Stability studies on orthosiphon stamineus (benth) tablet formulations

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Date
2006
Authors
Mohammad Alduais, Mohammad All
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Abstract
The chemical stability of Orthosiphon stamineus was evaluated based on the marker compounds of sinensetin, eupatorin and 3'-hydroxy-5,6,7,4'tetramethoxyflavone (TMF) by accelerating stability testing according to the ICH guidelines for stability testing of new drug substance and drug products. Orthosiphon stamineus Benth (Lamiaceae) is one of the popular traditional herbal medicines extensively used for many centuries in Southeast Asia like Indonesia and Malaysia. Evaluation of the chemical stability of herbal drugs is an important part of quality control of herbal drug preparation. Both 0. stamineus leaf powder and extract were prepared by wet granulation method using carboxymethyl cellulose (CMC) as binder. Half of the tablets were coated with hydroxypropylmethyl cellulose and polyethylene glycol as plasticizer. The dried extract and leaf powder of 0. stamineus were considered as drug substance while tablet and coated tablet as drug product. Samples were exposed for a 6- month period, under four different temperature conditions and relative humidity (30°C/ 65% RH, 40°C/ 75% RH, 50°C/ 85% RH, and 60°C/ 85% RH). Samples were analysed monthly for six months using chromatographic methods such as HPLC and HPTLC and spectroscopic methods such as FT-IR and UV-Visible spectrophotometry. The experimental data were used to evaluate rate constants, half-lives, and activation energies for the decomposition of marker compounds in 0. stamineus. The quantitative analysis for the determination of shelf life was carried out using HPLC method based on the quantification of major chemical markers, sinensetin, TMF and eupatorin. A prediction of the shelf life of the product was made by accelerating the decomposition process and extrapolating the results to normal storage conditions. Due to this reason stability tests were performed under exaggerated conditions (e.g. elevated temperatures) in order to accelerate degradation process for fast stability prediction. Arrhenius equation was applied to predict the shelf life (tgo) of marker compounds at room temperature. The chemical fingerprinting using HPTLC, UV-Vis and FTIR with Chemometrics showed that the active constituents in 0. stamineus stored at 30°C/ 65% RH remain stable during the period of study. Based on the shelf life of t90 (90% of active component of the drug still available) the shelf life at 25°C were as follows: leaf product 13.3 months, leaf tablet 14.2 months, leaf coated tablet 17.2 months, extract 12.9 months, extract tablet 16.2 months and extract coated tablet 23.2 months. Coated tablet gave higher degree of stability as compared to noncoated tablets and crude drug (leaf powder or extract) because the coating material reduces the effect of oxygen and moisture on the stability of the compound. Tablets also gave better shelf life as compared to crude drug (leaf powder or extract). This is may be due to the presence of excipients and binding agents which gives some degree of protection to the active compounds.
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Keywords
Orthosiphon stamineus (benth) , Tablet formulations
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