方 芳,王鳳忠

(中國(guó)農(nóng)業(yè)科學(xué)院農(nóng)產(chǎn)品加工研究所,北京 100193)

黃酮醇是廣泛存在于自然界中的一類重要的次生代謝產(chǎn)物,屬于植物類黃酮[1]。大量研究表明,黃酮醇作為自然界中重要的輔色物質(zhì),不僅與植物色澤的形成密切相關(guān)[2-3],同時(shí)作為重要的抗氧化劑,還具有重要的生理及保健功能,對(duì)包括癌癥、肥胖、腫瘤、心腦血管疾病及老年癡呆等的多種慢性疾病及老年疾病均具有重要的預(yù)防和治療作用[1,4-7]。因此,黃酮醇類化合物作為天然色素及功能活性因子目前在食品、保健品、醫(yī)藥及化妝品領(lǐng)域均有廣泛應(yīng)用[8]。

黃酮醇具有類黃酮類化合物典型的C6-C3-C6骨架,與其它多酚類化合物類似,其在植物細(xì)胞中多以結(jié)合態(tài)形式存在于細(xì)胞壁中,而極少數(shù)以游離態(tài)形式存在于細(xì)胞液泡中[9-11]。因此如何確保黃酮醇類化合物得到有效釋放,有效獲取植物細(xì)胞中的黃酮醇類化合物成為決定其工業(yè)應(yīng)用的重要制約因素。而提取技術(shù)作為從植物原料中獲取生物活性物質(zhì)的第一步和最重要的技術(shù)環(huán)節(jié)之一,了解其研究及應(yīng)用進(jìn)展對(duì)于有效獲取植物黃酮醇具有重要意義[12]。本文就植物原料中黃酮醇類物質(zhì)的提取方法研究進(jìn)展進(jìn)行綜述,旨在為黃酮醇類物質(zhì)分離提取及應(yīng)用研究提供理論依據(jù)及技術(shù)支持。

1 不同方法在植物黃酮醇提取中的應(yīng)用

1.1 溶劑提取法

溶劑提取法雖在植物黃酮醇的提取過(guò)程中應(yīng)用較多,但其有機(jī)溶劑殘留問(wèn)題成為困擾業(yè)界的一大難題,因此開(kāi)發(fā)綠色、無(wú)毒的新型替代性提取溶劑,同時(shí)兼顧提取時(shí)間短、溶劑用量少、可有效保護(hù)提取物風(fēng)味及活性、對(duì)目標(biāo)物質(zhì)溶解性進(jìn)行有效改善等特點(diǎn)的方法[21]成為溶劑提取法發(fā)展的必然趨勢(shì)。Parmar等通過(guò)響應(yīng)面法研究β環(huán)糊精水溶液對(duì)蘋果渣黃酮醇的提取效果時(shí)發(fā)現(xiàn),當(dāng)β-環(huán)糊精溶液濃度為2.8 g/100 mL,提取溫度為45 ℃,提取時(shí)間為25.6 h時(shí)黃酮醇的提取效率最高,且提取效果與傳統(tǒng)有機(jī)溶劑提取法相近,由此推測(cè)β-環(huán)糊精可作為提取植物多酚類化合物的環(huán)境友好型替代方法[21]。

傳統(tǒng)溶劑提取法雖在植物黃酮醇的提取過(guò)程中被廣泛應(yīng)用,但因其存在提取耗時(shí)長(zhǎng)、提取效率低、提取能耗大、有機(jī)溶劑殘留、目標(biāo)提取物易降解、所得產(chǎn)物在分析及應(yīng)用前需進(jìn)一步純化等弊端,導(dǎo)致其應(yīng)用和發(fā)展受到極大限制,因此開(kāi)發(fā)高效替代型提取方法勢(shì)在必行[22-25]。目前,應(yīng)用較多的提取方法包括超聲輔助提取法、微波輔助提取法、酶解輔助提取法、亞臨界水提取法等。

