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New greener alternatives for bioreduction of aromatic aldehydes and decarboxylation of aromatic acids using juice of fruits
Abstract
Cocos nucifera L. and Borassus flabellifer L. juices act as bio catalytic system for the reduction of aromatic aldehydes to alcohols and selective decarboxylation of substituted cinnamic acid to styrene and substituted benzoic acid to polyphenolic compound. Both juices exhibit good activity when aromatic aldehydes and aromatic acids contain electron-donating groups at specific positions. Moreover, C. nucifera juice exhibits good result for the reduction and decarboxylation properties than B. flabellifer juice under the same reaction condition.
... At the start of our investigations, we synthesized p-hydroxy substituted styrenes 2a-b via greener approach by using coconut juice ( agua-de-coco do Cear a or ACC) following published procedure (Scheme 2) by our laboratory. 31 It is readily available, inexpensive substrate-selective solvent, and reactant for the preparation of 4-vinylphenols from their corresponding electron-rich acids. The vinylphenols 2a-b were achieved followed by decarboxylation from respective cinnamic acids 1a-b in the presence of ACC without any polymerized product. ...
... To decarboxylation of p-hydroxy cinnamic acid, we have used ACC as a green reaction medium and purified by column chromatography (1 g compound in 1000 mL juice) (Misra et al., 2012). 31 ...
... To decarboxylation of p-hydroxy cinnamic acid, we have used ACC as a green reaction medium and purified by column chromatography (1 g compound in 1000 mL juice) (Misra et al., 2012). 31 ...
A simple, new, and cost-efficient alternative route has been designed for
the synthesis of unique beta-amino alcohols under metal-free condition from
new type of 1,2- disubstituted styrene epoxides obtained from substituted
p-hydroxycinnamic acids via greener approach. It was followed by density
functional theory (DFT) based computational study to investigate the
mechanistic path for generating acetylated amino alcohols i.e. the main
key step for the formation of beta-amino alcohols.
... In similar bioreduction studies, the bioconversion of other functional groups was observed; for example in Salvano work, it was observed the decarbonylation of vanillin in 73% yield (Salvano et al., 2011a,b). Additionally, Misra reported the decarboxylation of phydroxy-benzoic and cinnamic acids by the juices of Cocos nucifera and Borassus flabellifer L. (Misra et al., 2012). A concomitant reduction of alkene has been also reported for ␣,-unsaturated aromatic carbonyl derivatives (Bizerra et al., 2010;Fonseca et al., 2009;Alves et al., 2012;Assunç ão et al., 2008). ...
... Exploring the quimioselectivity of this biotransformation, the reduction of substituted benzoic acids (5-8), was tried (Scheme 3); resulting in the recovering of the starting materials, except for the p-hydroxybenzoic acid (8) which was decarboxylated to phenol (8a) in 80% and 92%, respectively, for banana and maize leaves. In a similar manner in the reduction of substituted cinnamic acids (9-11, Scheme 3), only those 4-hydroxy substituted (10 and 11) were decarboxylated producing (10a and 11a); this fact strongly suggests an effect of the hydroxyl substituent in the 4-position (Misra et al., 2012). In addition a TLC comparison of reactions of 10 and 11 with Coco nut water (Misra et al., 2012) and reactions with banana and maize leaves showed unique product; it is worth to mention that for leaves reactions the consumption of starting material was complete, although the isolated yields were moderate possibly due to polymerization. ...
... In a similar manner in the reduction of substituted cinnamic acids (9-11, Scheme 3), only those 4-hydroxy substituted (10 and 11) were decarboxylated producing (10a and 11a); this fact strongly suggests an effect of the hydroxyl substituent in the 4-position (Misra et al., 2012). In addition a TLC comparison of reactions of 10 and 11 with Coco nut water (Misra et al., 2012) and reactions with banana and maize leaves showed unique product; it is worth to mention that for leaves reactions the consumption of starting material was complete, although the isolated yields were moderate possibly due to polymerization. The reaction of 10 proceeded in moderate yield, 28% and 46%, respectively, for banana and maize R 2 R 4 R 5 OH O 5 R 1 = COOH, R 2 ,R 4 ,R 5 = H 6 R 1 = COOH, R 2 = OH; R 4 ,R 5 = H 7 R 1 = COOH, R 2 , R 5 = OH; R 4 = H 8 R 1 = COOH, R 4 = OH; R 2 , R 5 = H 9 R 2 , R 4 , R 5 = H 10 R 2 y R 5 = H, R 4 = OH 11 R 2 = H, R 4 = OH, R 5 = OMe leaves and 11 produced 11a in 48% yield using banana leaves and 56% using maize leaves. ...
