Anita M. Brinker

Plants and human health in the twenty-first century

The concept of growing crops for health rather than for food or fiber is slowly changing plant biotechnology and medicine. Rediscovery of the connection between plants and health is responsible for launching a new generation of botanical therapeutics that include plant-derived pharmaceuticals, multicomponent botanical drugs, dietary supplements, functional foods and plant-produced recombinant proteins. Many of these products will soon complement conventional pharmaceuticals in the treatment, prevention and diagnosis of diseases, while at the same time adding value to agriculture. Such complementation can be accelerated by developing better tools for the efficient exploration of diverse and mutually interacting arrays of phytochemicals and for the manipulation of the plants ability to synthesize natural products and complex proteins. This review discusses the history, future, scientific background and regulatory issues related to botanical therapeutics.

Glucosinolate composition of seeds from 297 species of wild plants

Abstract Seed samples from 22 species of the Capparidaceae (eight genera), one Caricaceae, 259 Cruciferae (88 genera), two Moringaceae, three Phytolaccaceae, one Pittosporaceae, six Resedaceae, one Salvadoraceae and two Tropaeolaceae were analysed for total and individual glucosinolate compositions. Glucosinolates with a wide variety of both alkyl and aryl substituents were quantified by GC of their hydrolysis products and, in certain cases, were confirmed by mass spectrometry.

Tobacco as a production platform for biofuel: overexpression of Arabidopsis DGAT and LEC2 genes increases accumulation and shifts the composition of lipids in green biomass

When grown for energy production instead for smoking, tobacco can generate a large amount of inexpensive biomass more efficiently than almost any other agricultural crop. Tobacco possesses potent oil biosynthesis machinery and can accumulate up to 40% of seed weight in oil. In this work, we explored two metabolic engineering approaches to enhance the oil content in tobacco green tissues for potential biofuel production. First, an Arabidopsis thaliana gene diacylglycerol acyltransferase (DGAT) coding for a key enzyme in triacylglycerol (TAG) biosynthesis, was expressed in tobacco under the control of a strong ribulose-biphosphate carboxylase small subunit promoter. This modification led to up to a 20-fold increase in TAG accumulation in tobacco leaves and translated into an overall of about a twofold increase in extracted fatty acids (FA) up to 5.8% of dry biomass in Nicotiana tabacum cv Wisconsin, and up to 6% in high-sugar tobacco variety NC-55. Modified tobacco plants also contained elevated amounts of phospholipids. This increase in lipids was accompanied by a shift in the FA composition favourable for their utilization as biodiesel. Second, we expressed in tobacco Arabidopsis gene LEAFY COTYLEDON 2 (LEC2), a master regulator of seed maturation and seed oil storage under the control of an inducible Alc promoter. Stimulation of LEC2 expression in mature tobacco plants by acetaldehyde led to the accumulation of up to 6.8% per dry weight of total extracted FA. The obtained data reveal the potential of metabolically modified plant biomass for the production of biofuel.

Enteroviruses harness the cellular endocytic machinery to remodel the host cell cholesterol landscape for effective viral replication.

Cholesterol is a critical component of cellular membranes, regulating assembly and function of membrane-based protein/lipid complexes. Many RNA viruses, including enteroviruses, remodel host membranes to generate organelles with unique lipid blueprints on which they assemble replication complexes and synthesize viral RNA. Here we find that clathrin-mediated endocytosis (CME) is harnessed by enteroviruses to traffic cholesterol from the plasma membrane (PM) and extracellular medium to replication organelles, where cholesterol then regulates viral polyprotein processing and facilitates genome synthesis. When CME is disrupted, cellular cholesterol pools are instead stored in lipid droplets, cholesterol cannot be trafficked to replication organelles, and replication is inhibited. In contrast, replication is stimulated in cholesterol-elevated cells like those lacking caveolins or those from Niemann-Pick disease patients. Our findings indicate cholesterol as a critical determinant for enteroviral replication and outline roles for the endocytic machinery in both the enteroviral life cycle and host cell cholesterol homeostasis.

ISOLATION AND IDENTIFICATION OF PICEATANNOL AS A PHYTOALEXIN FROM SUGARCANE

Abstract Piceatannol was isolated from sugarcane (Saccharum sp.) infected with Colletotrichum falcatum but not from healthy or wounded sugarcane, or C. falcatum itself. The compound inhibited both spore germination and germ tube growth of C. falcatum. This is the first report of a stilbene phytoalexin in the Poaceae.