1.2 超聲輔助提取法

超聲輔助提取法是從植物原料中提取酚類物質(zhì)常用的一種方法。其是在溶劑提取的基礎(chǔ)上,利用頻率在20 kHz以上的超聲波產(chǎn)生的能量對(duì)物料中的目標(biāo)物質(zhì)進(jìn)行提取的一種方法。較之其它提取方法,因其具有提取效率高、操作簡(jiǎn)單、成本低廉、技術(shù)可靠等優(yōu)點(diǎn)而在植物黃酮醇類物質(zhì)提取中得到廣泛應(yīng)用[26-28]。Jang等以提取溶液濃度、提取溫度、溶液pH、液料比及提取時(shí)間為因素,采用超聲輔助提取法對(duì)洋蔥固體廢棄物中的槲皮素進(jìn)行提取,發(fā)現(xiàn)在各因素中,提取溶液濃度及提取溫度是影響提取得率的主要因素,而溶液pH、液料比及提取時(shí)間對(duì)提取率無(wú)顯著影響。實(shí)驗(yàn)優(yōu)化所得的最佳提取條件為溶液濃度59%,提取溫度49 ℃,此時(shí)所得槲皮素的含量為11.08 mg/g DW[29]。Kumar等采用超聲輔助提取法對(duì)洋蔥(AlliumcepaL.)中的槲皮素進(jìn)行提取,發(fā)現(xiàn)當(dāng)超聲時(shí)間為40 min,溶液pH為6.25時(shí),槲皮素的提取效果最好,得率可達(dá)175.19 mg/100 g FW[30]。González-Centeno等以超聲輔助提取法對(duì)葡萄皮渣中的總黃酮醇進(jìn)行提取,通過(guò)響應(yīng)面法研究超聲頻率、功率密度及提取時(shí)間對(duì)總黃酮醇提取效果的影響,發(fā)現(xiàn)當(dāng)超聲頻率為40 kHz,功率密度為150 W/L,提取時(shí)間為25 min時(shí)提取效果最好[31]。Oniszczuk和Podgórski在對(duì)比研究不同提取方法對(duì)歐洲椴樹(shù)花序的蘆丁、槲皮素等黃酮醇類物質(zhì)的提取效果時(shí)發(fā)現(xiàn),超聲輔助提取、加速溶劑萃取、微波輔助提取、索氏提取、熱回流提取及固相萃取等不同提取方法對(duì)目標(biāo)化合物的提取量具有明顯差異,其中超聲輔助提取法的提取效率最高[32]。Soares等以巴西藥用植物(SiparunaguianensisAublet)葉子為對(duì)象,脫脂處理后分別以甲醇、乙醇、70%乙醇溶液及蒸餾水為提取溶液,通過(guò)連續(xù)超聲輔助提取法對(duì)其黃酮醇類化合物進(jìn)行提取,發(fā)現(xiàn)較之甲醇和蒸餾水,乙醇及70%乙醇溶液對(duì)黃酮醇的提取效果最佳,提取物得率分別為(99.73±0.64) mg RE/g和(77.31±0.33) mg RE/g。推測(cè)植物原料經(jīng)脫脂處理后,連續(xù)超聲輔助提取法可作為黃酮醇類物質(zhì)提取的有效方法[33]。由此可見(jiàn),應(yīng)用超聲輔助提取法對(duì)黃酮醇類物質(zhì)進(jìn)行提取目前已在多種果蔬及藥用植物原料中得到應(yīng)用。針對(duì)特定植物原料,超聲輔助提取較之其它提取方法具有提取效率高、提取成本低等優(yōu)點(diǎn),分析其原因,一方面超聲處理過(guò)程中所產(chǎn)生的超聲波會(huì)引起空化效應(yīng),而空化效應(yīng)會(huì)造成植物細(xì)胞壁發(fā)生破裂、胞內(nèi)物質(zhì)粒徑變小,從而導(dǎo)致目標(biāo)物質(zhì)可透過(guò)細(xì)胞膜發(fā)生大量轉(zhuǎn)運(yùn)[32,34-35],另一方面,超聲振蕩可加速溶劑迅速進(jìn)入物料內(nèi)部,溶劑與目標(biāo)物質(zhì)的接觸幾率加大可導(dǎo)致目標(biāo)物質(zhì)迅速溶出[36]。但其提取效率及目標(biāo)產(chǎn)物的得率與所采用的提取溶劑的種類、極性及提取溫度等密切相關(guān)[27,33]。