... As in the case of classical biocatalytic systems, the use of different parts of plants as biocatalysts has been mainly utilized to biocatalyze the stereoselective reduction of ketones (Cordell et al. 2007;Patil 2015). However, as mentioned above, this methodology has also been applied, but less frequently, to carry out the synthesis of primary alcohols obtained from aldehydes (Daucus corota, Conium maculatum, Manihot esculenta, Manihot dulcis, Cocos nuc ıfera, Zea maiz, Musa sapientum) (Yadav et al. 2002;Machado et al. 2006 andFonseca et al. 2009;Salvano et al. 2011;Misra et al. 2012;Luna et al. 2014;Sol ıs et al. 2019). ...
... After purification, all products were identified by comparing their retention times obtained by CG-FID analysis against the control samples, and by comparing their spectra of GC-MS, 1 H and 13 C NMR with literature data (Machado et al. 2006;Assunc¸ão et al. 2008;Misra et al. 2012;Alves-Ferreira, Da Silva, et al. 2012;Luna et al. 2014;Sol ıs et al. 2019). ...
Whole seeds of Bauhinia variegata L. (Fabaceae) were utilized as a biological reducer to transform benzaldehyde into benzyl alcohol. The effects of some variables such as temperature, the load of substrate and co-solvent, were established to optimize the reductive process. Utilizing the optimal reaction conditions, a laboratory-scale reaction (final concentration of the substrate: 21.2 mM) was performed to obtain benzyl alcohol (conversion: 95%; isolated yield: 49%; productivity: 1.11 g L⁻¹ or 0.046 g L⁻¹h⁻¹ of benzyl alcohol). In addition, using these optimal conditions, fourteen substituted benzaldehydes were reduced, with a conversion achieved to their corresponding benzyl alcohols ranging from 62% to >99% (isolated yields from 7% to 70%). Moreover, useful building blocks by the synthesis of the drugs and important commercial products were also obtained. The scope, limitations and advantages of this new biocatalytic synthetic method are also discussed.
... In addition they have noted that esters are hydrolyzed to carboxylic acids and nitrobenzene is reduced to azoxybenzene with coconut water (Fonseca et al., 2009). In another example Misra et al. have shown that aromatic electron rich aldehydes can be reduced to their corresponding alcohols using Cocos nucifera L. and Borassus flabellifer L. juices (Misra et al., 2012). Furthermore these vegetable juices were effective in decarboxylation of substituted cinnamic acids to the corresponding vinyl aromatics as well (Misra et al., 2012). ...
... In another example Misra et al. have shown that aromatic electron rich aldehydes can be reduced to their corresponding alcohols using Cocos nucifera L. and Borassus flabellifer L. juices (Misra et al., 2012). Furthermore these vegetable juices were effective in decarboxylation of substituted cinnamic acids to the corresponding vinyl aromatics as well (Misra et al., 2012). The catalytic reduction is one of the most important conversions in organic synthesis and biocatalytic reduction is a widely studied biochemical conversion due to their wide applications and potential in chemical and pharmaceutical industry (Huisman and Collier, 2013), (Chadha et al., 2016). ...
The hexose dehydration product and important renewable feedstock 5-hydroxymethylfurfural can be biocatalytically reduced to 2,5-furandimethanol in 96% yield using coconut (Cocos nucifera L.) water as the biocatalyst at room temperature. The dimer of 5-hydroxymethylfurfural 5,5'-[oxybis(methylene)]bis[2-furaldehyde] can also be reduced to the corresponding diol 5,5'-[oxybis(methylene)]bis-[2-furanmethanol] using coconut (Cocos nucifera L.) water in 95% yield under similar conditions. This biocatalytic system could be reused in four cycles without an appreciable loss in activity.
... Literature reports reveal that ACC is mostly composed of water more than 94% along with sugars, vitamins, minerals, amino acids and phytohormones [13]. Also, Lemos et al. and Nag et al. illustrated that ACC used as a reaction medium for the reduction of aromatic aldehydes [14,15]. ...
