the reproducibility of the extraction method can be inferred. pH presented a great influence in the extract functional stability. Major antioxidant activity decrease was found at pH 7.1, while lower changes were observed at pH 5. Glyceric solutions were stable throughout the test period. At 40 degrees C and pH 5, a marked decrease of activity was observed. Again, glyceric solutions were the most stable, even at 40 degrees C. Proper selection of pH and solvent is mandatory to ensure the stability of the studied extract after being incorporated in semisolid forms. In view of these results, glycerine is proposed as the best vehicle for topical formulations incorporating C. sativa leaf extract, which should have a pH around 5.
越来越多的证据表明，自由基是由紫外线照射产生的，负责皮肤损伤。在这方面，含有抗氧化活性的植物提取物的局部制剂的使用可能代表了预防光老化和氧化应激介导的疾病的一种有用策略。本研究的目的是评估栗树叶提取物的提取方法的重现性及其功能稳定性，以期将其作为局部抗氧化剂应用。通过 1,1-二苯基-2-苦基肼（DPPH）清除活性、总酚（Folin Ciocalteu 法测定）和酚类组成（高效液相色谱单元与紫外检测器耦合）对三个不同批次进行测量。在 3 个月的时间内，在水和甘油溶液（0.025%w/v）中评估了 pH 和温度对提取物 DPPH 清除活性的影响。在所评估的参数中，三个提取物批次之间的差异很小，因此可以推断出提取方法的重现性。pH 对提取物的功能稳定性有很大的影响。在 pH 7.1 时，发现主要抗氧化活性下降，而在 pH 5 时，观察到的变化较小。甘油溶液在整个测试期间均稳定。在 40°C 和 pH 5 时，观察到活性明显下降。同样，甘油溶液是最稳定的，即使在 40°C 时也是如此。在将提取物掺入半固体形式后，为确保其稳定性，必须正确选择 pH 和溶剂。鉴于这些结果，建议甘油是含有栗树叶提取物的局部制剂的最佳载体，其 pH 值应在 5 左右。