1.3 微波輔助提取法

微波輔助提取法是在溶劑提取法基礎(chǔ)上發(fā)展起來(lái)的利用微波能對(duì)目標(biāo)物質(zhì)進(jìn)行提取的一種新興提取方法[37]。因其與傳統(tǒng)溶劑提取法相比具有提取成本低、提取效率高、更加環(huán)保等優(yōu)點(diǎn),目前已被應(yīng)用于食品、藥品及化妝品等多個(gè)領(lǐng)域,在植物多酚及黃酮類物質(zhì)的提取中得到廣泛應(yīng)用[38-39]。Yao等以布朗斯特酸性離子液體為溶劑,對(duì)銀杏葉黃酮醇配糖體進(jìn)行微波輔助提取,發(fā)現(xiàn)當(dāng)離子濃度為1.5 M,微波輻射能為120 W,輻射時(shí)間為15 min,料液比為1∶30時(shí),銀杏葉黃酮醇的提取效果最好,與中國(guó)藥典、歐洲藥典及美國(guó)藥典所提供的傳統(tǒng)提取方法相比,提取時(shí)間明顯縮短,提取效率明顯提高,且前處理方法相對(duì)簡(jiǎn)單[22]。郭建敏等通過(guò)對(duì)比研究微波輔助提取法和水浴提取法對(duì)趕黃草中的槲皮素的提取效果發(fā)現(xiàn),微波輔助提取法較之水浴提取法具有提取時(shí)間短(傳統(tǒng)方法需要至少2 h以上,本方法僅需15 min)、提取效率高、提取質(zhì)量好等明顯優(yōu)勢(shì),且當(dāng)微波功率為255 W,微波時(shí)間為20 min,料液比為1∶10時(shí),槲皮素的提取得率最高[40]。Kumar等采用微波輔助提取法對(duì)洋蔥(AlliumcepaL.)中的槲皮素進(jìn)行提取,發(fā)現(xiàn)當(dāng)微波時(shí)間為150 s,溶液pH為6.25時(shí),槲皮素的提取得率最高,且其提取效果明顯優(yōu)于超聲輔助提取法[30]。Li等在研究均質(zhì)-微波輔助提取法對(duì)黑加侖果渣黃酮醇的提取效果時(shí)發(fā)現(xiàn),當(dāng)乙醇濃度為60%,均質(zhì)時(shí)間為3 min,液料比為28.3 mL/g,抗氧化劑用量為0.3%,提取環(huán)境pH為2.5,微波功率為551 W,微波時(shí)間為16.4 min時(shí),黃酮醇的提取得率最高,且提取時(shí)間較傳統(tǒng)溶劑提取法明顯縮短,推測(cè)均質(zhì)-微波輔助提取法可作為提取植物黃酮醇類天然產(chǎn)物的潛在方法[41]。孫雪等采用響應(yīng)面法對(duì)香菇柄槲皮素的微波輔助提取工藝條件進(jìn)行優(yōu)化,確定料液比、微波功率及微波時(shí)間為影響香菇柄中槲皮素提取得率的主要因素,當(dāng)料液比為30∶1,微波功率為385 W,微波時(shí)間為50 s時(shí),槲皮素的提取得率最高,證明微波輔助提取法對(duì)提取香菇柄槲皮素是可行的[42]。由此可見(jiàn),微波輔助提取法作為傳統(tǒng)溶劑提取法的重要替代方法之一,目前已在中草藥、食品原料及其廢棄物的黃酮醇類物質(zhì)提取中得到探索性應(yīng)用。盡管提取對(duì)象不同,微波輔助提取法的工藝參數(shù)存在一定差異,但總體而言,與傳統(tǒng)溶劑提取法相比,其具有提取時(shí)間短、溶劑用量低、目標(biāo)物質(zhì)提取得率高等特點(diǎn)。針對(duì)特定提取對(duì)象,其提取效果甚至優(yōu)于超聲輔助提取方法。分析其原因,一方面高頻微波能可導(dǎo)致物料及溶劑中的偶極分子發(fā)生離子傳導(dǎo)及偶極旋轉(zhuǎn),從而誘發(fā)物料內(nèi)部瞬時(shí)升溫,弱氫鍵發(fā)生斷裂,造成離子遷移,進(jìn)而加速溶劑分子的滲入;另一方面,微波又可對(duì)物料基質(zhì)進(jìn)行有效穿透,通過(guò)與物料內(nèi)部的極性分子發(fā)生反應(yīng),引起胞內(nèi)壓力迅速增加,導(dǎo)致細(xì)胞壁發(fā)生破裂,活性物質(zhì)迅速流出。因此與傳統(tǒng)溶劑提取法相比,微波輔助提取法可有效縮短提取時(shí)間,提高提取效率[43-44]。