... Nag et al. reported that reduction and decarboxylation of aromatic aldehydes and aromatic acids, which is single step reactions, both have been performed by the juice of ACC (Cocos nucifera L.), BFJ (Borassus flabellifer L.) and CSJ (Cucumus sativus L.) [9,15]. From this idea, we decided to apply our methodology for the multicomponent reactions for the synthesis of substituted biscoumarins and substituted pyranocoumarins using ACC. ...
Background
The conception of ‘Green chemistry’ is the much inventive chemistry which is potent and more environmentally benign. It is notable that many organic reactions take place in conventional organic solvents, known as volatile organic compounds. Being concerned about the environmental impact, we report a promoting medium, coconut juice (ACC) for one-pot synthesis of biscoumarins and pyranocoumarins which is safe, harmless, green and environmentally benign.
Methods and Results
Substituted biscoumarins have been achieved by the reaction of biscoumarin and substituted aromatic aldehydes in presence of ACC which acts as a green catalyst cum solvent. Each reaction showed good to excellent yield in presence of both electron donating as well as electron withdrawing group on aromatic aldehyde without formation of any by-products. Similarly, pyranocoumarins have been achieved by the reaction of biscoumarin, substituted aromatic aldehydes, active methylene nitrile in presence of ACC. All the reactions proceed smoothly and gave higher yields in case of malononitrile in comparison of ethyl-2-cyanoacetate.
Conclusion
A simple, eco-friendly and novel procedure was demonstrated for the synthesis of biscoumarins and pyranocoumarins using natural feedstock coconut juice. The major importance of using ACC juice is higher yields, no work-up and no column chromatography.
... Direct sulfonylation was used for the synthesis of benzenesulfonyl derivatives 5aeb to obtain the desired products in 61e82% yield. Additionally, to synthesize piperazine 6, the cinnamic acid was previously prepared through condensation between benzaldehyde and malonic acid as previously described [28]. Thereafter, the a,b-unsaturated acid was converted to the respective chloride and reacted with 1-(9H-fluoren-9-yl)-piperazine (3) in a one-pot synthesis to afford 6 with 26% yield. ...
... The cinnamic acid precursor was synthesized as previously described [28]. Thereafter, this acid (1 mmol, 0.148 g) was reacted with a solution of thionyl chloride in CH 2 Cl 2 (1 M, 6 mL) for 5 h in refluxing toluene (5 mL). ...
... But these methods only test 4-hydroxycinnamic acids bearing electron-donating groups (EDG) [20][21][22][23]28] and suffer some disadvantages such as the use of a base catalyst (Stamford/Joshi/Setti/Singh's work), the addition of polymerization inhibitor (Setti's work), need of microwave-assisted (Joshi/Setti's work) and long reaction times (Stamford/Kourist's work). Several catalyst-free decarboxylation methods of cinnamic acids have been reported, however, they need using some sort of biocatalysts [29,33,34]. ...
We report herein an efficient protocol for the synthesis of 4-vinylphenols by a catalyst-free decarboxylation of trans -4-hydroxycinnamic acids. A variety of 4-vinylphenols has been synthesized in moderate to excellent yields. This protocol also features no polymerization.
... Our group has already reported that fruit juices are very useful as a green reaction medium for multicomponent reactions, 22,23 reduction and decarboxylation of aromatic compounds. 24,25 This time to develop a safe, green and sustainable for chemical synthesis, we have diligently worked on tamarind seed which is obtained in huge amount as waste produced from fruit and vegetable industries. Literature reports reveal that tamarind seed is mostly composed with protein, essential amino acids, fatty acids, minerals such as calcium, potassium, phosphorous, and magnesium. ...
Herein, a new, bio-mass derived sustainable feedstock was employed for the synthesis of 4H-pyran derivatives. In context of this, water extract of tamarin-dus indica seed ash (WETSA) has been proven as a reaction media for one-pot three-component reaction between CÀH activated carbonyl compound, aryl aldehyde, and malononitrile which acts as a basic catalyst. This novel method offers several advantages such as simple work-up, excellent yield, short reaction time, green reaction conditions, and the reaction even proceeds smoothly without any external promoter. The catalyst was recycled up to four times without significant loss in catalytic activity. ARTICLE HISTORY
... Scheme -18b 2.19 A new greener alternative for bio reduction of aromatic aldehydes (Scheme -20a) and decarboxylation of substituted aromatic acids (Scheme -20b) using coconut water as a biocatalyst [32]. This is an effort towards the energy efficient, eco-friendly transformation of interesting organic molecule. ...
