Application of high performance liquid chromatography and Fourier-transform infrared spectroscopy techniques for evaluating the stability of Orthosiphon aristatus ethanolic extract and its nano liposomes

Abstract

Orthosiphon aristatus (Blume) Miq., Lamiaceae, is a medicinal plant from Southeast Asia. Pharmacological effects of O. aristatus are attributed to the presence of lipophilic flavones. This study aimed to carry out accelerated stability studies on O. aristatus ethanolic extract and its nano liposomes. The extracts were exposed to four different temperatures at 30, 40, 50 and 60 °C for 6 months. The samples were analyzed at 0, 1, 2, 3, 4, 5 and 6 months by high performance liquid chromatography using rosmarinic acid, 3′-hydroxy-5,6,7,4′-tetramethoxyflavone, sinensetin and eupatorin as markers. Different chemical kinetic parameters of the markers were evaluated by Arrhenius equation to predict shelf life (t90) at different storage conditions and at room temperature. Moreover, the stability of O. aristatus ethanolic extract and O. aristatus nano liposomes were analyzes by chemical fingerprinting using FTIR spectroscopy, principal component analysis and hierarchical clustering analysis. The degradation of markers in both O. aristatus ethanolic extract and O. aristatus nano liposomes followed the first order degradation reaction (dependening on their initial concentration). The loss of marker compounds in O. aristatus ethanolic extract, stored at 30, 40, 50 and 60 °C for six months were up to 25, 52, 72 and 89% for all compounds, respectively. However, in O. aristatus nano liposomes 16, 71, 85 and 100% of compounds were lost during 6 months of storage at 30, 40, 50 and 60 °C, respectively. Therefore, the markers in O. aristatus nano liposomes seems to be more stable at a temperature below 30 °C compared to O. aristatus ethanolic extract. However, markers present in O. aristatus ethanolic extract are more stable at a higher temperature (above 30 °C). principal component analysis or hierarchical clustering analysis analyses were applied to the FTIR results in order to demonstrate the discrimination between extracts based on the storage conditions. The results show that the functional group of the components in the extracts and their chemistry relationship is influenced by the temperature setup indicating the extracts are not stable during the storage conditions.