Optimization of Solvent Extraction of the Leaves of Premna serratifolia and Quantitation of Premnaodoroside A by Validated TLC-densitometric Method

Introduction: The leaves of Premna serratifolia have been widely used in traditional medicine. Its major constituents were iridoid glycosides and phenolic compounds. Antioxidation was one of its reported bioactivities. The aim of this study was to optimize the ethanol concentration used to obtain high quality extracts. Methods: Three sources of leaf samples were separately extracted by 0, 20, 40, 60, 80 and 100% ethanol. Their content of premnaodoroside A, the major glycoside, was determined by a TLCdensitometric method developed in this study. The content of total phenolic compounds and antioxidants were also determined by Folin-Ciocalteu and DPPH scavenging methods, respectively. Results: The developed TLC-densitometric method showed a good linearity (R2 > 0.99) in the range of 0.11-0.872 μg/spot. Its limit of detection and limit of quantitation were 0.13 and 0.04 μg/spot, respectively. The method had satisfactory specificity, precision and accuracy. The analysis results of all extracts showed that the 100% ethanolic extracts exhibited the highest contents of premnaodoroside A (3.23–5.25%), total phenolic compounds (7.56-8.24% GAE) and antioxidants (4.92–6.66% AAE), but its extractive yields (13.57-19.57%) were the lowest. Yields of the 40% and the 80% ethanolic extracts were the highest in two samples (36.37-45.96%) and one sample (47.53%), respectively. Considering of the extractive ability, the 80% ethanol could extract the highest amounts of all investigated compounds from plant material. Conclusion: The 100% ethanolic extract possessed the highest contents of the interesting compounds, but the 80% ethanolic extract had a higher extractive yield. Their benefits and drawbacks must be considered, depending on further application.