Chemical Study on Structure and Activity of Cucurbitane type Triterpene Glycosides.

从中国葫芦科植物块茎中分离鉴定了葫芦烷苷。分离得到8个新的糖苷化合物，命名为肉桂糖苷I-VI(C-I-CI)，并确定了它们的结构。从罗汉果中分离得到7个新的皂苷化合物，分别命名为罗汉果皂苷R1-7(S-R1-7)和C-1-III、V、VI，并鉴定了其结构。从罗汉果中分离得到罗汉果甜苷IV、V和两个新糖苷，其结构分别为11-酮-罗汉果苷-V和3-0-B-葡萄糖基-26-0-[B-葡萄糖基-(1)]-[B-葡萄糖基-(1)]-B-葡萄糖基-葡萄糖基对这些天然糖苷以及以天然糖苷为原料经化学或酶法分离得到的化合物，研究了其口感与结构的关系。(1)只有一个或两个葡萄糖基的化合物，如C-I，S-R1-4，是无味的。(2)11-0H糖苷具有3个以上的糖基单元，如罗汉果苷-V、C-V、-VI和S-R6，是甜味的。(3)11B-0H糖苷a，如S-R7，即使含有三个以上的糖基也是无味的。(4)11-酮苷有苦味。然而，葡萄糖基团的增加会导致口味由苦变甜。例如，11-酮-罗汉果苷V是一种表现出甜味的葡萄糖苷。11-酮基葡萄糖苷C-III的苦味通过与淀粉和环糊精-葡萄糖基转移酶在26-龙胆二糖基上的酶促糖基化来降低。

Isolation and structure elucidation of cucurbitane glycosides from Chinese cucubitaceous plants, were conducted.From tubers of Hemsleya carnosiflora. eight new glycoside named carnosifloside I-VI(C-I-CI) were isolated and their structures were established. From tubers of H.panacis-scandens, seven new glycosides named scandenoside R1-7(S-R1-7) were isolated together with C-1-III, V and VI. Structures of S-R1-7 were elucidated.From fruits of Siraitia siamensis, mogrosides-IV and V sweet principles of Siraitia grosvenorii (=Mordica grosvenori) together with two new glycosides, the structures of which were assigned as 11-keto-mogroside-V and 3-0-B-glucosyl-26-0-[B-glucosyl-(1 2)]-[B-glucosyl-(1 6)]-B-glucosyl-mogro, respectively.For these natural glycosides as well as compounds derived from the natural glycosides by chemical or enzymic procedures, the relationship between taste and structure was investigated. (1) Compounds with only one or two glucosyl units such as C-i, S-R1-4, are tasteless. (2) 11 -0H glycosides with more than three glucosyl units such as mogroside-V,C-V, -VI and S-R6, are sweet. (3) 11B-0H glycoside a such as S-R7 are tasteless even if they have more than three glucosyl units. (4) 11-keto glycoside a taste bitter. However, the increase of glucosyl unit results in change of taste from bitter to sweet. For example, 11-keto-mogroside V is a glucopentoside, exhibiting sweetss. The bitterness of an 11-keto glucotrioside, C-III is decreased by enzymic glucosylation at the 26-gentiobiosyl moiety with starch and cyclodextrin-glucosyl transferase.