... botrytis), spinach beet (Beta vulgaris var. cicla) and spinach (Spinacia oleracea) (Su arez-Franco et al. 2010), coconut (Cocos nucifera L.) and Asian palmyra palm (Borassus flabellifer L.) juices (Misra et al. 2012), Vietnamese coriander (Persicaria odorata Lour) leaves (Quynh et al. 2009), purple carrot (Daucus carota) roots (Omori et al. 2016), cassava (Manihot esculenta) (Machado et al. 2006), ginger (Zingiber officinale) (Alves et al. 2015), Aloe vera (Leyva et al. 2012), hemlock (Conium maculatum) (Salvano et al. 2011) and flax seeds (Linum usitatissimum) (Tavares et al. 2015). ...
The reduction of substituted benzaldehydes, benzaldehyde, acetophenone and 2-acetylpyridine to the corresponding alcohols was conducted under mild reaction conditions using plant enzyme systems as biocatalysts. A screening of 28 edible plants, all of which have reductase activity, led to the selection of pinto, Flor de Mayo, ayocote, black and bayo beans because these enabled the quantitative biocatalytic reduction of benzaldehyde to benzyl alcohol. The biocatalyzed reduction of substituted benzaldehydes was dependent on the electronic and steric nature of the substituent. Pinto beans were the most active reductase source, reduced 2-Cl, 4-Cl, 4-Me and 4-OMe-benzaldehyde with a conversion between 70% and 100%. All the beans reduced 2- and 4-fluorobenzaldehyde at a conversion between 83% and 100%. The reduction of the ketones was low, but bayo and black beans yielded (R)-1-(pyridin-2-yl)ethanol in enantiopure form.
... There are several reports on the possibility of using plants as biocatalysts for chemical transformations. The reduction of aromatic aldehydes has been carried out using broccoli, cauliflower, spinach beet, and spinach (Suárez-Franco, Hernández-Quiroz, Navarro-Ocaña, Oliart-Ros & Valerio-Alfaro, 2010), Conium maculatum (Salvano et al., 2011), Aloe vera (Leyva, Moctezuma, Santos-Díaz, Loredo-Carrillo & Hernández-González, 2012), banana and maize leaf wastes (Luna et al., 2014), coconut and palmyra palm juice (Misra, Maity, Chanda & Nag, 2012), passion fruit (Machado et al., 2008), and lentil (Alves et al., 2012). However, the investigation into the use of waste from plants as enzyme sources for the reduction of carbonyls is very scarce. ...
The aqueous extracts of the following vegetable wastes were used as an enzyme source to reduce benzaldehyde to benzyl alcohol: capulin, mamey, green pepper, chili, and avocado seeds; bean, turnip rape, fava bean, lima bean, and jinicuil pods; papaya peel, and chive leaves. The highest conversions of benzaldehyde were obtained with the capulin and mamey seeds, bean pods and chive leaves (86%, 77%, 54%, and 45% of benzyl alcohol
respectively). The biocatalytic methodology proposed avoids the generation of chemical toxic waste because metallic reducing agents are used in the chemical reduction; and the biological residues can be used as fertilizers. This procedure complies with some of the principles of green chemistry.
... Moreover, aldehydes could be reduced to alcohols by the hydroxyl in the polyphenols of HE. Similarly, the polyphenols in Cocos nucifera L. and Borassus flabellifer L. juices can act as bio catalytic system for the reduction of aromatic aldehydes to alcohols (Misra et al., 2012). In addition, the lowest value of (E)-2-octenal was found in T3. ...
... This bioconversion provides a significant role of green chemistry. 2.19 A new greener alternative for bioreduction of aromatic aldehydes (Scheme -20a) and decarboxylation of substituted aromatic acids (Scheme -20b) using coconut water as a biocatalyst [32]. This is an effort towards the energy efficient, eco-friendly transformation of interesting organic molecule. ...
