Chemistry of Essential Oils
K. Hüsnü Can Başer, Gerhard Buchbauer in Handbook of Essential Oils, 2020
Phenol (183) and related materials, such as guaiacol (188), were once isolated from coal tar, but the bulk of their supply is currently produced from benzene via cumene as shown in Figure 6.31. The use of these intermediates to produce shikimates is shown in Figure 6.32. In principle, anethole (53) and estragole (methyl chavicol) (52) are available from phenol, but in practice, the demand is met by extraction from turpentine. Carboxylation of phenol gives salicylic acid (38) and hence serves as a source for the various salicylate esters. Formylation of phenol by formaldehyde, in the presence of a suitable catalyst, has now replaced the Reimer–Tiemann reaction as a route to hydroxybenzaldehydes. The initial products are saligenin (189) and p-hydroxybenzyl alcohol (190), which can be oxidized to salicylaldehyde (191) and p-hydroxybenzaldehyde (192), respectively. Condensation of salicylaldehyde with acetic acid/acetic anhydride gives coumarin (50) and O-alkylation of p-hydroxybenzaldehyde gives anisaldehyde (44). As mentioned earlier, oxidation of phenol provides a route to catechol (184) and guaiacol (188). The latter is a precursor for vanillin, and catechol also provides a route to heliotropin (61) via methylenedioxybenzene (193).
Methods of Protein Iodination
Erwin Regoeczi in Iodine-Labeled Plasma Proteins, 2019
An additional difference between the iodination-catalyzing properties of both enzymes may be sought in the unequal bindings of substrate proteins. Iodinating efficiency using lactoperoxidase increases68,80 with more protein in the reaction mixture. In contrast, at a given concentration of 1–, the rate of horseradish enzyme-catalyzed incorporation of I into lysozyme is reversely proportional to the concentration of the protein.101 Moreover, proteins competitively inhibit the oxidation of guaiacol by horseradish peroxidase.72 It is tempting to hypothesize that horseradish peroxidase binds protein substrates more avidly than does lactoperoxidase, and this has a bearing on its overall performance as a halogenation catalyst. Parallel studies with both enzymes are clearly warranted.
Defective Organification of Iodide
Geraldo Medeiros-Neto, John Bruton Stanbury in Inherited Disorders of the Thyroid System, 2019
Three assays for TPO activity in thyroid tissue33-35 have been used and were developed based on the following peroxidase-catalyzed reactions in the presence of H2O2: Oxidation of I- to I—3. Formation of the latter can be followed by the measurement of AA353/time.Oxidation of guaiacol to the colored oxidation product tetraguaiacol A unit of activity is defined as ΔΑ470 = 1.0 in 60 s.Iodination of tyrosine residues or human goiter Tg (poorly iodinated) or albumin (Table 1). These iodination procedures are the most important and physiological of the three assay methods. Iodide incorporation into protein is expressed in nmol/min, and incorporation of 1 nmol/min was defined as the TPO unit of iodination activity.33
Antioxidant and in vitro cytogenotoxic properties of Amburana cearensis (Allemão) A.C.Sm. leaf extract
Published in Drug and Chemical Toxicology, 2023
José Rafael da Silva Araujo, Juliana Vieira de Barros Arcoverde, Marília Grasielly de Farias Silva, Edson Renan Barros de Santana, Persio Alexandre da Silva, Silvany de Sousa, Neide Santos, Pedro Marcos de Almeida, Cláudia Sampaio de Andrade Lima, Ana Maria Benko-Iseppon, Rafael Jorge Santos Aracati Padilha, Marccus Alves, Ana Christina Brasileiro-Vidal
Considering the EtOAc fraction, GC-MS also identified the presence of other phenolic groups, such as guaiacol (2-methoxyphenol) (6.52%), 2,3-dihydro-benzofuran (6.17%), 4-(ethoxymethyl)-phenol (0.97%), and a compound similar to isovanillic acid (isovanillic acid methyl ester, 2.37%), which were also found in barks from the same species in other studies (Negri et al.2004). The compounds 2-methoxy-4-vinylphenol (5.45%) and 4-hydroxybenzaldehyde (1.93%) have not been reported in the literature so far for A. cearensis. Guaiacol is a plant phenol with myeloperoxidase inhibitor activity (Jayaraj et al.2020). This compound can modulate oxidative stress due to its methoxy substitution in the ortho position, which increases the radical scavenging efficiency of guaiacol (Azadfar et al.2015). Excessive myeloperoxidase activity and reactive oxygen species production are associated with many inflammatory processes (Khan et al.2018), including atherosclerosis, cancer, and Alzheimer’s. Coumarans (2,3‐dihydrobenzofurans) do not exhibit a role in oxidative stress, but your derived compounds have cytotoxic and antiprotozoal activities (Ilya et al.2018). On the other hand, 2-methoxy-4-vinylphenol is a high value-added product widely used as a flavoring agent, with potential for food preservation (Rubab et al.2020).
Radiation induced mutagenesis, physio-biochemical profiling and field evaluation of mutants in sugarcane cv. CoM 0265
Published in International Journal of Radiation Biology, 2022
Madhavi V. Purankar, Ashok A. Nikam, Rachayya M. Devarumath, Suprasanna Penna
For enzyme activity estimations, 100 mg callus sample was used and all the steps in preparation of the enzyme extract were carried out at 4 °C. The samples were homogenized in 3 ml ice-cold 50 mM sodium phosphate buffer (pH 7.0) including 0.1 mM EDTA and 1% (w/v) PVP in pre-chilled mortar and pestle. The homogenate was centrifuged at 15,000 rpm for 20 min at 4 °C. The supernatant was used as a crude enzyme extract for determining the antioxidant enzyme assays at room temperature, and the activities of the enzymes were determined with a spectrophotometer (Shimadzu, Kyoto, Japan). The total soluble protein content in the enzyme extract was determined according to the Bradford method (Bradford 1976; Kruger 1996) using bovine serum albumin as a standard. The activity of the catalase was measured by following the decomposition of hydrogen peroxide (H2O2) as described by Cakmak and Marschner (1992). The guaiacol peroxidase (GPOX) activity was determined according to Karpe et al. (2012). The total superoxide dismutase (SOD) was assayed according to Becana et al. (1998).
Zinc improves sexual and erectile function in HAART-treated rats via the upregulation of erectogenic enzymes and maintenance of redox balance
Published in The Aging Male, 2023
R. E. Akhigbe, M. A. Hamed, A. F. Odetayo, T. M. Akhigbe, P. A. Oyedokun
Penile myeloperoxidase (MPO) activity was determined by the colorimetric method as earlier reported by Desser et al. [39]. This is based on its catalytic activity in the oxidation of guaiacol to oxidized guaiacol in the presence of hydrogen peroxide. Guaiacol has a brown color that is measured photometrically at 470 nm wavelength in its oxidized form. The color intensity produced is proportional to the concentration of oxidized guaiacol produced in the reaction.