Use of the natural compounds to inhibit growth of the indoor isolated toxigenic Aspergillus westerdijkiae

摘要

Toxigenic fungi are regularly found in the indoor environment. Such fungi may pose a health risk to occupants. Insulation material could be one of the possible places where the harmful fungi could accumulate. Thus, preventing the growth of harmful fungi in insulation material is one key factor to guarantee healthy indoor air. Earlier we isolated fungal strain Aspergillus westerdijkiae PP2 as the dominant fungus in settled dusts from the building where occupants suffered from indoor air associated illness. Aspergillus westerdijkiae PP2 produces avrainvillamide, stephacidin B and ochratoxin which are cytotoxic at low concentrations. Furthermore, Aspergillus westerdijkiae PP2 is highly tolerant to boric acid, used in insulation materials as a fire retardant and an antimicrobial agent, as well as to numerous biocides like polyhexamethylene biguanide and polyhexamethylene guanidine. This makes the control of such fungus in the indoor environment almost impossible using traditional biocides. The application of natural nontoxic compounds, thus, could be an attractive alternative to the synthetic biocides. The aim of this study was to investigate the fungicidal activity of natural nontoxic agents toward Aspergillus westerdijkiae PP2. Resveratrol, magnolol, curcumin, betulinic acid, isorhapontigenin, pinosylvin and eugenol were selected based on their antimicrobial properties, low toxicity and their beneficial effects. The antifungal activity was studied using agar diffusion method and 1 pg of each compound. Out of the tested compounds only magnolol resulted in a clear inhibition zone whereas pinosylvin only slightly inhibited the growth of Aspergillus westerdijkiae PP2. Magnolol (5,5'-Diallyl-2,2'-dihydroxybiphenyl) is lignan isolated e.g. from the bark of Magnolia officinalis and stilbenoid pinosylvin (trans-3,5-Dihydroxystilbene) is polyphenolic compound originating from pine. Magnolol and the related allyl dihydroxybiphenyls compounds as honokiol 5,3'-Diallyl-2,4'-dihydroxybiphenyl as well as stilbene polyphenolic compounds might be used as potential nontoxic agents to prevent the growth of harmful fungi in indoor air environment.