Comparison of antioxidant capacity of 4-vinylguaiacol with catechin and ferulic acid in oil-in-water emulsion

Molecular Insights on Coffee Components as Chemical Antioxidants

Coffee is not only a delicious beverage but also an important dietary source of natural antioxidants. We live in a world where it is impossible to avoid pollution, stress, food additives, radiation, and other sources of oxidants that eventually lead to severe health disorders. Fortunately, there are chemicals in our diet that counteract the hazards posed by the reactive species that trigger oxidative stress. They are usually referred to as antioxidants; some of them can be versatile compounds that exert such a role in many ways. This review summarizes, from a chemical point of view, the antioxidant effects of relevant molecules found in coffee. Their mechanisms of action, trends in activity, and the influence of media and pH in aqueous solutions, are analyzed. Structure-activity relationships are discussed, and the protective roles of these compounds are examined. A particular section is devoted to derivatives of some coffee components, and another one to their bioactivity. The data used in the analysis come from theoretical and computational protocols, which have been proven to be very useful in this context. Hopefully, the information provided here will pro-mote further investigations into the amazing chemistry contained in our morning coffee cup.   Resumen. El café no solo es una bebida deliciosa, sino también una importante fuente dietética de antioxidantes naturales. Vivimos en un mundo donde es imposible evitar la contaminación, el estrés, los aditivos alimentarios, la radiación y otras fuentes de oxidantes que eventualmente conducen a trastornos de salud graves. Afortunadamente, existen sustancias químicas en nuestra dieta que contrarrestan los peligros planteados por las especies reactivas que desencadenan el estrés oxidativo. Por lo general, se les denomina antioxidantes; algunos de ellos pueden ser compuestos versátiles que ejercen dicho papel de muchas maneras. Este artículo de revisión resume, desde un punto de vista químico, los efectos antioxidantes de moléculas relevantes encontradas en el café. Se analizan sus mecanismos de acción, tendencias en la actividad y la influencia del medio y el pH en soluciones acuosas. Se discuten las relaciones estructura-actividad, y se examinan los roles protectores de estos compuestos. Se dedica una sección particular a los derivados de algunos componentes del café, y otra a su bioactividad. Los datos utilizados en el análisis provienen de protocolos teóricos y computacionales, que han demostrado ser muy útiles en este contexto. Se espera que la información proporcionada aquí promueva investigaciones futuras sobre la química contenida en nuestra taza de café matutina.

Challenges and advances in biotechnological approaches for the synthesis of canolol and other vinylphenols from biobased p-hydroxycinnamic acids: a review

p-Hydroxycinnamic acids, such as sinapic, ferulic, p-coumaric and caffeic acids, are among the most abundant phenolic compounds found in plant biomass and agro-industrial by-products (e.g. cereal brans, sugar-beet and coffee pulps, oilseed meals). These p-hydroxycinnamic acids, and their resulting decarboxylation products named vinylphenols (canolol, 4-vinylguaiacol, 4-vinylphenol, 4-vinylcatechol), are bioactive molecules with many properties including antioxidant, anti-inflammatory and antimicrobial activities, and potential applications in food, cosmetic or pharmaceutical industries. They were also shown to be suitable precursors of new sustainable polymers and biobased substitutes for fine chemicals such as bisphenol A diglycidyl ethers. Non-oxidative microbial decarboxylation of p-hydroxycinnamic acids into vinylphenols involves cofactor-free and metal-independent phenolic acid decarboxylases (EC 4.1.1 carboxyl lyase family). Historically purified from bacteria (Bacillus, Lactobacillus, Pseudomonas, Enterobacter genera) and some yeasts (e.g. Brettanomyces or Candida), these enzymes were described for the decarboxylation of ferulic and p-coumaric acids into 4-vinylguaiacol and 4-vinylphenol, respectively. The catalytic mechanism comprised a first step involving p-hydroxycinnamic acid conversion into a semi-quinone that then decarboxylated spontaneously into the corresponding vinyl compound, in a second step. Bioconversion processes for synthesizing 4-vinylguaiacol and 4-vinylphenol by microbial decarboxylation of ferulic and p-coumaric acids historically attracted the most research using bacterial recombinant phenolic acid decarboxylases (especially Bacillus enzymes) and the processes developed to date included mono- or biphasic systems, and the use of free- or immobilized cells. More recently, filamentous fungi of the Neolentinus lepideus species were shown to natively produce a more versatile phenolic acid decarboxylase with high activity on sinapic acid in addition to the others p-hydroxycinnamic acids, opening the way to the production of canolol by biotechnological processes applied to rapeseed meal. Few studies have described the further microbial/enzymatic bioconversion of these vinylphenols into valuable compounds: (i) synthesis of flavours such as vanillin, 4-ethylguaiacol and 4-ethylphenol from 4-vinylguaiacol and 4-vinylphenol, (ii) laccase-mediated polymer synthesis from canolol, 4-vinylguaiacol and 4-vinylphenol.

