INVESTIGATION OF ANTIMICROBIAL AND NEMATICIDAL ACTIVITY OF SECONDARY METABOLITES FROM Armillaria SPECIES

Abstract

Infectious diseases caused by pathogens are the leading cause of death for both adults and children. These diseases are responsible for 18.4 % fatalities worldwide. The widespread of the infectious diseases caused by these pathogens arises due to antimicrobial drug resistance. Plant- parasitic nematodes are responsible for approximately 80% of vegetable output loss in Kenya. They have also caused havoc on agriculture throughout the world, jeopardizing agriculture's long-term viability. Currently, control of nematodes relies on synthetic nematicides, which unfortunately causes environmental and ecological pollution and threatens human health. The development of antimicrobial drug resistance and the safety hazards of synthetic nematicides have triggered a great research effort towards natural products. In this study, antimicrobial and nematicidal activities of bioactive secondary metabolites from Desarmillaria ectypa (MUCL 31078), A. gallica (STMA 12242) and A. mellea (STMA 12328) were studied. The three fungal strains were obtained from Helmholtz Centre for infection research (HZI). Subculturing was done on YM 6.3 media and fermented on rice and Q61/2 media. The metabolites from Q61/2 media were extracted with Ethyl acetate solvent and ethyl acetate crude extract was obtained. The metabolites from rice media were extracted with methanol solvent and methanol crude extract was obtained. The methanol extract was subjected to liquid-liquid partitioning using hexane and ethyl acetate solvents where hexane and ethyl acetate crude extracts were obtained. The ethyl acetate crude extracts from rice and Q61/2 media were then purified using Prep-high performance liquid chromatography. Nuclear magnetic resonance and high-resolution electrospray ionization mass spectrometry was used to obtain the structures of the pure compounds. One new compound, (3) alongside four known compounds, armillaridin (1), arnamiol (2), diatretol (4) and 3-chloro-6-hydroxy-4-methoxy-2-methylbenzoic acid (5) were isolated from D. ectypa. The known compounds, 5’-O-methylmelledonal (6), Melledonal C (7), 10α-hydroxydihydromelleolide (8) and melledonal (9) were isolated from A. mellea. Lepistamide B (10), which is also a known compound was isolated from A. gallica. The compounds were tested for antimicrobial and nematicidal activity in which a weak activity was observed against S. aureus (ATCC 25923) and E. coli (ATCC 25922). The compounds did not show nematicidal activity. Armillaridin (1) was active against Mucor hiemalis (DSM 2656) at 33.3 μg/mL and Bacillus subtilis (DSM 10) at 8.3 μg/mL. The study provides potential leads of antimicrobials from Armillaria species.