Use of Microcalorimetry in Monitoring Stability Studies. Example:  Vitamin A Esters

Runge, Frank; Heger, Robert

doi:10.1021/jf981163y

Cited by 22 publications

(13 citation statements)

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“…IMC measures the heat flow of biological processes (endo-or exothermic reactions) over time and has already been applied in various disciplines, including studies on food deterioration, drug shelf life (34), microbial processes, and the effects of different antimicrobial agents (6,39). We have already demonstrated the applicability of this method evaluating the antischisto-Motor activity analysis.…”

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confidence: 99%

Isothermal Microcalorimetry To Study Drugs against Schistosoma mansoni

et al. 2011

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Alternative antischistosomal drugs are required since praziquantel is virtually the only drug available for treatment and morbidity control of schistosomiasis. Manual microscopic reading is the current "gold standard" to assess the in vitro antischistosomal properties of test drugs; however, it is labor-intensive, subjective, and difficult to standardize. Hence, there is a need to develop novel tools for antischistosomal drug discovery. The in vitro effects of praziquantel, oxamniquine, artesunate, and mefloquine on metabolic activity and parasite motility of Schistosoma mansoni (newly transformed schistosomula [NTS] and 49-day-old adult worms) were studied using isothermal microcalorimetry (IMC). Results were compared to morphological readouts of viability. Results obtained for the four drugs tested with phenotypic evaluation by microscopy and IMC showed a good correlation, but IMC also identified drug effects that were not visible by microscopic evaluation, and IMC precisely determined the onset of action of the test drugs. Similar sensitivities on NTS and adult schistosomes were observed for praziquantel and mefloquine, while slight differences in the drug susceptibilities of the two developmental stages were noted with oxamniquine and artesunate. IMC is a useful tool for antischistosomal drug discovery that should be further validated. In addition, our data support the use of NTS in in vitro antischistosomal drug assays.Schistosomiasis, caused by blood flukes of the genus Schistosoma, is an important health problem affecting 779 million people mainly in sub-Saharan Africa (36). Praziquantel is virtually the only drug available and is increasingly deployed in mass drug administration programs, advocated by the World Health Organization (11). The annual estimated need for praziquantel in Africa exceeds 400 million tablets (http://www .who.int/wormcontrol/newsletter/PPC7_Eng_min.pdf). Two alternative drugs, oxamniquine and metrifonate, exist; however, they are rarely used today as they have a rather narrow activity profile and multiple doses have to be administered (12, 37). The extensive use and reliance on one single agent have raised concerns about the emergence of praziquantel resistance (3,8), and indeed, schistosome strains with increased drug tolerance have already been isolated from patients as well as selected in the laboratory (9, 26). Therefore, there is growing consensus that novel antischistosomal drugs should be discovered and developed (8,15,33).Antischistosomal drug discovery at many academic institutions (e.g., the Special Programme for Research and Training in Tropical Diseases; screening centers in London, United Kingdom, and Cairo, Egypt; the University of California, San Francisco, Sandler Center in San Francisco, CA; and the Swiss Tropical and Public Health Institute [Swiss TPH] in Basel, Switzerland) is based on in vitro whole-organism drug screening assays followed by in vivo tests in infected mice (15, 31). Stages used for in vitro assays are 1-to 7-day-old schistosomula (newly transfor...

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Isothermal Microcalorimetry To Study Drugs against Schistosoma mansoni

et al. 2011

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“…The heat evolved or adsorbed is proportional to the rate of the biological processes. 10,11 It is an online, kinetic and precise method to measure the bioactivity of compounds, which could be a useful tool in drug discovery.…”

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Study of Antimicrobial Effects of Different Types of Glycyrrhiza Extracts by Microcalorimetry

Wei¹,

Lin²,

Lian³

et al. 2014

Bulletin of the Korean Chemical Society

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Recently studies indicate that the microcalorimetry is a suitable measurement for metabolic activities of organisms by recording the rate of heat outputs. In this work, we investigated the growth thermogenic curves of Escherichia coli (E. coli) affected by three kinds of Glycyrrhiza extracts by microcalorimetry. The powertime and exponential phase power-time curves of the E. coli growth at various concentrations of extracts were generated. The kinetic parameters such as the growth rate constants (C), maximum power outputs (Pm), peak times (Tm), and inhibition ratios were calculated and the relationships between Pm or Tm and C were established. Also, the clear correlations among the antimicrobial effects, Pm and C were obtained. The results revealed the Glycyrrhiza extracts had inhibitory activities towards E. coli while the Glycyrrhiza polysaccharides showed the most potent effects.