Facile and green synthetic approaches are important issues in organic synthesis. Green chemistry has become a motivational and inspirational tool for organic chemists to develop mild and benign pathways for the synthesis of biologically active compounds. The naturally available fruit juice as a biocatalyst in synthesis fulfills almost all the terms and conditions of green chemistry and attracted the interest of researchers. The best thing is that most of fruits are easily available, cheap and can be easily extracted. The purpose of this review is to look out present aspects of fruit juice in organic transformations.
A bio-waste-originated heterogeneous solid acid catalyst (SO3H@PP) was easily prepared from cheap and easily available pomegranate peel (PP). The catalyst was characterized by IR, FE-SEM, XRD and EDX techniques. The prepared catalyst was efficiently applied for the Knoevenagel condensation of the various aromatic aldehydes and active methylene compounds (malononitrile and ethyl cyanoacetate) in water and EtOH at reflux conditions. The products were obtained with good to excellent yields. The catalysts were easily recovered by simple filtration and reused at least five times with a slight decrease in product yields. A bio-waste origin, easy availability, inexpensive, easy recovery and reusability are the prominent features of the reported catalysts. Cleaner reaction conditions, simple experimental and work-up procedures are the conspicuous features of this protocol.Graphical abstract
Agro-waste extracts are considered green solvents since they are easy to handle, readily accessible from natural waste feedstock, biodegradable and recyclable. Therefore, the employment of these extracts in reaction media has emerged as the most useful and eco-friendly alternative in modern organic chemistry. Here, we review recent developments for the generation of new carbon–carbon and carbon–heteroatom bonds mediated by agro-waste extracts. We show that these aqueous extracts have great applicability in several transformations, including condensations, oxidations, multicomponent and coupling reactions. The challenges and advantages on the use of water of agro-waste extracts in synthetic methodologies is also detail.
A simple, efficient, and facile heterogeneous multi‐walled carbon nanotubes‐zirconia nanocomposite (MWCNTs‐ZrO2) has been synthesized using natural feedstock coconut juice (água‐de‐coco do Ceará). The synthesized catalyst was characterized by Fourier transform infrared spectroscopy, X‐ray diffraction, field emission scanning electron microscopy, and X‐ray photoelectron spectroscopy analysis. The heterogeneous nanocomposite has been used for one‐pot synthesis of various N‐heterocyclic compounds like pyrazoles, 1,2‐disubstituted benzimidazoles, 2‐arylbenzazoles, and 2,3‐dihydroquinazolin‐4(1H)‐ones under green reaction medium at room temperature. This novel method has several advantages, such as short reaction time, simple work‐up, excellent yield, and green reaction conditions. The catalyst was recycled up to four times without significant loss in catalytic activity. The MWCNTs‐ZrO2 nanocomposite was synthesized from green reaction medium as well as natural feedstock água‐de‐coco do Ceará. The synthesized nanocomposite was shown to be a versatile, potent, and reusable catalyst for the synthesis of N‐heterocyclic compounds such as pyrazole, disubstituted benzimidazole, 2‐arylbenzazole, and dihydroquinazolinone derivatives.
A mild and practical method for the transition metal-free protodecarboxylation of aromatic acids using readily available and safe sodium persulfate as initiator was described. This environment-friendly decarboxylation approach was performed at 60. °C in ethanol and could easily scale up to the gram level with a good yield. In Particular, the tandem reactions of decarboxylation and halogenation were achieved by the addition of the corresponding halogenating reagents to the reaction system.
The first report on isolation and characterization of 2,3,4-trihydroxy-5-methylacetophenone (1), nicotinamide (2), and uracil (3) from palmyra palm syrup is described. Total phenolic content (TPC) and Total flavonoid content (TFC) of palm syrup were 244.70 ± 5.77 (mg gallic acid/kg of syrup) and 658.45 ± 27.86 (mg quercetin/kg of syrup), respectively. Compound 1 exhibited DPPH radical scavenging activity with an IC50 value of 20.02 ± 0.14 μM which was better than ascorbic acid (IC50 = 22.59 ± 0.30 μM). Compound 1 also showed broad spectrum antibacterial activity against Escherichia coli, Mycobacterium smegmatis, Staphylococcus aureus and Staphylococcus simulans.
