Flavanone

About: Flavanone is a research topic. Over the lifetime, 1965 publications have been published within this topic receiving 54729 citations. The topic is also known as: flavanones.

Enzymes do what is expected (chalcone isomerase versus chorismate mutase)

Abstract: Madicago sativa chalcone isomerase (CI) catalyzes the isomerization of chalcone to flavanone, whereas E coli chorismate mutase (CM) catalyzes the pericyclic rearrangement of chorismate to prephenate Covalent intermediates are not formed in either of the enzyme-catalyzed reactions, KM and kcat are virtually the same for both enzymes, and the rate constants (ko) for the noncatalyzed reactions in water are also the same This kinetic identity of both the enzymatic and the nonenzymatic reactions is not shared by a similarity in driving forces The efficiency (ΔGo⧧ − ΔGcat⧧) for the CI mechanism involves transition-state stabilization through general-acid catalysis and freeing of three water molecules trapped in the E·S species The contribution to lowering ΔGcat⧧ by an increase in near attack conformer (NAC) formation in E·S as compared to S in water is not so important In the CM reaction, the standard free energy for NAC formation in water is 84 kcal/mol as compared to 06 kcal/mol in E·S Because the va

Cytochrome P450 93G1 Is a Flavone Synthase II That Channels Flavanones to the Biosynthesis of Tricin O-Linked Conjugates in Rice

Abstract: Flavones are a major class of flavonoids with a wide range of physiological functions in plants. They are constitutively accumulated as C-glycosides and O-linked conjugates in vegetative tissues of grasses. It has long been presumed that the two structural modifications of flavones occur through independent metabolic routes. Previously, we reported that cytochrome P450 93G2 (CYP93G2) functions as a flavanone 2-hydroxylase (F2H) that provides 2-hydroxyflavanones for C-glycosylation in rice (Oryza sativa). Flavone C-glycosides are subsequently formed by dehydratase activity on 2-hydroxyflavanone C-glycosides. On the other hand, O-linked modifications were proposed to proceed after the flavone nucleus is generated. In this study, we demonstrate that CYP93G1, the closest homolog of CYP93G2 in rice, is a bona fide flavone synthase II (FNSII) that catalyzes the direct conversion of flavanones to flavones. In recombinant enzyme assays, CYP93G1 desaturated naringenin and eriodictyol to apigenin and luteolin, respectively. Consistently, transgenic expression of CYP93G1 in Arabidopsis (Arabidopsis thaliana) resulted in the accumulation of different flavone O-glycosides, which are not naturally present in cruciferous plants. Metabolite analysis of a rice CYP93G1 insertion mutant further demonstrated the preferential depletion of tricin O-linked flavanolignans and glycosides. By contrast, redirection of metabolic flow to the biosynthesis of flavone C-glycosides was observed. Our findings established that CYP93G1 is a key branch point enzyme channeling flavanones to the biosynthesis of tricin O-linked conjugates in rice. Functional diversification of F2H and FNSII in the cytochrome P450 CYP93G subfamily may represent a lineage-specific event leading to the prevalent cooccurrence of flavone C- and O-linked derivatives in grasses today.

Overexpression of a tea flavanone 3-hydroxylase gene confers tolerance to salt stress and Alternaria solani in transgenic tobacco.

Abstract: Flavan-3-ols are the major flavonoids present in tea (Camellia sinensis) leaves. These are known to have antioxidant and free radical scavenging properties in vitro. Flavanone 3-hydroxylase is considered to be an important enzyme of flavonoid pathway leading to accumulation of flavan-3-ols in tea. Expression analysis revealed the upregulation in transcript levels of C. sinensis flavanone 3-hydroxylase (CsF3H) encoding gene under salt stress. In this study, the biotechnological potential of CsF3H was evaluated by gene overexpression in tobacco (Nicotiana tabacum cv. Xanthi). Overexpression of CsF3H cDNA increased the content of flavan-3-ols in tobacco and conferred tolerance to salt stress and fungus Alternaria solani infection. Transgenic tobaccos were observed for increase in primary root length, number of lateral roots, chlorophyll content, antioxidant enzyme expression and their activities. Also, they showed lesser malondialdehyde content and electrolyte leakage compared to control tobacco plants. Further, transgenic plants produced higher degree of pectin methyl esterification via decreasing pectin methyl esterase (PME) activity in roots and leaves under unstressed and salt stressed conditions. The effect of flavan-3-ols on pectin methyl esterification under salt stressed conditions was further validated through in vitro experiments in which non-transgenic (wild) tobacco seedlings were exposed to salt stress in presence of flavan-3-ols, epicatechin and epigallocatechin. The in vitro exposed seedlings showed similar trend of increase in pectin methyl esterification through decreasing PME activity as observed in CsF3H transgenic lines. Taken together, overexpression of CsF3H provided tolerance to salt stress and fungus A. solani infection to transgenic tobacco through improved antioxidant system and enhanced pectin methyl esterification.

Bioevaluation of human serum albumin-hesperidin bioconjugate: insight into protein vector function and conformation.

Abstract: Hesperidin is a flavanone glycoside widely available for dietary intake in citrus fruits or citrus fruit derived products; however, exhaustive and reliable data are scarcely available for biologica...