The synthesis,properties, and applications of ascorbyl esters

Ascorbic acid is a naturally occurring antioxidant. Nevertheless, its primary applications as an antioxidant in the life science, food and pharmaceutical industries are limited because of its hydrophilic nature. Alternatively, ascorbyl acid esters are potential surfactants and antioxidants. Chemical methods for the synthesis of ascorbyl esters lead to the formation of side products and simultaneous decomposition of ascorbic acid due to harsh reaction conditions. In contrast, lipases are used as regioselective and mild catalysts for the synthesis of ascorbyl esters. So far, various acyl donors namely, fatty acids, fatty acid alkyl esters, fatty acid vinyl esters and triacylglycerols have been explored for the synthesis of ascorbyl fatty esters. Other compounds such as L‐methyl lactate, bixin, phenyl butyric acid are also used as acyl donors. This article is focused on the recent developments of lipase‐catalyzed synthesis of ascorbyl esters, their antioxidant properties and applications.     

Antioxidant effect of mono‐ and dihydroxyphenols in sunflower oil with different levels of naturally present tocopherols

Antioxidant properties of mono‐ and dihydroxyphenolic acids and their alkyl esters were examined, with emphasis on the relationship between their molecular structure and antioxidant activity. Test media with different tocopherol level were used for determining the oxidative stability: original refined sunflower oil (total tocopherols 149.0 mg/kg), partially tocopherol‐stripped sunflower oil (total tocopherols 8.7 mg/kg) and distilled fatty acid methyl esters (FAME) as a tocopherol‐free medium. The chemical reaction of tocopherols with diazomethane tested for the purpose to eliminate their antioxidant activity failed due to the negligible degree of methylation of hydroxyl group in the tocopherol molecule. Caffeic acid and protocatechuic acid (3,4‐dihydroxyphenolic acids) and their alkyl esters were found to be more active antioxidants than monohydroxyphenolic acid (p‐hydroxybenzoic acid), 2,5‐dihydroxyphenolic acid (gentisic acid), 3‐methoxy‐4‐hydroxyphenolic acids (vanillic and ferulic acids) and their corresponding alkyl esters. Naturally present tocopherols in refined sunflower oil proved to have a synergistic effect on gentisic acid but not on its alkyl esters. In contrast, tocopherols showed an antagonistic effect on alkyl esters of caffeic acid, because their protection factors decreased with increasing level of tocopherols in the test medium. Moreover, the antioxidant activity of these alkyl esters decreased with increasing length of their alkyl chain in conformity with the polar paradox hypothesis. Practical applications: Tocopherols as naturally present antioxidants influence considerably the antioxidant activity of other antioxidants added to plant oils used as a test medium. Distilled fatty acid methyl esters prepared from refined sunflower oil may serve as an optimal tocopherol‐free test medium. Some alkyl esters of phenolic acids were evaluated to be applicable as natural more lipophilic antioxidants in comparison with phenolic acids.     

Impact of Fatty Acid Structure on CALB‐Catalyzed Esterification of Glucose

Enzymatic synthesis of fatty acid glucose esters from different fatty acyl donors are performed via enzymatic catalysis in the presence of Candida antarctica lipase B (CALB), using acetonitrile as the solvent. The acyl donor nature (fatty acid or fatty acid vinyl ester) and structure are varied. Lower reaction rates and lower conversions are obtained with fatty acids in comparison to their corresponding vinyl esters. Moreover, the acyl donor with the longest chain length gives the highest conversions. The presence of unsaturation on the acyl donor chain is also shown to be detrimental to the conversion. Practical Applications: The practical applications of the present work are related to the production of gluco‐esters that could be used as nonionic surfactants as detergents, cosmetics and food emulsifiers, emollients or conservatives, respectively. In this study, it is shown that in order to get high production yields, each reaction parameter has to be tuned properly.     

