A human study was carried out to investigate whether tomato juice, rich in natural lycopene and fortified with vitamin C, is able to reduce several biomarkers of oxidative stress and inflammation and whether the effect can be attributed to lycopene, vitamin C or any other micronutrient. Following a 2-week depletion phase, volunteers were assigned randomly to ingest either tomato juice with (LC) or without (L) vitamin C fortification for 2 weeks (daily dose 20·6 mg lycopene and 45·5/435 mg vitamin C). Plasma and urine were analysed for carotenoids and vitamin C, lipid status, antioxidant capacity, thiobarbituric acid reactive substances (TBARS) and 8-epi-PGF2α, protein carbonyls, cytokines IL-1β and TNFα and C-reactive protein (CRP). The consumption of tomato juice led to a reduction in total cholesterol levels (L: 157·6v. 153·2 mg/dl,P = 0·008; LC: 153·4v. 147·4 mg/dl,P = 0·002) and that of CRP (L: 315·6v. 262·3 μg/l,P = 0·017; LC: 319·2v. 247·1 μg/l,P = 0·001) in both groups. The vitamin C-fortified juice slightly raised the antioxidant capacity in urine and decreased TBARS in plasma and urine. All other markers were affected to a lesser extent or remained unchanged. Cholesterol reduction was correlated with lycopene uptake (P = 0·003), whereas the other effects could not be related with particular micronutrients. Any beneficial effects of tomato consumption for human health cannot be attributed only to lycopene and, as the additional supplementation with ascorbic acid indicates, a variety of antioxidants might be needed to optimize protection against chronic diseases.

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Bioactive compounds and their relationship with antioxidant activity were determined in three tomato cultivars (Ronaldo, Siena and Copo) during vine ripening. The lycopene, chlorophyll (total, a and b), total phenolic, flavonoid, vitamin C and folate contents, and the antioxidant activity, by the ferric reducing/antioxidant power assay and the beta-carotene lineolate system, were determined in the samples. Tomato ripening involved the breakdown of chlorophylls, accompanied by a continuous increase in the lycopene content. Total phenolics, flavonoids and vitamin C increased significantly during ripening, whereas the folate content fell markedly as tomatoes turned from green to red. The lycopene and flavonoid content was highest in the Copo cultivar, vitamin C and folate highest in Ronaldo, and total phenolics highest in Siena. The antioxidant activity, as measured with the ferric reducing/antioxidant power assay, increased significantly during ripening in all extracts, and showed a positive correlation with the total phenolic and flavonoid contents. However, when measured with the beta-carotene lineolate system, the antioxidant activity decreased significantly during ripening; perhaps due to the antioxidant activity of chlorophylls and the peroxidation activity of vitamin C.

Tomatoes provide an optimal mix of dietary antioxidants that may be responsible for the reported health benefits of tomato consumption. However, technological processing, packaging materials, and storage conditions have an impact on the nutritional quality of tomato products by affecting the stability of antioxidant nutrients to different extents. In this study, we evaluated the stability of the antioxidant compounds (lycopene, ascorbic acid, total phenols, and total flavonoids) present in commercially available tomato juices during storage extended for 12 months at three different temperatures (8, 22, and 37 degrees C). To further characterize the impact of storage conditions, two commonly used packaging materials (Tetra pack and glass bottles) were used to determine whether packaging materials affect antioxidant stability. Overall, the total lycopene, total phenolic compounds, and total flavonoids remained almost stable during storage for 12 months, regardless of the packaging material used, indicating that tomato juices maintain their nutritional value in terms of antioxidant composition during their shelf life. However, ascorbic acid was the most labile antioxidant and was markedly affected by storage conditions. The hydrophilic total antioxidant activity (TAA) paralleled the losses in ascorbic acid content, whereas the lipophilic TAA remained substantially stable throughout the storage trial.

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