BackgroundA plant-based diet protects against chronic oxidative stress-related diseases. Dietary plants contain variable chemical families and amounts of antioxidants. It has been hypothesized that plant antioxidants may contribute to the beneficial health effects of dietary plants. Our objective was to develop a comprehensive food database consisting of the total antioxidant content of typical foods as well as other dietary items such as traditional medicine plants, herbs and spices and dietary supplements. This database is intended for use in a wide range of nutritional research, from in vitro and cell and animal studies, to clinical trials and nutritional epidemiological studies.MethodsWe procured samples from countries worldwide and assayed the samples for their total antioxidant content using a modified version of the FRAP assay. Results and sample information (such as country of origin, product and/or brand name) were registered for each individual food sample and constitute the Antioxidant Food Table.ResultsThe results demonstrate that there are several thousand-fold differences in antioxidant content of foods. Spices, herbs and supplements include the most antioxidant rich products in our study, some exceptionally high. Berries, fruits, nuts, chocolate, vegetables and products thereof constitute common foods and beverages with high antioxidant values.ConclusionsThis database is to our best knowledge the most comprehensive Antioxidant Food Database published and it shows that plant-based foods introduce significantly more antioxidants into human diet than non-plant foods. Because of the large variations observed between otherwise comparable food samples the study emphasizes the importance of using a comprehensive database combined with a detailed system for food registration in clinical and epidemiological studies. The present antioxidant database is therefore an essential research tool to further elucidate the potential health effects of phytochemical antioxidants in diet.

We assessed the contribution of culinary and medicinal herbs to the total intake of dietary antioxidants. Our results demonstrate that there is more than a 1000-fold difference among antioxidant concentrations of various herbs. Of the dried culinary herbs tested, oregano, sage, peppermint, garden thyme, lemon balm, clove, allspice and cinnamon as well as the Chinese medicinal herbs Cinnamomi cortex and Scutellariae radix all contained very high concentrations of antioxidants (i.e., >75 mmol/100 g). In a normal diet, intake of herbs may therefore contribute significantly to the total intake of plant antioxidants, and be an even better source of dietary antioxidants than many other food groups such as fruits, berries, cereals and vegetables. In addition, the herbal drug, Stronger Neo-Minophagen C, a glycyrrhizin preparation used as an intravenous injection for the treatment of chronic hepatitis, boosts total antioxidant intake. It is tempting to speculate that several of the effects due to these herbs are mediated by their antioxidant activities.

Between 2001 and 2002, plant collections from wild populations of Norwegian tansy (Tanacetum vulgare L.) were studied with a focus on essential oil (EO) yield and composition in order to characterize the chemotypical EO variability. Tansy collections of 40 different locations from North, Mid-, and South Norway were transplanted to the Apelsvoll Research Centre Div. Kise in 2000 and grown for 2 years before the aerial parts (leaves and flower buds) were harvested in June 2002. The EO from individual plants was isolated from dried plant material by hydrodistillation and analyzed by gas chromatography-mass spectrometry (GC-MS) on a DB5 column at the Plant Biocenter. The EO yield ranged between 0.35 and 1.90% (v/w) (average: 0.81%); the most abundant thujone plants were especially rich in EO volatiles (0.95%). On the basis of GC-MS data, seven chemotypes could be identified as follows: A, alpha-thujone (two individuals); B, beta-thujone (22); C, camphor (six); D, chrysanthenyl acetate/chrysanthenol (three); E, chrysanthenone (two); F, artemisia ketone/artemisia alcohol (three); and G, 1,8-cineole (two). The thujone chemotype was dominated by beta-thujone (81%) associated with alpha-thujone, but tansy plants rich in alpha-thujone were also detected (61%). The chemotypical classification of Norwegian tansy genotypes was underscored by preliminary studies from 2001, indicating the genetic uniformity and biochemical stability of the domesticated plants.

In the period from 2000 to 2002, studies on peppermint (Mentha x piperita) herb and essential oil (EO) production have been conducted at Planteforsk, Apelsvoll Research Centre Div. Kise in Norway. The trials were aimed at finding the optimal harvest date and suitable drying methods to maximize EO yield and to obtain a desirable oil quality. Peppermint plants from the first production year (2000 and 2001) and the second production year (2002) were harvested during flowering at three developmental stages (early, full, and late bloom). Biomass and leaf production were recorded, and the water content of the plant material was detected after the application of different drying methods: instantaneous drying at 30, 50, and 70 degrees C and prewilting (ground drying) for 1 or 5 days followed by final drying at 30 degrees C. Finally, plant samples were transferred to The Plant Biocentre at NTNU, Trondheim, Norway, for hydrodistillation and gas chromatography-mass spectrometry (GC-MS) analyses of the EOs. Peppermint oil yield increased from early to full bloom and late bloom (average of all years and drying methods except for 50 and 70 degrees C: 2.95, 4.13 and 4.20 L/daa, respectively) as an effect of biomass production and leaf growth. The flavor-impact compounds, menthol and menthone, reached their optimum at full bloom (43-54 and 12-30%, respectively). Prewilting led to slight decreased EO levels after 1 day (7.7%) and 5 days of ground drying (1.5%) and no EO quality changes, compared to direct drying at 30 degrees C. The plant weight (H2O content) was drastically decreased to the average under 80 and 45% in all years, thus reducing the energy supply and costs for the necessary final drying step.

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