Medium‐chain alkyl esters of tyrosol and hydroxytyrosol antioxidants by cuphea oil transesterification

Effective lipophilic antioxidants were prepared by non‐aqueous enzymatic transesterification of plant phenols with cuphea oil. Tyrosol and hydroxytyrosol, abundantly available phenols from olive oil processing byproduct, were found to be predominately acylated with capric acid derived from the triglyceride fraction of the Cuphea germplasm line PSR 23 (Cuphea Viscosissima × C. lanceolata). The reaction was complete within 2 h, with a >97% conversion of either phenol using immobilized Candida antarctica lipase B. The reaction products were good solvents for tyrosol or hydroxytyrosol, suggesting a facile manufacturing route not dependent on use of organic solvents. Phenolic derivatives were assessed for their ability to serve as antioxidants for preventing the oxidation of polyunsaturated fatty acyl groups. The antioxidant capacities of the cuphea‐derived fatty acyl derivatives of tyrosol or hydroxytyrosol were the same as their respective derivatives prepared from decanoic acid. These biobased antioxidants may improve the oxidative stability of sensitive fatty acids in food applications. Practical applications: A new biobased antioxidant was created for the food industry. Foods can contain fats and oils that are susceptible to deterioration during storage, which can limit product quality and shelf‐life. Synthetic antioxidants can slow the spoilage process, although there are limitations to how much can be added to foods. The food industry is interested in using natural ingredients to solve storage stability problems. We found that the oil from the plant Cuphea, cultivated in the upper Midwest region of the US, is very useful for modifying olive oil waste molecules to create antioxidants for use in foods. The developed process would be suitable for commercial production. This research creates a new commercial use for a specialty oil seed crop, expands the market for cuphea oil, and has developed two novel antioxidants to help the food industry improve food quality.     

Production and Emulsifying Effect of Polyglycerol and Fatty Acid Esters with Varying Degrees of Esterification

Esters with acyl groups can be formed by the esterification of polyglycerol. The purpose of the present study was to produce fatty acid esters [hexanoic (caproic), octanoic (caprylic), decanoic (capric), dodecanoic (lauric), tetradecanoic (myristic), hexadecanoic (palmitic), octadecanoic (stearic)] and polyglycerol (average number‐of degrees of polymerization of 5) with varying degrees of esterification and to examine their emulsifying properties. A number of fundamental catalysts of polyglycerol acylation reactions by methyl esters of carboxylic acid were studied, and sodium methoxide was found to be the best choice. The temperature rate of transesterification increased from 180 to 220 °C with the fatty acid chain alkyl residue. Synthesized mono‐, di‐, tri‐, tetra‐, and heptaesters of various fatty acids and polyglycerol provided the highest hydroxyl values from 15 to 815 mg KOH g^?1 and saponification values from 82 to 321 mg KOH g^?1. The emulsifying properties were assessed for all polyglycerol and fatty acid esters, with results showing maximum emulsifying effect for tri‐ and tetraesters of capric, lauric, and caprylic acids. Regardless of the hydrophilic–lipophilic balance value (HLB) of polyglycerol esters and carboxylic acid, a 4:1 ratio of sunflower oil to water formed a water‐in‐oil type emulsion. When mixing oil and water in a 1:1 ratio, mono‐ and diesters of polyglycerol formed an oil‐in‐water type emulsion, heptaesters formed a water‐in‐oil type emulsion, and tri‐ and tetraesters formed both of types of emulsions, depending on the length of the acid hydrocarbon radicals.     

