Mimosa tenuiflora Aqueous Extract: Role of Condensed Tannins in Anti-Aflatoxin B1 Activity in Aspergillus flavus

Abstract

Aflatoxin B1 (AFB1) is a potent carcinogenic mycotoxin that contaminates numerous crops pre- and post-harvest. To protect foods and feeds from such toxins without resorting to pesticides, the use of plant extracts has been increasingly studied. The most interesting candidate plants are those with strong antioxidative activity because oxidation reactions may interfere with AFB1 production. The present study investigates how an aqueous extract of Mimosa tenuiflora bark affects both the growth of Aspergillus flavus and AFB1 production. The results reveal a dose-dependent inhibition of toxin synthesis with no impact on fungal growth. AFB1 inhibition is related to a down-modulation of the cluster genes of the biosynthetic pathway and especially to the two internal regulators aflR and aflS. Its strong anti-oxidative activity also allows the aqueous extract to modulate the expression of genes involved in fungal oxidative-stress response, such as msnA, mtfA, atfA, or sod1. Finally, a bio-guided fractionation of the aqueous extract demonstrates that condensed tannins play a major role in the anti-aflatoxin activity of Mimosa tenuiflora bark.

Preservation of Mimosa tenuiflora Antiaflatoxigenic Activity Using Microencapsulation by Spray-Drying

“…Several plant extracts, essential oils or isolated components were found able to block aflatoxin B1 production [11,12], among them Mimosa tenuiflora aqueous extract (MAE). Contrary to what is observed using essential oils that inhibit AFB1 synthesis together with reducing fungal growth [13], MAE was shown to inhibit AFB1 in A. flavus with no impact on fungal development [14]. This result is interesting because if the extract is able to block AFB1 production without modifying fungal growth, its impact on biodiversity shall be limited.…”

“…MAE was prepared as described [14]. M. tenuiflora bark was extracted by maceration for 15 h at room temperature.…”

“…The strain used for all assays was Aspergillus flavus NRRL 62477 [35]. Ten µL of a spore suspension containing 1000 spores were inoculated centrally into the culture medium for all experiments [14].…”

“…In many cases, a positive correlation could be demonstrated between antioxidative ability of plant extracts/compounds and their impact on AFB1 synthesis [11,14,17,18]. This observation raises the question of the preservation of their efficacy with time.…”

Effects of tannic acid on growth performance, relative organ weight, antioxidative status, and intestinal histomorphology in broilers exposed to aflatoxin B1

“…Because of the polyphenolic hydroxyl structure, the TA has various biological activities, such as antimicrobial, anti-inflammatory, anticancer, and immunomodulatory effects (10)(11)(12). Moreover, studies have shown that dietary supplementation with antioxidants, including plant extracts and tannins can protect broilers from AFB 1 -induced toxicity by enhancing the antioxidant capacity and immunity (6,(13)(14)(15)(16)). Nevertheless, it remains unclear whether dietary supplementation with TA could alleviate acute aflatoxicosis by improving the antioxidant capacity of broilers fed AFB 1 contaminated diets.…”