Bioactive compounds in Diospyros mafiensis roots inhibit growth, sporulation and aflatoxin production by Aspergillus flavus and Aspergillus parasiticus
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Date
2017-01-20
Journal Title
Journal ISSN
Volume Title
Publisher
Wageningen Academic Publishers
Abstract
Diospyros mafiensis F. White is a medicinal shrub or small tree (6 m tall) widely distributed in the Zanzibar-
Inhambane regional mosaic and traditionally used to treat leprosy, diarrhoea, and skin fungal infections in Tanzania
and Mozambique. Our objective was to determine the anti-aflatoxigenic properties of compounds from D. mafiensis
root bark against vegetative growth, sporulation and aflatoxin production by Aspergillus flavus and Aspergillus
parasiticus. Bioassay-guided extraction, fractionation, and isolation of bioactive compounds using A. parasiticus B62
were employed. The bioactive compounds were elucidated using 1 H and 13 CNMR and LC-MS. Growth inhibition was
determined by measuring the colony diameter of A. flavus AF3357 and A. parasiticus SU-1 ATCC56775. Inhibitory
effects on sporulation were estimated using a haemocytometer. Total aflatoxin was quantified by direct competitive
enzyme-linked immunosorbent assay (ELISA). Bioactive compounds diosquinone (DQ) and 3-hydroxydiosquinone
(3HDQ) were identified. DQ weakly inhibited A. flavus and A. parasiticus vegetative growth (MIC 50 >100 μg/ml)
and 3HDQ strongly inhibited A. flavus (MIC 50 = 14.9 μg/ml) and A. parasiticus (MIC 50 = 39.1 μg/ml). DQ strongly
reduced total aflatoxin production by A. flavus from 157 to 36 ng/plate, and by A. parasiticus from 1,145 ng/plate
to 45 ng/plate at 100 μg/ml. 3HDQ reduced total aflatoxin production by A. parasiticus from 1,145 to 32 ng/plate;
stimulated production by A. flavus from 157 to 872 ng/plate at 12.5 μg/ml but reduced to 45 ng/plate at 100 μg/
ml. In summary, DQ and 3HDQ could be used as natural antifungal compounds to prevent mould growth and
aflatoxin accumulation in food and feed.
Description
Research article
Keywords
Diosquinone, 3-hydroxydiosquinone, Total aflatoxin, A. flavus, A. parasiticus