Structure–function relationships of immunostimulatory polysaccharides: A review

Mushrooms have been consumed since earliest history; ancient Greeks believed that mushrooms provided strength for warriors in battle, and the Romans perceived them as the “Food of the Gods.” For centuries, the Chinese culture has treasured mushrooms as a health food, an “elixir of life.” They have been part of the human culture for thousands of years and have considerable interest in the most important civilizations in history because of their sensory characteristics; they have been recognized for their attractive culinary attributes. Nowadays, mushrooms are popular valuable foods because they are low in calories, carbohydrates, fat, and sodium: also, they are cholesterol-free. Besides, mushrooms provide important nutrients, including selenium, potassium, riboflavin, niacin, vitamin D, proteins, and fiber. All together with a long history as food source, mushrooms are important for their healing capacities and properties in traditional medicine. It has reported beneficial effects for health and treatment of some diseases. Many nutraceutical properties are described in mushrooms, such as prevention or treatment of Parkinson, Alzheimer, hypertension, and high risk of stroke. They are also utilized to reduce the likelihood of cancer invasion and metastasis due to antitumoral attributes. Mushrooms act as antibacterial, immune system enhancer and cholesterol lowering agents; additionally, they are important sources of bioactive compounds. As a result of these properties, some mushroom extracts are used to promote human health and are found as dietary supplements.

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Edible Mushrooms: Improving Human Health and Promoting Quality Life

Fruit bodies of about 200 mushroom species are consumed throughout the world, preferably as a delicacy. Knowledge of their chemical composition, nutritional value and health-promoting effects has expanded dynamically during the last few years. Dry matter (DM) is low: commonly about 100 g kg⁻¹ . The usual contents of protein, lipids and ash are 200-250, 20-30 and 80-120 g kg⁻¹ DM, respectively. Various carbohydrates form the remaining DM. Nevertheless, great variations occur both among and within species. Energy is low, usually 350-400 kcal kg⁻¹ of fresh fruit bodies. The nutritional contribution of mushroom protein derived from earlier data seems to be overestimated. Fat content is low with markedly prevailing in linoleic acid and oleic acid, while the proportion of n-3 fatty acids is nutritionally marginal. The main carbohydrates are chitin, glycogen, trehalose and mannitol. Information on fibre content and composition is limited. Health-promoting β-glucans are an auspicious group of polysaccharides. High potassium content is characteristic of mushrooms. Several species can accumulate very high levels of both detrimental trace elements, particularly cadmium and mercury, and radiocaesium isotopes if growing on heavily polluted substrates. Mushrooms seem to be a considerable source of ergosterol, provitamin D₂, and phenolids with antioxidative properties. Hundreds of flavour constituents have been identified, particularly with eight-carbon aliphatic chains. Data on changes of mushroom components under various preservation conditions and culinary treatments have been fragmentary. Even more limited is knowledge of nutrient bioavailability.

A review of chemical composition and nutritional value of wild-growing and cultivated mushrooms.

Despite the huge diversity of antibacterial compounds, bacterial resistance to first-choice antibiotics has been drastically increasing. Moreover, the association between multiresistant microorganisms and nosocomial infections highlight the problem, and the urgent need for solutions. Natural resources have been exploited in the last years and among them, mushrooms could be an alternative source of new antimicrobials. In this review, we present an overview of the antimicrobial properties of mushroom extracts and highlight some of the active compounds identified, including low- and high-molecular weight (LMW and HMW, respectively) compounds. LMW compounds are mainly secondary metabolites, such as sesquiterpenes and other terpenes, steroids, anthraquinones, benzoic acid derivatives, and quinolines, but also primary metabolites such as oxalic acid. HMW compounds are mainly peptides and proteins. Data available from the literature indicate a higher antimicrobial activity of mushroom extracts against gram-positive bacteria. Among all the mushrooms, Lentinus edodes is the most studied species and seems to have a broad antimicrobial action against both gram-postive and gram-negative bacteria. Plectasin peptide, obtained from Pseudoplectania nigrella, is the isolated compound with the highest antimicrobial activity against gram-positive bacteria, while 2-aminoquinoline, isolated from Leucopaxillus albissimus, presents the highest antimicrobial activity against gram-negative bacteria.

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A Review on Antimicrobial Activity of Mushroom (Basidiomycetes) Extracts and Isolated Compounds

Factors affecting mushroom Pleurotus spp.

Bioactive proteins from mushrooms

Lentinus edodes has been valued as edible and medical resources. Polysaccharides have been known to be the most potent antitumor and immunomodulating substance in Lentinus edodes. In this review, we summarize the current knowledge of the polysaccharides isolated from Lentinus edodes, including extraction and purification methods, chemical structure and chain conformation, the effects on innate and adaptive immunity and their mechanism, relationship between structure and function, and the future prospects.

Polysaccharides in Lentinus edodes: Isolation, Structure, Immunomodulating Activity and Future Prospective

In this study, a new heteropolysaccharide, here called L2, was separated from the fruit body of Lentinula edodes. Chemical and physical analyses indicated that L2 has a molecular weight of 26 KDa and consists of glucose (87.5%), galactose (9.6%), and arabinose (2.8%), but it does not possess a triple-helical conformation. Stimulation of the production of nitric oxide (NO), tumor necrosis factor α (TNF-α), and interleukin 6 (IL-6) in RAW 264.7 cells showed that L2 has significant immune activities involving toll-like receptor 2 (TLR2). Further studies demonstrated that the activities of L2 exhibited high stability in wide range of pH from 4.0 to 10.0, when the thermal processing temperature was below 121 °C. Our findings revealed that a new heteropolysaccharide without triple-helical conformation from Lentinula edodes shows immuno-stimulating activities involving TLR2 at modest pH and thermal processing conditions, which enable it to act as an active component in foods.

Structure and immuno-stimulating activities of a new heteropolysaccharide from Lentinula edodes.

Polysaccharide is a major bioactive component of mushrooms. In this study, for the first time, starting from a new Lentinula edodes polysaccharide L2, we prepared a novel L2–calcium complex and the process was optimized. Scanning electron microscopy and Fourier Transform infrared spectrometry were used for characterization. The immunostimulating activities of L2 and L2–calcium complex were measured by enhancing the production of two cytokines TNF-α and IL-6 in RAW264.7 cells. While L2–calcium complex significantly stimulates the secretions of TNF-α and IL-6 compared with the control, complex with calcium ion decreased the secretion of them. These facts indicate that calcium ion can modulate immune stimulating activity of Lentinula edodes polysaccharide L2.

Huidan Yan

Papers

Bioactive proteins from mushrooms

Polysaccharides in Lentinus edodes: Isolation, Structure, Immunomodulating Activity and Future Prospective

Structure and immuno-stimulating activities of a new heteropolysaccharide from Lentinula edodes.

Preparation of Lentinula edodes polysaccharide-calcium complex and its immunoactivity.