檸檬(Citrus limon L. Burm. f.) 為世界上最重要的經濟作物之一。台灣檸檬年產量約為4.5萬噸，而屏東為主要產地，約佔全台總量75%。檸檬外果皮為生產檸檬精油最重要的原料之一，而生產精油後之外果皮多棄之不用，少有文獻探討廢棄檸檬外果皮經再次萃取後是否仍保有檸檬外果皮中的活性成分。因此本研究探討酵素水解及高壓加工對檸檬外果皮精油殘留物對碳水化合物水解酶抑制能力 (α-澱粉酶 及α-葡萄糖苷酶) 、抗氧化成分(總酚、總類黃酮含量)、抗氧化能力(DPPH自由基清除能力、FRAP還原能力、SOD-like活性)之影響，並進一步使用HPLC探討酚類化合物含量，且與未經過精油萃取之烘乾與凍乾外果皮進行比較。
研究結果顯示，酵素水解後檸檬外果皮α-澱粉酶及α-葡萄糖苷酶抑制能力約提升至90%及50%。HPLC分析顯示，芥子酸為檸檬外果皮中最主要酚類物質，約佔47-59%；水解後檸檬外果皮大部分酚類化合物皆有提升，其中以七葉素苷含量提升最多，成長約四倍。而七葉素苷與α-澱粉酶抑制率經統計分析顯示具有高度相關(r=0.913)。抗氧化成分及能力方面，總酚、總類黃酮含量、DPPH自由基清除能力、FRAP 還原能力以及SOD-like活性皆有提升，提升約一倍。高壓處理後之檸檬外果皮其α-澱粉酶及α-葡萄糖苷酶抑制能力各約為30%及36%。經HPLC分析顯示，高壓後檸檬外果皮酚類成分無明顯提升。綜合上述，在本研究條件下水解處理之檸檬外果皮其碳水化合物水解酶抑制活性、抗氧化成分及抗氧化能力皆優於高壓處理，故為一具有開發糖尿病相關保健食品潛力之原料。至於高壓處理效果不佳，可能受限於設備壓力僅到400 MPa，若能提高壓力可能有助於改善萃取效果。

Lemon (Citrus limon L. Burm. f.) is one of the most important economical crops in the world. The productivity of lemon in Taiwan is about 45,000 tons annually, while Pingtung is the main production area, accounting for around 75% of the total. Lemon flavedo (the outer layer of lemon peel), is one of the most important materials for producing lemon essential oil. After the essential oil production, the flavedo is often discarded. However, there is less study related to the functional compounds of lemon flavedo essential oil residue (EOR). Therefore, the ability of EOR on the inhibition of carbohydrate hydrolase (α-amylase and α-glucosidase), antioxidant compounds (total phenol and total flavonoid content), antioxidant capacities (DPPH free radical scavenging ability, FRAP reducing ability, and SOD-like activity), and HPLC analysis after enzymatic hydrolysis treatment and high-pressure processing was conducted in this study, and compared with the flavedo without essential extract but with oven-dry (VD) and freeze-dry (FD).
The results showed that the α-amylase and α-glucosidase inhibition of flavedo with enzymatic treatment increased to approximately 90% and 50%. HPLC analysis showed that sinapic acid is the most plentiful phenolic compound in the flavedo, accounting for about 47-59% of total phenolic compounds. Most of the phenolic compounds in the flavedo are improved after enzymatic treatment. While, the content of esculetin increased the most, about four times higher than that without treatment. The statistical analysis showed that esculetin exhibits a high correlation (r= 0.913) with α-amylase inhibition. In terms of antioxidant compounds and capacities, total phenol content, total flavonoid content, DPPH free radical scavenging ability, FRAP reducing ability, and SOD-like activity have all been improved about one-fold after enzymatic treatment. After high-pressure processing (HPP), the inhibition of α-amylase and α-glucosidase of flavedo is about 30% and 36%. Besides, HPLC analysis also showed that the phenolic composition of the flavedo did not increase significantly after HPP treatment. In summary, the flavedo with enzymatic treatment in this study has a better carbohydrate hydrolase inhibition, antioxidant components, and antioxidant capacity than HPP treatment. Thus, it could be a source of material that has the potential to develop diabetes-related health foods. As the poor effect of HPP might be due to the pressure limitation (400 MPa), it may ameliorate the extraction effect if the equipment pressure limit is improved.

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