Evaluation of radical scavenging activity of fresh and air-dried tomatoes by three model reactions

The radical scavenging activity and the antioxidant content of fresh and ai r-dried tomatoes were investigated. Tomato halves were dried in a pilot-sca le dryer under the following conditions: air temperature, 80 degrees C; air flow rate, 1.5 m/s; drying time, 400 min; final moisture, 25%. Carotenoid (lycopene, beta-carotene, lutein) and ascorbic acid were analyzed by HPLC w ith a spectrophotometric and an electrochemical detector, respectively. Tot al phenolics were determined by using the Folin-Ciocalteu reagent. The radi cal scavenging activity was studied in three model systems: (a) the xanthin e oxidase and xanthine system, which generates superoxide radical and hydro gen peroxide; (b) the 3-morpholinosydnonimine system, which releases sponta neously superoxide radical and nitrogen monoxide, forming peroxynitrite; (c ) the linoleic acid and CuSO4 system, which promotes lipid peroxidation. Th ese model systems allow the simulation of key reactions involved in the pat hogenesis of certain chronic diseases and may be related to the in vivo act ivity of tomato antioxidants. Hence, these measurements can be used for opt imizing tomato processing and storage. The drying process resulted in a dec rease of ascorbic acid content;, whereas phenol reagent; reducing compounds increased. Carotenoid levels were substantially unchanged upon drying. Fre sh and air-dried tomato extracts could act as radical scavengers both in th e reactive oxygen species-mediated reactions and in lipid peroxidation. Dry ing affected the antioxidant effectiveness as measured in the xanthine/xant hine oxidase system, which was found to be the most sensitive method for th e measurement of tomato antioxidant activity (lower I-50) but retained the antioxidant effectiveness in the other two systems.