1.4 酶解輔助提取法

酶解輔助提取法是近年來(lái)新興的一種提取方法,是在傳統(tǒng)溶劑提取法的基礎(chǔ)上,利用纖維素酶、半纖維素酶、果膠酶等生物酶對(duì)提取對(duì)象的細(xì)胞壁結(jié)構(gòu)進(jìn)行破壞,一方面降低溶劑的傳質(zhì)阻力,一方面使細(xì)胞內(nèi)容物充分暴露,從而加速細(xì)胞內(nèi)有效成分釋放的一種提取方法。因該方法具有提取效率高、反應(yīng)條件溫和且容易控制、可有效提高生物活性物質(zhì)的提取得率等特點(diǎn)而引起業(yè)界廣泛關(guān)注[45-48]。近年來(lái)其在黃酮醇類生物活性物質(zhì)的提取中也得到探索性應(yīng)用。Nguyen等分別采用復(fù)合植物水解酶Viscozyme L和α淀粉酶對(duì)花椰菜葉片黃酮進(jìn)行酶法輔助提取,發(fā)現(xiàn)當(dāng)提取溫度為35 ℃,溶液pH為4.0,復(fù)合植物水解酶和α淀粉酶與底物的用量比分別為0.2%和0.5%時(shí),提取效果最好,主要提取物為山奈酚糖苷類化合物及其羥基苯丙烯酸衍生物,與對(duì)照相比,采用復(fù)合植物水解酶和α淀粉酶混合物進(jìn)行輔助提取可顯著提高花椰菜葉片山奈酚糖苷等黃酮醇類化合物的得率[11]。張偉等采用纖維素酶對(duì)銀杏葉中黃酮類物質(zhì)進(jìn)行輔助提取,發(fā)現(xiàn)當(dāng)酶用量為0.3 mg/mL,酶解溫度為45 ℃,溶液pH為4.0,酶解時(shí)間為2 h時(shí),銀杏葉中總黃酮的得率最高,較之對(duì)照組總黃酮得率提高了45.83%,且提取物中的黃酮類物質(zhì)主要是槲皮素、山奈酚及異鼠李素等黃酮醇類物質(zhì)[49]。