The simple, new, greener and efficient alternatives to the existing protocols have been developed for the reduction of aromatic aldehydes to its corresponding alcohols, decarboxylation of substituted benzoic acids (C6–C1) and substituted cinnamic acids (C6–C3) having a hydroxyl group at the para position with respect to acid group to corresponding phenolic compounds and vinyl phenols respectively by using a natural feedstock cucumber juice (CSJ) which acts as a greener solvent system performing substrate selective reaction. Additionally, the hydrolysis of acetyl as well as benzoyl group of aromatic compounds has been carried out to afford excellent yield by CSJ.
Various vegetables as biological catalysts were evaluated in enantioselective reduction of carbonyl compounds. The stereoselectivity of the process was in agreement with Prelog's rule for twelve of the vegetables, whereas okra and green peppers formed anti-Prelog products. Zingiber officinale exhibited the best results with 30% conversion and 89% ee. The parameters of the reaction such as time, solvent and other substrates investigated, as well as the specie, showed good chemo-and enantioselectivity.
Two bacteria, Klebsiella oxytoca and Erwinia uredovora, which constituted epiphytic microftora on yacon (Polymnia sonchifolia) leaves, converted hydroxycinnamic acids into hydroxystyrenes decarboxylatively. Hydroxycinnamate decarboxylase was extracted as crude protein from the bacterial cells, and was substrate-inducible. This decarboxylation was for the bacteria a detoxification of hydroxycinnamic acids of plants, but the metabolites were toxic to other test bacteria and fungi, including some phytopathogens. The possible ecological role of these epiphytic bacteria on the host-plant was discussed. from the viewpoint of their chemical interaction via the styrene derivatives.
A series of aliphatic and aromatic aldehydes and ketones was reduced using plant cell preparations from coconut juice, Cocos nucifera, also called ACC (água-de-coco do Ceará). The reduced products were typically obtained in excellent yields (%) and with very high enantiomeric excess. Esters, amides, and nitrobenzene, yielded acids, amines and an azoxyderivative with satisfactory results.
Coconut water (coconut liquid endosperm), with its many applications, is one of the world's most versatile natural product. This refreshing beverage is consumed worldwide as it is nutritious and beneficial for health. There is increasing scientific evidence that supports the role of coconut water in health and medicinal applications. Coconut water is traditionally used as a growth supplement in plant tissue culture/micropropagation. The wide applications of coconut water can be justified by its unique chemical composition of sugars, vitamins, minerals, amino acids and phytohormones. This review attempts to summarise and evaluate the chemical composition and biological properties of coconut water.
4-Vinylphenols, useful compounds for industrial applications, were obtained by decarboxylation of 4-hydroxycinnamic acids under microwave irradiation in the presence of 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) as base and basic aluminum oxide as solid support. The reactions were fast (15–30 min). The selective extraction of the final products with ethyl acetate avoids chromatographic purifications. The conversions are quantitative and the yields are satisfactory. Only the unstable 4-vinylcatechol was obtained in moderate yield. This procedure was successfully extended to a natural sample of ferulic acid extracted from wheat bran to get the corresponding 4-vinylguaiacol, a FEMA GRAS (Flavor and Extract Manufacturer's Association; General Regarded as Safe) approved flavoring agent.
Decarboxylation of substituted cinnamic acids having a hydroxyl group at the para position gave predominantly the corresponding styrene derivatives in the presence of base with microwave heating. The reaction was conducted either under solvent-free conditions or using a solvent. When a primary amine was used as a base, the yield of the styrene or amide depended on the substituent of the cinnamic acid. Microwave heating for this reaction suppressed the side reactions compared with conventional heating.
A metal-free protocol for decarboxylation of substituted α-phenylcinnamic acid derivatives in aqueous media is developed, wherein a remarkable synergism between methylimidazole and aq NaHCO3 in polyethylene glycol under microwave furnished the corresponding para/ortho hydroxylated (E)-stilbenes in a mild and efficient manner. The critical role of water in facilitating the decarboxylation imparts an interesting facet to the synthetic utility of water mediated organic transformations. The developed protocol provides a clean alternative to the hitherto indispensable multistep approaches involving toxic quinoline and a copper salt combination as the common decarboxylating agent.
A series of compounds including aliphatic and aromatic aldehydes and ketone were reduced using a plant cell preparation from sugar cane (Saccharum officinarum). The products were obtained in poor to excellent yields (2.5–100%), and with good enantiomeric excess (25–100%) measured by GC chiral column. Other functional groups were also evaluated including ester, nitrile and amide, but were not reduced. Preliminary kinetic studies are reported. This represents the first report of the use of sugar cane as a biocatalytic agent.
