Phenolic contents and antioxidant activities of bitter gourd (Momordica charantia L.) leaf, stem and fruit fraction extracts in vitro Jittawan Kubola, Sirithon Siriamornpun * Department of Food Technology and Nutrition, Faculty of Technology, Mahasarakham University, Mahasarakham 44000, Thailand article info Article history: Received 29 August 2007 Received in revised form 14 January 2008 Accepted 26 February 2008 Keywords: Bitter gourd (Momordica charantia L.) DPPH assay Hydroxyl radical-scavenging activity b-Carotene–linoleate bleaching assay FRAP assay Total antioxidant capacity Total phenol content abstract Bitter gourd (Momordica charantia L.) has long been regarded as a food and medicinal plant. We investi- gated the antioxidant activity of the water extract of leaf, stem and fruit fractions by several in vitro systems of assay, namely DPPH radical-scavenging activity, hydroxyl radical-scavenging activity, b-carotene–linoleate bleaching assay, ferric reducing/antioxidant power (FRAP) assay and total antioxi- dant capacity. Total phenolic content was measured by Folin–Ciocalteu reagent. Identification of phenolic compounds was achieved using HPLC with the UV-diode array detection. The extracts of different frac- tions were found to have different levels of antioxidant activity in the systems tested. The leaf extract showed the highest value of antioxidant activity, based on DPPH radical-scavenging activity and ferric reducing power, while the green fruit extract showed the highest value of antioxidant activity, based on hydroxyl radical-scavenging activity, b-carotene–linoleate bleaching assay and total antioxidant capacity. The predominant phenolic compounds were gallic acid, followed by caffeic acid and catechin. The present study demonstrated that the water extract fractions of bitter gourd have different responses with different antioxidant methods. Total phenol content was shown to provide the highest association with FRAP assay in this present study (R 2 = 0.948). Ó 2008 Elsevier Ltd. All rights reserved. 1. Introduction Research on relationships between antioxidants and prevention of non-communicable disease, such as cardiovascular disease, can- cer, diabetes has been increasing sharply in recent years. Free rad- icals have been claimed to play a key role, affecting human health by causing severe diseases, such as cancer and cardiovascular dis- eases by cell degeneration. These free radicals can be generated during normal body function, and can be acquired from the envi- ronment. The oxygen radicals are associated with cellular and met- abolic injury, and accelerated aging, cancer, cardiovascular diseases, neurodegenerative diseases, and inflammation (Ames, 1983; Dasgupta & De, 2006; Stadtman, 1992; Sun, 1990). The oxi- dative damage might be prevented or limited by dietary antioxi- dants (Dasgupta & De, 2006). The most extensively used synthetic antioxidants, such as butylated hydroxyl anisole (BHA), and butylated hydroxyl toluene (BHT), have restricted use in food and have been suspected of being responsible for liver damage and carcinogenesis (Grice, 1986; Hettiarachchy, Glenn, Gnanasam- bandam, & Jonhnson, 1996; Ito, Fukushima, & Tsuda, 1986; Sene- virathne et al., 2006; Suja, Jayalekshmy, & Arumughan, 2005; Wichi, 1988). Epidemiological and in vitro studies strongly suggest that food containing phytochemicals with antioxidants have potentially protective effects against many diseases, including can- cer, diabetes and cardiovascular diseases (Senevirathne et al., 2006). Consumption of fruits and vegetables has contributed to the prevention of degenerative processes caused by oxidative stress (Kaur & Kapoor, 2001; Vinson, Xuehui, Ligia, & Bose, 2001). Foods such as fruits, vegetables and grains are reported to contain a wide variety of antioxidant components, including phytochemi- cals. Phytochemicals, such as phenolic compounds, are considered beneficial for human health, decreasing the risk of degenerative diseases by reduction of oxidative stress and inhibition of macro- molecular oxidation (Larson, 1988; Pereira et al., 2007; Pulido, Bra- vo, & Saura-Calixto, 2000; Silva et al., 2004; Velioglu, Mazza, Gao, & Oomah, 1998). These compounds have been reported to be well correlated with antioxidant potential (Katalinic, Milos, Modun, Music, & Boban, 2004). Bitter gourd (Momordica charantia L.) or Mara (in Thai) has long been used as a food and medicine (El Batran, El-Gengaihi, & El Shabrawya, 2006). Bitter gourd is called by different names since it grows in tropical regions such as India, Malaya, China, tropical Africa, MiddleEast, America (Kirtikar & Basu, 1993) and Thailand. As a medicinal plant, it has been reported to possess antilipolytic, analgesic, abortifacient, antiviral, cytotoxic, hypoglycemic and antimutagenic properties (Singh, Singh, & Bamezai, 1998). Extract powder of fresh and dried whole fruit of bitter gourd lowered blood sugar in diabetic rats, as reported by Virdi et al. (2003). El Batran et al. (2006) reported that bitter gourd extracts showed 0308-8146/$ - see front matter Ó 2008 Elsevier Ltd. All rights reserved. doi:10.1016/j.foodchem.2008.02.076 * Corresponding author. Tel.: +66 8 57474136; fax: +66 43 743135. E-mail address: sirithons@hotmail.com (S. Siriamornpun). Food Chemistry 110 (2008) 881–890 Contents lists available at ScienceDirect Food Chemistry journal homepage: www.elsevier.com/locate/foodchem