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“…20,21 The fraction of hydrate (α) was evaluated based on the area under the heat flow curve (AUC) at time t, assuming that 100% of fraction hydrate was the total AUC. The kinetic equation of crystallinity involves a function f (α), and its integrated form is the function g (α) (α = 0.05-0.95), where α is the function of crystallinity at time t.…”

Section: Isothermal Kinetic Analysis Of the Crystallizationmentioning

confidence: 99%

“…Isothermal microcalorimetry (IMC) was developed for an automatic analytical method in the chemical and pharmaceutical fields. [10][11][12][13][14][15][16][17][18][19][20][21][22][23] Since the instrument has a high sensitivity (0.1 µW) and a smaller sample capacity (several grams) and almost all chemical, physical, and biology processes that occur with the instrument are accompanied by small heat exchanges, IMC is an effective method of investigating changes in the physicochemical properties of pharmaceutical preparations under ambient conditions.…”

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confidence: 99%

Effect of surface modification on hydration kinetics of carbamazepine anhydrate using isothermal microcalorimetry

2003

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ABSTRACTeach temperature. The activation energy (E) of nuclei formation and crystal growth process for hydration of surface-modified CBZ anhydrate were evaluated to be 20.1 and 32.5 kJ/mol, respectively, from Arrhenius plots, but the Es of intact anhydrate were 56.3 and 26.8 kJ/mol, respectively. The dissolution profiles showed that the surface-modified sample dissolved faster than the intact sample at the initial stage. The dissolution kinetics were analyzed based on the Hixon-Crowell equation, and the dissolution rate constants for intact and surface-modified anhydrates were found to be 0.0102 ± 0.008 mg 1/3 min -1 and 0.1442 ± 0.0482 mg 1/3 ·min -1 . The surface-modified anhydrate powders were more stable than the nonmodified samples under high humidity and showed resistance against moisture. However, surface modification induced rapid dissolution in water compared to the control.The purpose of this research was to improve the stability of carbamazepine (CBZ) bulk powder under high humidity by surface modification. The surfacemodified anhydrates of CBZ were obtained in a specially designed surface modification apparatus at 60°C via the adsorption of n-butanol, and powder xray diffraction, Fourier-Transformed Infrared spectra, and differential scanning calorimetry were used to determine the crystalline characteristics of the samples. The hydration process of intact and surfacemodified CBZ anhydrate at 97% relative humidity (RH) and 40 ± 1°C was automatically monitored by using isothermal microcalorimetry (IMC). The dissolution test for surface-modified samples (20 mg) was performed in 900 mL of distilled water at 37 ± 0.5°C with stirring by a paddle at 100 rpm as in the Japanese Pharmacopoeia XIII. The heat flow profiles of hydration of intact and surface-modified CBZ anhydrates at 97% RH by using IMC profiles showed a maximum peak at around 10 hours and 45 hours after 0 and 10 hours of induction, respectively. The result indicated that hydration of CBZ anhydrate was completely inhibited at the initial stage by surface modification of n-butanol and thereafter transformed into dihydrate. The hydration of surface-modified samples followed a 2-dimensional phase boundary process with an induction period (IP). The IP of intact and surface-modified samples decreased with increase of the reaction temperature, and the hydration rate constant (k) increased with increase of the temperature. The crystal growth rate constants of nuclei of the intact sample were significantly larger than the surface-modified sample's at

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Use of Microcalorimetry in Monitoring Stability Studies. Example: Vitamin A Esters

Cited by 22 publications

References 13 publications

Isothermal Microcalorimetry To Study Drugs against Schistosoma mansoni

Isothermal Microcalorimetry To Study Drugs against Schistosoma mansoni

Study of Antimicrobial Effects of Different Types of Glycyrrhiza Extracts by Microcalorimetry

Effect of surface modification on hydration kinetics of carbamazepine anhydrate using isothermal microcalorimetry

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