Aflatoxins and Ochratoxin A in Tea Sold in Lebanon: Effects of Type, Packaging, and Origin.

Tea is among the oldest and most-known beverages around the world, and it has many flavors and types. Tea can be easily contaminated in any of its production steps, especially with mycotoxins that are produced particularly in humid and warm environments. This study aims to examine the level of ochratoxin A (OTA) and total aflatoxin (AF) contamination in black and green tea sold in Lebanon, evaluate its safety compared to international standards, and assess the effect of different variables on the levels of OTA and AFs. For this, the Lebanese market was screened and all tea brands (n = 37; 24 black and 13 green) were collected twice. The Enzyme-Linked Immunoassay (ELISA) method was used to determine OTA and AFs in the samples. AFs and OTA were detected in 28 (75.7%) and 31 (88.6%) samples, respectively. The average of AFs in the positive (above detection limit: 1.75 µg/kg) samples was 2.66 ± 0.15 µg/kg, while the average of OTA in the positive (above detection limit: 1.6 µg/kg) samples was 3.74 ± 0.72 µg/kg. The mean AFs in black and green tea were 2.65 ± 0.55 and 2.54 ± 0.40 µg/kg, respectively, while for OTA, the mean levels were 3.67 ± 0.96 and 3.46 ± 1.09 µg/kg in black and green tea samples, respectively. Four brands (10.8%) contained total aflatoxin levels above the EU limit (4 µg/kg). As for OTA, all samples had OTA levels below the Chinese limit (5 µg/kg). No significant association (p > 0.05) was found between OTA and tea type, level of packaging, country of origin, country of packing, and country of distribution. However, AF contamination was significantly (p < 0.05) higher in unpacked tea, and in brands where the country of origin, packing, and distributor was in Asia. The results showed that the tea brands in Lebanon are relatively safe in terms of AFs and OTA.

Inhibition of Aflatoxin B1 Synthesis in Aspergillus flavus by Mate (Ilex paraguariensis), Rosemary (Rosmarinus officinalis) and Green Tea (Camellia sinensis) Extracts: Relation with Extract Antioxidant Capacity and Fungal Oxidative Stress Response Modulation.

Plant extracts may represent an ecofriendly alternative to chemical fungicides to limit aflatoxin B1 (AFB1) contamination of foods and feeds. Mate (Ilex paraguariensis), rosemary (Romarinus officinalis) and green tea (Camellia sinensis) are well known for their beneficial properties, which are mainly related to their richness in bioactive phenolic compounds. AFB1 production is inhibited, with varying efficiency, by acetone/water extracts from these three plants. At 0.45 µg dry matter (DM)/mL of culture medium, mate and green tea extracts were able to completely inhibit AFB1 production in Aspergillus flavus, and rosemary extract completely blocked AFB1 biosynthesis at 3.6 µg DM/mL of culture medium. The anti-AFB1 capacity of the extracts correlated strongly with their phenolic content, but, surprisingly, no such correlation was evident with their antioxidative ability, which is consistent with the ineffectiveness of these extracts against fungal catalase activity. Anti-AFB1 activity correlated more strongly with the radical scavenging capacity of the extracts. This is consistent with the modulation of SOD induced by mate and green tea in Aspergillus flavus. Finally, rutin, a phenolic compound present in the three plants tested in this work, was shown to inhibit AFB1 synthesis and may be responsible for the anti-mycotoxin effect reported herein.

Phenolic Compounds Recovery from Blood Orange Peels Using a Novel Green Infrared Technology Ired-Irrad®, and Their Effect on the Inhibition of Aspergillus flavus Proliferation and Aflatoxin B1 Production.

