Solvent‐Free Enzymatic Synthesis of 1‐ o ‐Galloylglycerol Optimized by the Taguchi Method

Green synthesis of new and natural diester based on gallic acid and polyethylene glycol

Background

Antioxidant polyphenols like gallic acid (GA) and its esters called "gallates", which have health advantages for humans, have grown in significance in maintaining a healthy lifestyle and eating a significant amount of secondary plant phytochemicals. Here, for the first time, we suggest a green synthesis of a brand-new, all-natural diester based on gallic acid and polyethylene glycol.

Methods

This di-gallate is created in a single step without the use of a solvent (solid-solid reaction). This reaction has a potential yield of up to 90%. The bathochromic shift of the absorption bands from 277 nm to 295 nm in the UV-VIS spectra was caused by the addition of PEG to gallic acid. To confirm the structure of this di-gallate; Fourier-transform infrared (FTIR) spectroscopy, proton and carbon nuclear magnetic resonance ( 1H and 13C NMR), the thermal stability identified by thermogravimetric analysis (TGA), X-ray diffraction (XRD), and scanning electron microscopy (SEM) were all used to thoroughly analyze the manufactured product.

Results and conclusions

The acquired results, when compared to the literature spectrums, supported the establishment of the di-ester structure and created new opportunities for a large number of applications.

Combining antioxidants and processing techniques to improve oxidative stability of a Schizochytrium algal oil ingredient with application in yogurt

Oxidative instability limits incorporation of ω-3 fatty acids (FAs) into some products. This research combined processing techniques with antioxidant addition to overcome these barriers. Oleogels, microencapsulates, and microencapsulated gel ingredients were prepared using Schizochytrium spp. algal oil (AO) in combination with α, β, γ, and δ tocopherols or 1-o-galloylglycerol (GG) as antioxidants. Ingredients were tested for physicochemical stability and optimal ingredients were selected to prepare yogurts as a model food with ideal matrix. Yogurts were analyzed for physicochemical properties. After 24-days storage at 4 °C, yogurt containing microencapsulated oleogel with GG as antioxidant exhibited average peroxide and p-Anisidine values of 7.17 mmol O2/kg of oil and 118.85 abs/g, respectively. These values were similar to store-bought yogurt using saturated fat source, with values of 6.83 mmol O2/kg of oil and 117.95 absorbance/g, respectively. These results could lead to incorporation of ω-3 FAs into foods, cosmetics, and pharmaceuticals in the future.

Lipase-catalyzed one-step regioselective synthesis of 1,2-dioctanoylgalloylglycerol in a solvent-free system: Optimization of reaction conditions and structural elucidation

A multi-functional galloylated structured lipid, 1,2-dioctanoylgalloylglycerol (DOGG), was synthesized enzymatically via a regioselective transesterification of propyl gallate and trioctanoate using an immobilized food-grade Candida antarctica lipase B (Lipozyme® 435) as the biocatalyst under solvent-free condition. The variables that affect the reaction, including reaction temperature, substrate ratio, reaction time, and enzyme load, were evaluated and optimized using Taguchi method and response surface methodology. Both methods predicted the same optimal reaction condition, resulting in a 68.8 ± 1.3% DOGG yield with reaction selectivity of 82.9 ± 0.6% at 90 °C, 25/1 trioctanoate/PG (mol/mol), 72 h reaction, and 25% enzyme load relative to the total substrate weight. The structure of the reaction product was elucidated using NMR spectroscopy and ESI-HRMS, confirming the regioselectivity of the reaction. Enzyme retained 50% of its activity after 5 cycles of reuse. It is feasible to synthesize DOGG as a potential antioxidant and nutraceutical using Lipozyme® 435.

