Screening of mushrooms from the woodlands of Zimbabwe: Occurrence of lectins and partial purification of a mucin specific lectin from Boletus edulis.

Mushrooms are known to possess a diversity of bioactive compounds that include lectins, which are proteins or glycoproteins that bind specifically to cell surface carbohydrates, culminating in cell agglutination. The present study describes the screening of lectin activity from ten local mushrooms, namely, Amanita zambiana, Boletus edulis, Cantharellus heinemannianus, Cantharellus miomboensis, Cantharellus symoensii, Lactarius kabansus, Amanita sp., Coprinus sp., Ganoderma lucidum and Trametes strumosa. The lectin content was detected by the haemagglutination activity of mushrooms against sheep and goat erythrocytes. Among the different mushrooms screened Amanita sp., Boletus edulis and Lactarius kabansus showed high lectin activity (39, 617 and 77 HAU/mg mushroom, respectively). Boletus edulis was used for the haemagglutination inhibition assay. A total of twenty sugars and sugar derivatives, namely, α-lactose, D-glucose, D-mannose, D-raffinose, N-acetyl glucosamine, maltose, melibiose, D-ribose, porcine mucin, D-cellobiose, D-arabinose, α-methyl-D-glucoside, methyl-α-D-mannopyranoside, D-trehalose, L-arabinose, L-sorbose, L-lyxose, ß-lactose, DL-xylose, and D-galactose, were used for the haemagglutination inhibition assay. Of the various carbohydrates tested, only porcine mucin was found to be the most potent inhibitor of Boletus lectin. The lectin from Boletus mushroom was partially purified using ammonium sulphate precipitation. The highest lectin activity was observed in the 30%-60% fraction. This study revealed for the first time the occurrence of lectins in the local Zimbabwean mushrooms studied as well as isolation of a novel mucin-specific lectin. The information obtained can be used for further investigation of cell surface sugars, purification and characterisation of glycoproteins and their contribution towards the medicinal properties of local mushrooms.

Antimicrobial effects of craniopharyngioma cystic fluid.

BACKGROUND: Tumours are known to increase the risk of infections, especially those occurring in the central nervous system where insertion of surgical hardware/shunts such as in craniopharyngiomas may be required. However, infections are surprisingly scarce in craniopharyngioma cases. In this study, we explored the possibility of antimicrobial effects of craniopharyngioma cystic fluid. METHODS: The antibacterial effect of craniopharyngioma cystic fluid samples against selected human pathogens: Escherichia. coli, S. aureus and S. pneumoniae were determined using the agar disc diffusion method. Streptomycin and ampicillin were used as controls. The test organisms were cultured in Mueller-Hinton broth overnight at 37 °C. McFarland standard was used as a reference to adjust the inoculum size of each test organism to a concentration of 1 × 106 CFU/ml using sterile broth. RESULTS: The craniopharyngioma cystic fluid inhibited growth of Gram-positive bacteria S. aureus and S. pneumoniae, but not the Gram-negative bacteria, E. coli. The samples showed the highest zones of S. pneumoniae growth inhibition of up to 20.0 ± 1.0 mm compared with 18.0 ± 1.0 mm of streptomycin and 9.0 ± 0.0 mm of ampicillin. CONCLUSION: Craniopharyngioma cystic fluid showed significant antibacterial properties against Gram-positive bacteria. This novel finding has implications in the way we view infections in craniopharyngioma patients. More studies need to be carried out to further elucidate this unique finding and possibly exploit these antimicrobial properties.

Characterization of Anti-Salmonella typhi Compounds from Medicinal Mushroom Extracts from Zimbabwe.

Antibiotic resistance has become a global concern and threatens the clinical efficacy of many drugs, leading to increased screening of several sources of potential antimicrobial substances. Mushrooms have long been recognized as a valuable source of nutritive and pharmacologically active compounds. Our previous studies showed that the acetone, ethanol, methanol, and cold water crude extracts of various mushrooms-Amanita and Cantharellus species, Ganoderma lucidum, and Lactarius kabansus-exhibited high antibacterial activity against Salmonella typhi. The objective of this study was to isolate, characterize, and identify antibacterial compounds from these crude mushroom extracts. The crude extracts were separated by preparative thin-layer chromatography. Fractions (n = 99) were obtained and screened for antimicrobial activity against S. typhi by using the MTT assay. Of the isolated components, 13 exhibited high inhibitory activity against the growth of S. typhi, with half-maximal inhibitory concentrations ranging from 206 to 619 µg/mL. Some of the highly potent antibacterial compounds were identified by using liquid chromatography-mass spectrometry. Terpenoids (lucidenic acid M and cavipetin D), a phospholipid (C16 sphinganine), and fatty acid amines (stearamide and palmitic amide) were some of the compounds found to be responsible for the antibacterial activity observed. The importance of local mushrooms as sources of antibacterial compounds was revealed. The high inhibitory activity of some mushroom extracts strongly suggests that the mushrooms contain compounds that have great potential for use in developing therapeutic agents against infections caused by S. typhi.

Effect of cooking and preservation on nutritional and phytochemical composition of the mushroom Amanita zambiana.

The effect of different cooking and preservation methods on the nutritional and phytochemical composition of the mushroom, Amanita zambiana, was investigated. Fresh mushrooms were boiled in water, fried, or microwaved. In addition, fresh mushrooms were either air-dried for 7 days or frozen at -20°C for 14 days. The protein, lipid, carbohydrate, and phenolic content of the treated mushrooms were measured and compared to the fresh mushroom contents. Frying increased the protein (2.01% ± 0.2% [fresh mushroom] to 2.23% ± 0.09%), lipid (14.68% ± 0.9% to 15.56% ± 0.34%), and carbohydrate (0.89% ± 0.01% to 2.69% ± 0.03%) content, while microwaving increased the protein (2.01% ± 0.2% to 3.64% ± 0.08%) and carbohydrate content (0.89% ± 0.01% to 2.26% ± 0.09%). Boiling only increased the carbohydrate content (0.89% ± 0.01% to 1.71% ± 0.05%) of the mushroom and significantly decreased (p < .05) the phenolic content (8.77 ± 0.1 to 1.46 ± 0.2 mg gallic acid equivalent (GAE)/g mushroom). Drying resulted in significant increase (p < .05) in protein (2.01 ± 0.2% to 24.36 ± 0.09%), carbohydrate (0.89% ± 0.01% to 58.67% ± 3.29%), and phenolic contents (8.77 ± 0.1 to 119.8 ± 0.7 mg GAE/g mushroom), while freezing only increased the carbohydrate content (0.89% ± 0.01% to 1.77% ± 0.03%). From the three cooking methods studied, frying is recommended as the most effective cooking procedure in retaining or enhancing the mushroom nutrients, while drying is a better preservation method than freezing.