Journal of Chromatography A, 990 (2003) 215–223 www.elsevier.com / locate / chroma Analysis of catechins in extracts of Cistus species by microemulsion electrokinetic chromatography a a b a, * Romeo Pomponio , Roberto Gotti , N. Alfredo Santagati , Vanni Cavrini a ` Dipartimento di Scienze Farmaceutiche, Universita di Bologna, Via Belmeloro 6, 40126 Bologna, Italy b ` Dipartimento di Scienze Farmaceutiche, Universita di Catania, Viale A. Doria 6, 95125 Catania, Italy Abstract A microemulsion electrokinetic chromatographic (MEEKC) method was developed for the separation of six catechins, specific marker phytochemicals of Cistus species. The MEEKC method involved the use of sodium dodecyl sulfate (SDS) as surfactant, heptane as organic solvent and butan-1-ol as co-solvent. In order to have a better stability of the studied catechins, the separation was performed under acidic conditions (pH 2.5 phosphate buffer). The effects of SDS concentration and of the amount of organic solvent and co-solvent on the analyte resolution were evaluated. The optimized conditions (heptane 1.36% (w/v), SDS 2.31% (w/v), butan-1-ol 9.72% (w/v) and 50 mM sodium phosphate buffer (pH 2.5) 86.61% (w/v)) allowed a useful and reproducible separation of the studied analytes to be achieved. These conditions provided a different separation profile compared to that obtained under conventional micellar electrokinetic chromatography (MECK) using SDS. The method was validated and applied to the determination of catechin and gallocatechin in lyophilized extracts of Cistus incanus and Cistus monspeliensis.  2002 Elsevier Science B.V. All rights reserved. Keywords: Cistus species; Microemulsion electrokinetic chromatography; Plant materials; Catechins; Gallocatechins 1. Introduction and the aqueous extract from Cistus incanus was found to have a gastroprotective effect. The main The genus Cistus (Cistaceae family) includes component of Cistus species are polyphenolic com- many typical species of Mediterranean flora. Cistus pounds, commonly known as catechins, which repre- species are used as general remedies in folk medicine sent a group of compounds belonging to the flavo- for treatment of various skin diseases and as anti- noid family. These compounds have shown several inflammatory agents. Phytochemical studies on dif- biological activities including anti-inflammatory, an- ferent Cistus species have revealed the presence of tiallergic, antiplatelet, antiviral and antitumoral. Epi- several flavonoid compounds [1,2] with an anti- demiological studies have shown a correlation be- oxidant activity [3]. tween a higher content of bioflavonoids (catechins) The antifungal activity of Cistus incanus extract in the diet and a lower risk of cancer and car- was attributed to the presence of condensed tannins diovascular diseases, due to their ability to protect against the damaging action of free radicals [3]. The analysis of catechins in plant extracts has traditionally been carried out by reversed-phase *Corresponding author. Tel.: 139-51-209-9731; fax: 139-51- liquid chromatography (HPLC) with UV detection 209-9734. E-mail address: vcavrini@alma.unibo.it (V. Cavrini). [4–7]. 0021-9673 / 02 / $ – see front matter  2002 Elsevier Science B.V. All rights reserved. doi:10.1016 / S0021-9673(02)02010-1