Wild and commercial mushrooms as source of nutrients and nutraceuticals

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Abstract

In order to promote the use of mushrooms as source of nutrients and nutraceuticals, several experiments were performed in wild and commercial species. The analysis of nutrients included determination of proteins, fats, ash, and carbohydrates, particularly sugars by HPLC-RI. The analysis of nutraceuticals included determination of fatty acids by GC-FID, and other phytochemicals such as tocopherols, by HPLC-fluorescence, and phenolics, flavonoids, carotenoids and ascorbic acid, by spectrophotometer techniques. The antimicrobial properties of the mushrooms were also screened against fungi, Gram positive and Gram negative bacteria. The wild mushroom species proved to be less energetic than the commercial sp., containing higher contents of protein and lower fat concentrations. In general, commercial species seem to have higher concentrations of sugars, while wild sp. contained lower values of MUFA but also higher contents of PUFA. α-Tocopherol was detected in higher amounts in the wild species, while γ-tocopherol was not found in these species. Wild mushrooms revealed a higher content of phenols but a lower content of ascorbic acid, than commercial mushrooms. There were no differences between the antimicrobial properties of wild and commercial species. The ongoing research will lead to a new generation of foods, and will certainly promote their nutritional and medicinal use.

Introduction

A nutraceutical can be defined as a substance that may be considered a food or part of a food and provides medical or health benefits like the prevention and treatment of disease. Nutraceuticals may range from isolated nutrients and dietary supplements to genetically engineered “designer” foods, herbal products and processed products such as cereals, soups and beverages. Some examples of nutritive nutraceuticals or “functional food ingredients” are dietary fiber, polyunsaturated fatty acids (PUFA, fish oil), proteins, peptides, amino acids, keto acids, minerals, antioxidative vitamins and other antioxidants (glutathione, selenium, etc) (Andlauer and Fürst, 2002, Kruger and Mann, 2003). PUFAs, especially the n-3 fatty acid family, are claimed to exert a protective effect against the development of cardiovascular and inflammatory diseases (Fürst and Kuhn, 2000, Fang et al., 2002). Epidemiological studies have consistently shown an inverse association between consumption of vegetables and fruits and the risk of cardiovascular diseases (Bazzano et al., 2001) and certain forms of cancer (Liu, 2003). Although the protective effects have been primarily attributed to well-known antioxidants, such as ascorbic acid, tocopherols and β-carotene, plant phenolics may also play a significant role (Soobrattee et al., 2005).

Different mushrooms were studied by the scientific community, in searching for new therapeutic alternatives, and the results proved their bioactive properties (Lindequist et al., 2005). Mushrooms are rich sources of nutraceuticals (Çağlarirmak, 2007, Elmastas et al., 2007, Ribeiro et al., 2007) responsible for their antioxidant (Mau et al., 2002, Lo and Cheung, 2005, Barros et al., 2007a), antitumor (Wasser and Weis, 1999), and antimicrobial properties (Smânia et al., 1995, Hirasawa et al., 1999, Hatvani, 2001, Barros et al., 2007b, Turkoglu et al., 2007). Besides their pharmacological features (Lindequist et al., 2005), wild mushrooms are becoming more important in our diet due to their nutritional value, related to the high protein and low fat/energy contents (Diéz and Alvarez, 2001, Agahar-Murugkar and Subbulakshmi, 2005, Barros et al., 2007c).

Our research group has been interested in nutritional and bioactive properties of wild mushrooms such as antioxidant activity (Barros et al. 2007a), antimicrobial activity (Barros et al., 2007b), and the influence of conservation treatment/cooking (Barros et al., 2007d) and fruiting body maturity stage (Barros et al., 2007e) on these properties.

In the present study we intend to evaluate the composition of wild and commercial mushrooms in nutrients and nutraceuticals. The evaluation of nutrient composition included the determination of proteins, fats, ash, carbohydrates, and individual profile of sugars. The evaluation of nutraceutical composition included the determination of fatty acids, phenolics, flavonoids, carotenoids, ascorbic acid and tocopherols. Antimicrobial activity was screened against fungi, Gram positive and Gram negative bacteria, and correlated to the bioactive compounds present in the extracts.

Section snippets

Samples

Eight mushrooms species: Boletus edulis Fr., Calocybe gambosa (Fr.) Donk, Cantharellus cibarius L. ex Fr., Craterellus cornucopioides Pers., Marasmius oreades (Bolt. ex Fr.) Fr. were commercial dried samples obtained in several supermarkets. All the others (Agaricus bisporus (Lange) Imbach, Agaricus silvaticus Schaeff., Agaricus silvicola (Vittad.) Peck were wild species and were collected under grassland in Bragança (Northeast of Portugal), in autumn 2006. The morphological identification of

Nutrient composition

The results of the chemical composition and estimated energetic value (expressed on dry weight basis) of the wild and commercial edible mushrooms are shown in Table 1. Protein was found in high levels and varied between 17.18 g/100 g in B. edulis and 80.93 g/100 g in A. bisporus. Fat ranged from 0.92 g/100 g in A. bisporus and 4.88 g/100 g in C. cornucopioides. In general, wild mushrooms were richer sources of protein and had a lower amount of fat than commercial mushrooms. Carbohydrates, calculated by

Discussion

Among all the studied species, only the chemical composition of A. bisporus (Manzi et al., 2001, Krbavčić and Barić, 2004), B. edulis (Manzi et al., 2004) and C. cibarius (Agahar-Murugkar and Subbulakshmi, 2005) was described previously but from different countries. Similar to our samples, the Indian C. cibarius contained protein as the principal macronutrient, while in the Italian B. edulis, carbohydrates dominated. The Italian A. bisporus sample contained higher levels of carbohydrate than

Conflict of interest statement

The authors declare that there are no conflicts of interest.

Acknowledgement

The authors are grateful to Foundation for Science and Technology (PPCDT/AGR/56661/2004) for financial support of this work.

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