Study of the state of water in a rutin standard

Abstract

Determination of the content and state of water bound in medicinal phytopreparations is necessary for establishing a scientifically justified methodological approach to standardization of these substances and the regime of their drying, packaging, and storage. The accuracy and reliability of the evaluation methods can be significantly increased by using standard substances. One of these standards is rutin, or 3-{[6-O-(cc-L-rhamnopyranosyl)-13-D-glucopyranosyl]oxy}-5,7,3',4'-tetrahydroxyflavone, used for determination of the content of vitamin P in drugs and raw plant materials and their classification with respect to the total content offlavonoids [1].As is known, rutin contains three water molecules [2]. Crystal hydrates are the most difficult objects for investigation: despite a huge number of works in this field, the results are frequently ambiguous, especially when the state of water is considered. It was demonstrated that the state of water in hydrated compounds is affected by a number of factors, ineluding the presence of polar groups and their interaction with water molecules, incorporation of water into the crystal lattice, donor-acceptor interactions, etc. [3]. Crystal hydrates are stable within certain intervals of the temperature and the pressure of water vapor in the environment. These regions of parameters are individual for each crystal hydrate. The amount of crystallization water entering into a particular crystal hydrate may vary within wide limits, depending on the external conditions.The purpose of this work was to study the content and state of water in rutin in order to elaborate a correct methodological approach to standardization of this substance and its use for the analysis of raw plant materials and medicinal preparations containing phenolic compounds such as flavonoids. E~ERIMENT~P~TThe amount of bound water and the character of its bonding in rutin were determined by methods of thermal analysis in combination with potentiometric titration and determination of the weight loss upon drying to a constant weight in a dry box. This approach, combining physical and chemical methods, is widely employed in the practice of pharmaceutical analysis [4][5][6].The thermal analysis was performed on a Perkin-Elmer DSC-2 differential scanning calorimeter. Rutin samples weighing 5 -8 mg were placed into standard aluminum cells and hermetically sealed so as to avoid drying. The thermograms were measured in the temperature range from 20 to 220~ scanned at a heating rate of 10K/rain. The total water content in the rutin preparations was determined either by the method ofpotentiometric titration using the Fischer reagent or by the thermoanalytical method using the DSC-2 instrument. The hygroscopicity ofrutin was studied by the conventional technique at a relative humidity of 90% [7]. The isotherms of water vapor sorption by rutin were obtained under static conditions at a relative humidity of air varying within 2 -98%. RESULTS AND DISCUSSIONAs is seen from the thermoanalytical curves depicted in Fig. 1, the...

Solubility of Rutin in Ethanol + Water at (273.15 to 323.15) K

“…The crystals of rutin trihydrate were dried in a vacuum oven at T ) 408.2 K for 12 h to eliminate the water of crystallization and then stored in a desiccator to avoid absorbing water. 5 The mass fraction purity was higher than 0.99, determined by high-performance liquid chromatography (Shimadzu LC-10AD).…”

“…The yellow powder of rutin (mass fraction 0.98) was supplied by Skyherb Natural Product Co., Ltd. (China) and recrystallized twice in boiling water. The crystals of rutin trihydrate were dried in a vacuum oven at T = 408.2 K for 12 h to eliminate the water of crystallization and then stored in a desiccator to avoid absorbing water . The mass fraction purity was higher than 0.99, determined by high-performance liquid chromatography (Shimadzu LC-10AD).…”