B-ring Of Flavonoids Research Articles

Gap-free genome assembly and CYP450 gene family analysis reveal the biosynthesis of anthocyanins in Scutellaria baicalensis.

Scutellaria baicalensis Georgi, a member of the Lamiaceae family, is a widely utilized medicinal plant. The flavones extracted from S. baicalensis contribute to numerous health benefits, including anti-inflammatory, antiviral, and anti-tumor activities. However, the incomplete genome assembly hinders biological studies on S. baicalensis. This study presents the first telomere-to-telomere (T2T) gap-free genome assembly of S. baicalensis through the integration of Pacbio HiFi, Nanopore ultra-long and Hi-C technologies. A total of 384.59Mb of genome size with a contig N50 of 42.44Mb was obtained, and all sequences were anchored into nine pseudochromosomes without any gap or mismatch. In addition, we analysed the major cyanidin- and delphinidin-based anthocyanins involved in the determination of blue-purple flower using a widely-targeted metabolome approach. Based on the genome-wide identification of Cytochrome P450 (CYP450) gene family, three genes (SbFBH1, 2, and 5) encoding flavonoid 3'-hydroxylases (F3'Hs) and one gene (SbFBH7) encoding flavonoid 3'5'-hydroxylase (F3'5'H) were found to hydroxylate the B-ring of flavonoids. Our studies enrich the genomic information available for the Lamiaceae family and provide a toolkit for discovering CYP450 genes involved in the flavonoid decoration.

Structure characteristics of flavonoids for heterocyclic aromatic amines inhibition using quantitative structure-activity relationship modeling.

The objective of this study was to investigate the structure characteristics of flavonoids that act as inhibitors for heterocyclic aromatic amines (HAAs) formation. Five quantitative structure-activity relationship models for predicting the inhibitory rates of HAAs (norharman, harman, PhIP, MeIQx, and 4,8-DiMeIQx) were established using selected chemometric parameters (R2 : 0.591-0.920), and indicated that the hydrophobicity, hydroxyl groups, and topological structure of flavonoids played important roles in the inhibition of HAAs formation. The 5,7-dihydroxyls in meta-position of the A-ring and the 4'-hydroxyl in the B-ring of flavonoids were critical for the inhibitory effects of HAAs, whereas the introduction of 3-hydroxyl and 3-O-glucoside in the C-ring reduced the inhibitory effects. Catechin served as the most effective inhibitor of HAAs followed by luteolin and genistein. The study can bring us a broader idea for controlling the formation of HAAs according to the structure of flavonoids. PRACTICAL APPLICATIONS: Heterocyclic aromatic amines (HAAs) are a class of organic substances with carcinogenic and mutagenic effect formed during the heating process of meat products. The formation of HAAs can be inhibited by adding natural antioxidants such as flavonoids to the meat during pretreatment. This inhibition is influenced by the unique structure of flavonoids. Thus, there has been an increasing demand to exploit the effective HAAs inhibitors from flavonoids by structure characteristics. Our study showed that the inhibitory effect of flavonoids on the formation of HAAs was mainly depended on their hydrophobicity, hydroxyl groups, and topological structure using the multiple QSAR models. Thus, effective HAAs inhibitors can be explored from dietary flavonoids according their structure characteristics.

Functional analysis of flavonoid 3′-hydroxylase and flavonoid 3′,5′-hydroxylases from tea plant (Camellia sinensis), involved in the B-ring hydroxylation of flavonoids

Flavonoids are major polyphenol compounds in plant secondary metabolism. The hydroxylation pattern of the B-ring of flavonoids is determined by the flavonoid 3′-hydroxylase (F3’H) and flavonoid 3′,5′-hydroxylase (F3′5′H). In this paper, one CsF3′H and two CsF3′5′Hs (CsF3′5′Ha and CsF3′5′Hb) were isolated. The phylogenetic tree results showed that F3′H and F3′5′Hs belong to the CYP75B and CYP75A, respectively. The Expression pattern analysis showed that the expression of CsF3′5′Ha and CsF3′5′Hb in the bud and 1st leaf were higher than other tissues. However, the CsF3′H had the highest expression in the 4th and mature leaf. The correlation analysis showed that the expression of CsF3′5′Hs is positively associated with the concentration of B-trihydroxylated catechins, and the expression of CsF3′H is positively associated with the Q contentration. Heterologous expression of these genes in yeast showed that CsF3′H and CsF3′5′Ha can catalyze flavanones, flavonols and flavanonols to the corresponding 3′, 4′ or 3′, 4′, 5′-hydroxylated compounds, for which the optimum substrate is naringenin. The enzyme of CsF3′5′Hb can only catalyze flavonols (including K and Q) and flavanonols (DHK and DHQ), of which the highest activities in catalyzing are DHK. Interestingly, The experiment of site-directed mutagenesis suggested that two novel sites near the C-terminal were discovered impacting on the activity of the CsF3′5′H. These results provide a significantly molecular basis on the accumulation B-ring hydroxylation of flavonoids in tea plant.

