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Plant secondary metabolites in defence and allelopathy.

ABSTRACT: Recent findings from culture-dependent and culture independent methods have demonstrated that indigenous marine actinomycetes exist in the oceans and are widely distributed in different marine ecosystems. There is tremendous diversity and novelty among the marine actinomycetes present in marine environments. Progress has been made to isolate novel actinomycetes from samples collected at different marine environments and habitats. These marine actinomycetes produce different types of new secondary metabolites. Many of these metabolites possess biological activities and have the potential to be developed as therapeutic agents. Marine actinomycetes are a prolific but underexploited source for the discovery of novel secondary metabolites.

This article is part of the Thematic Series

Metabolism1.0 Global and overview maps1.1 Carbohydrate metabolism1.2 Energy metabolism1.3 Lipid metabolism1.4 Nucleotide metabolism1.5 Amino acid metabolism1.6 Metabolism of other amino acids1.7 Glycan biosynthesis and metabolism1.8 Metabolism of cofactors and vitamins1.9 Metabolism of terpenoids and polyketides1.10 Biosynthesis of other secondary metabolites1.11 Xenobiotics biodegradation and metabolism1.12 Chemical structure transformation maps

Figure 1. Metabolic fate of aliphatic ketones and secondary alcohols

The marine environment harbors millions of species of microorganisms that play important role in mineralization of complex organic matter, degradation of dead plankton, plants, animals, degradation of pollutants and toxicants and primary and secondary productivity. Marine microorganisms have a diverse range of enzyme activity and capable of catalyzing various biochemical reaction with novel enzymes such as amylase, lipase, deoxyribonuclease, lipase and protease.

In the case of a methyl ketone, the terminal methyl group may undergo oxidation, eventually yielding -ketoacid, which is the substrate for further oxidation in the fatty acid pathway and citric acid cycle (Annex 1, reference ). In the case of ,-unsaturated ketones, glutathione may conjugate at the -position, yielding cysteine and mercapturic acid derivatives, which are also excreted primarily in the urine as the conjugated secondary alcohol (Williams, 1959; Portoghese et al., 1989).

Plant secondary metabolism - Wikipedia

Waterman PG (1992) Roles for secondary metabolites in plants. In: Davies J (ed.) Secondary Metabolites: Their Evolution and Function. Ciba Foundation Symposium 171, pp. 255–275. Chichester: Ciba Foundation, Wiley.

Single high doses of a homologous series of aliphatic secondary alcohols and ketones were administered individually by gavage to rabbits, principally to identify the extent of urinary glucuronide metabolite formation. The level of urinary excretion of glucuronic acid conjugates was determined over 24 h. The results showed that secondary alcohols, either administered directly or formed via ketone reduction, are largely excreted as glucuronic acid conjugates (Kamil et al., 1953). The substances, doses, and average urinary output of glucuronide as a percentage of the dose administered are listed in Table 3.

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INTRODUCTION: Actinomycetes are high GC, Gram-positive bacteria with fungal morphology. They are rich source of secondary metabolites with diverse biological activity. The Gram-positive bacteria fall into two major phylogenetic divisions, “low-GC” and “high-GC". GC content is an abbreviation for the percentage of GC base pairs in an organisms DNA. Those that have a low GC content, have more AT base pairs in their DNA.

Biosynthesis of Secondary Metabolites | SpringerLink

This section summarizes the data relevant to the safety evaluation of 39 aliphatic ketones, secondary alcohols and related esters (see Table 1). The group of flavouring agents includes three saturated ketones (Nos 1118, 1155 and 1156), 24 unsaturated ketones (Nos 1119–1139 and 1147–1149), seven secondary alcohols (Nos 1140, 1141 and 1150–1154) and five esters formed from saturated secondary alcohols (Nos 1142–1146). The esters in this group are readily hydrolysed to the corresponding secondary alcohols. After hydrolysis, the resulting secondary alcohols, ketones and other secondary alcohols in the group are readily absorbed. Secondary alcohols are interconvertible with the corresponding ketones in vivo (McMahon, 1982). Therefore, all the substances in this group are expected to participate in common routes of absorption, metabolism, distribution and excretion and have similar toxicological profiles.


,-Unsaturated ketones are also reduced to the corresponding secondary alcohols. Cytoplasmic NADPH-dependent ,-unsaturated ketone reductase isolated from human liver catalysed the reduction of aliphatic ,-unsaturated ketones to the corresponding secondary alcohols (Fraser et al., 1967). The resulting alcohols can then be excreted as glucuronic acid conjugates (Williams, 1959). Glucuronic acid conjugates of substances like secondary alcohols are frequently the end-products of metabolism and are excreted in the urine or the bile (Kasper & Henton, 1982).

Biosynthesis and regulation of secondary metabolites …

Sato F and Matsui K (2011) Engineering the biosynthesis of low molecular weight metabolites for quality traits (essential nutrients, health‐promoting phytochemicals, volatiles, and aroma compounds). In: Altman A and Hasegawa PM (eds) Plant Biotechnology and Agriculture, pp. 443–462. Oxford: Academic Press.

MetaCyc Secondary Metabolites Biosynthesis

Twenty aliphatic secondary ketones and related esters are methyl ketones (Nos 1119–1124, 1127, 1128, 1130–1132, 1134–1139 and 1149) or are secondary alcohols or related esters that are readily converted to methyl ketones in vivo (Nos 1140 and 1142) (see Table 1). Additional metabolic options are available for these substances. Methyl ketones undergo -hydroxylation and subsequent oxidation of the terminal methyl group to eventually yield corresponding ketocarboxylic acids (Gabriel et al., 1972). The ketoacids are intermediary metabolites (e.g. -ketoacids) that undergo oxidative decarboxylation to yield carbon dioxide and simple aliphatic carboxylic acids. The acids may be completely metabolized in the fatty acid pathway and citric acid cycle. The metabolism of -hydroxyacids and -ketoacids was recently reviewed (Annex 1, reference ).

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