Journal of Medicinal Plants Research Vol. 4(13), pp. 1269-1272, 4 July, 2010 Available online at http://www.academicjournals.org/JMPR DOI: 10.5897/JMPR09.388 ISSN 1996-0875 ©2010 Academic Journals Full Length Research Paper Phytochemical screening, antioxidant, antibacterial and cytotoxic activities of Knema angustifolia extracts M. Phadungkit*, R. Rattarom and S. Rattana Faculty of Pharmacy, Mahasarakham University, Kantarawichai, Mahasarakham 44150, Thailand. Accepted 9 June, 2010 Knema angustifolia Warb (Myristicaceae) is used in traditional Thai medicine as a whole body tonic agent. The current study sought to evaluate the antioxidant, antibacterial and cytotoxic activities of extracts from this herb and to screen their chemical constituents. Antioxidant, antibacterial and cytotoxic activities were determined by the DPPH scavenging method, the disk diffusion method and the colorimetric method, respectively. Phytochemical screening was performed using standard procedures. The results showed that the ethanol extract had high antioxidant activity with an EC 50 value of 13.90 ± 1.35 μg/ml. The ethanol and the dichloromethane extracts were active against Staphylococcus aureus. The ethanol extract showed a strong cytotoxic activity against the lung cancer cell line with an IC50 value of 4.55 ± 4.60 μg /ml. Phytochemical screening of the extracts showed the presence of condensed tannins, phenolic compounds and triterpenes. In conclusion, the apparent antioxidant and cytotoxic activities of K. angustifolia suggest its potential usefulness in the prevention of cancer and other diseases. Key words: Knema angustifolia, antioxidant, antibacterial, cytotoxicity. INTRODUCTION Knema angustifolia Warb. (Myristicaceae) is a species of plant that is distributed widely in Thailand. It is known by the common name as “horse blood” because of the red resin exudated from its bark (Madalena et al., 1990). It is used in traditional Thai medicine as a whole body tonic agent (Chuakul et al., 2004). Other traditional uses include blood tonic and anticancer (Madalena et al., 1990). Despite its common uses in traditional Thai medicine, there has been minimal investigation of its chemical constituents and biological activities. However, it was reported that the plant from the same genus (Knema laurina) is being used to treat inflamed wounds and rheumatism (Ines, 2009). Previous phytochemical studies revealed resorcinols and anacardic acids (6-alkenylsalicylate) in the stem bark of K. laurina (Gonzales et al., 1996; Kijjoa et al., 1991). The aims of the current investigation were to screen the chemical constituents and to test the free radical scavenging, antibacterial and cytotoxic activities of the ethanol and dichloromethane extracts of this herb. *Corresponding author. E-mail: phadang_p@hotmail.com. Tel/Fax: 664-37-54360. MATERIALS AND METHODS Plant material The plant sample (stem) of K. angustifolia was collected from the Nongkhai province of Thailand and identified by one of the authors (M. Phadungkit). A voucher specimen has been deposited in the Herbarium at the Faculty of Phamacy, Mahasarakham University, Thailand. Preparation of the plant extracts The sample was extracted with petroleum ether (defatting), dichloromethane and 95% ethanol, respectively by the maceration method. The solvents were evaporated by a rotary evaporator yielding the herbal extracts. The dichloromethane and the ethanol extracts were tested for biological activities. Antioxidant testing by DPPH free radical scavenging assay The test was carried out using the DPPH (1,1-diphenyl-2-picryl hydrazyl) free radical scavenging assay. The free radical scavenging activity of the extracts and standard ascorbic acid solutions in absolute ethanol were determined based on their ability to react with the stable DPPH free radical (Yamasaki et al., 1994). A 750 μL aliquot of the extract (50 to 1000 μg/ml, dissolved in absolute ethanol) was added to 750 μL of DPPH in absolute