Square wave voltammetric analysis of polyphenol content and antioxidant capacity of red wines using glassy carbon and disposable carbon nanotubes modified screen-printed electrodes

The polyphenols present in different French red wines were characterized electrochemically using square wave voltammetry (SWV). The voltammetric measurements were carried out using a glassy carbon electrode and disposable screen-printed carbon electrodes unmodified and modified with single- and multi-walled carbon nanotubes. The single-walled carbon nanotubes-modified screen-printed carbon electrode (SWCNTs-SPCE) showed the best results for the voltammetric analysis of polyphenols in red wine samples, allowing using disposable electrodes to perform measurements. The obtained voltammograms contained three characteristic oxidation peaks. The first peak at the lowest potential was ascribed to oxidation of catechol and galloyl groups of polyphenols (on the flavonoid B-ring), the second peak to the oxidation of malvidin anthocyanins and the third peak was due mainly to the second oxidation wave of flavonoid phenolic groups. The total polyphenols content was determined by spectrophotometric and chromatographic methods as well as antioxidant capacity by the ABTS method, and were in good agreement with the SWCNTs-SPCE results. Thus, SWV is a satisfying fast electrochemical technique for the polyphenol characterization and antioxidant capacity determination of red wine compared to the more frequently used cyclic voltammetry or differential pulse voltammetry, especially using SWCNTs-SPCE.

Front Cover: Synthesis of Nontoxic Protoflavone Derivatives through Selective Continuous‐Flow Hydrogenation of the Flavonoid B‐Ring (ChemPlusChem 2/2018)

Front Cover: Synthesis of Nontoxic Protoflavone Derivatives through Selective Continuous‐Flow Hydrogenation of the Flavonoid B‐Ring (ChemPlusChem 2/2018)

Synthesis of Nontoxic Protoflavone Derivatives through Selective Continuous-Flow Hydrogenation of the Flavonoid B-Ring.

Invited for this month's cover is the group of Prof. Ferenc Fülöp (University of Szeged, Hungary). The cover picture shows an aerial view of the Bicaz Gorge (Transylvania) with a set of twisty hairpin turns symbolizing the challenges of selective hydrogenation of the flavonoid B-ring. The synthetic method presented can help suppress the toxic bioactivity properties of protoflavonoids thereby opening new avenues in the pharmacological investigation of these unique natural products and their synthetic analogs. Read the full text of the article at 10.1002/cplu.201700463.

Role of hydroxyl groups in the B-ring of flavonoids in stabilization of the Hoogsteen paired third strand of Poly(U).Poly(A)*Poly(U) triplex

We have reported the interaction of two flavonoids namely quercetin (Q) and morin (M) with double stranded poly(A).poly(U) (herein after A.U) and triple stranded poly(U).poly(A)*poly(U) (herein after U.A*U, dot represents the Watson–Crick and asterisk represents Hoogsteen base pairing respectively) in this article. It has been observed that relative positions of hydroxyl groups on the B-ring of the flavonoids affect the stabilization of RNA. The double strand as well as the triple strand of RNA-polymers become more stabilized in presence of Q, however both the duplex and triplex remain unaffected in presence of M. The presence of catechol moiety on the B-ring of Q is supposed to be responsible for the stabilization. Moreover, after exploiting a series of biophysical experiments, it has been found that, triple helical RNA becomes more stabilized over its parent duplex in presence of Q. Fluorescence quenching, viscosity measurement and helix melting results establish the fact that Q binds with both forms of RNA through the mode of intercalation while M does not bind at all to either forms of RNA.

