ResearchArticle EFFECT OF DRYING AND FREEZING ON ANTIOXIDANT CAPACITY AND POLYPHENOLIC CONTENTS OF TWO SOUTH ALGERIAN EGGPLANTS CULTIVARS CHÉRIFA BOUBEKRI 1 , TOUHAMI LANEZ* 2 , ASSIA DJOUADI 2 AND ABDELKERIM REBIAI 2 1 University of Biskra, Chemistry department, PO Box 145, Biskra 07000, Algeria 2 University of El Oued, VTRS Laboratory, B.P.789, 39000, El Oued, Algeria Email: touhami-lanez@univ-eloued.dz Received: 16 May 2013, Revised and Accepted: 07 Jun 2013 ABSTRACT Objective: The aim of this present study was to evaluate the effect of temperature on polyphenolic contents and antioxidant capacity of different parts (whole fruit, pulp and peel) of dark-purple and white eggplant variety cultivated in different regions of south Algeria. Methods: Folin-Ciocalteu method and cyclic voltammetry assays have been applied to quantify the polyphenolic contents and antioxidant capacity of dried and frozen dark-purple and white eggplant verities. Results: High phenolic content was found for peel of dark-purple variety in following order fresh (548.77 mg GA/g) > frozen (106.11) > dry (93.48). The antioxidant capacity of different parts of eggplant was measured using ascorbic acid equivalent antioxidant capacity assays. Antioxidant capacity is in the order, peel of fresh dark-purple eggplant (324.34 mg AA/g) > whole fruit of frozen dark-purple eggplant (182.69 mg/g) > peel of fresh white eggplant (89.52 mg/g). Conclusion: Our results indicate that antioxidant capacity and phenolics content of eggplant varied depending on the part of the fruit and of the eggplant cultivar analyzed. Correlation of phenolic content and antioxidant capacity shows excellent linearity, which demonstrates that phenolic compounds have a significant contribution to the total antioxidant capacity. Finally, cyclic voltammetry results suggest that ethanolic extract of different parts of eggplant do not reveal similar electrochemical responses to that of ascorbic acid suggesting a different electro-active chemical composition. Keywords: Eggplant; Solanum melongena L; Antioxidant capacity; Total phenolic content; Cyclic voltammetry. INTRODUCTION Eggplant or aubergine (Solanum melongena L) a non-tuberous crop of Solanaceae family was first domesticated in southern India from the wild nightshade and can exist under different size, shape, and colour, depending on the cultivar. Fruits are purple, white or striped [1] and are ranked amongst the top ten vegetables in terms of antioxidant capacity due to the fruit phenolic and flavonoic constituents [2]. Extracts from eggplant are effective for curing a number of diseases, including cancer, high blood pressure, and hepatosis due to content of anthocyanins and strychnine [3,4]. The two varieties cultivated eggplant in Algeria are dark purple and white and are widely used in cooking; their highest growing season is from November to January. The total phenolic contents and antioxidant activity of eggplant of many countries have been widely studied by many scientific research groups [5-9], however only a few information concerning the total phenolic contents and antioxidant activity of eggplant from Algeria can be found in literature. This motivated us to explore the antioxidant capacity and the total phenolic contents of south Algerian eggplants. The objective of this study is to quantify, using cyclic voltammetry, the polyphenolic content and antioxidant capacity of the ethanolic extract of south Algerian eggplants [10-17]. MATERIALS AND METHODS Chemical Ethanol (99%), was purchased from Sigma-Aldrich Co. ascorbic acid (99.7%), sodium carbonate (99%), were both purchased from Merck Co. Folin-Ciocalteu reagent was purchased from biochem chemopharma Co (Canada). all other reagents used were of analytical grade. Plant material Dark purple and white eggplant fruits were purchased fresh from a local market in Guemar (Algeria), in November 2011. After collection, the samples were analysed for phenolic contents and antioxidant evaluation within 8 months after harvest. For each variety of eggplant, we prepared three types of sampling (material to be extracted) as follows: fresh dark purple eggplant labelled as FDPE, fresh white eggplant labelled as FWE, dry dark purple eggplant labelled as DDPE, dry white eggplant labelled as DWE, frozen dark purple eggplant labelled as GDPE and frozen white eggplant labelled as GWE. Extraction of eggplant constituents Fresh eggplant samples Immediately after receipts of fresh eggplant, all samples were peeled using a knife kitchen, the pulp and the peels of the fruit were separated. Each part was chopped into small pieces. The fresh samples (5 g) were then extracted with 100 mL of ethanol for 2 hours using Soxhlet extractor. The samples were then filtered using Whatman filter No. 4 paper; the filtrate was recovered and evaporated at reduced temperature and pressure. All dry fractions were sealed in a glass flask and stored at low temperature until used. Dry eggplant samples Each part of fresh eggplant (peel, pulp and whole fruit) was cleaned, air dried for 4 weeks and ground to a powder. The powdered samples were treated in the same manner as fresh eggplant samples. Frozen eggplant samples The frozen parts of the fruit (peel, pulp and whole fruit) were ground in a food-mixer and treated in the same manner as fresh eggplant samples. Total phenolic content The total phenolic contents of the eggplant samples were measured using a colorimetric Folin-Ciocalteu method [18]. 0.1 mL of the extract was diluted with ultrapure water to 1 mL; 0.5 mL of Folin- Ciocalteu reagent diluted ten fold with ultrapure water was then added. After a period of 3 minutes, 2 ml of saturated sodium carbonate solution was added. The mixture was incubated at room temperature for 30 minutes. The absorbance was measured against International Journal of Pharmacy and Pharmaceutical Sciences ISSN- 0975-1491 Vol 5, Suppl 3, 2013 A A c c a a d d e e m mi i c c S S c c i i e e n n c c e e s s