Synthesis and Properties of Ascorbyl Esters Catalyzed by Lipozyme TL IM using Triglycerides as Acyl Donors

Esters of l-ascorbic acid with long-chain fatty acids (E-304) are employed as antioxidants in foods rich in lipids. Although their enzymatic synthesis offers some advantages compared with the current chemical processes, most of the reported methods employ the immobilized lipase from Candida antarctica as biocatalyst and free fatty acids or activated esters as acyl donors. In order to diminish the cost of the process, we have investigated the synthesis of ascorbyl oleate and ascorbyl palmitate esters with the immobilized Thermomyces lanuginosus lipase Lipozyme TL IM—which is significantly less expensive than Novozym 435—and triglycerides as source of fatty acids. Lipozyme TL IM gave rise to a lower yield of 6-O-ascorbyl oleate than Novozym 435 when using triolein (64 vs. 84%) and olive oil (27 vs. 33%) as acyl donors. Both 6-O-ascorbyl oleate and 6-O-ascorbyl palmitate displayed excellent surfactant and antioxidant properties. The Trolox Equivalent Antioxidant Capability values for the oleate and palmitate were 71 and 84%, respectively, of those obtained with l-ascorbic acid; however, both derivatives were able to stabilize soybean oil towards peroxide formation.     

The Inhibitory Effect of Gallic Acid Alkyl Esters on Lipid Oxidation of Intactly Soaked Oyster Meats and Oyster Meat Homogenates during Refrigerated Storage

In this study, the antioxidant effects of gallic acid (GA) and its alkyl esters including methyl gallate (MG), butyl gallate (BG), octyl gallate (OG), and lauryl gallate (LG) in whole oyster meats and oyster meat homogenates during cold storage are investigated. The oxidation degree of lipid is measured by peroxide value (POV), thiobarbituric acid active substances (TBARS), and polyunsaturated fatty acid (PUFA) percentage. The results show that the lipid oxidation in the two types of samples is inhibited by GA alkyl esters, and the antioxidant effects first increase and then decrease along with the extension of the chain length, among the esters, BG and OG are relatively more effective. Therefore, it is speculated that the antioxidant capacity of GA alkyl esters may be influenced by hydrophobicity and follows a “cut-off effect” in whole oyster meats and oyster meat homogenates. Practical application: Seafood is easily oxidized even under cold storage because it contains more PUFA. Antioxidants are widely used to inhibit lipid oxidation. In this study, the antioxidant capacity of GA alkyl esters in whole oyster meats and oyster meat homogenates is investigated, which improves the selection of suitable antioxidants to strengthen the oxidation stability of oyster samples for cold storage.     

Kinetic resolution of 1‐phenylethanol integrated with separation of substrates and products by a supported ionic liquid membrane

BACKGROUND: In the present study, the kinetic resolution of rac‐1‐phenylethanol by transesterification with several vinyl esters catalysed by a commercial immobilized Candida antarctica lipase B (Novozym 435) was carried out in n‐hexane at different water contents. The subtrates and products involved in the kinetic resolution were separated using a membrane bioreactor containing a supported liquid membrane based on the ionic liquid 1‐butyl‐3‐methylimidazolium tetrafluoroborate [bmim⁺][BF₄^?]. RESULTS: Variables affecting the kinetic resolution performance of the enzyme were studied. First, the influence of water content of the medium on the synthetic activity, selectivity and enantioselectivity of the enzyme was analysed in order to establish the optimal amount of water. The use of vinyl esters of different alkyl chain length (vinyl propionate, vinyl butyrate and vinyl laurate) as acyl donors to kinetic resolution was studied. Finally, the integrated reaction/separation process for the resolution of rac‐1‐phenylethanol was carried out in the optimal conditions found. CONCLUSION: These investigations demonstrate that the coupling of lipase enantioselectivity with the selective separation of supported liquid membranes based on ionic liquids provides a promising basis for practical production of enantiomerically pure or enriched compounds. Copyright © 2008 Society of Chemical Industry     

Enzymatic synthesis of medium‐chain triacylglycerols by alcoholysis and interesterification of copra oil using a crude papain lipase preparation