Flavonoids as promoters of the (pseudo-)halogenating activity of lactoperoxidase and myeloperoxidase

In this study several flavonoids were tested for their potential to regenerate the (pseudo-)halogenating activity (hypothiocyanite formation) of the heme peroxidases lactoperoxidase (LPO) and myeloperoxidase (MPO) after hydrogen peroxide-mediated enzyme inactivation. Several flavonoid subclasses with varying hydroxylation patterns (especially of the flavonoid B-ring) were examined in order to identify structural properties of efficient enzyme regenerators. Kinetic parameters and second-order rate constants were determined. A 3′,4′-dihydroxylated B-ring together with C-ring saturation and hydroxylation were found to be important structural elements, which strongly influence the flavonoid binding and oxidizability by the LPO/MPO redox intermediates Compounds I and II. In combination with docking studies these results allow an understanding of the differences between flavonoids that promote the hypothiocyanite production by LPO and MPO and those that inhibit this enzymatic reaction.

Defining Key Structural Determinants for the Pro-osteogenic Activity of Flavonoids.

Epidemiological studies suggest that fruits and vegetables may play a role in promoting bone growth and preventing age-related bone loss, attributable, at least in part, to phytochemicals such as flavonoids stimulating osteoblastogenesis. Through systematically screening the effect of flavonoids on the osteogenic differentiation of human mesenchymal stem cells in vitro and correlating activity with chemical structure using comparative molecular field analysis, we have successfully identified important structural features that relate to their activity, as well as reliably predicted the activity of compounds with unknown activity. Contour maps emphasized the importance of electronegativity, steric bulk, and a 2-C-3-C double bond at the flavonoid C-ring, as well as overall electropositivity and reduced steric bulk at the flavonoid B-ring. These results support a role for certain flavonoids in promoting osteogenic differentiation, thus their potential for preventing skeletal deterioration, as well as providing a foundation for the lead optimization of novel bone anabolics.

Number of Hydroxyl Groups on the B-Ring of Flavonoids Affects Their Antioxidant Activity and Interaction with Phorbol Ester Binding Site of PKCδ C1B Domain: In Vitro and in Silico Studies.

Although flavonoids have been reported for their benefits and nutraceutical potential use, the importance of their structure on their beneficial effects, especially on signal transduction mechanisms, has not been well clarified. In this study, three flavonoids, pinocembrin, naringenin, and eriodictyol, were chosen to determine the effect of hydroxyl groups on the B-ring of flavonoid structure on their antioxidant activity. In vitro assays, including DPPH scavenging activity, ROS quantification by flow cytometer, and proteins immunoblotting, and in silico analysis by molecular docking between the flavonoids and C1B domain of PKCδ phorbol ester binding site were both used to complete this study. Eriodictyol (10 μM), containing two hydroxyl groups on the B-ring, exhibited significantly higher (p < 0.05) antioxidant activity than pinocembrin and naringenin. The IC50 values of eriodictyol, naringenin, and pinocembrin were 17.4 ± 0.40, 30.2 ± 0.61, and 44.9 ± 0.57 μM, respectively. In addition, eriodictyol at 10 μM remarkably inhibited the phosphorylation of PKCδ at 63.4% compared with PMA-activated RAW264.7, whereas pinocembrin and naringenin performed inhibition activity at 76.8 and 72.6%, respectively. According to the molecular docking analysis, pinocembrin, naringenin, and eriodictyol showed -CDOCKER_energy values of 15.22, 16.95, and 21.49, respectively, reflecting that eriodictyol could bind with the binding site better than the other two flavonoids. Interestingly, eriodictyol had a remarkably different pose to bind with the kinase as a result of the two hydroxyl groups on its B-ring, which consequently contributed to greater antioxidant activity over pinocembrin and naringenin.

Multiple evolution of flavonoid 3',5'-hydroxylase.

Multiple F3'5'H evolution from F3'H has occurred in dicotyledonous plants. Efficient pollinator attraction is probably the driving force behind, as this allowed for the synthesis of delphinidin-based blue anthocyanins. The cytochrome P450-dependent monooxygenases flavonoid 3'-hydroxylase (F3'H) and flavonoid 3',5'-hydroxylase (F3'5'H) hydroxylate the B-ring of flavonoids at the 3'- and 3'- and 5'-position, respectively. Their divergence took place early in plant evolution. While F3'H is ubiquitously present in higher plants, the distribution of F3'5'H is scattered. Here, we report that F3'5'H has repeatedly evolved from F3'H precursors at least four times in dicotyledonous plants: In the Asteraceae, we identified F3'5'Hs specific for the subfamilies Cichorioideae and Asteroideae, and additionally an F3'5'H that seems to be specific for the genus Echinops of the subfamily Carduoideae; moreover, characterisation of a sequence from Billardiera heterophylla (formerly Sollya heterophylla) (Pittosporaceae) showed that the independent evolution of an F3'5'H has occurred at least once also in another family. The evolution of F3'5'H from an F3'H precursor represents a gain of enzymatic function, probably triggered by an amino acid change at one position of substrate recognition site 6. The gain of F3'5'H activity allows for the synthesis of delphinidin-based anthocyanins which usually provide the basis for lilac to blue flower colours. Therefore, the need for an efficient pollinator attraction is probably the driving force behind the multiple F3'5'H evolution.