Synthesized alkyl ferulates with different chain lengths inhibited the formation of lipid oxidation products in soybean oil during deep frying

The hydrophilic nature of ferulic acid limits its applications under lipophilic conditions. This study set out to evaluate the antioxidant efficacy of alkyl ferulates with different chain lengths in soybean oil under frying conditions. Ferulic acid was esterified with four unbranched fatty alcohols (C4:0-C16:0), and tert-butylhydroquinone (TBHQ) served as a standard for comparison. The antioxidant effect of alkyl ferulates increased with the alkyl chain length. The addition of antioxidants could inhibit increases in the levels of p-anisidine, total polar compounds, conjugated dienes, conjugated trienes, oxidized triglyceride monomers, triglyceride dimers, triglyceride oligomers, and glycerol core aldehydes efficiently, and the inhibitory effects of hexadecyl ferulate was the strongest. Moreover, hexadecyl ferulate and TBHQ exhibited better inhibitory effects on the generation of n-alkanals, (E)-2-alkenals, and 4-oxo-alkanals determined by ¹H nuclear magnetic resonance than others. Hence, the long-chain alkyl ferulates meet the industrial demands for ideal antioxidants with strong antioxidant capacity at high temperatures.

Improve stability and application of rice oil bodies via surface modification with ferulic acid, (-)-epicatechin, and phytic acid

Rice bran oil bodies (RBOBs) are one of the most exploited functional components from rice bran by-products and are predominantly based on oleosin stabilization. In this study, we explored the effects of different concentrations of added (-)-epicatechin, ferulic acid, and phytic acid on the RBOBs stability. The results revealed that the incorporation of all three natural phytoconstituents could reduce the RBOBs particle size and increase emulsifying properties, demonstrating increasing surface hydrophobicity (p < 0.05), and a good antioxidant effect, which was especially obvious with (-)-epicatechin incorporation. Fourier transform infrared (FT-IR) spectroscopy data demonstrated that these three small molecule substance classes can modify with oleosin on RBOBs surface by covalent and noncovalent effects. Raman spectroscopic analysis illustrated that the vibrational modes of disulphide bonds in oleosin were modified by these three plant natural ingredients. The interactions between the three phytoconstituents and the model protein were investigated by molecular docking experiments.

Dissecting the biochemical and molecular-genetic regulation of diverse metabolic pathways governing aroma formation in indigenous aromatic indica rice varieties

BACKGROUND

Aromatic rice is characterized by its distinct flavor and fragrance, imparted by more than 200 volatile organic compounds. The desirable trait of aroma relies on the type of the variety, with some varieties exhibiting considerably higher aroma content. This prompted us to undergo an exhaustive study of the aroma-associated biochemical pathways and expression of related genes, encoding the enzymes involved in those pathways in indigenous aromatic rice cultivars.

METHODS AND RESULTS

The higher aroma level in aromatic rice varieties was attributed to higher transcript levels of PDH, P5CS, OAT, ODC, DAO and TPI, but lower P5CDH and BADH2, as revealed by comparative expression profiling of genes in 11 aromatic and four non-aromatic varieties. Some of the high-aroma containing varieties exhibited lower expression of SPDS and SPMS genes, concomitant with higher PAO expression. Protein immunoblot analyses showed lesser BADH2 protein accumulation in the aromatic varieties. The involvement of shikimate pathway in aroma formation was justified by higher levels of shikimic and ferulic acids due to higher expression of SK1, SK2 and ARD genes. The aromatic varieties exhibited higher expression of LOX3 and HPL, with higher corresponding enzyme activity, accompanied with lower accumulation of lipid hydroperoxides and higher level of total terpenoids, signifying the role of oxylipin pathway and terpene-related volatiles in aroma formation. The pattern of transcript level and metabolite accumulation followed the same trend in both vegetative (seedling) and reproductive (seed) tissues. Sequence analyses revealed several mutations in the upstream region and different exons and introns of BADH2 in the examined aromatic varieties. The allele specific marker system acted as fingerprint to distinguish the selected aromatic rice varieties. The cleaved amplified polymorphic sequence marker established the absence of any mutation in the 14th exon of BADH2 in the aromatic varieties.

