Protection of photo-aged skin by nano/submicron yam peel

近來皮膚老化(skin-aging)議題備受矚目，除了內在因素，外在環境因素中以紫外線曝曬為最主要造成皮膚老化的外因之一，此種老化稱為光老化(photo-aging)。抗老化的方法很多，最常見的如攝取天然或機能性食品。山藥是目前常見的中國傳統重要食、藥用植物，為薯蕷科(Dioscoraceae)薯蕷屬(Dioscorea)多年生蔓生性的根莖類植物，營養價值高，且富含具生理活性之黏質、膽鹼、尿囊素、固醇類皂素(steroidal saponins)及植物固醇(phytosterol)等。一般山藥皮為不被食用之廢棄物，但卻含有比塊莖高量的薯蕷皂配基(diosgenin)，其為固醇類皂素去除醣基的部份，是合成部份固醇類荷爾蒙重要的前驅物質，結構類似雌激素E2 (17β-estradiol)，推測應具有類似E2的功能，可調節皮膚老化現象。利用介質研磨處理，發現可有效降低材料粒徑至1-100 nm，增加奈米/次微米微粒之比例。本實驗的研究目的是探討以介質研磨處理來提高山藥皮中diosgenin釋出量的可能性，並進一步探討奈米/次微米化山藥皮對皮膚經UVA照射所誘導的皮膚光老化現象之保護作用。結果顯示，山藥皮經介質研磨，與細碎組相比，可顯著降低粒徑大小，並可增加可溶性膳食纖維之含量。在diosgenin含量分析結果顯示，經介質研磨處理後之山藥樣品，diosgenin釋出量有顯著增加的趨勢，研磨組分別為原料與細碎組的2.5倍與1.75倍。型態分佈與穩定性分析中，顯示研磨組之粒子大小分佈較細碎組均一，且懸浮性也優於細碎組。此外，由細胞實驗結果顯示，山藥皮可降低皮膚纖維母細胞中經UVA照射產生之基質金屬蛋白酶(MMP-1)之表現量，增加膠原蛋白(collagen)之生成量，而研磨組效果優於細碎組。由此可知，山藥皮經介質研磨處理後，可有效降低粒徑，提昇diosgenin之釋出量，並具有較佳之皮膚抗光老化的保護作用。In recent years, skin aging is a popular issue. Skin aging is a complex biological process that is a consequence of both intrinsic and extrinsic aging. Extrinsic aging is caused by environmental factors such as exposure to ultraviolet rays (UV). Chronic exposure to UV irradiation is the major factor of causing premature skin aging (photo-aging). Today, there are many methods for anti-aging and the most common way is to eat food from nature or to consume functional food. Yam, consumed and regarded as medicinal food in traditional Chinese herbal medicine, is a seasonal food. Yam is perennial trailing rhizome plants of the Dioscorea species and they belong to Dioscoreaceae family. Yam possesses many nutrients and active compounds such us mucilage, choline, allantoin and steroidal saponins. Yam peel is not edible and is treated as waste. However, yam peel contains more diosgenin than yam tuber. Diosgenin extracted from many plants has been a valuable precursor for the synthesis of pharmaceutical steroids. Furthermore, some literatures show that it has similar structure to 17β-estradiol (E2) and speculate it might have the efficacy against skin aging. Media milling can reduce the particle size to 1-100 nm and increase the percentage of nano/submicron particle. Therefore, the objectives of this study are to investigate the diosgenin content through media milling and to investigate the protective efficacy of nano/submicron yam peel on skin photo-aging induced by UV- light. It also can increase the release of some nutrients and active compounds such as soluble dietary fiber and diosgenin. The content of diosgenin from media milled sample is 2.5 folds and 1.75 folds higher than untreated and blended samples. It also reveals that media milled sample possesses more suspensibility than blended sample. Then, in cell experiment, it indicates that yam peel can reduce the expression of MMP-1/TIMP-1 and increases the content of collagen in human skin fibroblasts, and the protective efficacy of media milled sample is better than blended sample. As a result, media milling can reduce the particle size of yam peel and increase the release of diosgenin from yam peel. It also has better protective efficacy of skin photo-aging induced by UVA-light than blended sample