Advance in Dietary Polyphenols as Aldose Reductases Inhibitors: Structure-Activity Relationship Aspect

The dietary polyphenols as aldose reductases inhibitors (ARIs) have attracted great interest among researchers. The aim of this review is to give an overview of the research reports on the structure-activity relationship of dietary polyphenols inhibiting aldose reductases (AR). The molecular structures influence the inhibition of the following: (1) The methylation and methoxylation of the hydroxyl group at C3, C3′, and C4′ of flavonoids decreased or little affected the inhibitory potency. However, the methylation and methoxylation of the hydroxyl group at C5, C6, and C8 significantly enhanced the inhibition. Moreover, the methylation and methoxylation of C7-OH influence the inhibitory activity depending on the substitutes on rings A and B of flavonoids. (2) The glycosylation on 3-OH of flavonoids significantly increased or little affected the inhibition. However, the glycosylation on 7-OH and 4′-OH of flavonoids significantly decreased the inhibition. (3) The hydroxylation on A-ring of flavones and isoflavones, especially at positions 5 and 7, significantly improved the inhibition and the hydroxylation on C3′ and C4′ of B-ring of flavonoids remarkably enhanced the inhibition; however, the hydroxylation on the ring C of flavones significantly weakened the inhibition. (4) The hydrogenation of the C2˭C3 double bond of flavones reduced the inhibition. (5) The hydrogenation of α=β double bond of stilbenes hardly affected the inhibition and the hydroxylation on C3′ of stilbenes decreased the inhibition. Moreover, the methylation of the hydroxyl group of stilbenes obviously reduced the activity. (6) The hydroxylation on C4 of chalcone significantly increased the inhibition and the methylation on C4 of chalcone remarkably weakened the inhibition.

Identification of the flavonoid 3′-hydroxylase and flavonoid 3′,5′-hydroxylase genes from Antarctic moss and their regulation during abiotic stress

Flavonoids are ubiquitous plant secondary metabolites, and their hydroxylation pattern determines their color, stability, and antioxidant capacity. The hydroxylation pattern of the B-ring of flavonoids is determined by the activity of two members of cytochrome P450 protein (P450) family, the flavonoid 3'-hydroxylase (F3'H) and flavonoid 3',5'-hydroxylase (F3',5'H). However, they are still not well documented in lower plants such as bryophytes. We report the identification of gene encoding F3'H, F3',5'H from Antarctic moss Pohlia nutans and their transcriptional regulation under different stress conditions. Totally, sixteen cDNAs were isolated from P. nutans by RT-PCR and RACE techniques, all of which were predicted to code for F3'Hs or F3',5'Hs based on their annotations of Blast results. Amino acid alignment showed that they possessed the featured conserved domains of flavonoid hydroxylase, including proline-rich "hinge" region, EXXR motif, oxygen binding pocket motif, heme binding domain and substrate recognition sites. Phylogenetic analysis indicated that moss F3'Hs and F3',5'Hs were highly conserved and have independent evolution from the monocots, dicots and ferns. Meanwhile, real-time PCR analysis revealed that the expression profiling of flavonoid hydroxylase genes was influenced by diverse abiotic stresses including cold, salinity, drought or UV-B radiation and plant hormone abscisic acid (ABA) or jasmonic acid (JA) treatment. Since 3',4',5'-hydroxylated flavonoid-derivatives may serve a multitude of functions, including antioxidant activity and UV filters, the evolution and expression profile of flavonoid hydroxylase probably reflect the adaptive value of Antarctic moss in the acclimation of polar environment.

