Quantitative determination of four water-soluble compounds in herbal drugs from Lamiaceae using different chromatographic techniques

HPTLC-densitometric and HPLC-UV techniques were used for qualitative and quantitative determination of luteolin-7-O-glucuronide, lithospermic acid, rosmarinic acid and caffeic acid in several herbal drugs from the Lamiaceae family: Thymi herba, Serpylli herba, Majoranae herbo and Menthae piperitoe folium. Unmodified silica gel (HPTLC Si60) and silica gel chemically modified with aminopropyl groups (HPTLC NH2) were used during the investigation process. Among HPTLC methods the best resolution and selectivity was achieved with mobile phases: diisopropyl ether-acetone-formic acid-water (50:30:10: 10, v/v/v/v) and acetone-formic acid (85:15, v/v), respectively. Plates were densitometrically evaluated. Contents of analyzed compounds in the studied aqueous extracts prepared from herbal drugs were established using both techniques. The results from the HPTLC-densitometric analysis have been compared with those from HPLC-UV on a Cl 8 column with acetonitrile-water-formic acid as a mobile phase. The chromatographic methods were validated for linearity, LOD, LOQ, repeatability, intermediate precision and recovery. An analysis of variance showed that the HPTLC-densitometric and HPLC-UV methods are equivalent and sufficiently precise for the estimation of polyphenolic compounds mentioned above, in investigated herbal drugs. All of the suggested methods (HPTLC NH2, HPTLC Si60 and HPLC RP18) give results with good agreement.