Comparison of antioxidant activities of selected phenolic compounds in O/W emulsions and bulk oil

Antioxidant activities of 1-o-galloylglycerol (GG), propyl gallate, rosmarinic acid (RA), tocopherols (TOC), and 1:1 combinations of GG/RA and GG/TOC were evaluated using in vitro assays including 2,2-diphenyl-1-picrylhydrazyl (DPPH), 2,2'-azino-bis (3-ethylbenzothiazoline-6-sulphonic acid) (ABTS⁺), and ferric reducing antioxidant power (FRAP). Soybean oil stripped of TOC was utilized as bulk oil and as the oil phase in O/W emulsions for accelerated oxidation test with the selected phenolic compounds. Efficacies of antioxidants were evaluated by monitoring total oxidation (TOTOX) values and fatty acid profiles of oil and O/W samples during the accelerated oxidation. In bulk oil, GG outperformed other singular antioxidants, preventing 39.04% of oxidation for ω-3 fatty acids with a TOTOX value of 166.68. In emulsions, TOC outperformed other singular antioxidants, preventing 38.04% of oxidation with a TOTOX value of 196.72. Considering the polarities of the antioxidants and our testing systems, these results provide supporting evidence for the polar paradox theory.

Phenolic compounds as antioxidants to improve oxidative stability of menhaden oil-based structured lipid as butterfat analog

Phenolic compounds, including propyl gallate, 1-o-galloylglycerol, ferulic, gallic, caffeic, rosmarinic, and carnosic acids, tocopherols, and butylated hydroxytoluene (BHT), were investigated as antioxidants to improve the oxidative stability of a structured lipid (SL) produced by the enzymatic acidolysis of menhaden oil with caprylic and stearic acids. SL had similar physical properties to butterfat but was more susceptible to oxidation. The above phenolic compounds were each added to SL as antioxidants. SL with 1-o-galloylglycerol, rosmarinic acid, or BHT showed the highest oxidative stability during an accelerated oxidation test with the total oxidation (TOTOX) value around 250 after 18 days. Oxidation induction time (OIT) using differential scanning calorimetry showed a good correlation with the accelerated oxidation test. A mixture of 1-o-galloylglycerol and tocopherols at 50:50 ppm had the strongest protective effect on SL (OIT = 115.1 min) compared to the other tested compounds or combinations at the same concentration (OIT < 100 min).

Solvent-free enzymatic synthesis of 1,2-dipalmitoylgalloylglycerol: Characterization and optimization of reaction condition

A novel diacylglycerol-based galloyl structured lipid, 1,2-dipalmitoylgalloylglycerol (DPGG), was synthesized using the enzymatic transesterification of propyl gallate (PG) and tripalmitin under solvent-free condition. An immobilized and commercially available food-grade Candida antarctica lipase B, Lipozyme® 435, was used as the biocatalyst. The reaction variables that affect the yield of DPGG were optimized using a 3³ full factorial design. At 70 °C, DPGG was obtained at a yield of 33.0 ± 2.0% with PG conversion at 44.8 ± 1.8% when the following condition was used: 25 substrate molar ratio of tripalmitin to PG, 120 h reaction time, and 25% enzyme load relative to the total substrate weight. The structure of reaction product was elucidated using Fourier-transform infrared spectroscopy (FT-IR), electrospray ionization high-resolution accurate-mass tandem mass spectrometry (ESI-HRAM-MS/MS), and 1D and 2D nuclear magnetic resonance spectroscopy (NMR). The effects of different lipases and galloyl donors/acceptors on the transesterification were also investigated.

Antioxidant property and characterization data of 1-o-galloylglycerol synthesized via enzymatic glycerolysis

This article provides comprehensive experimental data characterizing antioxidant activity, as well as chemical and physical properties of 1-o-galloylglycerol (GG), synthesized by enzymatic glycerolysis of propyl gallate (PG) using a food-grade lipase (Lipozyme® 435) [1]. GG was characterized by Fourier-transform infrared spectroscopy (FT-IR), ¹H, ¹³C, ¹H–¹H gradient correlation spectroscopy (gCOSY), ¹H–¹³C gradient heteronuclear single quantum coherence (gHSQC), ¹H–¹³C gradient heteronuclear multiple quantum coherence (gHMQC), and ¹H–¹³C gradient heteronuclear multiple bond correlation (gHMBC) nuclear magnetic resonance spectroscopies (NMR), and ultraviolet–visible spectrophotometry (UV–Vis). The antioxidant property of GG, which was evaluated through 1,1-diphenyl-2-picrylhydrazyl (DPPH^•), 2,2′-azinobis (3-ethylbenzthiazoline-6-sulfonic acid) (ABTS^•+), ferric reducing antioxidant power (FRAP), and hydrogen peroxide (H₂O₂) scavenging assays, is also presented.