Investigation of the inhibition of respiratory bacterial pathogens and HIV-1 enzymes by twenty-one South African mushroom species

Abstract

The medicinal properties of South African mushroom species and their associated biological activities have been poorly documented. Increased resistance to antimicrobial drugs is a global problem and growing concern. Ethanol (80 %) and/or aqueous extracts of twenty-one mushroom species were screened against bacterial species infecting the respiratory system (i.e., Pseudomonas aeruginosa, Klebsiella pneumoniae, Streptococcus pyogenes, S. pneumoniae, Staphylococcus aureus and Mycobacterium tuberculosis H37), and the minimum inhibitory concentrations (MIC) determined using the p-iodonitrotetrazolium chloride (INT) and microplate Alamar Blue assays. Transmission electron microscopy (TEM) was used to detect morphological changes. Ethanol extracts were screened for HIV-1 reverse transcriptase (RT) and protease inhibition using colourimetric and fluorometric assay kits, respectively. The ethanol extracts showed better antibacterial activity against gram-positive bacteria. Extracts of Rhodofomitopsis lilacinogilva and Pisolithus tinctorius caused cell membrane damage. Gymnopilus junonius (MIC: 62.5 µg/mL) and R. lilacinogilva (MIC: 31.25 µg/mL) showed promising antimycobacterial activity. P. tinctorius (IC50: 1.35 µg/mL) inhibited HIV-1 reverse transcriptase activity. Chloropyllum molybdites, P. tinctorius and Pycnoporus sanguineus inhibited HIV-1 protease activity. South African mushroom species contain biologically active compounds with antibacterial- and anti-HIV-1 activities, which may play an important role in the development of novel therapies and antiretrovirals (ARVs) against respiratory associated pathogens.