<i>Cyclopia genistoides苦味</i>素糖苷的苦味影响和热转化<i></i>,Journal of Natural Products

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Cyclopia genistoides苦味素糖苷的苦味影响和热转化
Journal of Natural Products ( IF 3.3 ) Pub Date : 2018-12-04 00:00:00 , DOI: 10.1021/acs.jnatprod.8b00710
Ombeline Danton ₁ , Lara Alexander _{2,

3} , Cindy Hunlun ₂ , Dalene de Beer _{2,

3} , Matthias Hamburger ₁ , Elizabeth Joubert _{2,

3}

Affiliation

甲柚皮素衍生物，分离自独眼genistoides，苦味凉茶，尤其是当在绿色（未氧化）的形式，被确定为（2小号）-5- [α-升-rhamnopyranosyl-（1→2）-β- d -葡萄糖吡喃糖基氧基]柚皮苷（1）。在不同温度（80、90、100、110和110°C）下加热时，该化合物部分差向异构化为（2 R）-5- [α- 1-鼠李糖基吡喃糖基-（1→2）-β- d-吡喃葡糖基氧基]柚皮素（2）。 pH值为5的磷酸盐缓冲液中可在120°C的温度下延长时间。分数转化模型预测化合物1的浓度降低最好的。转化反应的活化能经计算为99.16 kJ mol ^–1。长时间加热不仅导致化合物2的形成，而且最终导致其浓度的降低和另一种转化产物（E）-2'-[α- 1-鼠李糖基-（1→2）-β- d-葡萄糖基吡喃糖基氧基的形成] -4′，6′，4-三羟基查耳酮（3）。相反，在相同条件下（pH 5于100°C加热6小时），在C-7糖基化的柚皮苷保持稳定。化合物1的苦味强度显着低于柚皮苷，两者均在0.04 mM（化合物1的典型浓度）下进行测试在凉茶中注入绿色的C. genistoides。该比较表明糖部分的位置在确定柚皮苷苷的苦味强度和热稳定性中起重要作用。

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Bitter Taste Impact and Thermal Conversion of a Naringenin Glycoside from Cyclopia genistoides

A naringenin derivative, isolated from Cyclopia genistoides, a bitter tasting herbal tea, especially when in green (unoxidized) form, was identified as (2S)-5-[α-l-rhamnopyranosyl-(1→2)-β-d-glucopyranosyloxy]naringenin (1). The compound partially epimerizes to (2R)-5-[α-l-rhamnopyranosyl-(1→2)-β-d-glucopyranosyloxy]naringenin (2) when heated at different temperatures (80, 90, 100, 110, and 120 °C) for a prolonged period in a phosphate buffer at pH 5. The fractional conversion model predicted the decrease in the concentration of compound 1 the best. The activation energy of the conversion reaction was calculated as 99.16 kJ mol^–1. Prolonged heating resulted not only in formation of compound 2 but eventually a decrease in its concentration and the formation of another conversion product, (E)-2′-[α-l-rhamnopyranosyl-(1→2)-β-d-glucopyranosyloxy]-4′,6′,4-trihydroxychalcone (3). In contrast, naringin, glycosylated at C-7, remained stable when heated under the same conditions (100 °C for 6 h at pH 5). The bitter intensity of compound 1 was substantially less than that of naringin, both tested at 0.04 mM, a concentration typical of compound 1 in an herbal tea infusion of green C. genistoides. This comparison indicates that the position of the sugar moiety plays an important role in determining both bitter intensity and heat stability of naringenin glycosides.

更新日期：2018-12-04

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