Enzymatic reduction of 2-substituted tetrahydropyran-4-ones with Daucus carota, plant cells as biocatalyst occurred in water under extremely mild and environmentally benign conditions giving a 1:1 mixture of diastereoselectively (2R,4S)- and (2S,4S)-2-aryl- or 2-alkyl-tetrahydropyranols in high yields.
An efficient synthesis of 4-vinylphenol (4-VP) from para-hydroxycinnamic acid (pHCA) that uses the enzyme para-hydroxycinnamic acid decarboxylase (PDC) in a two-phase aqueous−organic solvent has been developed. The 4-VP titer and catalyst productivity (17 g L-1; 1010 g 4-VP isolated g-1 catalyst) greatly exceed those for intact cells expressing PDC or calcium alginate bead-immobilized PDC-expressing cells in an aqueous buffer (5 g L-1; 4.4 to 64 g of isolated 4-VP per gram of catalyst). In this two-phase reaction design, the organic solvent (e.g., toluene) enabled continuous extraction of 4-VP into the organic phase and either its recovery as a crystalline solid with low color or its direct conversion to 4-acetoxystyrene.
Rapeseed oil is usually expelled from the seed at high temperatures. Refining removes most of the non-triacylglycerol components, including many sinapic acid derivatives typical for rapeseed. The effect of these phenolic constituents on the oxidative stability of the oil was studied using rapeseed and turnip rapeseed oil samples resulting from different expelling conditions and refinement steps. The polar fraction was isolated, analyzed and tested for antioxidative activity in various lipid oxidation models. The amount of phenols was greatest in the post-expelled crude rapeseed oil, decreasing with an increasing degree of refining. The polar phenol content correlated with oxidative stability. The most active antioxidant component of the polar fraction was identified as vinylsyringol, a decarboxylation product of sinapic acid. This is the first report of vinylsyringol in rapeseed oil. It was abundant in the post-expelled crude oils and apparently responsible for their high phenol content and oxidative stability. Some vinylsyringol was present in the superdegummed oil but not in the fully refined oils.
Plants use multiple defence mechanisms comprising both constitutive and inducible barriers to prevent entering of phytopathogenic micro-organisms. In many plant species one of the most efficient responses to combat attacking microbes is the rapid synthesis of antimicrobial low molecular weight phytoalexins, for example, resveratrol, 3,5,4'-trihydroxystilbene (1). Resveratrol and its natural derivatives, however, display only moderate antimicrobial effects. Nevertheless, resveratrol may be a useful lead structure for the chemical synthesis of antimicrobials. In this study, several series of stilbenes have been synthesized, starting from the aldehydes using Wittig reactions to access the corresponding styrenes that were subjected to Mizoroki-Heck reactions to yield the stilbenes in good yields. The stilbenes were tested in an agar diffusion assay against several bacteria and fungi. For some of these compounds the inhibiting zones for bacteria and fungi were comparable with those of the antibiotics tetracycline, streptomycin, ampicillin, or kanamycin, directed against prokaryotes, and nourseothricin or hygromycin controlling fungi, respectively.
p-Coumaric acid decarboxylases (PDCs) catalyze the nonoxidative decarboxylation of hydroxycinnamic acids to generate the corresponding vinyl derivatives. Despite the biotechnological relevance of PDCs in food industry, their catalytic mechanism remains largely unknown. Here, we report insights into the structural basis of catalysis for the homodimeric PDC from Lactobacillus plantarum (LpPDC). The global fold of LpPDC is based on a flattened beta-barrel surrounding an internal cavity. Crystallographic and functional analyses of single-point mutants of residues located within this cavity have permitted identifying a potential substrate-binding pocket and also to provide structural evidences for rearrangements of surface loops so that they can modulate the accessibility to the active site. Finally, combination of the structural and functional data with in silico results enables us to propose a two-step catalytic mechanism for decarboxylation of p-coumaric acid by PDCs where Glu71 is involved in proton transfer, and Tyr18 and Tyr20 are involved in the proper substrate orientation and in the release of the CO(2) product.
