Comparison of HPLC and ATR-FTIR Methods for the Determination of Rosmarinic Acid in Aqueous Leaf Extract of Orthosiphon stamineus.

Background: Rosmarinic Acid (RA) is an important natural bioactive compound widely distributed in food plants. ATR-FTIR and HPLC methods for comparative determination of RA in aqueous methanolic extracts of Orthosiphon stamineus leaf samples are described. Methods: The quantitative determination of RA was performed by using HPLC with UV detection at 340 nm and ATR-FTIR based on peak height location at 1712.29 cm^-1. Results: The mean recovery of RA was 99.54 ± 1.23% by the HPLC method and 105.48 ± 2.76 by the ATR-IR method. The relative standard deviation for the intra-day and inter-day precision was less than 5% for the HPLC method and less than 8% for the ATR-FTIR method. The limit of detection and limit of quantification values for the HPLC method were 2 ng/ml and 10 ng/ml, respectively. The limit of detection and limit of quantification values for the ATR-FTIR method were 0.34% and 0.86% w/w, respectively. The validated methods were used for the quantification of RA in leaf samples of O. staminues. The results of HPLC and ATR-FTIR methods were comparable. Conclusion: ATR-FTIR method is suitable for the routine determination of RA in herbal medicinal products of O. stamineus.