Publications by authors named "Mounir Maafi"

Since the dawn of photochemistry 150 years ago, photoreactions have been conducted under polychromatic light. However, despite the pivotal role that photokinetics should naturally play for such reactive photosystems, the literature lacks a comprehensive description of that area. Indeed, one fails to identify explicit model integrated rate laws for these reactions, a characteristic type for their kinetic behavior, or their kinetic order.

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The properties of photokinetics under monochromatic light have not yet been fully described in the literature. In addition, for the last 120 years or so, explicit, handy model equations that can map out the kinetic behaviour of photoreactions have been lacking. These gaps in the knowledge are addressed in the present paper.

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The photokinetic behaviour of drugs driven by polychromatic light is an area of pharmaceutics that has not received a lot of attention. Most often, such photokinetic data is treated by thermal kinetic models (i.e.

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A new Φ-order kinetic method was proposed in this study for the investigation of trans-cis photoisomerization reaction of Oxyresveratrol (ORVT) subjected to non-isosbestic irradiation. In ethanolic media, it has been proven that forward (Φ) and reverse (Φ) reaction quantum yields were dependent on the monochromatic irradiation wavelength according to sigmoid patterns over the spectral ranges of their electronic absorption (260-360nm). An 11.

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New semi-empirical rate-law system of equations is proposed for the first time for consecutive photoreactions that involve up to 4 photoreaction steps, AB(4Φ). The equation system was developed, tested, and validated against synthetic kinetic traces generated by fifth-order Runge-Kutta calculations. The model accurately fitted the kinetic traces of Riboflavin photodegradation in ethanol which decomposes via the AB(2Φ) mechanism involving 2 consecutive photoreaction steps.

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The characterization of drugs' photodegradation kinetics is more accurately achieved by means of the recently developed Φ-order kinetics than by the zero-, first-, and/or second-order classical treatments. The photodegradation of anti-cancer dacarbazine (DBZ) in ethanol has been investigated and found to obey Φ-order kinetics when subjected to continuous and monochromatic irradiation of various wavelengths. Its photochemical efficiency was proven to be wavelength dependent in the 220-350 nm range, undergoing a 50-fold increase.

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The photodegradation reaction of Sunitinib (SUT), occurring via Z-E photoisomerisation, has been evaluated in this study using the recently developed Φ-order kinetics. In ethanol, the forward (Z → E) photoreaction of SUT was invariant with irradiation (its quantum yield, Φ(E-->Z)(λ)(irr) ≈ 0.019) in contrast to the E → Z isomerisation whose Φ(E-->Z)(λ)(irr) undergoes a 30-fold, sigmoid-shaped, increase with increasing irradiation wavelength.

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Despite the numerous concerns that have been raised in relation to considering 0(th), 1(st) and 2(nd)-order kinetic treatments for photodegradation characterisation and assessment of drugs, they still are employed, as they are the only tools available for these types of studies. The recently developed Φ-order kinetic models have opened new perspectives in the treatment of photoreaction kinetics and stand as the best known alternative to the classical approach. The Φ-order kinetics have been applied here to Fluvoxamine (Fluvo) with the aim of setting out a detailed and comprehensive procedure capable of rationalising photodegradation/photostability of drugs and proposing a platform for photosafety studies.

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Background: Drug photodegradation data are usually treated by zero-, first- or second-order kinetic equations. Such treatments would lack reliability since the aforementioned equations have been originally developed for pure thermal reactions. In this respect, it has recently been shown that unimolecular photodegradations obey Ф-order kinetics (Maafi and Maafi, 2013).

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A recently developed Ф-order semi-emperical integrated rate-law for photoreversible AB(2Ф) reactions has been successfully applied to investigate Montelukast sodium (Monte) photodegradation kinetics in ethanol. The model equations also served to propose a new stepwise kinetic elucidation method valid for any AB(2Ф) system and its application to the determination of Monte's forward (Ф(λ(irr))(A-->B)) and reverse (Ф(λ(irr))(B-->A)) quantum yields at various irradiation wavelengths. It has been found that Ф(λ(irr))(A-->B) undergoes a 15-fold increase with wavelength between 220 and 360 nm, with the spectral section 250-360 nm representing Monte effective photodegradation causative range.

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Background: The photodegradation of drugs obeying unimolecular mechanisms such as that of nifedipine (NIF) were usually characterised in the literature by zero-, first- and second-order kinetics. This approach has been met with varying success. This paper addresses this issue and proposes a novel approach for unimolecular photodegradation kinetics.

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A new actinometric procedure based on the analysis of kinetic traces of the actinometer is proposed in this study. It is suitable for thermally-stable photochromes, such as diaryethenes, which may be useful candidates for visible-range actinometry. The treatment of the traces employs a rate law which was achieved via the closed-form integration of the differential equation describing the kinetics of unimolecular photoreactions (i.

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Two new spectrokinetic methods aimed at solving the identifiability problem and leading to the true solutions of AB(1k,2phi) and AB(2phi) kinetics are proposed in this paper. The methods consider the systems under two respective assumption conditions relating to the variability of the quantum yields with irradiation wavelengths. It is shown through a detailed mathematical analysis that a set of only two traces, obtained under isosbestic and non-isosbestic irradiations of the reactive system are sufficient to reach a solution.

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This review reports on the main results of a set of kinetic elucidation methods developed by our team over the last few years. Formalisms, procedures and examples to solve all possible AB photochromic and thermophotochromic kinetics are presented. Also, discussions of the operating conditions, the continuous irradiation experiment, the spectrokinetic methods testing with numerical integration methods, and the identifiability/distinguishability problems, are included.

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