Calystegines Convolvulaceae family

Calystegines appear to be vddely distributed in the Convolvulaceae family [78,80]. Eich and coworkers focused on the occurrence of seven calystegines (A3, A5, Bi, B2, B3, B4, Cl) identified by GC-MS analysis with authentic samples as references and analyzed the extracts of 65 Convolvulaceae species from predominantly tropical... 

Both alkaloids have (+) and (-) forms but only the (-) hyoscyamine and (-) scopolamine are active. The biosynthetic pathway of tropane alkaloids, Fig. (1) is not totally understood, especially at the enzymatic level. Edward Leete has pioneered the biosynthetic studies of tropane alkaloid since 1950"s using whole plants and isotope labels [85-86]. The tropane alkaloid hyoscyamine is bioconverted by the enzyme H6H (hyoscyamine 6p-hydroxylase, EC 1.14.11.11) to scopolamine via 6p-hydroxyhyoscyamine. Hyoscyamine is the ester of tropine and (S)-tropic acid. The (S)-tropic acid moiety derives from the amino acid L-phenylalanine, while the bicyclic tropane ring derives from L-omithine primarily or L-arginine via tropinone. Tropinone is stereospecifically reduced to form either, tropine which is incorporated into hyoscyamine, or on the other hand into pseudotropine which proceeds to calystegines, a group of nortropane derivates that were first found in the Convolvulaceae family [87]. 

Unusual pyronotropane tropane alkaloids have been fotmd in the family Proteaceae. Tropine and pseudotropine esters of benzoic acid have been isolated from the family Euphorbiaceae. Novel dithiolane esters, along with tropine esters of acetic, propionic, n-butyric, isobutyric, isovaleric, and benzoic acids have been fotmd in the Rhizophoraceae. Calystegines, as well as a 3-hydroxybenzoate ester, have been fotmd in Brassicaceae. The calystegines have been used as chemotaxonomic markers in the Convolvulaceae family [20]. Tropine esters with methoxy-substituted benzoic acids are also characteristic for the later family. 

However, at least one group of subclass B type metabolites, namely Tl-type tropane alkaloids as well as calystegines (see Sect. 3.5) represent plesiomotphic characters since both are also metabolites of the Convolvulaceae family. Such metabolites are found throughout the family. Obviously, they are the basis for apomorphic developments. 

N-raethyl group and occur occasionally as minor constituents in plants producing tropane alkaloids [76,77]. A recent survey of the occurrence of calystegines in Solanaceae and Convolvulaceae plants discovered that they are widely distributed in these families [1,2,78-80],... 

The detection of calystegines in so many genera of the Solanaceae suggests that additional investigation of this plant family could prove fruitful, if only to attempt to define the subfamilies and tribes in which these alkaloids occur. However, caution should be exercised in adopting this approach due to the fact that calystegines also occur in the taxonomically disparate families Convolvulaceae and Moraceae. 

Calystegines have been identified in the plant families Convolvulaceae, Solanaceae, Moraceae and Brassicaceae and have been found in numerous edible fruits and vegetables, especially members of the Solanaceae family, such as potatoes, tomatoes, eggplants and sweet and chili peppers, but also in mulberries and some Brassica vegetables and spices, such as kohlrabi, Brussel sprouts and black mustard leaves. 

Calystegines were initially detected in the Convolvulaceae, and today this plant family is the most thoroughly investigated for the occurrence of calystegines. There were earlier reports of tropane alkaloids in the Convolvulaceae. Tropine esters and nortropine esters with vanillic acid and veratric acid had been isolated from Convolvulus species, C. erinacius, C. krauseanus, and C. lineatus and reported between 1965 and 1977 (68-70). Several Convolvulaceae root tissues. 

Tropane alkaloids (TAs), a class of specialized metabolites with a bicyclic tropane ring in their structures, include clinically important hyoscyamine and scopolamine, the stimulant and narcotic cocaine, and the nortropane alkaloids calystegines. Plants producing TAs are distributed, sometime sporadically, across separate angiosperm families (e.g., Proteaceae, Convolvulaceae, Brassicaceae, Euphorbiaceae, Rhizophoraceae, Solanaceae, and Erythroxylaceae) (Griffin and Lin 2000). Studies of TA biosynthesis have been performed predominantly in Solanaceae plants, and thus little is known regarding TA pathways in other families. 

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