BIOSYNTHESIS OF DIELS-ALDER TYPE ADDUCTS IN MORUS ALBA L. CELL CULTURES

通过对桑树幼苗或叶片诱导的愈伤组织进行筛选，获得了高产量的Diels-Alder型加合物愈伤组织和细胞悬浮培养物。用[1-^<13>C]-、[2-^<13>]-和[1,2-^<13>C_2]-乙酸酯对桑树叶片诱导的细胞悬浮液进行处理，结果表明，两种具有光学活性的Diels-Alder型加合物chalcomoracin和kuwanon J是细胞培养物的主要成分。都是由两个肉桂酰基衍生骨架分子缩合而成的。^<13> c -乙酸标记的查尔莫拉辛（chalcomoracins）被认为是脱氢苯乙烯- 1-2-芳基苯并呋喃衍生物和戊基查尔酮衍生物的加合物，2-芳基苯并呋喃骨架是由肉桂基聚酮的醛醇型环化形成的，然后是脱羧，查尔酮部分是由前体的Claisen型环化形成的。kuwanon J被认为是脱氢丙烯基查尔酮和丙烯基查尔酮的加合物，其^<13> c标记模式表明，在芳环中包含了三个连续的乙酸单元，证实了kuwanon J是由两个肉桂基聚酮衍生的查尔酮骨架组成的，并且排除了作为后查尔酮成员的可能性。另一方面，在^<13>C-aceate标记的chalcomoracins中，[2-^<13> C]醋酸盐在preny1部分的生物合成过程中几乎没有结合到发酵剂醋酸碳中，而[1-^<13> C]醋酸盐没有结合到preny1部分。这可能是由于三羧酸（TCA）循环的参与。这些标记模式清楚地证明了不同来源的桑树戊烯基查尔酮的混合生物合成。从以上结果可以看出，桑树细胞培养物中的Diels-Alder型加合物、查尔酮酸和kuwanon J可能是查尔酮和preny1部分的，-双键的环加成产物。

Callus and cell suspension cultures of high Diels-Alder type adducts productivity have been obtained through the selection of callus tissues induced from the seedlings or the leaves of Morus alba L. Experiments with [1-^<13>C]-, [2-^<13>]-, and [1,2-^<13>C_2]-acetates administered to the cell suspension induced from the leaves revealed that both optically active Diels-Alder type adducts chalcomoracin and kuwanon J, main components in the cell cultures, are formed through the condensation of two molecules of cinnamoy1-polkkeide-derived skeletons. In the ^<13>C-acetate labeled chalcomoracins, which is regarded as adduct of a dehydropreny1-2-arylbenzofuran derivative and a prenylchalcone derivative, the 2-arylbenzofuran skeleton is formed by a aldol type cyclization of the cinnamoylpolyketide, followed by decarboxylation, and the chalcone moiety is formed by a Claisen type cyclization of the precursor. The ^<13>C-labeling pattern in kuwanon J, which is regarded as a adduct of a dehydroprenylchalcone and a prenylchalcone, indicating the incorporation of three successive acetate units into the aromatic rings corroborates that kuwanon J is composed of two cinnamoylpolketide-derived chalcone skeletons, and that the possibility as a member of retrochalcone has been ruled out. On the other hand, in the ^<13>C-aceate labeled chalcomoracins, the [2-^<13> C]acetate was barely incorporated into the starter acetate carbons in the biosynthesis of the preny1 moieties, while the [1-^<13> C] acetate was not incorporated into the preny1 moieties. This may be due to the participation of the tricarboxylic acid (TCA) cycle. These labeling patterns clearly demonstrated that mixed biosynthesis of mulberry prenylchalcones from different origins. From the above results, the Diels-Alder type adducts, chalcomoracin and kuwanon J in the Morus alba cell cultures could be cycloaddition products of the , -double bond of the chalcone and the preny1 portion.