| Abstract: | 本研究將番石榴葉以快速且低耗能的超音波輔助0、25、50 及75%乙醇進行萃取，分別以GLE0、GLE25、GLE50 及GLE75 表示。首先比較各萃取物的抗氧化性及抑制醣解酵素之作用。結果顯示，四種萃取物的總類黃酮含量 (Total flavonoid content, TFC) 以GLE50 最高，可達35.1 mg quercetin equivalent/g extract，而總酚含量 (Total phenolic content, TPC) 以GLE25 最高，可達254.3 mg gallic acid equivalent/g extract，但GLE25 及GLE50 兩者之間的TFC 及TPC均無顯著差異 (p < 0.01)。清除自由基能力以Trolox equivalent (TE)表示，TE 越高其總抗氧化能力 (TE antioxidant capacity, TEAC) 越高，其中以GLE25 效果最佳，可達59.1 μg TE/mL，其次為GLE50 的49.2 μg TE/mL。至於還原力也是以GLE25 最高，可達113.1μg AAE/mL，其次為GLE50 的110.5 μg ascorbic acid equivalent/mL。至於抑制α-glucosidase 及α-amylase 的結果指出GLE25 及GLE50均具有最高的抑制作用。綜合以上結果，GLE25 被篩選作為後續C2C12 細胞調節血中葡萄糖之機制探討。依據細胞毒性試驗結果顯示，小於300 μg/mL 的GLE25 對C2C12 細胞不具毒性，最後探討200 μg/mL GLE25 對棕櫚酸誘導胰島素阻抗C2C12 細胞中葡萄糖調節的影響，結果指出GLE25 於胰島素傳遞路徑中可活化IRS1/PI3K/Akt，增加葡萄糖的攝入作用，且亦能活化AMPdependent/actived protein kinase (AMPK) 抑制Acetyl-CoA carboxylase (ACC) 進而促進游離脂肪酸的氧化，釋放大量的能量提供細胞使用，降低脂肪酸的儲存，進而能改善游離脂肪酸誘導的胰島素阻抗情形。
Gjuava leaves extracts (GLE) were prepared by ultrasound-assisted extractionwith 0, 25, 50, and 75% ethanol and denoted as GLE0, GLE25, GLE50 and GLE75,respectively. At first, antioxidant activity and glycolytic activity inhibition of the extracts were compared. The results showed that GLE50 had the highest total flavonoid content (TFC) up to 35.1 mg QE/g extract among four extracts, where as GLE25 had the highest total phenolic content (TPC) up to 254.3 mg GAE /g extract. However there were no significant difference in the TFC and TPC between GLE25 and GLE50 (p > 0.01). The free radical scavenging capacity was expressed as trolox equivalent (TE).TE is proportional to total antioxidant capacity (TEAC). GLE25 showed the hightest TEAC, reaching 59.1 μg TE/mL, followed by GLE50 with 49.2 μg TE/mL. GLE25 also had the highest reducing power reaching 113.1 μg ascorbic acid equivalent/mL, followed by GLE50 with 110.5 μg AAE/mL. Furthermore, GLE25 and GLE50 also showed the highest inhibitory effect of α-glucosidase and α- amylase. According to the above resules, GLE25 was selected to study regulation mechanism of blood glucose in C2C12 cells. Based on cytotoxicity test, GLE25 less than 300 μg/mL was no toxicity to C2C12 cells. Finally, the effect of 200 μg/mL GLE25 on glucose regulation in palmitate-induced insulin resistance C2C12 cells was investigated. The results indicated that GLE25 could activate the increase of IRS1/PI3K/Akt resuled in glucose uptake in the insulin delivery pathway. GLE25 also activated AMPK to inhibit ACC, thereby promoting the oxidation of free fatty acids, releasing a large amount of energy to provide cells for use, reducing the storage of fatty acids, and improving the insulin resistance induced by free fatty acids. |