We have examined the possibility of producing analogs of medium‐chain triglycerides (MCT) from copra oil, i.e. a triacylglycerol mixture with a high content of medium‐chain fatty acid moieties (C₆–C₁₀). A two‐step enzymatic process was used in which copra triacylglycerols were first split with papain lipase by alcoholysis with an alkyl alcohol and then subjected to interesterification with the alkyl esters recovered using papain lipase. Effects of temperature, water activity content, substrate ratio, biocatalyst amount, and alcohol chain length were also investigated. On the one hand, the sn‐3 stereoselectivity of the lipase in the alcoholysis of copra oil with butanol has permitted a direct enrichment of caproic, caprylic and capric moieties in the synthesized butyl esters. Thus, in the batch reactor, the reaction led to about 31% conversion of the oil after 24 h, and the content of C₆–C₁₀ acids in the synthesized esters increased from about 16% in the starting oil to almost 42%. A similar enzymatic alcoholysis in a packed‐bed column bioreactor gave 31% conversion of the oil after 120 min of reactor residence time. The reaction was also very selective because the C₆–C₁₀ fatty acyl groups represented about half of the newly formed butyl esters, whereas they accounted for only 16% of total fatty acids in the starting oil. On the other hand, the transesterification of the alkyl esters recovered (highly enriched in C₆–C₁₀ fatty acyl groups) with native copra oil directly led to an increase in the content of MCT in the oil, from 18 mol‐% at the beginning of the reaction to 61 mol‐% of MCT after a time period of 72 h in the batch reactor.     

Enzymatic esterification of glycerol II. Lipase-catalyzed synthesis of regioisomerically pure 1(3)-rac-monoacylglycerols

Regioisomerically pure 1(3)-rac-monoacylglycerols are conveniently prepared in high yields (>75%) and in multigram quantities by enzymatic esterification of glycerol in the presence of various lipases(Chromobacterium viscosum, Rhizopus delemar, Rhizomucor miehei) with a variety of different acyl donors, such as free fatty acids, fatty acid alkyl esters, vinyl esters and triacylglycerols, as well as natural fats and oils. All reactions are carried out in aprotic organic solvents with low water content, namelyn-hexane, diethyl ether, tBuOMe or mixtures of these solvents. Essential for the success of these transformations were the following two factors. First, the creation of an artificial interphase between the solvent-immiscible hydrophilic glycerol and the hydrophobic reaction medium by its adsorption onto a solid support. Second, a facile system for the separation of the desired monoacylglycerol from the reaction mixture, coupled with the continuous recycling of acyl donor and undesirable by-products.     

Functionalization of soy fatty acid alkyl esters as bioplasticizers

The combination of various functional groups, such as epoxy, acetoxy, methoxy, thiirane, and aziridine, on the fatty acyl chain of soy fatty acid alkyl esters have been synthesized and evaluated as plasticizers in poly(vinyl chloride) (PVC) applications. Numerous synthetic procedures, such as epoxidation, methoxylation, acetylation, thiiration, and aziridination, were used for synthesizing multifunctional soy fatty acid alkyl esters. Epoxidized soybean oil fatty acid alkyl ester served as the key intermediate for functionalization. Partial or complete ring opening of the epoxide by reacting with methanol and the subsequent etherification or acetylation of the hydroxyl function produced epoxy, alkoxy, and acetoxy derivatives. The nucleophilic substitution of epoxide with sulfur by reacting with ammonium thiocyanate produced thiirane and epoxy thiiranes. Although the aziridine derivatives were synthesized by reacting unsaturated fatty acid alkyl esters with chloramine‐T, the compounds were fully characterized and their physical and analytical properties were determined. The high viscosity and darker color of aziridine and thiirane derivatives limit their usefulness, whereas the physical properties of the other derivatives were acceptable. The plasticizer evaluation of methoxy and acetoxy soy fatty acid esters (methyl and n‐butyl) demonstrated good compatibility with PVC, high efficiency (Shore hardness), and gelling properties were comparable to commercial plasticizer, di‐isoonyl phthalate. The abundant availability and cost‐effectiveness of starting materials and the readily adoptable chemical processes make the fatty acid ester derivatives viable bioplasticizers to replace the fossil fuel‐derived phthalates. J. VINYL ADDIT. TECHNOL., 23:93–105, 2017. © 2015 Society of Plastics Engineers     

