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Microemulsions in Pharmaceuticals
Published in Promod Kumar, K. L. Mittal, Handbook of Microemulsion Science and Technology, 2018
Considering the solubilizing capacity of microemulsions, these are expected to significantly affect the structure of the stratum corneum lipid self-assemblies, with obvious consequences for drug penetration. There have been several studies of the penetration enhancement due to microemulsion drug carriers. For example, Gasco et al. [25] studied the transport of azelaic acid, a bioactive substance used for treating a number of skin disorders, from a viscosified microemulsion and from the corresponding polymer solution through full-thickness abdominal skin. (The viscosity of microemulsions frequently has to be increased to make them suitable for topical application.) It was found that an O/W microemulsion formed by water-propylene glycol, decanol-dodecanol, Tween 20, 1-butanol, and Carbopol 934 gave significantly better penetration than the corresponding water-propylene glycol-Carbopol “gel” (Fig. 3).
Engineering and Technology of Environmentally Friendly Lubricants
Published in Brajendra K. Sharma, Girma Biresaw, Environmentally Friendly and Biobased Lubricants, 2016
Carlton J. Reeves, Pradeep L. Menezes, Michael R. Lovell, Tien-Chien Jen
Another type of synthetic ester is the diester, a biolubricant derived partly from renewable resources. Synthetic diesters are derived from dicarboxylic acid and monovalent alcohols. The dicarboxylic acid can be prepared from natural sources, such as azelaic acid (from ozonolysis of oleic acid), sebacic acid, dimeric fatty acid, or from purely petrochemical sources, such as adipic acid or malelic acid. Diesters generally consist of branched alcohols, such as EH (iscooctanol), isodecanol, or guerbet alcohols to offer better low-temperature properties than those of conventional synthetic ester lubricants. Additionally, branched fatty acids, for example, 12-hydroxystearic acid derived from ricinoleic acid, can be utilized to form diester-based lubricants that also exhibit improved low-temperature properties [56,57]. Isostearic acid, a synthetic ester-based lubricant consisting of branched and straight-chain C18 fatty acids, has very low levels of unsaturation, resulting in excellent oxidative stability.
Modified Vegetable Oils for Environmentally Friendly Lubricant Applications
Published in Leslie R. Rudnick, Synthetics, Mineral Oils, and Bio-Based Lubricants, 2020
Brajendra K. Sharma, Gobinda Karmakar, Sevim Z. Erhan
The double bond at unsaturation sites of VOs provides a point of attack for oxidative scission. Ozonides are formed initially in the ozonolysis reaction which is a highly selective reaction [99] as shown in Scheme 24.2. These can undergo scission either reductively to mono-and dialdehydes, or oxidatively to mono- and dicarboxylic acids. By the oxidative route, ester of oleic acid gives nonanoic acid (pelargonic acid) and ester of nonane-1,9-dioic acid (azelaic acid) (Scheme 24.2) [100]. The later can be converted to diester after esterification. This kind of oxidative scission in triacylglycerol molecule can improve their thermo-oxidative stability by removing the sites of unsaturation. Lubricants with optimal performance can be obtained by an alteration of the hydrocarbon chain (of transesterified product of more resistant polyols such as PE, TMP, or NPG) using ozonolysis reaction leading to short esters after combination with an alcohol [101]. The linear diacid portion of the diester contributes to good viscosity index (VI), while the branched ends give the lubricant a good pour point. The only disadvantage of diesters is their low molecular weight, which makes them an attractive solvent because of their high polarity. It can be blended with VOs/CMVOs to make different viscosity blends. Another solution is esterification of these dicarboxylic acids with polyols, which can increase the viscosity of these products and also have high shear stability [69]. Ozonolysis of unsaturated fatty acid (oleic) ester.
Interpretation of Volatility Tandem Differential Mobility Analyzer (V-TDMA) data for accurate vapor pressure and enthalpy measurement: Operational considerations, multiple charging, and introduction to a new analysis program (TAO)
Published in Aerosol Science and Technology, 2020
Christopher R. Oxford, Audrey J. Dang, Charles M. Rapp, Brent J. Williams
Therefore, the singly charged experimental size distribution will separate from the remaining experimental size distributions first, regardless of the pure component aerosol tested. Multiple phases are still possible, but the reason for the peaks observed in the diacids experiments are explained by charge separation alone, not multiple phases. If multiple phases occurred during the evaporation of pure component aerosols, an increase in observed peaks would occur. The peak representing the singly charged particles would separate into two peaks, and the 72 nm peak in Figure 2 panel (a) may exhibit multiple peaks as well. We observed no more than two peaks in the CPC response during the evaporation of levoglucosan, all dicarboxylicacids between malonic acid and azelaic acid, caffeine, and oleic acid. Some experiments resulted in a single CPC response peak or shoulder in contrast to the two CPC response peaks shown above. To explain these different shapes, we investigate V-TDMA specific settings in the next section.
