探討高靜水壓對青花菜中異硫氰酸鹽含量變化及其功效性評估

Abstract

異硫氰酸鹽 (isothiocyanate, ITCs) 普遍存於十字花科作物中，主要透過黑芥子酶水解芥子油苷所產生，其中蘿蔔硫素 (sulforaphane, SFN) 為青花菜主要的異硫氰酸鹽，其次為芥酸 (erucin, ERN)。異硫氰酸鹽具有多種功效，不僅可刺激II型酶活性，提升人體抗癌能力，亦具有抑制發炎相關因子生成、延緩發炎反應、降低氧化應激等作用。然而，多篇文獻指出，異硫氰酸鹽不耐高溫，於烹煮的過程中會隨之流失，且其生成系統中的黑芥子酶在溫度超過60℃的環境時，活性便會受到影響。因此，本研究以青花菜42號品種作為實驗對象，探討高靜水壓與截切處理對異硫氰酸鹽含量、黑芥子酶活性及其他機能性成分之影響，並且藉由細胞試驗分別評估其抗發炎與抗氧化功效。 本實驗以80%甲醇萃取青花菜，經由回收率與精密度試驗搭配HPLC分析後，可穩定且有效的萃取與分離SFN與ERN。青花菜經過高壓處理後，SFN與ERN含量顯著提升，其中以400 MPa處理15分鐘之條件可生成最多的異硫氰酸鹽，含量分別為154.79±7.64 mg‧100 g-1及109.86±7.45 mg·100 g-1，遠高於控制組。在不同截切形式部分，由於截切過程中易導致氧化或成分流失，故於不截切狀態下，更能保留其異硫氰酸鹽含量。於同樣處理時間下，探討不同加壓次數對青花菜之影響，結果顯示，相較於多次處理，單次高壓處理可產生較多的異硫氰酸鹽。綜合以上結果，最終以400 MPa單次處理15分鐘之條件作為最適加工條件。 青花菜中含有豐富的機能性成分，其經過高壓加工後，類黃酮與維生素C不受加工影響，總酚含量則顯著增加。在黑芥子酶 (myrosinase, MYR) 活性方面，經過殺菁處理後，活性顯著降低；而在高壓處理下，MYR活性明顯提升，並且趨勢與異硫氰酸鹽相同，顯示異硫氰酸鹽生成量深受黑芥子酶活性變化所影響。 在抗發炎方面，高壓處理後的青花菜可於不影響細胞活性之狀態下，抑制NO生成，並降低iNOS與COX-2表現量，且不論是先以LPS誘導或後處理，皆是SFN濃度為60 mg·mL-1時，效果更為顯著；然而PGE2含量沒有受到SFN濃度的提升所影響，變化趨勢也與COX-2不同，推測PGE2除了受COX-2調控外，亦被COX-1所調節。總結而言，高壓加工可提升青花菜中異硫氰酸鹽含量，於細胞評估上，亦有抗發炎之效果，更具有作為保健食品原料或添加物之潛力。

Isothiocyanate is commonly found in Cruciferae crops and is mainly produced by the hydrolysis of glucosinolates by myrosinase. In broccoli, the main isothiocyanate is sulforaphane (SFN), followed by erucin (ERN). Isothiocyanate has many benefits, such as stimulating type II enzyme activity, enhancing the anti-cancer ability of humans, inhibiting the production of inflammation-related factors, delay inflammation, and reducing oxidative stress. However, isothiocyanate is not resistant to high temperature and is lost during cooking. Thus, the activity of myrosinase in the isothiocyanate-synthetic production system could be affected when the temperature exceeds 60°C. This study investigates the changes in isothiocyanate content, myrosinase activity and other functional components in response to high hydrostatic pressure in broccoli No. 42. The anti-inflammatory and anti-oxidative effects were also evaluated with in vitro cell experiments. In this experiment, 80% of methanol was used to extract SFN and ERN from broccoli. Through recovery and precision tests combined with HPLC analysis, SFN and ERN could be effectively extracted and separated. After the high-pressure treatment of the broccoli '42', the contents of SFN and ERN increased significantly. Among all processing conditions, the treatment with 400 MPa for 15 min generated the highest SFN and ERN contents, which were 154.79±7.64 mg·100 g-1 and 51.39±1.62 mg·100 g-1, respectively. Due to the oxidation or component loss during the cutting processes, the isothiocyanate contents were retained better without cutting. Under the same treatment duration, the frequency of high-pressure processing was divided into one to three times, and the results showed that a single high-pressure treatment could produce more isothiocyanate contents. We found that a single treatment at 400 MPa for 15 minutes was the optimal condition. After high-pressure processing, the total phenol content in broccoli increased significantly, with unchanged levels of flavonoids and vitamin C. We also analyzed the activity of myrosinase (MYR) in broccoli were analyzed. After blanching, the activity of myrosinase was significantly reduced. High-pressure treatment increased the activity of MYR, and its trend was the same as that of isothiocyanate. This showed that the content of isothiocyanate was deeply affected by changes in myrosinase activity. High-pressure treatments could inhibit nitric oxide (NO) production and reduce the expression of inducible nitric oxide synthase (iNOS) and cyclooxygenase-2 (COX-2) without affecting cell activity. Whether it was pre- or post-treated with lipopolysaccharides (LPS), the inhibitory effects of iNOS and COX-2 of 60 mg·mL-1 SFN were more significant than other treatments. However, the prostaglandin E2 (PGE2) content was not affected by an increase in SFN concentration, and the changes were also different from those of COX-2. In summary, high-pressure processing can increase the content of isothiocyanate in broccoli. The broccoli after high-pressure processing exhibits good anti-inflammatory effect in cell experiments, and has the potential to be used as a material or additive in functional foods.