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Evaluation of the Dermal Irritancy of Chemicals
Published in David W. Hobson, Dermal and Ocular Toxicology, 2020
The greatest potential for percutaneous absorption occurs when a high concentration of compound is spread over a large surface area of the body.8 Nonpolar compounds (lipophilic) are generally better skin penetrators than polar (hydrophilic) compounds. Vehicles such as dimethylsulfoxide (DMSO) readily permeate skin, and can greatly enhance absorption of test chemicals. Repetitive dosing of a chemical can also greatly increase absorptivity over a single application, even if the same total dose is applied.8
Nutraceutical Bioactives
Published in Raj K. Keservani, Anil K. Sharma, Rajesh K. Kesharwani, Nutraceuticals and Dietary Supplements, 2020
Andrew G. Mtewa, Kennedy J. Ngwira, Stephen Lutoti, Davies Mweta, Patrick E. Ogwang, Duncan C. Sesaazi
After the isolation and purification of compounds, tested for their bioactivities starting from cell line to animal and patient studies (Park et al., 2016), derivatives may be modified if necessary in order to improve the bioavailability of the compounds to biological targets. This is basically the chemistry of the compounds that will determine their absorptivity across membranes, distribution in the body, their metabolism, and excretion which are fundamental characteristics of a compound that must function in the body. This process takes a long time and requires huge monetary and time investments. Where products are to be labeled as drug supplements or functional foods, regulatory requirements need to be followed, (Sardana, 2012) to avoid fines and other charges for ethical and other misconducts later.
Instrumentation for Assessing mTBI Events
Published in Mark A. Mentzer, Mild Traumatic Brain Injury, 2020
Once the deformation is read from the kinetics spectrum, several quantities may be extracted, which can be used to further characterize different candidate materials. These parameters are illustrated in Figure 3.7. The principle used is the Beer–Lambert law, which is normally used to determine the concentration dependence C of a solute in a solvent from absorbance data A: A = εlC, where l is path length and ε is the extinction coefficient or molar absorptivity. In our case all material parameters may be assumed fixed, with the path length l being replaced by mass m due to delamination. Thus, the transmittance T is proportional to the variation ion path length or, equivalently, the mass change. Therefore a priori measurement of T(t) versus known m can be used to compute the change of mass: T(t) = εmρ where ρ is the density and t is the observation time.
Preparation, characterization, and anti-colon cancer activity of oridonin-loaded long-circulating liposomes
Published in Pharmaceutical Development and Technology, 2021
Chunxiao Gao, Liang Zhang, Zhan Tang, Zhengyu Fang, Xiaoli Ye, Wenying Yu
Oridonin (ORI) is a tetracyclic diterpene compound with kaurene as the skeleton. It is extracted from Rabdosia rubescens (Hemsl.) Hara, a plant from the genus Isodon in the Labiatae family (Figure 1) (Yang et al. 2020). ORI has a strong antitumor activity and can inhibit the proliferation and promote the apoptosis of various tumor cells involved in colon cancer, lung cancer, and gastric carcinoma (Yao et al. 2017; Ren et al. 2020; Xu et al. 2020). However, its clinical applications are greatly limited because of its poor water solubility, low absorptivity, and short biological half-life in vivo (Liu et al. 2019). The solubility of ORI can be enhanced for parenteral administration by formulating it in a vehicle containing ethanol, propylene glycol, and Tween 80, but the delivery of such miscible solvents can cause adverse effects such as vasculitis and topical pain (Tian and Chen 2013). Therefore, designing an appropriate drug delivery system (DDS) and improving the solubility and bio-availability of ORI are urgent problems that need to be solved.
Clinical treatment of intra-epithelia cervical neoplasia with photodynamic therapy
Published in International Journal of Hyperthermia, 2020
Antonio Carlos Figueiredo Vendette, Henrique Luis Piva, Luis Alexandre Muehlmann, Delfrank Ananias de Souza, Antonio Claudio Tedesco, Ricardo Bentes Azevedo
The class of molecules eligible to clinically work as PS should present a long life of the triplet reactive excited species generated by photoactive pathways (greater than 500 ns), enough time to react with molecular oxygen and induce ROS production. We also expected this molecule to present a high absorptivity coefficient in the electromagnetic spectral region, called phototherapeutic window, in the range of visible light, between 600 nm and 800 nm [16]. Furthermore, this molecule should present good solubility and biocompatibility, with the absence of any phototoxicity in the dark, associated with a fast clearance of healthy tissues and body (generally from 24 to 48 h). With such characteristics, a good penetration of visible light, greater than 2 or 3 cm is possible even in slightly pigmented tissues, with minimal risk of undesired side effects such as the destruction of healthy tissues that do not contain the therapeutic agent, mainly when used topically or transmitted with target-specific delivery systems (DDS).
Improvement of solubility, dissolution and stability profile of artemether solid dispersions and self emulsified solid dispersions by solvent evaporation method
Published in Pharmaceutical Development and Technology, 2018
Muhammad Tayyab Ansari, Muhammad Sohail Arshad, Altaf Hussain, Zeeshan Ahmad
Assay development for artemether, using HPLC (Perkin Elmer, Waltham, MA), required reverse phase C18 columns (4.6 mm × 250 mm, 5 μ) and UV detector recording absorbance at 215 nm wavelength. The mobile phase comprised a mixture of acetonitrile and water (75:25 v/v) at a flow rate of 1 ml min−1. The injection volume was maintained at 20 μl20,21. A calibration curve was established by plotting the area of absorbance peak (recorded from the injection of known quantities of artemether) as a function of concentration (over a range 78–625 μg ml−1) and the data were modeled using a linear regression equation (y = mx + b). A correlation coefficient of 0.9996 indicated that the data are explained using this model. The linear part of the calibration curve infers the samples follow Beer Lambert Law, suggesting that the absorbance (A) of a sample depends on absorptivity coefficient (a), path length (b) and concentration of the analyte (c); A = a(λ) · b · c22. Providing parameters a and b are constant, the absorbance of a sample will be directly proportional to the concentration of drug. This phenomenon is expressed by the linear regression model. This relationship (concentration dependent linear increase for absorbance) is used reliably to determine unknown concentration of drug in samples. The HPLC method was validated according to the guidelines published by ICH. The results of validation parameters are described Table 2.