INTRODUCTION Reactive oxygen species (ROS) are a class of oxygen containing free radicals produced by oxidation reactions in organisms. These free radicals viz., single oxygen (1O2), hydrogen peroxide (H2O2), superoxide radical (•O−2) and hydroxyl radical (•OH) are chemical substances that can exist individually with one or more unpaired electrons, produced as undesirable byproducts (Das and Roychoudhury 2014). Free radical production can result in thousands of reactions and significant tissue damage, which in turn leads to harm DNA, proteins, and lipids (Sreejayan, 1997; Basile et al., 1999). Oxidative stress (OS) is the imbalance between cellular ROS production and cellular ROS scavenging ability (Khan et al., 2013). Antioxidants are crucial in providing resistance to OS by scavenging free radicals. The ability to contribute hydrogen atoms or electrons to free radicals and displace them is what is known as the antioxidant property. This prevents the damage that free radicals would otherwise inflict (Tan and Lim 2015). Recent studies have shown that the abundance of antioxidants present in a variety of foods and beverages such as fruits, vegetables, medicinal herbs, tea, coffee etc., have a positive impact on human health (Gulcin, 2012). Anthocyanins are blue, red, or purple pigments that are present in plants, particularly in their flowers, fruits, and tubers, while it is blue and red in alkaline and acidic conditions, respectively. Despite having a positive charge on the oxygen atom of the C-ring of the basic flavonoid structure; nevertheless, it is regarded as one of the flavonoids (Khoo et al., 2017). Anthocyanins are known for their high antioxidant properties which by giving the hydrogen atom to free radicals, they can either directly scavenge free radicals or indirectly prevent them by chelating free metal ions (Mishra et al., 2013). In addition, it provides more health advantages in terms of antimicrobial, antiproliferative, hypoglycemic, and others (Yoon et al., 2018; Li et al., 2019; Yue et al., 2019; Gamage et al., 2021). One of the crops that contains abundance of anthocyanin pigment is Clitoria ternatea L., known as butterfly pea, blue pea, Cord of an pea, and Asian pigeon wings belongs to the Fabaceae family, which yield edible flowers with colours ranging from dark blue, light blue to white and it is one of the important plants widely cultivated in tropical and temperate regions worldwide including Asia, Southeast Asia, the Caribbean, and Central and South America (Adisakwattana et al., 2020). Anthocyanins in butterfly pea flowers are distinctive for their profusion of polyacylated anthocyanins, or "ternatins" which are polyacylated derivatives of delphinidin 3,3′,5′-triglucoside (Gamage et al., 2021). As a result butterfly pea flowers with greater potential to be used as a natural source of anthocyanin pigment with blue hue besides health benefits as a supplement in the food and pharmaceutical industries (Jeyaraj et al., 2020). The first crucial stage in recovering active compounds from plant materials is extraction (Panda et al., 2022; Jeyaraj et al., 2020). The goal of choosing an effective extraction technique is to produce the highest yield with the highest concentration of the target chemicals (Gamage et al., 2021). It is crucial to use an appropriate extraction technique to obtain the most number of anthocyanins without degrading them because these are sensitive to heat, light, acids and alkalis (Chandrasekhar et al., 2012; Jeyaraj et al., 2020). In this regard, the experiment was conducted to evaluate the free radical scavenging activity of the anthocyanin pigment concentrate obtained by different extraction methods. MATERIALS AND METHODS The laboratory experiment was conducted at Department of Post Harvest Technology, College of Agriculture, Vellanikkara, Kerala Agricultural University, Thrissur, Kerala during 2021-22. Sample preparation. Fresh flowers were gathered in the early morning from Medicinal and Aromatic field block, College of Agriculture, Vellanikkara. The flowers were rinsed under running water from the tap and then drained free of water. The petals were separated from the sepals and dried in a cabinet dryer at 40±2 °C until they reached a consistent weight. The dried petals were then pulverised in a commercial blender and sieved through an 80 mesh size sieve. The petal powder was then sealed in a laminated pouch of aluminium foil and kept in the freezer until pigment extraction. Extraction of anthocyanin pigment. The experiment was laid out in a Completely Randomized Design with five treatments. The extraction was carried out by using the following methods: T1 - Aqueous (distilled water) extraction, T2 - Acidified aqueous (1% citric acid) extraction, T3 - Solvent extraction (50% ethanol), T4 - Acidified solvent extraction (50% ethanol with 1% citric acid) and T5 - Microwave assisted extraction with aqueous solvent (distilled water). At a temperature of 45 °C, the sample was agitated in the solvent for 45 min. The solvent and plant samples were mixed in a 1:20 (w/v) ratio. In microwave-assisted extraction method, the sample was combined with distilled water, and the tube containing the suspension was heated between 45 and 50 °C by being exposed to a 300-watt microwave for 120 seconds. Filter paper was used to filter the extract and a rotary vacuum evaporator (Heidolph rotary evaporator, Germany) was used to evaporate the filtrate at 60 °C and 114 mbar (Azima et al., 2017). The concentrated filtrates were preserved in glass vials, enclosed inside a laminated aluminium foil bag and kept refrigerated (4–7 °C) condition until analysis. Hydrogen peroxide scavenging activity (%). The free radical scavenging activity of the anthocyanin pigment concentrate was determined by hydrogen peroxide assay (Mahendran et al., 2021). Hydrogen peroxide (10 mM) solution was prepared in phosphate buffered saline (0.1 M, pH 7.4). One mL of the pigment sample was rapidly mixed with two mL of hydrogen peroxide solution. The absorbance was measured at 230 nm in the UV spectrophotometer (Agilent Cary 60 Spectrophotometer, Australia) after 10 min of incubation at 37 °C against a blank (distilled water with hydrogen peroxide solution). The percentage of scavenging of hydrogen peroxide was calculated using the following formula. In which, Ao and A1 is Absorbance of control and sample, respectively. Statistical analysis. The experiment was carried out in triplicates and results were expressed as mean values with standard deviation (±SD) (Panse and Sukhatme, 1989). One-way analysis of variance (ANOVA) was carried out to determine significant group differences (p≤0.05) between means. Duncan Multiple Range Test (DMRT) was used to compare mean values. RESULTS AND DISCUSSION The free radical scavenging activity of anthocyanin pigment concentrates of butterfly pea flowers was determined by hydrogen peroxide scavenging activity (%) and the results pertaining to it are shown in Fig. 1. The anthocyanin pigment concentrates obtained using different extraction methods have demonstrated their ability to diminish the free radicals. Significantly higher (79.28±0.47%) scavenging activity was noted in microwave assisted extraction method using aqueous solvent (T5) and significantly lower (64.39±1.75%) scavenging activity was observed in aqueous method of extraction (T1). The hydrogen-donating activity, measured utilizing hydrogen peroxide radicals as the hydrogen acceptor, demonstrated that a strong association could be found between anthocyanin pigment concentrates obtained using different extraction methods and their rate of inhibition (Al-Amiery et al., 2012). In addition, during the process of pigment extraction, the extract will not only contain the anthocyanin pigment but a mixture of bioactive components. Since the butterfly pea flowers are known to contain higher amount of polyphenols (Tuan Putra et al., 2021), the main polyphenol constituent being the anthocyanin itself (Pasukamonset et al., 2016) might have contributed to its higher free radical scavenging activity depending upon the method of extraction and solvent used. The phenolics play an important role in the absorption or neutralization of free radicals (Basile et al., 1999).