Apiin Apiose

The evidence for any formula for petroselinin is very indefinite beyond the fact that the aglycon is diosmetin. Analytical values for samples of crude apiin that contained much petroselinin suggest that the carbohydrate component of petroselinin is also a disaccharide and the inference has been made by Vongerichten that it is composed of apiose and D-glucose but such matters are speculation at present because petroselinin has not yet been obtained in even approximately pure condition. 

Fifty years after the discovery of apiose, a review of the literature1 showed that it was still a curiosity, and had been found only in the parsley plant. Apart from its structure, and those of the flavonoids from which it was isolated (primarily, apiin), little else was known about apiose. In the next two decades, this branched-chain sugar was shown to have very widespread occurrence in the plant kingdom, being identified, in most of the plants investigated,4-6 by paper chromatography. 

III. Occurrence of Apiose in Nature The chemistry of D-apiose (1) and apiin (4), from which this... 

The parsley plant, Petroselinum crispum, for example, contains at least two of the D-apiose flavonoids, namely, apiin 4, 5-dihydroxy-flavon-7-yl 2-0- [3-C (hydroxymethyl)-/3-D-erythrofuranosyl] -/3-D-glucopyranoside (4) and petroselinin 3, 4, 5-trihydroxyflavon-7-yl 2-0- [3-C-(hydroxymethyl)-/3-D-erythrofuranosyl]-/3-D-glucopyrano-side. 1 The principal compound containing D-apiose in parsley... 

A free disaccharide containing apiose has been extracted from an Australian shrub, the native hop bush, Daviesia latifolia.40 The disaccharide was isolated as a dibenzoate. Methylation followed by de-benzoylation, as well as comparison with the disaccharide of D-apiose from apiin, suggested that they are similar in every aspect measured. Thus, the structure of the disaccharide without its two benzoyl groups is, tentatively, 2-O-D-apiofuranosyl-D-gIucose.40 The... 

The metabolism of apiose in plants has not been investigated extensively. It has been suggested80 that apiose could give rise to simple terpenes by condensation and reduction. Incubation of [ -,4C]apiose in parsley plants resulted in negligible, but unspecified, amounts of carbon-14 incorporated into apiin.66 The specific activity of the [ -14C]apiose administered was low (5 X 105 d.p.m./jumole) for this reason, the data suggested only that no highly active mechanism is available in parsley for the metabolism of this branched-chain sugar. 

L. gifofoa,65-79-83 and P. crispum.m,7 , H2 H4,H5 In general, the results of these in vivo investigations, as well as those of in vitro biosynthetic studies, support the hypothesis proposed for the synthesis of D-apiose polysaccharides and apiin (4) by Grisebach and Dobereiner82 (see Fig. 1). They postulated that decarboxylation of a nucleoside... 

FIG. l.-Transglycosylation of D-Apiose from UDP-D-apiose (5). (Studies in vitro showed that UDP-D-apiose uridine 5 -[3-C-(hydroxymethyl)-a-D-erythrofiiranosyl pyrophosphate] functions in a transglycosylation reaction. The product is apiin, 4, 5-dihydroxyflavon-7-yl 2-0-[3-C-(hydroxymethyl)-/3-D-erythrofuranosyl]-/8-D-glucopyran-oside (4), formed through the aid of an acceptor molecule.7 Additional products that may be formed by transglycosylation from an apiose donor-molecule include, principally, apiose-containing polysaccharides.)... 

The enzyme catalyzing the transfer of D-apiose from UDP-apiose to 4, 5-dihydroxyflavon-7-yl /3-D-glucopyranoside is commonly called apiin synthetase.7 Activity is measured by the formation of [14C]apiin from UDP-[U-14C]apiose. Apiin synthetase can be measured by the rapid separation and isolation, by poly(ethylenimine)-paper chromatography, of a product of the reaction, namely, [14C] apiin, from UDP-D-[U-14C]xylose and degradation products of UDP-[U-14C]apiose.31 There are reports of the isolation and purification of apiin synthetase from parsley leaves,31 from cell-suspension cultures of parsley,121 and from foxglove (Digitalis purpurea).31 Apiin synthetase isolated from parsley does not require metal ions, NAD+, or other cofactors, and is soluble. It is inhibited by several heavy metals, but not by tetra-N-... 

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