以磷脂包覆紫檀芪提升穩定性及生物利用率

Abstract

紫檀芪具有多種藥理性質，包括抗氧化、抗衰老、抗癌與保護心血管等功效，然而紫檀芪的低水溶性與小腸中的低吸收效果，限制其在人體中的實際效用，因此需開發合適的紫檀芪遞送系統，以增強其水溶性、穩定性，從而提高口服生物利用率。磷脂複合物為一種以磷脂作為載體的藥物遞送系統，將活性化合物或植物提取物透過磷脂包覆，可以增強疏水性化合物的口服生物利用率。故本研究之目的是以磷脂醯膽鹼包覆紫檀芪，希望有效提升口服生物利用率；而磷脂複合物之評估可透過高速離心技術研究紫檀芪的包覆效率，也透過傅里葉轉換紅外光譜（Fourier-transform infrared spectroscopy, FTIR）、X光繞射儀（X-ray diffractometer, XRD）、差示掃描量熱儀（Differential scanning calorimetry, DSC）與掃描式電子顯微鏡（Scanning Electron Microscope, SEM）確認磷脂複合物結構之形成，而界面電位分析儀用以測定磷脂複合物之囊泡顆粒尺寸、多分散指數與界面電位，最後，Caco-2細胞滲透性試驗可模擬紫檀芪磷脂複合物之腸吸收效果。根據實驗結果，紫檀芪與磷脂醯膽鹼的比例為1：3時，紫檀芪磷脂複合物之包覆效率為92%，FTIR證實了紫檀芪與磷脂醯膽鹼之間有氫鍵之分子間作用力，因此增強了紫檀芪的穩定性，紫檀芪磷脂複合物於DSC熱分析發現紫檀芪之吸熱峰有消失的現象，以XRD與SEM分析紫檀芪磷脂複合物，皆顯示紫檀芪之結晶性有消失的現象，因此上述實驗均證實磷脂有成功包覆紫檀芪，另外，細胞毒性試驗顯示紫檀芪磷脂複合物與紫檀芪相比，有較強之生物活性，對Caco-2結腸癌細胞有較佳之抑制效果，以Caco-2滲透性試驗模擬小腸吸收之體外模型，證實紫檀芪磷脂複合物有較佳之腸通透性，可改善紫檀芪於人體小腸之吸收效果，提升其生物利用率，因此本研究結果可望擴展紫檀芪於健康食品與功能性食品中的適用性，亦可以作為具有類似化學性質的化合物欲開發口服配方的參考。

Pterostilbene possess several protective effects including anti-oxidant, anti-aging, anticancer, cardiovascular protection. However, the low aqueous solubility and poor intestinal absorption of pterostilbene limit its practical use in the biological system. Therefore, it is desirable to develop a suitable delivery system for pterostilbene to enhance its aqueous solubility, stability, bioaccessibility, and, thus, the oral bioavailability. In this sense, phospholipid complex, a lipid compatible molecular complex, could incorporate active compound or extract into its phospholipids backbone could be a suitable carrier system to enhance oral bioavailability of hydrophobic compound like pterostilbene. Here in this work, we would like to encapsulate pterostilbene into an optimized phospholipid complex system. Phospholipid complex was prepared by refluxing followed by solvent evaporation technique. Evaluation entrapment efficiency was evaluated by ultracentrifugation techniques. The formation of the phospholipid complex was assessed by Fourier transform-infrared (FTIR), differential scanning calorimetry (DSC), X-ray diffraction (XRD) and scanning electron microscope (SEM). Vesicle size, polydispersity index, and zeta potential were determined by dynamic light scattering (DLS) and electrophoretic light scattering (ELS). Finally, the intestinal absorption of pterostilbene phospholipid complex was simulated using the Caco-2 cell permeability assay. According to the experimental results, the 1:3 ratio of pterostilbene to phosphatidylcholine would be the optimum formulation giving 92% encapsulation efficiency. FTIR spectra showed some peaks that validated the presence of chemical interactions between pterostilbene and phosphatidylcholine and, thus, enhanced the stability of pterostilbene. The formation of the pterostilbene phospholipid complex was also determined by XRD, DSC and SEM analysis. Moreover, the anti-cancer effects on human colon cancer cells demonstrated that the pterostilbene phospholipid complex enhanced the cytotoxic activity of the pterostilbene alone. The positive effect of prepared phospholipid complex system on the bioavailability of pterostilbene was studied and confirmed by Caco-2 monolayer models. Thus, the result from this work could not only extend the applicability of pterostilbene in the health and functional foods, but also serve as reference for development of oral formulation for compound with similar chemical properties.