The role of free fatty acids on antioxidant effectiveness in unsaturated oils

1. In purified, unsaturated esters and triglycerides NDGA is a superior antioxidant to EMQ at all levels of unsaturation.
2. In long-chain unsaturated fatty acids EMQ is a superior antioxidant to NDGA.
3. The addition of free fatty acids to triglycerides, even in amounts as small as 0.05%, modifies the comparative effectiveness of antioxidants. The effect on the antioxidant activity of NDGA is more marked than is that on the activity of EMQ.
4. The effect of free fatty acid on relative antioxidant activity is demonstrable with long- and shortchain, saturated and unsaturated fatty acids.
5. Comparisons are given of the effect of the addition of free fatty acids on various antioxidants in various substrates.
6. The effectiveness of tocopherols in triglycerides is decreased by the addition of free fatty acid. Similarly the induction period of several vegetable oils is reduced when free fatty acids are added.

     

Enzymatic esterification of glycerol I. Lipase-catalyzed synthesis of regioisomerically pure 1,3-sn-diacylglycerols

Regioisomerically pure 1,3-sn-diacylglycerols are conveniently prepared in high yields (>80%) and in large quantities by enzymatic esterification of glycerol in the presence of various 1,3-selective lipases(Chromobacterium viscosum, Rhizopus delemar, Rhizomucor miehei) and a variety of different acyl donors like free fatty acids, fatty acid alkyl esters and vinyl esters. All reactions are carried out in aprotic organic solvents of low water content, namelyn-hexane, diethyl ether or tBuOMe. The creation of an artificial interphase between the solvent-immiscible hydrophilic glycerol and the hydrophobic reaction media by the adsorption of glycerol onto a solid support prior to use was essential for the success of these transformations. The effects of reaction conditions and the regioselectivities of the lipases on the product yields are described in detail.     

Comparative Oxidative Stability of Fatty Acid Alkyl Esters by Accelerated Methods

Several fatty acid alkyl esters were subjected to accelerated methods of oxidation, including EN 14112 (Rancimat method) and pressurized differential scanning calorimetry (PDSC). Structural trends elucidated from both methods that improved oxidative stability included decreasing the number of double bonds, introduction of trans as opposed to cis unsaturation, location of unsaturation closer to the ester head group, and elimination of hydroxyl groups. Also noticed with EN 14112 was an improvement in oxidative stability when a larger ester head group was utilized. Methyl esters that contained ten or less carbons in the fatty acid backbone were unacceptable for analysis at 110 °C (EN 14112) due to excessive sample evaporation. With respect to PDSC, a correlation was noticed in which the oxidation onset temperature (OT) of saturated fatty esters increased with decreasing molecular weight (R ² 0.7328). In the case of the monounsaturates, a very strong inverse correlation was detected between molecular weight and OT (R ² 0.9988), which was in agreement with EN 14112. Lastly, a strong direct correlation (R ² 0.8759) was elucidated between OT and oil stability index (OSI, EN 14112, 80 °C). The correlation was not as strong (R ² 0.5852) between OSI obtained at 110 °C and OT. Disclaimer: Product names are necessary to report factually on available data; however, the USDA neither guarantees nor warrants the standard of the product, and the use of the name by USDA implies no approval of the product to the exclusion of others that may also be suitable.     

Enzymatic Modification of Menhaden Oil to Incorporate Caprylic and/or Stearic Acid