酶解輔助提取法除在植物原料總黃酮醇類物質(zhì)的提取中得到應(yīng)用外,也在單一黃酮醇的提取上得到一定應(yīng)用,目前應(yīng)用較多的為植物原料中槲皮素的高效提取。韓建軍等采用響應(yīng)面法對(duì)地錦草中槲皮素的酶解輔助提取方法進(jìn)行優(yōu)化,發(fā)現(xiàn)當(dāng)提取時(shí)間為45 min,溶液pH為4.5,酶解溫度為50 ℃,纖維素酶用量為0.6%時(shí),槲皮素的提取得率與理論預(yù)測(cè)值最為接近,可達(dá)1.87 mg/g,從而證明纖維素酶可作為從地錦草中提取槲皮素等黃酮醇類化合物的重要輔助手段[50]。田佳琦等以玉米須為研究對(duì)象,采用纖維素酶-超聲輔助提取方法對(duì)其槲皮素進(jìn)行提取并對(duì)其提取方法進(jìn)行優(yōu)化,發(fā)現(xiàn)當(dāng)纖維素酶用量為0.014 mg,乙醇濃度為50%(V/V)、料液比為25∶1,超聲功率為200 W,超聲時(shí)間為40 min時(shí),槲皮素的得率最高,證明采用纖維素酶-超聲輔助提取法對(duì)玉米須中的槲皮素進(jìn)行提取是可行的[51]。施偉梅等采用響應(yīng)面法對(duì)酶解輔助提取紫花苜蓿中槲皮素的工藝參數(shù)進(jìn)行優(yōu)化,發(fā)現(xiàn)當(dāng)提取溶液濃度為22%,酶解時(shí)間為92 min,料液比為1∶40時(shí),槲皮素的提取量最大,可達(dá)12.56 μg/g,證明酶解輔助提取方法可作為提取紫花苜蓿槲皮素的一種簡(jiǎn)單高效的提取方法[48]。由此可見(jiàn),酶解輔助提取法作為一種新興的生物活性物質(zhì)提取方法,其適用范圍廣、提取效率高、操作簡(jiǎn)單,不僅適用于總黃酮醇類物質(zhì)的提取,同時(shí)可用于單體黃酮醇的高效提取,目前已在多種植物原料中得以驗(yàn)證,且其提取效率較之傳統(tǒng)溶劑提取法明顯提高。分析其原因可能是由于酶解輔助提取法不僅可對(duì)植物細(xì)胞壁進(jìn)行有效降解,破壞其細(xì)胞壁結(jié)構(gòu),從而使胞內(nèi)物質(zhì)得以更好地釋放提高提取效率,同時(shí)各種生物酶還可促使目標(biāo)化合物發(fā)生轉(zhuǎn)糖基反應(yīng),提高目標(biāo)化合物的可溶性,從而實(shí)現(xiàn)提高提取效率的目的[52-54]。