Structures Required of Flavonoids for Inhibiting Digestive Enzymes

The natural flavonoids as human digestive enzymes, such as α-glucosidase, α-amylase and aldose reductases inhibitors, have attracted great interest among researchers. The objective of this review is to overview the structures required of flavonoids for inhibiting these digestive enzymes. The hydroxylation on rings A and B of flavonoids improved the inhibition against these digestive enzymes. The hydroxylation on A-ring of flavones and isoflavones, especially at C-5 and C-7, significantly enhanced the inhibitory activities against digestive enzymes and the hydroxylation on positions C-3' and C-4' of B-ring of flavonoids remarkably improved the inhibition. The hydrogenation of the C2=C3 double bond on flavonoids decreased the inhibitory effects. The glycosylation of hyroxyl group on flavonoids weakened the inhibition against α-amylases and α-glucosidases. The glycosylation on 7-OH and 4'-OH of flavonoids significantly decreased the inhibition for aldose reductases. The glycosylation on 3-OH of flavonoids significantly increased or little affected the inhibition on aldose reductases. The methylation and methoxylation of flavonoids obviously weakened the inhibitory effects against α-amylase. The methylation and methoxylation of the hydroxyl group at C-3, C-3' and C-4' of flavonoids decreased or little affected the inhibitory potency against aldose reductases. And, the methylation and methoxylation of the hydroxyl groups at 5, 6, and 8 significantly increased the inhibitory capacity for aldose reductases. The methylation and methoxylation of flavonoids obviously affected the inhibitory effect for α-glucosidase in vitro depending on the replaced site.

NovQ is a prenyltransferase capable of catalyzing the addition of a dimethylallyl group to both phenylpropanoids and flavonoids

NovQ is a member of a recently identified CloQ/NphB class of prenyltransferases. Although NphB has been well characterized as a prenyltransferase with flexibility against aromatic substrates, few studies have been carried out on characterization of NovQ. Hence, in this study, we investigate the kinetics, substrate specificity and regiospecificity of NovQ. The corresponding novQ gene was cloned from Streptomyces niveus, which produces an aminocoumarin antibiotic, novobiocin. Recombinant NovQ was overexpressed in Escherichia coli and purified to homogeneity. The purified enzyme was a soluble monomeric 40-kDa protein that catalyzed the transfer of a dimethylallyl group to 4-hydroxyphenylpyruvate (4-HPP) independently of divalent cations to yield 3-dimethylallyl-4-HPP, an intermediate of novobiocin. Steady-state kinetic constants for NovQ with the two substrates, 4-HPP and dimethylallyl diphosphate, were also calculated. In addition to the prenylation of 4-HPP, NovQ catalyzed carbon-carbon-based and carbon-oxygen-based prenylations of a diverse collection of phenylpropanoids, flavonoids and dihydroxynaphthalenes. Despite its catalytic promiscuity, the NovQ-catalyzed prenylation occurred in a regiospecific manner. NovQ is the first reported prenyltransferase capable of catalyzing the transfer of a dimethylallyl group to both phenylpropanoids, such as p-coumaric acid and caffeic acid, and the B-ring of flavonoids. This study shows that NovQ can serve as a useful biocatalyst for the synthesis of prenylated phenylpropanoids and prenylated flavonoids.

Elastase Release by Stimulated Neutrophils Inhibited by Flavonoids: Importance of the Catechol Group

Pathogenesis of chronic inflammatory diseases is associated with excessive elastase release through neutrophil degranulation. In the present study, inhibition of human neutrophil degranulation by four flavonoids (myricetin, quercetin, kaempferol, galangin) was evaluated by using released elastase as a biomarker. Inhibitory potency was observed in the following order: quercetin > myricetin > kaempferol = galangin. Quercetin, the most potent inhibitor of elastase release also had a weak inhibitory effect on the enzyme catalytic activity. Furthermore, the observed effects were highly dependent on the presence of a catechol group at the flavonoid B-ring. The results of the present study suggest that quercetin may be a promising therapeutic agent in the treatment of neutrophil-dependent inflammatory diseases.

QSAR Analysis of the Lipid Peroxidation Inhibitory Activity with Structure and Energetics of 36 Flavonoids Derivatives

AbstractThe biological activity relationship of 36 flavonoid compounds was investigated using theoretical methods including quantitative structure activity relationships (QSAR) and quantum chemistry calculation. The results suggested that the 5 and/or 8 positions of the substituents of the hydroxyl group in the A ring and the 3′ and 4′ positions of substituents of the hydroxyl group in the B ring play an important role in flavonoid biological activity. This is probably due to the formation of an intra‐molecular hydrogen bond. In addition, the electronic energy, electrostatic energy and bond energy may have an effect on the biological activity of flavonoids. Also, our analysis has shown that the presence of the 1,4 and 1,2‐hydroquinone in the A ring and/or the Bring of flavonoids and the contribution of electronic energy, electrostatic energy and bond energy required consideration in the generation of the QSAR model and that the potential compounds will be predicted out of 36 flavonoids.

