Antioxidant, radical-scavenging, anti-inflammatory, cytotoxic and antibacterial activities of methanolic extracts of some Hedyotis species Rohaya Ahmad a , Abdul Manaf Ali b , Daud A. Israf c,d, T , Nor Hadiani Ismail a , Khozirah Shaari d , Nordin Hj. Lajis d a Faculty of Applied Science, Universiti Teknologi MARA, 40450 Shah Alam, Selangor, Malaysia b Department of Biotechnology, Faculty of Food Science and Biotechnology, Universiti Putra Malaysia, 43400 Serdang, Selangor, Malaysia c Faculty of Medicine and Health Sciences, Universiti Putra Malaysia, 43400 Serdang, Selangor, Malaysia d Laboratory of Natural Products, Institute of Bioscience, Universiti Putra Malaysia, 43400 Serdang, Selangor, Malaysia Received 19 April 2004; accepted 10 August 2004 Abstract The antioxidant, radical-scavenging, anti-inflammatory, cytotoxic and antibacterial activities of methanolic extracts of seven Hedyotis species were investigated. The antioxidant activity was evaluated by the ferric thiocyanate (FTC) and thiobarbituric acid (TBA) methods while the radical scavenging activity was measured by the 1,1-diphenyl-2-picrylhydrazyl (DPPH) method. The anti-inflammatory activity related to NO inhibition of the plant extracts was measured by the Griess assay while cytotoxicity were measured by the MTT assay against CEM- SS cell line. The antibacterial bioassay (against 4 bacteria, i.e. Bacillus subtilis B28 (mutant), Bacillus subtilis B29 (wild-type), Pseudomonas aeruginosa UI 60690 and methicillin resistant Staphylococcus aureus , (MRSA) was also carried out using the disc-diffusion method. All tested extracts exhibited very strong antioxidant properties when compared to Vitamin E (a-tocopherol) with percent inhibition of 89–98% in the FTC and 60–95% in the TBA assays. In the DPPH method, H. herbacea exhibited the strongest radical scavenging activity with an IC 50 value of 32 Ag/ml. The results from the Griess assay showed that the tested extracts are weak inhibitors of NO synthase. However, all tested extracts exhibited moderate cytotoxic properties against CEM-SS cell line giving CD 50 values in the range of 21–41 Ag/ml. In the 0024-3205/$ - see front matter D 2005 Elsevier Inc. All rights reserved. doi:10.1016/j.lfs.2004.08.039 T Corresponding author. Tel.: +603 89468063; fax: +603 89468080. E-mail address: daud@ibs.upm.edu.my (D.A. Israf). Life Sciences 76 (2005) 1953 – 1964 www.elsevier.com/locate/lifescie