1.5 亞臨界水提取法

亞臨界水提取法,又稱高壓熱水提取法或超加熱水提取法,是以溫度介于沸點(diǎn)(100 ℃)和臨界點(diǎn)(374 ℃)間的水為提取溶劑的一種新興的提取方法,因其在提取過(guò)程中無(wú)需引入有機(jī)溶劑,又被認(rèn)為是新興“綠色”提取方法[25,55]。亞臨界水提取法依據(jù)在適當(dāng)壓力下通過(guò)提高水溫可有效降低水的表面張力和粘性的原理,使亞臨界水獲得類似有機(jī)溶劑的極性,從而達(dá)到對(duì)物料中目標(biāo)物質(zhì)有效提取的目的[56-57]。由于與其它提取方法相比,亞臨界水提取法具有提取效率高、提取效果好、安全無(wú)毒、無(wú)污染等特點(diǎn)而在食品及醫(yī)藥領(lǐng)域廣受歡迎。黃酮醇作為與人體健康密切相關(guān)的一類生物活性物質(zhì),亞臨界水提取法在其分離提取過(guò)程中得到廣泛應(yīng)用。Ko 等采用亞臨界水提取法對(duì)洋蔥皮中的槲皮素進(jìn)行提取,發(fā)現(xiàn)當(dāng)提取溫度為165 ℃,提取時(shí)間為15 min,洋蔥皮與硅藻土的混合比例為1.5∶2.5時(shí),槲皮素提取量最高,可達(dá)16.29 mg/g。同時(shí)通過(guò)與傳統(tǒng)溶劑法對(duì)比發(fā)現(xiàn),亞臨界水提取法對(duì)洋蔥皮中的槲皮素提取率明顯優(yōu)于其它方法,其提取率分別較乙醇提取法、甲醇提取法及沸水提取法高出8倍、6倍和4倍。從而推測(cè)亞臨界水提取法可作為傳統(tǒng)溶劑提取法的有效替代方法[58]。Lekar等同樣通過(guò)亞臨界水提取法對(duì)洋蔥皮中的槲皮素進(jìn)行提取,發(fā)現(xiàn)經(jīng)120 ℃亞臨界水提取60 min可實(shí)現(xiàn)對(duì)洋蔥皮中槲皮素的有效提取。亞臨界水提取法對(duì)洋蔥皮槲皮素的提取效力與傳統(tǒng)溶劑提取法相當(dāng),但其提取時(shí)間較之傳統(tǒng)溶劑提取法縮短了3～4倍,且提取成本低,可有效避免有機(jī)溶劑殘留問(wèn)題[59]。次年,Lekar等又采用亞臨界水提取法對(duì)水辣蓼(PolygonumHydropiperL.)中的槲皮素進(jìn)行提取,發(fā)現(xiàn)當(dāng)提取溫度為250 ℃,提取時(shí)間為30 min時(shí),亞臨界水提取法的槲皮素提取量為傳統(tǒng)溶劑提取法的7.6倍,進(jìn)一步證明亞臨界水提取法是從植物原料中提取槲皮素等黃酮醇類化合物的可行方法[56]。Khoza等以苦瓜為對(duì)象,通過(guò)亞臨界水提取法對(duì)其黃酮醇類物質(zhì)進(jìn)行提取,并通過(guò)UHPLC-Qtof-MS對(duì)提取效果進(jìn)行檢測(cè),發(fā)現(xiàn)當(dāng)提取溫度介于150～250 ℃時(shí),是黃酮醇類物質(zhì)提取的最佳條件,提取所得槲皮素、山奈酚、異鼠李素及其相應(yīng)衍生物多達(dá)15種[60]。Cheigh等分別以紅茶、芹菜和人參為對(duì)象,以提取溫度、提取時(shí)間及提取壓力為影響因素,對(duì)比研究亞臨界水提取法、熱水提取法及甲醇、乙醇等有機(jī)溶劑提取法對(duì)其黃酮醇類物質(zhì)的提取效果,發(fā)現(xiàn)在4種提取方法中,亞臨界水提取法的提取效率明顯高于熱水提取法及有機(jī)溶劑提取法,亞臨界水提取法所得楊梅酮、槲皮素及山奈酚等黃酮醇類物質(zhì)的得率分別比乙醇提取法和甲醇提取法高出2.0～22.7倍和1.8～23.6倍。由此可見(jiàn),亞臨界水提取法不僅提取效率高、提取效果好、無(wú)有機(jī)溶劑殘留、可實(shí)現(xiàn)對(duì)目標(biāo)提取物的最大挖掘,同時(shí)其提取時(shí)間短、反應(yīng)敏感,通過(guò)對(duì)不同物料的提取證明未來(lái)其可作為有機(jī)溶劑提取法提取植物原料中黃酮醇類物質(zhì)的有效替代方法[61]。亞臨界水提取法之所以可以實(shí)現(xiàn)對(duì)植物原料中黃酮醇類物質(zhì)的高效提取,可能是由于當(dāng)水溫達(dá)到預(yù)定值,水處于亞臨界狀態(tài)時(shí),一方面植物原料中結(jié)合態(tài)的黃酮醇類物質(zhì)被有效釋放,另一方面黃酮醇糖苷類結(jié)合物可能發(fā)生了水解反應(yīng),從而導(dǎo)致游離態(tài)黃酮醇類化合物的含量增加所致[56]。