The intensification of total phenolic compound (TPC) extraction from blood orange peels was optimized using a novel green infrared-assisted extraction technique (IRAE, Ired-Irrad®) and compared to the conventional extraction using a water bath (WB). Response surface methodology (RSM) allowed for the optimization of ethanol concentration (E), time (t), and temperature (T) in terms of extracted TPC and their antiradical activity, for both WB extraction and IRAE. Using WB extraction, the multiple response optimums as obtained after 4 h at 73 °C and using 79% ethanol/water were 1.67 g GAE/100 g for TPC and 59% as DPPH inhibition percentage. IRAE increased the extraction of TPC by 18% using 52% ethanol/water after less than 1 h at 79 °C. This novel technology has the advantage of being easily scalable for industrial usage. HPLC analysis showed that IRAE enhanced the recovery of gallic acid, resveratrol, quercetin, caffeic acid, and hesperidin. IR extracts exhibited high bioactivity by inhibiting the production of Aflatoxin B1 by 98.9%.

Identification of the Anti-Aflatoxinogenic Activity of Micromeria graeca and Elucidation of Its Molecular Mechanism in Aspergillus flavus.

Of all the food-contaminating mycotoxins, aflatoxins, and most notably aflatoxin B1 (AFB1), are found to be the most toxic and economically costly. Green farming is striving to replace fungicides and develop natural preventive strategies to minimize crop contamination by these toxic fungal metabolites. In this study, we demonstrated that an aqueous extract of the medicinal plant Micromeria graeca-known as hyssop-completely inhibits aflatoxin production by Aspergillus flavus without reducing fungal growth. The molecular inhibitory mechanism was explored by analyzing the expression of 61 genes, including 27 aflatoxin biosynthesis cluster genes and 34 secondary metabolism regulatory genes. This analysis revealed a three-fold down-regulation of aflR and aflS encoding the two internal cluster co-activators, resulting in a drastic repression of all aflatoxin biosynthesis genes. Hyssop also targeted fifteen regulatory genes, including veA and mtfA, two major global-regulating transcription factors. The effect of this extract is also linked to a transcriptomic variation of several genes required for the response to oxidative stress such as msnA, srrA, catA, cat2, sod1, mnsod, and stuA. In conclusion, hyssop inhibits AFB1 synthesis at the transcriptomic level. This aqueous extract is a promising natural-based solution to control AFB1 contamination.

Essential Oils Modulate Gene Expression and Ochratoxin A Production in Aspergillus carbonarius.

Ochratoxin A (OTA) is a mycotoxin, mainly produced on grapes by Aspergillus carbonarius, that causes massive health problems for humans. This study aims to reduce the occurrence of OTA by using the ten following essential oils (E.Os): fennel, cardamom, anise, chamomile, celery, cinnamon, thyme, taramira, oregano and rosemary at 1 µL/mL and 5 µL/mL for each E.O.As a matter of fact, their effects on the OTA production and the growth of A. carbonarius S402 cultures were evaluated, after four days at 28 °C on a Synthetic Grape Medium (SGM). Results showed that A. carbonarius growth was reduced up to 100%, when cultured with the E.Os of cinnamon, taramira, and oregano at both concentrations and the thyme at 5 µL/mL. As for the other six E.Os, their effect on A. carbonarius growth was insignificant, but highly important on the OTA production. Interestingly, the fennel E.O at 5 µL/mL reduced the OTA production up to 88.9% compared to the control, with only 13.8% of fungal growth reduction. We further investigated the effect of these E.Os on the expression levels of the genes responsible for the OTA biosynthesis (acOTApks and acOTAnrps along with the acpks gene) as well as the two regulatory genes laeA and vea, using the quantitative Reverse Transcription-Polymerase Chain Reaction (qRT-PCR) method. The results revealed that these six E.Os reduced the expression of the five studied genes, where the ackps was downregulated by 99.2% (the highest downregulation in this study) with 5 µL/mL of fennel E.O.As for the acOTApks, acOTAnrps, veA and laeA, their reduction levels ranged between 10% and 96% depending on the nature of the E.O and its concentration in the medium.