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Ecological Consequences of Enhanced UV Radiation on the Phenolic Content of Brassica Oleracea: a Review
Published in Donald L. Wise, Debra J. Trantolo, Edward J. Cichon, Hilary I. Inyang, Ulrich Stottmeister, Remediation Engineering of Contaminated Soils, 2000
Jeffrey M. Lynch, Alicja M. Zobel
The biosynthesis of coumarins is complex and involves several different enzymes (see Appendix). Hydroxycinnamic acids and coumarins are phenylpropanoids (58,60), as they contain at least one phenylpropane C6C3 structure. All of these compounds are derived from the aromatic amino acid phenylalanine. Phenylalanine is synthesized by the shikimic acid pathway and is converted by PAL to cinnamic acid, a key intermediate in phenylpropanoid biosynthesis (63,64). From cinnamic acid, derivatives are synthesized by the substitution of hydroxyl and methoxy groups to the aromatic ring. Two such derivatives are o-coumaric acid and sinapic acid.
Structure and Biosynthesis of Lignin
Published in Jean-Luc Wertz, Magali Deleu, Séverine Coppée, Aurore Richel, Hemicelluloses and Lignin in Biorefineries, 2017
Jean-Luc Wertz, Magali Deleu, Séverine Coppée, Aurore Richel
Lignin is the generic term for a large group of aromatic polymers resulting from the oxidative combinatorial coupling of 4-hydroxyphenylpropanoids (monolignols).3–5 It is the only naturally synthesized polymer with an aromatic backbone.6 The name of phenylpropanoids is derived from the phenyl group and the propene tail of cinnamic acid, which is synthesized from the amino acid phenylalanine (Phe) in the first step of phenylpropanoid biosynthesis. The three most abundant monolignols are p-coumaryl (4-hydroxycinnamyl), coniferyl (3-methoxy 4-hydroxycinnamyl), and sinapyl (3,5-dimethoxy 4-hydroxycinnamyl) alcohols (Figure 6.1).1
Explicating the effect of the ozonation on quality parameters of onion (Allium cepa L.) in terms of pungency, phenolics, antioxidant activity, colour, and microstructure
Published in Ozone: Science & Engineering, 2023
Pramod S. Shelake, Debabandya Mohapatra, Manoj Kumar Tripathi, Saroj Kumar Giri
Phenylalanine ammonia-lyase (PAL; EC 4.3.1.5) is known for initiating the phenylpropanoid biosynthesis pathway and is generally found in most of the higher plants. It helps in breaking down of ammonia group from L-phenylalanine, resulting in the formation of trans-cinnamate, initiating the biosynthesis of plant-specific phenylpropanoid derivatives, such as phenolics (Benkeblia 2000). Ozone treatment to onion could be attributed to the activation of PAL (Ali, Ong, and Forney 2014), which resulted in increased phenolic and flavonoids content. Another reason for the increase in phenol might be the cell wall modification during ozone treatment that caused enhanced extractability and release of some conjugated phenolic compounds. At higher concentrations, however, ozone decomposition produces numerous free radicals that scavenge phenolic compounds in commodity, resulting in a decrease in the phenolic and flavonoid contents (Alothman et al. 2010). This might have resulted in a decrease in phenolics after an effective ozone concentration of 400 ppm.
Leptolyngbya fragilis ISC 108 is the most effective strain for dodecane biodegradation in contaminated soils
Published in International Journal of Phytoremediation, 2019
Mahboobe Ghanbarzadeh, Vahid Niknam, Neda Soltani, Hasan Ebrahimzadeh
PAL is the key enzyme in the phenylpropanoid biosynthesis pathway which catalyzes the deaminating reaction of the amino acid phenylalanine from the primary metabolism into the secondary phenylpropanoid metabolism in the cell (Singh et al.2017). It is known that PAL undergoes significant changes in the cell under various biotic and abiotic environmental stresses (Singh et al.2017). Increased PAL activity under environmental stresses may lead to increased phenolic compounds accumulation (Rivero et al.2001). There is compelling evidence showing that oxidative stress defense-related enzymes can eliminate detrimental effects of ROS, as a response against DOD. This may be one of the reasons for the higher tolerance to oil contamination in the tolerant species.
Flavonoids – flowers, fruit, forage and the future
Published in Journal of the Royal Society of New Zealand, 2023
Nick W. Albert, Declan J. Lafferty, Sarah M. A. Moss, Kevin M. Davies
The biosynthesis of flavonoids begins with the aromatic amino acid phenylalanine, and is part of the larger phenylpropanoid biosynthesis pathway, which produces lignin, phenolic acids and volatiles, in addition to flavonoids. The first committed step to flavonoid biosynthesis (Figure 1B, refer for enzyme abbreviations) is catalysed by CHS, after which a series of isomerisation (CHI), hydroxylation (F3H, F3′H, F3′5′H), reduction (DFR, LAR, ANR) or oxidation (FLS, ANS) reactions occur to generate various flavonoid compounds, which are further modified or ‘decorated’ by glycosylation, methylation or acylation. Martin and Gerats (1993) coined the term ‘early’ and ‘late’ flavonoid biosynthesis genes. The ‘early biosynthetic genes’ were steps that did not show substantially reduced expression in anthocyanin regulatory mutants (typically CHS, CHI, F3H), while the ‘late biosynthetic genes’ showed substantial or a complete loss of expression (DFR, ANS, UFGT). This term has been widely adopted in the literature, but is often misinterpreted to suggest the early biosynthetic genes are not targeted by regulators of anthocyanin biosynthesis. More recently, studies have identified genes encoding non-enzymatic biosynthetic proteins, such as CHI-Like and the PR10 proteins, which are necessary for efficient production of flavonoids (Muñoz et al. 2010; Morita et al. 2014; Ban et al. 2018; Clayton et al. 2018; Berland et al. 2019), possibly by binding metabolite intermediates and channelling them to enzymes (e.g. CHS) efficiently, with correct stereochemistry (Dastmalchi 2021). The regulation of different branches of flavonoid production is complex, nuanced, and involves redundant regulation of some biosynthetic genes, particularly genes common to multiple pathways. Central to the regulation of flavonoids are R2R3-MYB transcription factors, which have diversified into sub-groups that have specialised in regulating the production of different metabolites (Figure 2A).