CONCLUSION

The present work clearly highlighted the biochemical and molecular-genetic mechanism of differential aroma levels which could be attributed to differential regulation of metabolites and genes, belonging to 2-acetyl-1-pyrroline, shikimate, oxylipin and terpenoid metabolic pathways in the indigenous aromatic rice varieties.

Review on the Antioxidant Activity of Phenolics in o/w Emulsions along with the Impact of a Few Important Factors on Their Interfacial Behaviour

This review paper focuses on the antioxidant properties of phenolic compounds in oil in water (o/w) emulsion systems. The authors first provide an overview of the most recent studies on the activity of common, naturally occurring phenolic compounds against the oxidative deterioration of o/w emulsions. A screening of the latest literature was subsequently performed with the aim to elucidate how specific parameters (polarity, pH, emulsifiers, and synergistic action) affect the phenolic interfacial distribution, which in turn determines their antioxidant potential in food emulsion systems. An understanding of the interfacial activity of phenolic antioxidants could be of interest to food scientists working on the development of novel food products enriched with functional ingredients. It would also provide further insight to health scientists exploring the potentially beneficial properties of phenolic antioxidants against the oxidative damage of amphiphilic biological membranes (which link to serious pathologic conditions).

Chemical composition, in vitro antioxidant, anticholinesterase, and antidiabetic potential of essential oil of Elaeagnus umbellata Thunb

Background

Elaeagnus umbellata Thunb. (autumn olive) is a high valued medicinal plant. It belongs to Elaeagnaceae family and is widely distributed in Himalayan regions of Pakistan. In the present study essential oil were extracted from the fruit of this plant and their antioxidant, anticholinesterase and antidiabetic potentials were also evaluated.

Methods

Essential oils were extracted from the fruit of E. umbellata using hydro-distillation method and were characterized by GC-MS. The extracted oil were tested for its antioxidant, anticholinesterase, and antidiabetic potentials using standard protocols.

Results

About 68 compounds were identified by GC-MS. The extracted oil exhibited a fairly high free radical scavenging activities against DPPH and ABTS radicals with IC₅₀ values of 70 and 105 μg/mL respectively (for ascorbic acid, used as standard, the IC₅₀ values were 32 and 29 μg/mL, respectively against the mentioned radicals). The essential oil also exhibited anticholinesterase activities with IC₅₀ values of 48 and 90 μg/mL respectively against AChE and BChE (for galantamine used as standard, the IC₅₀ values were 25 and 30 μg/mL respectively). The essential oil also exhibited antidiabetic potential with IC₅₀ values of 120 and 110 μg/mL respectively against α-glucosidase and α-amylase (IC₅₀ values for standard acarbose = 28 and 30 μg/mL respectively).

Conclusion

Essential oil extracted from the fruits of E. umbellata exhibited reasonable antioxidant, anticholinesterase, and antidiabetic potentials that could be used as alternative medicine in treating diabetes and neurodegenerative disorders. However, further studies are needed to isolate responsible compounds and evaluate the observed potential in animal models.

Graphical abstract

Supplementary Information

The online version contains supplementary material available at 10.1186/s12906-021-03228-y.

Phenolic Acids of Plant Origin-A Review on Their Antioxidant Activity In Vitro (O/W Emulsion Systems) Along with Their in Vivo Health Biochemical Properties

Nature has generously offered a wide range of herbs (e.g., thyme, oregano, rosemary, sage, mint, basil) rich in many polyphenols and other phenolic compounds with strong antioxidant and biochemical properties. This paper focuses on several natural occurring phenolic acids (caffeic, carnosic, ferulic, gallic, p-coumaric, rosmarinic, vanillic) and first gives an overview of their most common natural plant sources. A summary of the recently reported antioxidant activities of the phenolic acids in o/w emulsions is also provided as an in vitro lipid-based model system. Exploring the interfacial activity of phenolic acids could help to further elucidate their potential health properties against oxidative stress conditions of biological membranes (such as lipoproteins). Finally, this review reports on the latest literature evidence concerning specific biochemical properties of the examined phenolic acids.