Research Article ANTIOXIDANT AND FREE RADICAL SCAVENGING CAPACITY OF PHENOLIC EXTRACT FROM RUSSULA LAUROCERASI SOMANJANA KHATUA, TULIKA ROY, KRISHNENDU ACHARYA* Molecular and Applied Mycology and Plant Pathology Laboratory, Department of Botany, University of Calcutta, Kolkata, West Bengal India. Email: krish_paper@yahoo.com Received: 20 August 2013, Revised and Accepted: 14 September 2013 ABSTRACT Objectives: Cellular damage caused by reactive oxygen species has been implicated in several diseases; hence antioxidants have significant importance in human health. The objective of this study was to evaluate antioxidant properties of phenolic extract from Russula laurocerasi and presence of components responsible for the activity. Methods: The antioxidant properties were studied using various in vitro assays. Qualitative determination of different bioactive constituents such as phenol, flavonoid, β-carotene, lycopene and ascorbic acid were also done. Results: The extract was strong hydroxyl radical scavenger reflected by its low EC 50 value i.e. 0.03 mg/ml. EC50 values of the extract was in the order of hydroxyl radical scavenging< chelating ability of ferrous ion< DPPH scavenging< superoxide radical scavenging< β-carotene bleaching< reducing power. The extract presented a relatively strong antioxidant effect which was found to be correlated with total phenols (R 2 = 0.969) and flavonoids (R 2 = 0.888) implying that the polyphenols was partly responsible for the antioxidant activities. Conclusion: Our result thus indicates that the fraction of R. laurocerasi may be utilized as a promising source of therapeutics. Keywords: Antioxidant activity, edible mushroom, flavonoid, phenol, reactive oxygen species. RUNNING HEAD: Antioxidant capacity of phenolic extract of Russula laurocerasi INTRODUCTION Reactive oxygen species (ROS) are known to control various normal physiologic functions of organisms by acting as secondary messengers. But excessive stimulation of NAD(P)H by cytokines or mitochondrial electron transport chain, xanthin oxidase and some exogenous sources (such as UV radiation, pathogen invasion, herbicide action, oxygen shortage) can overproduce ROS resulting in numerous diseases [1, 2]. Organisms possess several defense mechanisms to control the level of ROS [3]. When such defense mechanisms become unbalanced, antioxidant supplement can be used to reduce the oxidative damage. Repairing such damages by naturally occurring substances mainly by supplementation of food having antioxidant property is becoming one of the most acceptable modes of modern therapy [4]. For thousands of years, edible mushrooms have been used to maintain health and increase longevity [5]. Mushrooms are rich sources of antioxidant compounds, mainly phenolic compounds (phenolic acids and flavonoids), tocopherols, ascorbic acid, carotenoids and polysaccharide [4]. They may act directly as antioxidant [6] or prevent underlying oxidative stress related pathological conditions such as cancer [7], heart ailments [8], diabetes [9], inflammation [10], hepatic damage [11, 12], microbial pathogens [13, 14] etc. Some members of Russulaceae family have already been assessed for potent antioxidant activity such as Russula virescens, Russula delica and antimicrobial activity like R. delica [15, 16]. But there are no conclusive reports on chemical composition and antioxidant activities about Russula laurocerasi, a well-known mycorrhizal fungus, which is used as food in West Bengal, India. So this study was focused on the antioxidant activity of phenol rich fraction obtained from R. laurocerasi by their ability to scavenge free radicals. The contents of antioxidant components were also determined. MATERIAL AND METHODS Mushroom sampling Basidiocarps of R. laurocerasi were collected in the month of July from the lateritic region of West Bengal and identified using standard literature [17]. A voucher specimen (AMFH 602) has been deposited in the same department of University of Calcutta. Standards and reagents All chemicals used were of analytical grade and freshly prepared before use. L-methionine, nitro-blue tetrazolium (NBT), riboflavin, 2- Deoxy-D-ribose, ferric chloride, hydrogen peroxide (H2O2), trichloro acetic acid (TCA), thiobarbituric acid (TBA), ferrous chloride, ferrozine, potassium ferricyani de, β-carotene, Tween 20, linoleic acid, 2,2-Diphenyl-1-picrylhydrazyl (DPPH), sodium bicarbonate, Folin-ciocalteu reagent, aluminium nitrate, potassium acetate, acetone, n-hexane, standards such as L-ascorbic acid, ethylenediamine tetraacetic acid (EDTA), butylated hydroxyanisole (BHA), gallic acid, quercetin were purchased from Sigma Chemicals Co. (St. Louis, MO, USA). Preparation of extract Polyphenol rich fraction was extracted according to the method of Cui et al. [18] with slight modification. The fruiting bodies of R. laurocerasi were cleaned to remove residual compost and dried to remove moisture content. 10 gram of desiccated material were ground and macerated in ethanol at the ratio of 1:20 (w/v) at 25°C for 2 days to eliminate the alcohol soluble constituents such as coloured material, small organic molecules (steroid, terpenoids etc.) and fat. The extracts were filtered through Whatman No. 1 filter paper and the entire extraction process was repeated on the residue. The filtrate was air dried, extracted by stirring with distilled water at 100°C for 8 hrs. After filtration, 4 volume of ethanol was Vol 6, Issue 4, 2013 ISSN - 0974-2441