Berberis aetnensis C. Presl. extracts: antimicrobial properties and interaction with ciprofloxacin Rosario Musumeci a, *, A. Speciale a , R. Costanzo a , A. Annino b , S. Ragusa c , A. Rapisarda d , M.S. Pappalardo b , L. Iauk a a Department of Microbiological and Gynaecological Sciences, Section of Microbiology, University of Catania,Via Androne 81, 95124 Catania, Italy b Department of Pharmaceutical Sciences, University of Catania, Catania, Italy c Department of Pharmacobiological Sciences, University of Catanzaro, Catanzaro, Italy d Pharmacobiological Department, University of Messina, Messina, Italy Received 27 August 2002; accepted 16 December 2002 Abstract Previous research showed that berberine-containing Berberis species synthesise the substances 5?-methoxyhydnocarpin-D (5?- MHC-D) and pheophorbide a , which have no antimicrobial activity but inhibit the expression of multidrug resistant efflux pumps (MDRs) in Staphylococcus aureus and potentiate the action of berberine. The MDR pumps extrude synthetic and natural antimicrobials from bacterial cells. We searched for these compounds in Berberis aetnensis C. Presl. (Berberidaceae), an endemic plant of the volcano Mount Etna. This work confirms the presence of pheophorbide a and permits us to hypothesise the presence of 5?-MHC-D in leaf extracts. In fact, the activity of ciprofloxacin was improved when two chromatographic fractions isolated from leaf extracts were added. These results are indicative of the presence of MDR pump inhibitors. Moreover, crude extracts were tested on several micro-organisms and showed antimicrobial activity mainly against Gram-positive bacteria and yeasts. # 2003 Elsevier Science B.V. and the International Society of Chemotherapy. All rights reserved. Keywords: Berberis aetnensis ; Berberine; Efflux pump inhibitors; Pheophorbide a ;5?-MHC-D 1. Introduction In traditional medicine the extracts of various Berber- idaceae (Berberis aquifolium , Berberis vulgaris and Berberis aristata ) are used for rheumatic complaints and other types of chronic inflammations [1]. Some authors demonstrated that these extracts have a sig- nificant activity against bacteria, viruses, fungi, proto- zoa, helminthes and chlamydia [2]. Studies carried out on the properties and chemical composition of the extracts show that their principal activity is due to their alkaloid constituents with an isoquinolinic nucleus such as berberine, oxyacanthine, berbamine and palmatine [1]. It has been shown that berberine has febrifugal, hypotensive, immuno-stimulating, anti-inflammatory and antimicrobial properties and there are on-going studies regarding a possible anti-tumour activity [1  /5]. The most prominent clinical uses include bacteria related diarrhoea, parasitic intestinal infections and ocular infections (conjunctivitis, trachoma) [2,6]. As Stermitz et al. [7,8] stated, the weak antibacterial activity of berberine in some bacterial strains could be due to the expression of multidrug resistant efflux pumps (MDRs) that extrude the drugs, rather than their intrinsic activity. MDR efflux pumps are important mechanisms of active and unidirectional transport. Their presence makes bacterial strains resistant to various classes of antibiotics and prevents the intracellular action of berberinic alkaloids that are thus promptly expelled [9]. Several studies have shown that plants of the genus Berberis (Berberis repens , B. aquifolium and Berberis fremontii ) producing berberine (Fig. 1a) synthesise two substances, the flavonolignan 5?-MHC-D and the por- phyrin pheophorbide a (Fig. 1b and c), which have no antibacterial activity but have an inhibiting property against MDR efflux pumps found so far in Staphylo- * Corresponding author. Tel.:  /39-095-31-2386; fax:  /39-095-32- 5032. E-mail address: docsaro@yahoo.it (R. Musumeci). International Journal of Antimicrobial Agents 22 (2003) 48  /53 www.ischemo.org 0924-8579/03/$30 # 2003 Elsevier Science B.V. and the International Society of Chemotherapy. All rights reserved. doi:10.1016/S0924-8579(03)00085-2