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Analysis of Essential Oils
Published in K. Hüsnü Can Başer, Gerhard Buchbauer, Handbook of Essential Oils, 2020
Adriana Arigò, Mariosimone Zoccali, Danilo Sciarrone, Peter Q. Tranchida, Paola Dugo, Luigi Mondello
In addition, the well-known property of odor-activity recognized for several isomers, can be assessed by means of Es-GC-MS-O and can represent an outstanding tool for precise enantiomer characterization (see Figure 7.3). As demonstrated by Mosandl and his group (Lehmann et al., 1995), Es-GC-O is a valid tool for the simultaneous stereo-differentiation and olfactive evaluation of the volatile optically active components present in essential oils. It is worthwhile to point out that the preponderance of one of the enantiomers, defined by the enantiomeric excess, results in a characteristic aroma (Boelens et al., 1993) and is of great importance for the olfactive characterization of the sample.
An Overview of Experimental Methods
Published in Richard Beasley, Neil E. Pearce, The Role of Beta Receptor Agonist Therapy in Asthma Mortality, 2020
All of the aforementioned studies have involved acute effects of beta agonists. More recently, some studies have reported deterioration in lung function with long-term use of regular beta agonists.68 The underlying cause for such occurrences is not known, although they may relate to increases in bronchial hyperresponsiveness. However, not all studies with regular beta agonist use have been able to demonstrate deterioration in lung function,23,69 and it may relate to certain beta agonists, such as isoprenaline and fenoterol.22,23,68 Study designs to assess the underlying mechanism and incidence of potential deterioration in respiratory function are difficult to define. At present, such basic questions as what dosage constitutes regular use sufficient to downregulate beta receptors and duration of treatment, remain elusive. Studies with enantiomers instead of racemic mixtures may also be relevant in assessing this problem.70 Plainly it is of major importance with the introduction of new long-acting beta agonists, such as salmeterol and formoterol.
Adrenergic Agonists
Published in Sahab Uddin, Rashid Mamunur, Advances in Neuropharmacology, 2020
Dobutamine interacts with β and α receptors and was earlier thought being a selective β1 receptor agonist. It is similar in structure to dopamine. Both enantiomeric forms exist as a racemic mixture. The levo (−) isomer is an α1 receptor agonist while the dextro (+) isomer is an antagonist of α1 receptors. Both isomers have agonist effects on beta receptors although dextro isomer is more potent. Dobutamine produces more inotropic effects binding to the α1 receptors than the chronotropic effects on the heart. Cardiac output rises and then there is a change in the peripheral resistance. In some of the patients, there might be a significant increase in the heart rate and blood pressure and long-term effect is unclear. There might be a chance to develop tolerance. Dobutamine is used for a short-term period for treating decompensation of heart which happens in congestive heart failure or MI or after heart surgery. The onset of activity is fast, within 1–10 min and has a 2-min half-life (Brunton et al., 2011; Golan, 2012; Stevens et al., 2008). It penetrates well into CNS because of the absence of catechol in structure. Metabolism happens in the tissues and in the liver. The plasma half-life of the drug is approximately 2 min and excreted via urine (Rataboli, 2010; Florey, 2008).
New stability chiral RP-HPLC method for degradation products determination in midodrine hydrochloride
Published in Drug Development and Industrial Pharmacy, 2021
Gowramma Byran, Jenifer Ashwini, Kaviarasan Lakshmanan, Kalirajan Rajagopal, Gomathy Subramanian, S. N. Meyyanathan
For the enantiomeric drugs midodrine hydrochloride and mefloquine, there were no HPLC methods reported for their stability in different stress conditions and estimation of their enantiomers in pharmaceutical formulations by HPLC method were developed. The chromatographic conditions namely mobile phase, wavelength/mass range, flow rate, etc., were optimized by trial and error method and followed by forced degradation studies on the selected drugs. In accordance with the ICH guidelines, the developed HPLC method was validated and the results were found to be within the acceptable limits. The developed HPLC method for the chiral separation of enantiomeric drugs were found to be rapid, simple, precise, accurate, and specific. The selected enantiomeric drugs were stable in all the studied stress conditions such as acidic, basic, neutral, oxidative, and photolytic/UV. The proposed method is suitable for the estimation of the selected drugs in their formulations, clinical, pharmacokinetic, and toxicity studies. For the first time, a highly precise stability suggesting chiral HPLC method was developed to quantify the enantiomers of midodrine in the presence of degradation products. The enantioseparation was carried out by the use of cellulose based chiral column. The method provides good sensitivity and excellent precision and reproducibility. The method was highly selective, where degradation products and coformulated compounds did not interfere. The proposed method was successfully applied in pharmaceutical preparations.
Comparative toxicity and toxicokinetic studies of oxiracetam and (S)-oxiracetam in dogs
Published in Xenobiotica, 2019
Tian-tian Liu, Xin-miao Guo, Zu-yuan Rong, Xiang-feng Ye, Jin-feng Wei, Ai-ping Wang, Hong-tao Jin
As a consequence of the rapid advances in chiral synthesis and separation technologies, combined with new regulatory policies for chiral pharmaceuticals, chiral drugs have become an important focus for research and development of new molecular entities (Calcaterra & D'Acquarica, 2018; Nunez et al., 2009; Srinivas, 2004). Stereoisomers (enantiomers and diastereoisomers) not only differ from one another in their pharmacological effects, but also in their pharmacokinetic (adsorption, distribution, biotransformation, and excretion) profiles (Brocks, 2006; Hutt, 2007) and toxicological properties (Natarajan & Basak, 2011; Smith, 2009). Understanding the stereospecificity of in vitro and in vivo pharmacokinetics/toxicokinetics may assist in delineating the developmental path of the racemate and/or the pure enantiomers. The differential actions and toxicities determine enantiomer selection to maximize clinical effects or mitigate drug toxicity. Toxicological evaluation of chiral drugs, therefore, deserves increased attention.
Usnic acid and its derivatives for pharmaceutical use: a patent review (2000–2017)
Published in Expert Opinion on Therapeutic Patents, 2018
Olga A. Luzina, Nariman F. Salakhutdinov
Usnic acid (1) has two optical isomers; both are isolated from many species of lichen by a simple procedure and with high optical purity. Both enantiomers possess interesting biological and pharmacological activities. The study on the biological effects of UA was initiated in the 1930s, but unfortunately, further pharmacological studies were terminated in 2008 due to its toxic side effects [17]. An analysis of the published patents about UA since 2000 indicated that this compound is employed often to treat various external imperfections (skin lesions), mostly targeting microorganisms. These studies were concerned with many kinds of diseases, including acne, scurf, seborrheic dermatitis, atopic dermatitis, and psoriasis. Many studies were conducted in order to improve the low bioavailability of UA. It has been repeatedly demonstrated that the so-called pharmacologically accessible form of the UA – sodium, potassium or copper (II) usnate – shows more pronounced antibacterial properties, with an IC50 several times lower. Often, the antibacterial action of salts takes a bactericidal character in contrast to the bacteriostatic one of UA itself. One more method designed to increase bioavailability is the use of a carrier to dissolve the UA and increase its percutaneous permeability. Several patents are devoted to this area, from the selection of the carrier to the creation of liposomes or a nanoscale pharmacological form. In addition, the successful use of UA in compositions for processing medical instruments or creating antibacterial coatings for them has been patented.