Over-Expression of Monoacylglycerol Lipase (MGL) in Small Intestine Alters Endocannabinoid Levels and Whole Body Energy Balance, Resulting in Obesity

The function of small intestinal monoacylglycerol lipase (MGL) is unknown. Its expression in this tissue is surprising because one of the primary functions of the small intestine is to convert diet-derived MGs to triacylglycerol (TG), and not to degrade them. To elucidate the function of intestinal MGL, we generated transgenic mice that over-express MGL specifically in small intestine (iMGL mice). After only 3 weeks of high fat feeding, iMGL mice showed an obese phenotype; body weight gain and body fat mass were markedly higher in iMGL mice, along with increased hepatic and plasma TG levels compared to wild type littermates. The iMGL mice were hyperphagic and displayed reduced energy expenditure despite unchanged lean body mass, suggesting that the increased adiposity was due to both increased caloric intake and systemic effects resulting in a hypometabolic rate. The presence of the transgene resulted in lower levels of most MG species in intestinal mucosa, including the endocannabinoid 2-arachidonoyl glycerol (2-AG). The results therefore suggest a role for intestinal MGL, and intestinal 2-AG and perhaps other MG species, in whole body energy balance via regulation of food intake as well as metabolic rate.

ABHD5/CGI-58 facilitates the assembly and secretion of apolipoprotein B lipoproteins by McA RH7777 rat hepatoma cells

Lipolysis of stored triacylglycerols provides lipid precursors for the assembly of apolipoprotein B (apoB) lipoproteins in hepatocytes. Abhydrolase domain containing 5 (ABHD5) is expressed in liver and facilitates the lipolysis of triacylglycerols. To study the function of ABHD5 in lipoprotein secretion, we silenced the expression of ABHD5 in McA RH7777 cells using RNA interference and studied the metabolism of lipids and secretion of apoB lipoproteins. McA RH7777 cells deficient in ABHD5 secreted reduced amounts of apoB, triacylglycerols, and cholesterol esters. Detailed analysis of liquid chromatography-mass spectrometry data for the molecular species of secreted triacylglycerols revealed that deficiency of ABHD5 significantly reduced secretion of triacylglycerols containing oleate, even when oleate was supplied in the culture medium; the ABHD5-deficient cells partially compensated by secreting higher levels of triacylglycerols containing saturated fatty acids. In experiments tracking the metabolism of [(14)C]oleate, silencing of ABHD5 reduced lipolysis of cellular triacylglycerols and incorporation of intermediates derived from stored lipids into secreted triacylglycerols and cholesterol esters. In contrast, the incorporation of exogenous oleate into secreted triacylglycerols and cholesterol esters was unaffected by deficiency of ABHD5. These findings suggest that ABHD5 facilitates the use of lipid intermediates derived from lipolysis of stored triacylglycerols for the assembly of lipoproteins.

Determination of Cyanide and Cyanogenic Glycosides from Plants

Many plants have the capacity to release hydrogen cyanide (HCN) when the tissues are damaged. The entire plant or any plant part may exhibit this property. Most commonly the compounds responsible are cyanogenic glycosides [O-β-glycosides of α-hydroxynitriles (cyanohydrins)], relatively polar, water-soluble compounds, usually accompanied by β-glycosidases that cleave sugars from the glycosides (Fig. 1). Associated hydroxynitrile lyases catalyze decomposition of the resultant cyanohydrins to carbonyl compounds and free hydrogen cyanide; this last step also may occur spontaneously. About 60 cyanogenic glycosides are known from higher plants (Nahrstedt 1987; Seigler 1991); probably the best known of these is amygdalin, which is widespread in seeds of plants such as apples, peaches, cherries, and apricots. Examples of the different structural classes of cyanogenic compounds are given in Fig. 2. The ability to produce and accumulate cyanogenic glycosides is found in all major vascular plant groups (Hegnauer 1977; Saupe 1981; Seigler 1991). Several major reviews are available (Seigler 1977, 1981a,b; Conn 1979, 1980a,b, 1981a,b; Nahrstedt 1981, 1985, 1987; Vennesland et al. 1981; Evered and Harnett 1988).

4-Hydroxymandelonitrile glucosides, dhurrin in Suckleya suckleyana and taxiphyllin in Girgensohnia oppositiflora (Chenopodiaceae)☆

Abstract The cyanogenic glucosides dhurrin [2S-β- d -glucopyranosyloxy-2-(4-hydroxy)-phenylacetonitrile] and taxiphyllin [2R-β- d -glucopyranosyloxy-2-(4-hydroxy) -phenylacetonitrile] have been isolated as the only cyanogenic glycosides from all parts of Suckleya suckleyana (dhurrin) and a herbarium specimen of Girgensohnia oppositiflora (taxiphyllin) of the Chenopodiaceae. The leaves of S. suckleyana contain the highest concentration of dhurrin followed by fruits, stems and roots.

Herbicidal activity of sulforaphene from stock (Matthiola incana).

A herbicidal compound was isolated from extracts ofMatthiola incana and identified as sulforaphene (4-methylsulfinyl-3-butenyl isothiocyanate). The ED50 of this compound against velvetleaf seedlings was approximately 2×10−4 M. Glucoraphenin, the glucosinolate that is the natural precursor of sulforaphene, was less phytotoxic, with an ED50 of near 6×10−3M.