以奈米乳化包埋提升紫檀芪之生物可利用率

Abstract

紫檀芪（Pterostilbene）為芪類（stilbene）化合物的一種，是白藜蘆醇（resveratrol）的甲基化衍生物，主要存在於藍莓、杏仁、葡萄和越橘中，紫檀芪具有許多藥理功能，包含抗氧化、抗發炎、抗癌等等…。但由於其水溶性低，且本身容易被氧化而失去活性，故紫檀芪的生物可利用率不高。在本篇實驗中，是以奈米乳液系統包覆紫檀芪，希望可以有效提升其生物可利用率，並增加紫檀芪作為保健食品的利用。 本實驗所使用的乳液配方，是由水相、中鏈脂肪酸以及卵磷脂所組成的。卵磷脂（Lecithin）為一歷史悠久的天然乳化劑，經由本實驗的介電電位、粒徑、黏度以及包覆效率等測試，發現其中可以使用相對低量的乳化劑，以及高比例油相的組別為使用，油相和水相以1：1組成，整體含有1.5%卵磷脂的配方為最適合利用於本實驗的組合。在上述乳液配方中，加入含有整體10.4%的紫檀芪後，使用高壓均質機以500bar的壓力進行均質5個循環，比較粗乳液及不同組經均質的奈米乳液間的各種性質，發現以高壓均質機處理三次的組別，是相對穩定的組別。此組別在放置一個月的過程中，其包覆效率並不會有顯著的差異，且以介電電位判定奈米乳液的穩定性，也發現此組的介電電位的絕對值，在一個月的存放過程中不會出現顯著的差異，這代表此乳液配方相當穩定。 綜合上述的實驗結果，以水相、中鏈脂肪酸和卵磷脂所形成的奈米乳液，可以有效包覆紫檀芪，且是目前文獻中可以包覆最高量紫檀芪的配方，未來可以將此配方包覆其他生物活性物質，以提升相關物質的穩定性和生物可利用率。

Pterostilbene, a dimethylether analog of resveratrol, had been found to have strong antioxidative potential as well as ability to reduce tumorigenesis, chronic inflammation and diabetes development. However, the bioavailability of Pterostilbene in the biological system is limited due to its poor solubility in aqueous gastrointestinal environment. Moreover, the fact that pterostilbene is a strong antioxidant leads to extensive oxidation before and during digestion, which further decrease its chance of reaching the target site of action. In this work, nanoemulsiosn system were designed and prepared for this purpose. Lecithin-based nanoemulsion was formed after passing 5 cycles through high pressure homogenizer at 500 psi. The rheological properties and particle size were measured by dynamic light scattering and viscosmeter. The storage stability of prepared formulations were determined based on its ability to maintain its particle size and loading concentration, which is analyze using dynamic light scattering method and HPLC, respectively. According to the experimental results, the nanoemulsion system composed of 3% lecithin （w/w） could produce the the optimum nanoemulsion formulation that allow up to 20.8% loading of pterostilbene. Over the 1-month stability test, the particle size and loading concentration of the prepared emulsiosn system did not change significnalty indicating good storage stability regardless of the storage temperature. The positive effect of prepared nanoemulsion system on the bioavailability was studied and confirmed by in vitro lipolysis and Caco-2 monolayer model. That is, the future develop of functional food product using pterostilbene as main bioactive component could be realized using emulsion-based formulation.