Menhaden oil was enzymatically modified with caprylic (8:0) and/or stearic acid (18:0) to produce structured lipids (SL). The goal was to produce SL with high amounts of polyunsaturated fatty acids (PUFA), a low level of saturation, and a melting point of 25–35 °C. Substrate (menhaden oil to acyl donor) molar ratios were 1:1, 1:3, and 1:5 for 8:0, and 1:1, 1:2, and 1:3 for 18:0. Enzyme load was 10% of the total weight of substrates. Time course study determined optimal time for maximum acyl donor incorporation. Linear interpolation estimated molar ratios that yielded SL with 20 or 30 mol% incorporation of 8:0 or 18:0. Enzymatic reactions were also conducted with molar ratios of menhaden oil to acyl donors:8:0:18:0 (1:1:3, 1:2:2, and 1:3:1). Lipases from Candida antarctica, Lipozyme® 435, and Rhizomucor miehei, Lipozyme® RM IM (Novozymes North America, Inc., Franklinton, NC, USA), were compared for all reactions. Total and sn-2 fatty acid compositions, triacylglycerol (TAG) molecular species, thermal behavior, volatile lipid oxidation products, solid fat contents, and oxidative stability were compared. When 8:0 was the acyl donor, the 1:3.03 and 1:4.58 ratios resulted in incorporation of 20 and 30 mol% 8:0, respectively. With 18:0 as the acyl donor, the 1:1.32 and 1:2.41 ratios led to incorporation of 20 and 30 mol% 18:0, respectively. The 1:3:1 ratio SL had a crystallization onset (C₀) of 15.3 °C and a melting completion (M_c) of 33.1 °C. The physicochemical properties of these SL suggest that some may be useful in formulating food products such as margarines and spreads.     

Biotransformation of glycidol by the unspecific wax ester synthase/acyl‐CoA:diacylglycerol acyltransferase of Acinetobacter baylyi ADP1

Glycidol was biologically derivatized by the unspecific wax ester synthase/acyl coenzyme A (acyl‐CoA): diacylglycerol acyltransferase (WS/DGAT) from Acinetobacter baylyi ADP1 into glycidyl acyl ester. Catalysis of in vitro conversion of glycidol to glycidyl acyl ester by the WS/DGAT from A. baylyi was verified by (i) a radiometric assay, (ii) thin‐layer chromatography and (iii) also by ESI‐MS. A specific activity of 50 nmol·mg^–1·min^–1 was obtained when 10 mM glycidol and 5 µM palmitoyl‐CoA were used. In vivo synthesized glycidyl acyl esters in recombinant E. coli were detected and quantified by staining with the epoxide‐specific reagent 4‐(4‐nitrobenzyl)‐pyridine. Of glycidyl acyl esters, 1.5 mg/L was obtained from the culture in the presence of 10 mM glycidol and 10 mM oleate.     

Formation of Polar Compounds During Deep‐frying—Determination by 1H NMR and ESR

The present study aims to elucidate the factors influencing the generation of polar compounds in oils during deep‐frying. Oils with different fatty acid compositions, including palm oil (PO), refined palm kernel oil (RPKO), and refined coconut oil (RCO), are applied in successive frying processes. ¹H NMR spectra reveal that heated PO has a higher percentage of allyl acyl group and is more prone to formation of non‐polar dimeric triglycerides as compared to other types of oils. In addition, electron spin resonance (ESR) spectra indicate that alkyl radicals are more predominant than alkoxy radicals in heated PO. In contrast, RPKO and RCO are inclined to generation of alkoxy radicals during the thermal treatment. The results reveal that oils with high unsaturated fatty acid content are more prone to generation and oxidation of non‐polar dimeric triglycerides. Practical Applications: The change in free radical profile and concentration is one of the indicators of lipid oxidation and polymerization. Alterations in the levels of alkyl and alkoxyl radicals, revealed by ESR, can be used to illustrate the formation of polar compounds in deep‐fried oils with different fatty acid compositions. The percentage of allyl acyl group, revealed by ¹H NMR, can be used to predict the generation of polar compounds. Therefore, this study provides useful information for the development of different methods to reduce polar compound formation in oils during thermal processing depending on the fatty acid composition of different deep‐fried oils.     

