Traditional Salads and Soups with Wild Plants as a Source of Antioxidants: A Comparative Chemical Analysis of Five Species Growing in Central Italy

Abstract

The interest and demand for nutraceuticals are rapidly increasing in many industrialized countries due to the emergence of health risks associated with the increased consumption of processed foods. Several wild Mediterranean plants used as traditional foods are an extraordinary source of nutraceutical substances with antioxidant properties. This study has two main aims: (1) to quantify the antioxidant properties of traditional wild food plants and (2) to determine if their use in soups (i.e., the cooking process) can alter their beneficial properties. We have evaluated the antioxidant capacity (ABTS, DPPH) and the Total Phenolic Content (Folin-Ciocalteu) of five herbaceous plants traditionally consumed in several areas of Central Italy: (A) Reichardia picroides (L.) Roth, (B) Hypochaeris radicata L., (C) Cichorium intybus L., (D) Tordylium apulum L., and (E) Helminthotheca echioides (L.) Holub. Our analyses show good levels of antioxidant capacity for all plants, with Reichardia picroides and Helminthotheca echioides having the highest levels. There is a high correlation between the antioxidant activity and the Total Phenolic Content especially in Reichardia picroides (R²=0.92) and Hypochaeris radicata (R²=0.93). Boiling the species caused a general decrease in the antioxidant activity and polyphenols. Our study confirms the health benefits of consuming wild plants, especially raw ones in salads. It also supports the use of ethnobotanical information to study and then promote the consumption of wild food plants.

Figure 1

DPPH assay of the raw and cooked plant extracts. The average antioxidant capacity for four plants of each species either raw (A-E) or cooked (BC, CC, and EC) is presented as IC_50, i.e., the inhibition concentration that halves the DPPH radical activity. Lower IC₅₀ values indicate higher antioxidant capacity. Statistical analyses of all average data were performed using ANOVA.

Figure 2

ABTS assay of the raw and cooked plant extracts. The average antioxidant capacity for four plants of each species either raw (A-E) or cooked (BC, CC, and EC) is presented as TEAC, i.e., mmol of Trolox equivalent per kg of fresh weight (kgfw). Statistical analyses of all average data were performed using ANOVA.

Figure 3

Total Phenolic Content of the raw and cooked plant extracts determined using the Folin-Ciocalteu assay. The averages data of all raw (A-E) and cooked (BC, CC, and EC) species are presented as Gallic Acid Equivalents (GAE); i.e., mg of Gallic acid corresponding to the polyphenols contained per gram of dry weight (gdw). Statistical analyses of all average data were performed using ANOVA.

Figure 4

Correlation between the Antiradical Activity (ARA) and Total Phenolic Content (TPC) for all data of the crude plant extracts: y = 0.047x - 0.14; R² = 0.59; p <0.0001. Linear regressions and best fit values were calculated using the Graphpad Prism 4.1 program (http://www.graphad.com).

Figure 5

Correlation between the Antiradical Activity (ARA) and Total Phenolic Content for each raw species (A-E). A Reichardia picroides (◆) y = 0.047x +0.25; R² = 0.92; B Hypochaeris radicata (■) y = 0.031x +0.009; R² = 0.93; C Cichorium intybus (Δ) y = 0.011x +0.34; R² = 0.52; D Tordylium apulum (x) y = 0.004x +0.45; R² = 0.33; and E Helminthotheca echioides (•) y = 0.03x+0.25; R² = 0.45. A (p< 0.05), B (p< 0.05), C (p< 0.1), D (p< 0.3), and E (p< 0.1). Linear regressions and best fit values were calculated using the Grahpad Prism 4 program (http://www.graphad.com).