An improved analytical depolymerization method for characterizing condensed tannins was developed with menthofuran (3,6-dimethyl-4,5,6,7-tetrahydro-1-benzofuran) as the nucleophilic trapping reagent. Herein, menthofuran was compared with routinely used nucleophiles, phloroglucinol and 2-mercaptoethanol. At 30°C and in the presence of 0.1 M HCl, menthofuran displayed the outstanding ability to enable the fast and full depolymerization of procyanidin B2 using only a 1:1 molar ratio of both reactants. In the same conditions, phloroglucinol and 2 mercaptoethanol led to a reaction equilibrium with significantly lower conversion yields. Application to commercial tannin extracts showed that a menthofuran to extract weight ratio of 1 gave the same yields of procyanidin constitutive units as 10-fold higher mol. eq. phloroglucinol and 100 fold 2-mercaptoethanol. Finally, guidelines for implementing the menthofuran depolymerization method are proposed to assess the tannin content and composition of extracts as well as of plant materials without prior extraction.

Aflatoxin B1 (AFB1) is a mycotoxin considered a potent carcinogen for humans that contaminates a wide range of crops. Various strategies have been established to reduce or block the synthesis of AFB1 in food and feed. The use of aqueous extracts derived from plants with high antioxidant activity has been a subject of study in recent years due to their efficacy in inhibiting AFB1. In this study, we assessed the effect of Aloysia citrodora aqueous extract on Aspergillus flavus growth and on AFB1 production. A bio-guided fractionation followed by High Performance Liquid Chromatography (HPLC) and Mass spectrometry analysis of the active fraction were applied to identify the candidate molecules responsible for the dose-effect inhibition of AFB1 synthesis. Our results revealed that polyphenols are the molecules implicated in AFB1 inhibition, achieving almost a total inhibition of the toxin production (99%). We identified luteolin-7-diglucuronide as one of the main constituents in A. citrodora extract, and demonstrated that it is able to inhibit, by itself, AFB1 production by 57%. This is the first study demonstrating the anti-Aflatoxin B1 effect of this molecule, while other polyphenols surely intervene in A. citrodora anti-AFB1 activity.

Aflatoxin B₁ (AFB₁), primarily produced by Aspergillus flavus and A. parasiticus, is the most dangerous mycotoxin for humans and contaminates a variety of crops. To limit fungal growth and aflatoxin production in food and feed, research has been increasingly focusing on alternatives to pesticides. Studies show that some aqueous plant extracts with strong antioxidant properties could significantly impact AFB₁ production, representing an eco-friendly and sustainable method to protect crops. The present study demonstrates that aqueous extracts of Anonna muricata (AM) and Uncaria tomentosa (UT) inhibit AFB₁ synthesis in a dose-dependent manner with a half-maximal inhibitory concentration of 0.25 and 0.28 mg dry matter per milliliter of culture medium, respectively. This effect correlates with the presence of polyphenols and, more precisely, with condensed tannins. It is also related to the subsequent antioxidant activity of both extracts. A bio-guided fractionation followed by high-performance liquid chromatography and mass spectrometry analysis of the active fractions identifies procyanidins and, more precisely, catechin (5.3% w/w for AM and 5.4% w/w for UT) and epicatechin (10.6% w/w for AM and 25.7% w/w for UT) as the major components in both extracts. The analysis of how pure standards of these molecules affect AFB₁ production demonstrates that catechin plays an essential role in the inhibition observed for both plant extracts, since the pure standard inhibits 45% of AFB₁ synthesis at a concentration close to that of the extracts.