Antioxidant and anti-tyrosinase activities of quercetin-loaded olive oil nanoemulsion as potential formulation for skin hyperpigmentation
Published in Journal of Dispersion Science and Technology, 2022
Cristiane C. Silva, Rogério B. Benati, Taís N. C. Massaro, Karina C. Pereira, Lorena R. Gaspar, Priscyla D. Marcato
Hyperpigmentation disorders, which include postinflammatory hyperpigmentation, solar lentigos and melasma, are characterized by dark spots on the skin.[1] Specifically, melasma is a chronic acquired condition of hypermelanosis characterized by homogeneous spots with irregular borders from light to dark brown, distributed on the epidermis, very frequent on the face.[2,3] The conventional treatment for this hyperpigmentation[2] consists of applying sunscreen and using 2-5% topical hydroquinone alone or in combination with retinoic acid (0.05-0.1%) since both interfere in melanogenesis and also retinoic acid, as a chemical peel, which acts on the desquamation of the epidermis.[2,4,5] Hydroquinone is a gold standard for skin hyperpigmentation as it prevents melanin synthesis with the inhibition of the tyrosinase enzyme. However, it can cause skin irritation, allergy, dermatitis and, in the case of chronic use, exogenous ochronosis, characterized as a rare bluish-black dermatosis.[6,7] There are other treatments, for example, kojic acid and azelaic acid as tyrosinase inhibitors, chemical peels, and laser therapy, in the place of the widely used hydroquinone. However, they also have limitations and undesirable effects. Kojic acid and azelaic acid have difficulty reaching the epidermis and they require long periods of treatment.[8] Furthermore, kojic acid, as a well-known ingredient for skin depigmentation, is unstable during the storage, has limited tyrosinase inhibitory activity, and may cause contact dermatitis and, over a long period, photodamaged skin.[9,10] Lastly, laser therapy and chemical peels have a high safety risk, with the possibility of inflammation, scarring, changes in skin color, or even rebound hyperpigmentation.[8,11]
HPLC-MS/MS chemical characterization and biological properties of Origanum onites extracts: a recent insight
Published in International Journal of Environmental Health Research, 2019
Mohamad Fawzi Mahomoodally, Gokhan Zengin, Mustafa Onur Aladag, Haluk Ozparlak, Alina Diuzheva, József Jekő, Zoltán Cziáky, Muhammad Zakariyyah Aumeeruddy
It is important to highlight that the high enzyme inhibitory activities of the methanol extract was not in proportional with its TPC since it showed lower TPC compared to the aqueous extract. Nonetheless, the methanol extract possessed higher TFC which could have contributed to its higher enzyme inhibitory effects. A number of previous studies have also found that plant extracts containing high level of total flavonoids also displayed high inhibition against AChE, BChE, tyrosinase, α-amylase, and α-glucosidase (Oskoueian et al. 2011; Sarikurkcu et al. 2014; Russo et al. 2015). Also, several compounds which were identified in the methanol extract are known to be potent inhibitors of the studied enzymes. For instance, azelaic acid has been shown to inhibit tyrosinase directly KI = (2.73 x 10−3M) or indirectly by inhibiting free radical reduction on plasma membrane associated thioredoxin reductase (KI = 1.25x10−5M). Consequently, electrons flow from NADPH and reduce intracellular thioredoxin, which in turn, inhibits tyrosinase by forming a bis-cysteinate inhibitors complex (Schallreuter and Wood 1990). Genkwanin was also found to induce a decrease of melanin synthesis by inhibiting tyrosinase activity in a dose and time dependent manner (Bouzaiene et al. 2016). In addition, a number of methoxyflavones, isolated from Kaempferia parviflora, was found to inhibit the enzymes AChE and BChE (Sawasdee et al. 2009). Quercetin has also been shown to be a competitive inhibitor of AChE, BChE, and mushroom tyrosinase (Chen and Kubo 2002; Khan et al. 2009). Quercetin also inhibited the activity of yeast α-glucosidase (IC50 = 0.53 mM) (Escandón-Rivera et al. 2012). Isoferulic acid, another compound present in the methanol extract, was found to be inactive in pancreatic α-amylase inhibition, nevertheless, displayed intestinal maltase and sucrase inhibition (IC50 values of 0.76 and 0.45 mM, respectively) (Adisakwattana et al. 2009). Also, besides their individual contribution, these compounds could interact with each other in the O. onites extract to produce a synergistic or additive enzyme inhibitory effect. Nonetheless, these type of interactions need to be further studied to reach a final conclusion.