1116 Advances in Natural and Applied Sciences, 6(7): 1116-1124, 2012 ISSN 1995-0772 This is a refereed journal and all articles are professionally screened and reviewed ORIGINAL ARTICLE Corresponding Author: R.J. Fatin, School of International Tropical Forestry, Universiti Malaysia Sabah (UMS), 88999, Kota Kinabalu, Sabah, Malaysia. E-mail: fatinruzana83@hotmail.com Total phenolic contents and free-radical scavenging activities from methanolic extracts of Nauclea subdita (Korth) Steud. heartwood 1 Fatin Ruzanna Jamaluddin, 2 Razak Wahab, 3 Jamaluddin M. Daud and 2 Shafiqur Rahman 1 School of International Tropical Forestry, Universiti Malaysia Sabah, 88999, Kota Kinabalu, Sabah, Malaysia 2 Faculty of Earth Science, Universiti Malaysia Kelantan, 17600 Jeli, Kelantan, Malaysia 3 Department of Biotechnology, Kulliyyah of Science, International Islamic University Malaysia, Kuantan Campus, 25200, Kuantan, Pahang, Malaysia Fatin Ruzanna Jamaluddin, Razak Wahab, Jamaluddin M. Daud and Shafiqur Rahman; Total phenolic contents and free-radical scavenging activities from methanolic extracts of Nauclea subdita (Korth) Steud. heartwood ABSTRACT Investigation on the total phenolic content (TPC) and free-radical scavenging activity of Nauclea subdita (Korth) Steud. were carried out. Information on these activities might reflect the potency of the plant extract as an antioxidant. Young and matured trees of N. subdita were harvested and cut into three heartwood parts (top, middle and bottom) and grounded into powdered forms. Soxhlet extraction of the heartwood samples using polar (methanol) and non-polar (hexane) solvents, and phytochemical screening tests were carried out. The total phenolic contents of the methanolic crude extracts from heartwood parts were determined by colorimetry at 760 nm using Folin-Ciocalteau’s reagent, and gallic acid was used as standard. The methanolic extracts were also checked for primary antioxidant activities using an in vitro method, measured by free-radical scavenging activity of 2, 2’-diphenyl-1- picrylhydrazyl (DPPH) radical. The absorbances were measured at 517 nm by UV/VIS spectrophotometer and compared with standards Trolox and butylated hydroxyanisole (BHA). The results from this study suggest that N. subdita heartwood extract may serve as a potential source of natural antioxidant for future development in food and nutraceutical applications. Key words: Nauclea subdita, antioxidant activity, TPC, 2, 2', diphenyl-1-picrylhydrazyl (DPPH) radical, methanolic extract. Introduction Nauclea subdita is a plant from the Rubiaceae family that composes many species. It is a tropical plant that is indigenous to most regions in Asia and Africa. Generally, the plant grows in lowland to hill forests, also in swampy areas and habitually along streams and rivers and normally planted to stabilize slopes and river banks. It is a timber species (Lim et al., 2004). Young leaves are edible, and a source of traditional medicine based on the great experience of people in different countries, especially the Sabahan ethnic in Semporna, Sabah, Malaysia. The plant is normally used for treating stomach ache, blood pressure, diabetes and skin problems. The information on the traditional usage of the plant was a useful basis for further research and development. Medicinal tall trees, as we know play an important role in our forest structure, biodiversity, eco- balance and usually as timber production in wood product industries (Lim et al., 2004). An important case, as this forest product can use as medicinal materials for human. Many medicinal materials are destructively obtained from plants such as roots, bark, sapwood, heartwood and other plant parts in the forest (Kaviarasan et al., 2007). More sustainable ways of harvesting the medicinal materials from the forest should be introduced. Since there are not many studies on Nauclea subdita has been carried out, this paper reports the results of antioxidant activities on heartwood of the plant. These studies were carried out at the School of International Tropical Forestry, Universiti Malaysia Sabah, and Department of Biotechnology, Kulliyyah of Science, International Islamic University Malaysia, Kuantan Campus, from July 2010 to Jan. 2012.