REV. CHIM. (Bucharest) ♦ 64 ♦ No. 1 ♦ 2013 http://www.revistadechimie.ro 49 Antioxidant Properties and Chemical Compositions of Various Extracts of the Edible Commercial Mushroom, Pleurotus Ostreatus, in Romanian Markets EMANUEL VAMANU * University of Agronomical Sciences and Veterinary Medicine Bucharest, Faculty of Biotechnology, 59 Marasti Blv, 011464, Bucharest, Romania The purpose of this study was to determine the antioxidant activities of four different extracts from the mushroom Pleurotus ostreatus available in Romanian markets. Antioxidant activity was calculated by the reducing power assay, the scavenging effect on free radicals, inhibition of lipid peroxidation and chelating effects on ferrous ions. Ethanolic extract presented the highest free radicals scavenging and metal chelating activities. Thus, significant positive correlations proved that the antioxidant effects of ethanolic extract were a result of the presence of the phenolic and flavonoidic compounds. However, the ability to inhibit lipid peroxidation depended on the solvent: methanol > ethanol > cold water > hot water. In the four extracts, different types of molecules with antioxidant properties were determined. Key words: antioxidant; food property; freeze drying; functional properties; medicinal properties. * email: email@emanuelvamanu.ro Pleurotus ostreatus is an edible mushroom with major medical and biotechnological applications. Fermentation biotechnologies today are using this mycelium for cultivation in liquid medium [1]. Mycelium, or mushroom extracts, are used to obtain functional products, or for isolating compounds with pharmaceutical effects [2]. P. ostreatus extract has a number of therapeutic qualities: stimulating the immune system; lowering blood cholesterol; preventing arterial hypertension; and atherosclerosis and hypoglycemic effect. Damages caused by free radicals, often leading to these diseases, cannot be entirely controlled by the human body’s self-defense mechanisms. This type of product, based on extractive processes, compensates for these needs due to their diverse composition in antioxidant substances [3,4]. Our objective was to evaluate the antioxidant properties of the edible commercial mushroom P. ostreatus sold in Romanian markets, and its study including reducing power, scavenging effects on free radicals, inhibition on lipid peroxidation and chelating effects on ferrous ions. The potential antioxidant components of these medicinal mushrooms were also determined. Experimental part Chemicals. All chemicals used were of analytical grade and obtained from from Sigma-Aldrich (Germany). Preparation of samples Mushrooms, P. ostreatus (trays weighing 500 g, collected in one day), were purchased from supermarkets in Bucharest. Undamaged mushrooms were selected and dried in a stream of dry air. The drying process took place at a constant temperature of 25 0 C in the oven for 15 days, until a constant weight was reached. Obtaining of extracts. The dried samples were subject to 70% ethanol extraction. 10 g of the dried mushroom sample was extracted using 100 mL solvent (ethanol and methanol), for 24 h, at 25 0 C and at 150 rpm. For hot water extract, 10 g of the sample was boiled in 500 mL of water for 30 min. For cold water extraction, a sample of 10 g was extracted by stirring with 100 mL cold water at 4°C for 24 h (5). The extracts were filtered using a Whatman No. 4 filter paper [6]. The solvents used for extraction were removed using a rotary vacuum evaporator Buchi R215, with a vacuum controller V-850, and a heating bath for parallel evaporation Multivapor P-6 at 50 0 C under vacuum [7]. The resulting extracts was lyophilized in a freeze dryer ALPHA 1-2/LD plus (Martin Christ Gefriertrocknungsanlagen GmbH), at – 55 0 C, for 48 hr DPPH radical scavenging assay The DPPH scavenging activity was measured using spectrophotometry. First, 0.05 mL of the samples dissolved in ethanol were added to an ethanolic solution of DPPH (200 μm) at different concentrations (varying from 2-10 mg/mL). An equal amount of ethanol was added to the control. After 20 min, the absorbance was read at 517 nm and the inhibition was calculated using the formula: DPPH scavenging effect (%) = A 0 – A P /A 0 × 100, where A 0 was the absorbance of the control and A P was the absorbance in the presence of the sample [8, 9]. Ascorbic acid was used for comparison. Reducing power First, 200 μL of the samples were mixed with sodium phosphate buffer (pH 6.6), 1 mM FeSO 4 and 1% potassium ferricyanide. After incubation of the mixture for 20 min at 50 o C, thricloroacetic acid was added and the mixtures were centrifuged. Next 2.5 mL of the resulting supernatant was mixed with an equal volume of water and 0.5 mL 0.1% FeCl 3 . The absorbance was measured at 700 nm [9,10]. Ascorbic acid was used for comparison. Superoxide radical scavenging assay The reaction mixture contained the same volume of 120 μM PMS (phenazine methosulfate), 936 μM NADH, freeze-dried extract, and 300 μM NBT, in a total volume of 1 mL of 100 mM phosphate buffer (pH 7.4). After 5 min of incubation at ambient temperature, absorbance of the resulting solution was measured at 560 nm. The superoxide