The oxidation of green tea catechins by polyphenol oxidase/O2 and peroxidase/H2O2 gives rise to o-quinones and semiquinones, respectively, which inestability, until now, have hindered the kinetic characterization of enzymatic oxidation of the catechins. To overcome this problem, ascorbic acid (AH2) was used as a coupled reagent, either measuring the disappearance of AH2 or using a chronometric method in which the time necessary for a fixed quantity of AH2 to be consumed was measured. In this way, it was possible to determine the kinetic constants characterizing the action of polyphenol oxidase and peroxidase toward these substrates. From the results obtained, (-) epicatechin was seen to be the best substrate for both enzymes with the OH group of the C ring in the cis position with respect to the B ring. The next best was (+) catechin with the OH group of the C ring in the trans position with respect to the B ring. Epigallocatechin, which should be in first place because of the presence of three vecinal hydroxyls in its structure (B ring), is not because of the steric hindrance resulting from the hydroxyl in the cis position in the C ring. The epicatechin gallate and epigallocatechin gallate are very poor substrates due to the presence of sterified gallic acid in the OH group of the C ring. In addition, the production of H2O2 in the auto-oxidation of the catechins by O2 was seen to be very low for (-) epicatechin and (+) catechin. However, its production from the o-quinones generated by oxidation with periodate was greater, underlining the importance of the evolution of the o-quinones in this process. When the [substrate] 0/[IO4 (-)] 0 ratio = 1 or >1, H2O2 formation increases in cases of (-) epicatechin and (+) catechin and practically is not affected in cases involving epicatechin gallate, epigallocatechin, or epigallocatechin gallate. Moreover, the antioxidant power is greater for the gallates of green tea, probably because of the greater number of hydroxyl groups in its structure capable of sequestering and neutralizing free radicals. Therefore, we kinetically characterized the action of polyphenol oxidase and peroxidase on green tea catechins. Furthermore, the formation of H2O2 during the auto-oxidation of these compounds and during the evolution of their o-quinones is studied.
A novel and efficient reduction of various prochiral ketones such as acetopehones, alpha-azido aryl ketones, beta-ketoesters, and aliphatic acyclic and cyclic ketones to the corresponding optically acive secondary alcohols with moderate to excellent chemical yield was achieved by using Daucus carota, root plant cells under extremely mild and environmentally benign conditions in aqueous medium, has been described. Many of these optically active alcohols are the potential chiral building blocks for the synthesis of pharmaceutically important molecules and asymmetric chiral ligands. Hence, this biocatalytic approach is found to be the most suitable for the preparation of a wide range of chiral alcohols and gave inspiration for the development of a new biotechnological process.
Biocatalysis constitutes an important tool in organic synthesis, especially for the preparation of chiral molecules of biological interest. A series of aliphatic and aromatic aldehydes and two ketones were reduced using plant cell preparations from Manihot esculenta and Manihot dulcis roots. The reduced products were typically obtained in excellent yields (80-96%), and with excellent enantiomeric excess (94-98%), except for vanillin. Esters, a nitrile, and an amide were also examined, but were not reduced. Preliminary conversion rate studies are reported. This is the first attempt to perform the biotransformation of carbonyl compounds using Manihot species.
It was previously reported that cell cultures from Lactobacillus plantarum CECT 748 (T) were able to decarboxylate phenolic acids, such as p-coumaric, m-coumaric, caffeic, ferulic, gallic, and protocatechuic acid. The p-coumaric acid decarboxylase (PDC) from this strain has been overexpressed and purified. This PDC differs at its C-terminal end when compared to the previously reported PDC from L. plantarum LPCHL2. Because the C-terminal region of PDC is involved in enzymatic activity, especially in substrate activity, it was decided to biochemically characterize the PDC from L. plantarum CECT 748 (T). Contrarily to L. plantarum LPCHL2 PDC, the recombinant PDC from L. plantarum CECT 748 (T) is a heat-labile enzyme, showing optimal activity at 22 degrees C. This PDC is able to decarboxylate exclusively the hydroxycinnamic acids p-coumaric, caffeic, and ferulic acids. Kinetic analysis showed that the enzyme has a 14-fold higher K(M) value for p-coumaric and caffeic acids than for ferulic acid. PDC catalyzes the formation of the corresponding 4-vinyl derivatives (vinylphenol and vinylguaiacol) from p-coumaric and ferulic acids, respectively, which are valuable food additives that have been approved as flavoring agents. The biochemical characteristics showed by L. plantarum PDC should be taken into account for its potential use in the food-processing industry.
- Bernini