Synthesis and aging properties of reactive antioxidant NAPM in natural rubber vulcanizates

The rubber antioxidant N‐(4‐anilinophenyl) methacrylamide (NAPM) was synthesized by a two‐step reaction using thionyl chloride (SOCl₂) with methacrylic acid (MAA) and consequently 4‐aminodiphenylamine (ADPA) as precursors. NAPM was characterized by IR, ¹H NMR and elemental analysis. Thermal stability, aging property of NAPM and mechanical properties of natural rubber (NR) vulcanizates containing NAPM were investigated and compared with two other commercial antioxidants N‐isopropyl‐N′‐phenyl‐p‐phenylene diamide (4010NA) and N‐(1, 3‐dimethyl butyl)—N′‐phenyl‐p‐phenylene diamide (4020). It was found that NAPM was an effective antioxidant with a better thermal stability and higher antiaging resistance than unreactive antioxidants 4010NA and 4020. And unsaturation level of NR vulcanizates containing NAPM was lower than that of 4010NA and 4020. Moreover, an antiaging resistant mechanism of a surface reaction between NAPM and cis‐1, 4‐polyisoprene in NR was proposed to explain the better properties of NAPM based on the IR and SEM analyses. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Chemical Composition and Antioxidant Activity of Seeds of Various Halophytic Grasses

Increasing population has resulted in overexploitation of conventional seeds. The limited supply of water and salinization of agricultural lands are threats to crop production. This creates food insecurity and results in ever‐increasing prices of crops and edible oils. Halophytes that produce high‐quality seeds can serve as sources of oil and edible products. We analyzed the chemical composition and antioxidant activity of seeds from 5 halophytic grasses, i.e., Aeluropus lagopoides, Eragrostis ciliaris, Eragrostis pilosa, Panicum antidotale, and Sporobolus ioclados. These seeds contained crude protein (10–29%), carbohydrates (32–55%), crude fiber (4–21%), minerals (3.8–9.2%), and oil (4–11%), indicating their nutritional potential. Oils of these seeds had suitable fatty‐acid composition with 62–82% unsaturation and only 17–24% saturation. Out of this, 91–94% of the total oil constituted by linoleic, oleic, and palmitic acids. High contents of total phenols (2.8–4.2 mg gallic acid equivalent [GAE] g^?1), flavonoids (0.5–1.3 mg Quercetin equivalent [QE] g^?1), and tannins (0.3–1.3 mg catechin equivalent [CE] g^?1) supported their high antioxidant activity (1,1‐Diphenyl‐2‐picryl‐hydrazyl (DPPH) activity in terms of half maximal inhibitory concentration‐IC₅₀ 1.1–5.86 mg mL^?1; 2,2′‐azino‐bis3‐ethylbenzothiazoline‐6‐sulphonic acid (ABTS) 18.8–72.8 mmol Trolox g^?1; ferric‐reducing antioxidant power 2.0–4.4 mmol Fe⁺² g^?1). The reverse phase‐high‐pressure liquid chromatography analysis identified the presence of bioactive phenolic antioxidants (mainly gallic acid, chlorogenic acid, coumaric acid, ferulic acid, kaempferol, and quercetin). Due to these characteristic composition and salt tolerability, these plants can serve as potential sources of industrial raw materials for food, edible oil, phytochemicals, and oliochemicals.     

Production and properties of chlorogenic acid lipophilic esters

Chlorogenic acid is a dietary polyphenol with important bioactivities. However, its high hydrophilicity prevents its applications as an antioxidant for lipid protection in a complex matrix such as food. Grafting an aliphatic chain onto chlorogenic acid, so‐called lipophilisation, via lipase‐catalysed esterification represents an efficient means of increasing its lipophilicity. A series of alkyl esters with various chain lengths were produced and used to explore the structure‐antioxidant activity relationship of amphiphilic antioxidants. Data obtained from complex systems (oil‐in‐water emulsion and cell culture) concluded that short or medium chain lengths enhance the antioxidant activity while longer chains tend to decrease the antioxidant ability of chlorogenic acid. This phenomenon remains to be fully explained. Acyl esters, in which the carboxylic acid group remains free were also produced and were shown to be interesting antioxidant candidates as well as useful tools for the understanding of antioxidant activities.