Quantification of Rosmarinic acid inSalviaspecies indigenous to South Africa by HPTLC

Abstract

Summary The genus Salvia (Lamiaceae) encompasses about 900 species worldwide of which 26 are found in southern Africa. Salvia spp have several medicinal uses in South Africa such as antimicrobial, anticancer, antimalarial, and antituberculosis properties. Rosmarinic acid (RA) has been identified as one of the major molecules responsible for these various medicinal properties. Eleven Salvia species (18 samples) collected at different localities in South Africa were extracted with methanol in order to determine the level of RA present in the extracts. High-performance thin-layer chromatography (HPTLC) analysis was performed on glass silica gel 60 F 254 plates developed with ethyl acetate, toluene, and formic acid (6:3:1, v/v), while a gradient of acetic acid and methanol was used for high-performance liquid chromatography–ultra violet (HPLC–UV) analysis. Densitometric quantification was performed at λ = 328 nm (the wavelength of maximum absorption of RA) by fluorescence scanning using a CAMAG TLC Scanner 3. Polynomial (HPTLC) and linear (HPLC–UV) regression analyses were used to determine the amount of RA in the extracts. The mobile phase used for HPTLC produced good separation for RA (R F = 0.42). A good polynomial regression model was obtained in the range of 200–1000 ng and peak areas with the correlation coefficient (R2) of 0.9995. The coefficient of variation (%) of intra-day and inter-day precision of RA at 400 ng per band were 1.44 and 4.48, respectively. Salvia runcinata contained the highest (145.71 mg g–1) RA content. The paired sample ttest showed no statistical significant difference in the estimation of the amount of RA in the solvent extracts using the two chromatographic techniques. The prescribed method is simple, fast, reliable, sensitive and here proposed for the routine assay of Salvia extracts containing RA.