Occurrence, biological activity and synthesis of drimane sesquiterpenoids

Research on the use of plants and other complementary medicines in Hawai’i drew our attention toMorinda citrifolia (Rubiaceae). Noni, as it is commonly known, is representative of both currently popular medicinal plants in Ha-wai’i and the pharmacopoeias of traditional cultures of this poly ethnic population. It is also prominent among the increasing number of botanicals currently promoted by the “herbal” and “health foods/supplements” industry. Noni is unique in view of the large number of medical indications that characterize claims for its efficacy, the little that is known about its pharmacologic potential compared with other popularly used botanicals, and its rapidly evolving commercial success. This paper explores how the cultural novelty of noni, in conjunction with its equivocal pharmacology, contribute to its explosive market success in contemporary Hawai’i, and worldwide.

Ferment this: The transformation of Noni, a traditional polynesian medicine (Morinda Citrifolia, Rubiaceae)

A beta-primeverosidase from tea (Camellia sinensis) plants is a unique disaccharide-specific glycosidase, which hydrolyzes aroma precursors of beta-primeverosides (6-O-beta-D-xylopyranosyl-beta-D-glucopyranosides) to liberate various aroma compounds, and the enzyme is deeply concerned with the floral aroma formation in oolong tea and black tea during the manufacturing process. The beta-primeverosidase was purified from fresh leaves of a cultivar for green tea (C. sinensis var sinensis cv Yabukita), and its partial amino acid sequences were determined. The beta-primeverosidase cDNA has been isolated from a cDNA library of cv Yabukita using degenerate oligonucleotide primers. The cDNA insert encodes a polypeptide consisting of an N-terminal signal peptide of 28 amino acid residues and a 479-amino acid mature protein. The beta-primeverosidase protein sequence was 50% to 60% identical to beta-glucosidases from various plants and was classified in a family 1 glycosyl hydrolase. The mature form of the beta-primeverosidase expressed in Escherichia coli was able to hydrolyze beta-primeverosides to liberate a primeverose unit and aglycons, but did not act on 2-phenylethyl beta-D-glucopyranoside. These results indicate that the beta-primeverosidase selectively recognizes the beta-primeverosides as substrates and specifically hydrolyzes the beta-glycosidic bond between the disaccharide and the aglycons. The stereochemistry for enzymatic hydrolysis of 2-phenylethyl beta-primeveroside by the beta-primeverosidase was followed by (1)H-nuclear magnetic resonance spectroscopy, revealing that the enzyme hydrolyzes the beta-primeveroside by a retaining mechanism. The roles of the beta-primeverosidase in the defense mechanism in tea plants and the floral aroma formation during tea manufacturing process are also discussed.

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Cloning of β-Primeverosidase from Tea Leaves, a Key Enzyme in Tea Aroma Formation

Plants and their derived cell and tissue cultures in the family Rubiaceae accumulate a number of anthraquinones. There are two main biosynthetic pathways leading to anthraquinones in higher plants: the polyketide pathway and the chorismate/o-succinylbenzoic acid pathway. The latter occurs in the Rubiaceae for the biosynthesis of Rubia type anthraquinones. In this pathway, ring A and B of the Rubia type anthraquinones are derived from shikimic acid, α-ketoglutarate via o-succinylbenzoate, whereas ring C is derived from isopentenyl diphosphate, a universal building block for all isoprenoids. At present, it is known that isopentenyl diphosphate is formed via the mevalonic acid pathway or the 2-C-methyl-D-erythritol 4-phosphate pathway. Recent findings demonstrate that the 2-C-methyl-D-erythritol 4-phosphate pathway, not the mevalonic acid pathway, is involved in the formation of isopentenyl diphosphate, which constitutes ring C of anthraquinones in the Rubiaceae. This review summarizes the latest results of studies on the biosynthetic pathways, the enzymology and regulation of anthraquinone biosynthesis, as well as aspects of the metabolic engineering. Furthermore, biochemical and molecular approaches in functional genomics, which facilitate elucidation of anthraquinone biosynthetic pathways, are briefly described.

Biosynthesis of anthraquinones in cell cultures of the Rubiaceae

Histochemical Localization of Citral Accumulation in Lemongrass Leaves (Cymbopogon citratus (DC.) Stapf., Poaceae)

Activities of enzymes presumably involved in starch biosynthesis (ADP-glucose pyrophosphorylase, AGPase) and/or breakdown (starch phosphorylase, STP; amylases) were determined during potato (Solanum tuberosum L.) tuber dormancy and sprouting. Overall activities of all these enzymes decreased during the first stage of tuber dormancy. No clear changes were detected at the time of dormancy breaking and sprouting. However, when AGPase activity was monitored by in situ staining during the entire dormancy period, a clear decrease during the dormant period and a large increase before visible sprouting could be observed. This increase was especially evident near the vascular tissue and at the apical bud, which showed a very intensive staining. In situ staining of STP activity in sprouting tubers showed that the tissue distribution of STP was the same as for AGPase. As a possible explanation, direct starch cycling is suggested: STP produces glucose-1-phosphate during starch breakdown, which can be directly used as a substrate by AGPase for starch synthesis. Gene expression studies with the AGPaseS promoter coupled to the firefly luciferase reporter gene also clearly showed a higher activity in sprouting tubers as compared to dormant tubers, with the highest expression levels observed around the apical buds. The presence of amylase activity at dormancy initiation and AGPase activity persistent at the sprouting stage suggest that starch was cycling throughout the entire dormancy period. According to the in situ studies, the AGPase activity increased well before visible sprout growth and could therefore be one of the first physiological determinants of dormancy breakage.

Starch-related enzymes during potato tuber dormancy and sprouting

Anthraquinone glycosylation and hydrolysis in Morinda citrifolia cell suspensions: regulation and function.

Cell division versus secondary metabolite production in morinda citrifolia cell suspensions.

Occurrence of polygodial in plant organs and tissue culture of Polygonum hydropiper [Polygonum persicaria, secondary metabolites, tepals, cavities, sesquiterpene dialdehyde, accumulation]

Shoots of Polygonum hydropiper L. (waterpepper), especially in the leaves and flower-heads, contain significant amounts of the sesquiterpenoid polygodial, a compound with a potential use as a natural pesticide. The polygodial content of the tepals is particularly high: up to 8.5% of the dry weight. Roots and seeds do not contain detectable amounts of polygodial. Polygodial containing organs e.g. leaves and tepals, were found to contain cavities. Fourier transform infra-red (FTIR) microspectroscopy demonstrated that polygodial or its congeners are found in these cavities but not in other tissues or cells. Comparable cavities containing polygodial-like compounds were absent in the closely related species Polygonum persicaria L.



Callus cultures and cell suspensions as well as root- and shoot cultures were initiated from mature P. hydropiper plants. Polygodial could be detected only in shoot cultures. Our results indicate that functioning plastids may be essential for polygodial production and cavities for its accumulation.

Diaan C.L. Jamar

Papers

Starch-related enzymes during potato tuber dormancy and sprouting

Anthraquinone glycosylation and hydrolysis in Morinda citrifolia cell suspensions: regulation and function.

Cell division versus secondary metabolite production in morinda citrifolia cell suspensions.

Occurrence of polygodial in plant organs and tissue culture of Polygonum hydropiper [Polygonum persicaria, secondary metabolites, tepals, cavities, sesquiterpene dialdehyde, accumulation]

Occurrence of polygodial in plant organs and tissue culture of Polygonum hydropiper.