Inhibition of horseradish peroxidase catalytic activity by new 3-phenylcoumarin derivatives: Synthesis and structure–activity relationships

Twenty hydroxylated and acetoxylated 3-phenylcoumarins were synthesized, and the structure–activity relationships were investigated by evaluating the ability of these compounds to modulate horseradish peroxidase (HRP) catalytic activity and comparing the results to four flavonoids (quercetin, myricetin, kaempferol and galangin), previously reported as HRP inhibitors. It was observed that 3-phenylcoumarins bearing a catechol group were as active as quercetin and myricetin, which also show this substituent in the B-ring. The presence of 6,2′-dihydroxy group or 6,7,3′,4′-tetraacetoxy group in the 3-phenylcoumarin structure also contributed to a significant inhibitory effect on the HRP activity. The catechol-containing 3-phenylcoumarin derivatives also showed free radical scavenger activity. Molecular modeling studies by docking suggested that interactions between the heme group in the HRP active site and the catechol group linked to the flavonoid B-ring or to the 3-phenyl coumarin ring are important to inhibit enzyme catalytic activity.

Flower colour and cytochromes P450

Flavonoids are major constituents of flower colour. Plants accumulate specific flavonoids and thus every species often exhibits a limited flower colour range. Three cytochromes P450 play critical roles in the flavonoid biosynthetic pathway. Flavonoid 3′-hydroxylase (F3′H, CYP75B) and flavonoid 3′,5′-hydroxylase (F3′5′H, CYP75A) catalyze the hydroxylation of the B-ring of flavonoids and are necessary to biosynthesize cyanidin-(red to magenta) and delphinidin-(violet to blue) based anthocyanins, respectively. Pelargonidin-based anthocyanins (orange to red) are synthesized in their absence. Some species such as roses, carnations and chrysanthemums do not have violet/blue flower colour due to deficiency of F3′5′H. Successful expression of heterologous F3′5′H genes in roses and carnations results in delphinidin production, causing a novel blue/violet flower colour. Down-regulation of F3′H and F3′5′H genes has yielded orange petunia and pink torenia colour that accumulate pelargonidin-based anthocyanins. Flavone synthase II (CYP93B) catalyzes the synthesis of flavones that contribute to the bluing of flower colour, and modulation of FNSII gene expression in petunia and tobacco changes their flower colour. Extensive engineering of the anthocyanin pathway is therefore now possible, and can be expected to enhance the range of flower colours.

Cloning, Functional Identification and Sequence Analysis of Flavonoid 3′-hydroxylase and Flavonoid 3′,5′-hydroxylase cDNAs Reveals Independent Evolution of Flavonoid 3′,5′-hydroxylase in the Asteraceae Family

Flavonoids are ubiquitous secondary plant metabolites which function as protectants against UV light and pathogens and are involved in the attraction of pollinators as well as seed and fruit dispersers. The hydroxylation pattern of the B-ring of flavonoids is determined by the activity of two members of the vast and versatile cytochrome P450 protein (P450) family, the flavonoid 3'-hydroxylase (F3'H) and flavonoid 3',5'-hydroxylase (F3'5'H). Phylogenetic analysis of known sequences of F3'H and F3'5'H indicated that F3'5'H was recruited from F3'H before the divergence of angiosperms and gymnosperms. Seven cDNAs were isolated from species of the Asteraceae family, all of which were predicted to code for F3'Hs based on their sequences. The recombinant proteins of four of the heterologously in yeast expressed cDNAs exhibited the expected F3'H activity but surprisingly, three recombinant proteins showed F3'5'H activity. Phylogenetic analyses indicated the independent evolution of an Asteraceae-specific F3'5'H. Furthermore, sequence analysis of these unusual F3'5'H cDNAs revealed an elevated rate of nonsynonymous substitutions as typically found for duplicated genes acquiring new functions. Since F3'5'H is necessary for the synthesis of 3',4',5'-hydroxylated delphinidin-derivatives, which normally provide the basis for purple to blue flower colours, the evolution of an Asteraceae-specific F3'5'H probably reflects the adaptive value of efficient attraction of insect pollinators.