The Biosynthesis of Secondary Metabolites

Plant-based diets contain a plethora of secondary metabolites that may impact on health and disease prevention. Much attention has been focused on the potential bioactivity and nutritional relevance of several classes of phytochemicals such as flavonoids, carotenoids, phyto-oestrogens and glucosinolates. Less attention has been paid to simple phenolic acids that are widely found in fruit, vegetables, herbs, spices and beverages. Daily intakes may exceed 100 mg. In addition, bacteria in the gut can perform reactions that transform more complex plant phenolics such as anthocyanins, procyanidins, flavanones, flavonols, tannins and isoflavones into simple phenolic metabolites. The colon is thus a rich source of potentially active phenolic acids that may impact both locally and systemically on gut health. Both the small and large intestine (colon) contain absorption sites for phenolic acids but low post-prandial concentrations in plasma indicate minimal absorption early in the gastrointestinal tract and/or rapid hepatic metabolism and excretion. Therefore, any bioactivity that contributes to gut health may predominantly occur in the colon. Several phenolic acids affect the expression and activity of enzymes involved in the production of inflammatory mediators of pathways thought to be important in the development of gut disorders including colon cancer. However, at present, we remain largely ignorant as to which of these compounds are beneficial to gut health. Until we can elucidate which pro-inflammatory and potentially carcinogenetic changes in gene expression can be moderated by simple phenolic acids, it is not possible to recommend specific plant-based foods rich in particular phenolics to optimise gut health.

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“…The resulting bioactive polyketides have a range of applications. These include use as stimulant laxatives, antibiotics and antifungals (11) .…”

Section: Secondary Metabolites Of the Acetate Pathwaymentioning

confidence: 99%

Plant secondary metabolites and gut health: the case for phenolic acids

2011

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“…Although this convergence of pathways has been demonstrated for aflatoxin biosynthesis in fungi (15), examples in plants have not been completely elucidated but have been derived from incomplete experimental data complemented with biogenetic assumptions that have not necessarily been demonstrated for these compounds (14). In the case of 1, Fate and Lynn (16) demonstrated that exogenous isotopically labeled acetate was incorporated into the quinone head but not into the tail.…”

Section: Sorgoleone (2-hydroxy-5-methoxy-3-[(zz)-8ј11ј14ј-pentadecmentioning

confidence: 99%

Elucidation of the Biosynthetic Pathway of the Allelochemical Sorgoleone Using Retrobiosynthetic NMR Analysis

Dayan

Kagan

Rimando

2003

Journal of Biological Chemistry

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NMR analyses of the labeling pattern obtained using various 13 C-labeled precursors indicated that both the lipid tail and the quinone head of sorgoleone, the main allelopathic component of the oily root exudate of Sorghum bicolor, were derived from acetate units, but that the two moieties were synthesized in different subcellular compartments. The 16:3 fatty acid precursor of the tail is synthesized by the combined action of fatty-acid synthase and desaturases most likely in the plastids. It is then exported out of the plastids and converted to 5-pentadecatriene resorcinol by a polyketide synthase. This resorcinol intermediate was identified in root hair extracts. The lipid resorcinol intermediate is then methylated by a S-adenosylmethionine-dependent O-methyltransferase and subsequently dihydroxylated by a P450 monooxygenase to yield the reduced form of sorgoleone.Sorgoleone (2-hydroxy-5-methoxy-3-[(Z,Z)-8Ј,11Ј,14Ј-pentadecatriene]-p-benzoquinone) (1) is the main allelopathic component of the oily root exudate of sorghum (Sorghum bicolor (L.) Moench) ( Fig. 1) (1-3). The term sorgoleone is also used to describe a group of lipophilic p-benzoquinones structurally related to 1 that are also produced by sorghum roots having a hydroxy and a methoxy substitution at positions 2 and 5, respectively, and either a 15-or 17-carbon aliphatic tail with various degrees of unsaturation at position 3 (3).The primary mechanism of phytotoxic action of 1 is associated with inhibition of photosynthesis in higher plant systems by competing for the binding site of plastoquinone on photosystem II (4 -6). This lipophilic p-benzoquinone is also known to hinder electron transfer reactions involved in mitochondrial respiration and to inhibit the enzyme p-hydroxyphenylpyruvate dioxygenase (7,8).The herbicidal and allelopathic properties of 1 make isolation of the genes responsible for its biosynthesis desirable, as manipulation of those genes in sorghum or their introduction in other plant species could provide a better understanding of the role of 1 in plant-plant interaction and natural weed control. To identify the genes and characterize the enzymes they encode, it is necessary to determine the steps involved in the biosynthesis of 1. Little has been reported on this subject.Sorgoleone is found exclusively as a hydrophobic droplet exuding from the tips of root hairs (2), and a recent investigation of sorghum roots suggested that the production of 1 is compartmentalized in the highly physiologically active root hairs (9). The biosynthesis of secondary metabolites occurring in root hairs has not been studied in detail, although other specialized cells at the interface between a plant surface and its environment (i.e. trichomes) are known to produce unique secondary metabolites (10 -12).It has been postulated that the biosynthesis of 1 and related resorcinolic lipids is the result of the convergence of two pathways, namely the fatty acid biosynthetic pathway for the synthesis of the aliphatic tail and the activity of polyketide synthase-...

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“…These metabolites very important evolution of plants. 1,2 These metabolites play important role of biological activity. The most important of these biological activities is antioxidant property.…”

Section: Introductionmentioning

confidence: 99%

Investigation of Antioxidant Activity and Phytochemical Compositions of Celtis Tournefortii

Yildirim

Yılmaz²,

Kutlu

2017

FRA

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Context: Phytochemicals are non-nutritive plant chemicals that have protective or disease preventive properties. Because they have antioxidant property and protect our cells against oxidative damage. Aim: This work aimed to determination of phytochemical composition which total phenol content(TPC), total flavonoid content(TFC), total flavones content, alkaloid, acidity, pH, total carotenoid content, amount of carotene, β-carotene concentration, anthocyanin, amount of saponin and tannin, ascorbic acid levels, mineral profile and antioxidant activity of fresh Celtis tournefortii due to the importance of secondary metabolites. Material and method: Celtis tournefortii was used for this study Phytochemical compositions were determined by spectrometric methods excluding phenolic acid and mineral profile. Antioxidant activity were determined by different antioxidant method. Consequently: Celtis tournefortii may be an antioxidant source.

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The Biosynthesis of Secondary Metabolites

Cited by 87 publications

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Plant secondary metabolites and gut health: the case for phenolic acids

Plant secondary metabolites and gut health: the case for phenolic acids

Elucidation of the Biosynthetic Pathway of the Allelochemical Sorgoleone Using Retrobiosynthetic NMR Analysis

Investigation of Antioxidant Activity and Phytochemical Compositions of Celtis Tournefortii

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