Advance Access Publication 28 January 2008 Original Article eCAM 2010;7(3)323–330 doi:10.1093/ecam/nen004 Antimicrobial, Antioxidant and Cytotoxic Activities and Phytochemical Screening of Some Yemeni Medicinal Plants 1 2 2 2 Ramzi A. A. Mothana , Salah A. A. Abdo , Sidgi Hasson , Faisal M. N. Althawab , Sama A. Z. Alaghbari2 and Ulrike Lindequist3 1Department of Pharmacognosy, Faculty of Pharmacy, Sana’a-University, PO Box 33039, 2Institute of Pharmacy, College of Medical science, University of Science and Technology, Sana’a, Yemen and 3Department of Pharmaceutical Biology, Institute of Pharmacy, Ernst-Moritz-Arndt-University, Greifswald, F-L-Jahn Str. 15a, D-17487 Greifswald, Germany The traditional medicine still plays an important role in the primary health care in Yemen. The current study represents the investigation of 16 selected plants, which were collected from different localities of Yemen. The plants were dried and extracted with two different solvents (methanol and hot water) to yield 34 crude extracts. The obtained extracts were tested for their antimicrobial activity against three Gram-positive bacteria, two Gram-negative bacteria, one yeast species and three multiresistant Staphylococcus strains using agar diffusion method, for their antioxidant activity using scavenging activity of DPPH radical method and for their cytotoxic activity using the neutral red uptake assay. In addition, a phytochemical screening of the methanolic extracts was done. Antibacterial activity was shown only against Gram-positive bacteria, among them multiresistant bacteria. The highest antimicrobial activity was exhibited by the methanolic extracts of Acalypha fruticosa, Centaurea pseudosinaica, Dodonaea viscosa, Jatropha variegata, Lippia citriodora, Plectranthus hadiensis, Tragia pungens and Verbascum bottae. Six methanolic extracts especially those of A. fruticosa, Actiniopteris semiflabellata, D. viscosa, P. hadiensis, T. pungens and V. bottae showed high free radical scavenging activity. Moreover, remarkable cytotoxic activity against FL-cells was found for the methanolic extracts of A. fruticosa, Iris albicans, L. citriodora and T. pungens. The phytochemical screening demonstrated the presence of different types of compounds like flavonoids, terpenoids and others, which could be responsible for the obtained activities. Keywords: antibacterial – cytotoxicity – medicinal plants – radical scavenging – Yemen Introduction Plant-derived drugs remain an important resource, especially in developing countries, to combat serious diseases. Approximately 60–80% of the world’s popula- tion still relies on traditional medicines for the treatment of common illnesses (1,2). Traditional remedies have a long-standing history in many locations in Yemen and For reprints and all correspondence: Ramzi Mothana, Department of Pharmacognosy, Faculty of Pharmacy, Sana‘a-University, PO Box 33039, Sana‘a, Yemen. Tel: +9671-225097; Fax: +9671-374682; E-mail: r_mothana@yahoo.com continue to provide useful and applicable tools for treating ailments (3–5). Nevertheless, little scientific research was done to investigate the plants of Yemen used in herbal medicine. In the course of our investiga- tions we found that several plants of the Yemeni ethno- medicine possess really interesting biological activities, which could be of interest for all parts of the world (6–11). The aim of this work was to continue these investigations and to determine the antimicrobial, anti- oxidant and cytotoxic activities of till now uninvestigated medicinal plants collected from different locations of Yemen. In this study, a total of 34 extracts prepared from 2008 The Author(s). This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/ licenses/by-nc/2.0/uk/) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.