Shelf life determination of herbal medicines is of paramount importance as it relates to activity of constituents of the product. This work sought to determine shelf life of four herbal products (Nibima, Asena, Lippia tea and NPK 500 capsules). The method involved determination of marker content of products (three batches each) at time points (0,3,6,9,12 and18 months) at storage temperature and humidity of 30 °C ± 2 °C/70 % RH ± 5 % RH using HPLC analyses. Batch blending was employed for preparation of reference samples of products. In UV analyses, λ max of 289, 291, 327 and 289 nm were obtained from spectra for (Nibima, Asena, Lippia tea and NPK 500 capsules respectively. A common 230 nm UV marker was observed for all products. Optimized HPLC conditions were developed for products using methanol: water: 0.1 %v/v acetic acid system with mobile phase ratios of 9:0:1 (Nibima), 7:2:1 (Asena), 8:1:1 (Lippia tea)and 90:5:5 (NPK 500 capsules). Wavelength of detection used for HPLC analyses were 283, 290, 332 and 290 nm for Nibima, Asena, Lippia tea and NPK 500 capsules respectively. HPLC marker content analyses with time produced shelf life of 23.14, 21.16, 32.91 and 62.97 months for (Nibima, Asena, Lippia tea and NPK 500 capsules respectively. Obtained shelf life indicates relative stability of products.
Key words: Stability, shelf life, markers, herbal products, UV-Vis Spectroscopy, HPLC
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