1.6 其它提取方法

除上述提取方法外,近年來(lái)一些新興的提取方法也在植物黃酮醇的提取過(guò)程中得到探索性應(yīng)用。Li等以黃蜀葵花為原料,以提取溫度、提取壓力及提取溶液濃度為因素,采用改良的超臨界二氧化碳提取法對(duì)其黃酮醇等類黃酮類化合物進(jìn)行提取,發(fā)現(xiàn)在提取溫度為52 ℃,提取壓力為20 MPa,乙醇溶液濃度為85%時(shí),黃酮醇的提取得率最高[62]。Xu等以超微殼聚糖為吸附劑,采用分散微固相萃取技術(shù)對(duì)槐花茶中的黃酮醇類化合物進(jìn)行分離提取,發(fā)現(xiàn)當(dāng)殼聚糖吸附劑的濃度為0.4 μg/mL,pH為7.0,提取時(shí)間為1.0 min,洗脫溶劑甲醇用量為100 μL時(shí),提取方法的線性最佳,證明分散微固相萃取技術(shù)為提取槐花茶黃酮醇類化合物的有效方法[63]。Pakade等采用分子印跡聚合物固相萃取法對(duì)加熱回流制得的辣木甲醇提取物中的黃酮醇糖苷配基進(jìn)行再提取,并通過(guò)HPLC對(duì)所得黃酮醇提取物進(jìn)行定性定量分析,發(fā)現(xiàn)該提取方法對(duì)辣木葉和花的甲醇提取物中的槲皮素及山奈酚的回收率可分別達(dá)到77%～85%和75%～86%,證明分子印跡聚合物固相萃取法可作為從加熱回流法所得復(fù)雜提取物中進(jìn)一步提純黃酮醇提取物的可行方法[64]。由此可見(jiàn),包括超臨界二氧化碳提取法、分散微固相萃取法及分子印跡聚合物固相萃取法等在內(nèi)的多種新興提取方法均可用于植物黃酮醇提取的替代性方法。其中,超臨界二氧化碳提取法作為一種高效、低成本、無(wú)有機(jī)溶劑殘留的“綠色”提取方法,因其極性較低,常被用于非極性化合物提取,且通過(guò)添加輔助溶劑,還可實(shí)現(xiàn)對(duì)植物黃酮醇等極性化合物的有效提取[62]。分散微固相萃取法及分子印跡聚合物固相萃取法作為簡(jiǎn)單、高效、靈敏度高、溶劑用量少、提取時(shí)間短的提取方法,是傳統(tǒng)固相萃取法的有效改良[63],利用化合物在固定相和流動(dòng)相中進(jìn)行選擇性分布的特性,可通過(guò)對(duì)作為固定相的吸附劑的組成及性質(zhì)進(jìn)行優(yōu)化來(lái)實(shí)現(xiàn)對(duì)目標(biāo)化合物的有效提取[12]。

2 問(wèn)題與展望

隨著經(jīng)濟(jì)的發(fā)展和人們生活水平的提高,國(guó)民的營(yíng)養(yǎng)健康意識(shí)日益增強(qiáng),對(duì)與人體健康密切相關(guān)的營(yíng)養(yǎng)及生物活性物質(zhì)的需求日益旺盛。黃酮醇作為與人類多種慢性疾病的預(yù)防和治療密切相關(guān)的一類營(yíng)養(yǎng)功能因子,在食品、保健品、醫(yī)藥及日化產(chǎn)業(yè)中均得到廣泛關(guān)注。因此如何從植物原料中有效提取黃酮醇則顯得尤為重要。提取技術(shù)作為從自然界中獲取目標(biāo)物質(zhì)的第一步,其決定著目標(biāo)物質(zhì)的得率和后續(xù)研究及應(yīng)用工作能否順利開(kāi)展,近年來(lái)包括溶劑提取、超聲輔助提取、微波輔助提取、酶解輔助提取、亞臨界水提取等多種提取方法已在植物黃酮醇的提取過(guò)程中得到一定應(yīng)用,但相關(guān)研究工作缺乏連貫性和系統(tǒng)性,同時(shí)所采用的提取方法存在一定局限性,缺乏創(chuàng)新性。

針對(duì)上述問(wèn)題,未來(lái)在植物黃酮醇提取方法的研究中,應(yīng)注意加強(qiáng)工作的連貫性、系統(tǒng)性和創(chuàng)新性。在對(duì)傳統(tǒng)提取方法的工藝參數(shù)進(jìn)行優(yōu)化的過(guò)程中,應(yīng)注意與新興實(shí)驗(yàn)設(shè)計(jì)方法相結(jié)合,加強(qiáng)對(duì)多實(shí)驗(yàn)因素的綜合考察,打破僅對(duì)提取時(shí)間、提取溫度、料液比等常規(guī)因素的考察。在提取方法的選擇上,則應(yīng)盡可能多的探索新興、綠色提取方法在植物黃酮醇提取領(lǐng)域的應(yīng)用。

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