Parallel determination of rosmarinic and caffeic acids by TLC-densitometry

Abstract

SummaryA TLC-densitometric method was introduced for the parallel determination of rosmarinic and caffeic acids. Experiments performed to establish the optimal measurement parameters related to the excitation wavelength, colour stability, linearity of the calibration curves, sensitivity and reproducibility. The application of TLC permits utilization of the fluorescence of both phenols, often without the need for prior purification. This fluorescence measurement makes the detection extremely sensitive. The densitometric quantification allows the routine analysis of many samples in a short time with reasonable accuracy. The practical application of the elaborated method will be demonstrated on 5 Salvia species.

TLC-densitometry of rosmarinic and caffeic acids in the evaluation of lamiaceae species growing in central Europe

“…20 μl samples from the stock-solution were spotted 10 mm from the buttom. Tolueneethyl acetate -formic acid (5:4:1) solvent system served as developing agent in an unsaturated chamber [1,14]. All solvents were of analytical grade.…”

“…80 mm length) the plates were dried for 20 min. at room temperature with a hair-drier and for an additional 20 min they were exposed to normal light in order to obtain better light emission [1]. In all cases RA and CA reference samples (Roth, Germany) were co-chromatographed with the plant samples.…”

“…The compounds or their derivatives that are to be measured should have a suitable chromophore for light absorption (and light emission) of which should show linear concentration dependence. The method that was usedearlier for measuring rosmarinic acid (RA) and caffeic acid (CA) fulfils these requirements [1].…”

“…In many cases only a small amount of plant material is available and at the same time, because of various reasons, fast measurement is necessary. For such purposes the accuracy of TLC-densitometry may be acceptable [1,[11][12][13]. We should keep in mind that plant materials themselves can vary significantly.…”

“…Both compounds contribute to the activities of the medicinal plants of the Lamiaceae family, predominantly because of their antioxidant capacities [9,10]. In our former publications we also have given information about the subfamiliar distribution of RA and CA and have provided some quantitative data on their presence in many Lamiaceae species by using a TLC-densitometric assay [1,3,[11][12][13]. The quantitative data on the drugs obtained by this method reflect both the differences due to the measuring processes and those due to the variation to plant sources.…”