Buckwheat Hull Extracts Inhibit Aspergillus flavus Growth and AFB1 Biosynthesis

Abstract

Fungal contamination poses at risk the whole food production chain - from farm to fork - with potential negative impact on human health. So far, the insurgence of pathogens has been restrained by the use of chemical compounds, whose residues have gradually accumulated determining toxic effects in the environment. Modern innovative techniques imply the use of natural and eco-sustainable bioactive plant molecules as pathogens and pests-control agents. These may be profitably recovered in large amounts at the end of industrial milling processes. This is the case of the non-digestible hull of common buckwheat ( Fagopyrum esculentum Moench), a natural source of polyphenols, tocopherols, phytosterols and fatty acids. We extract these compounds from the hull of buckwheat; apply them to Aspergillus flavus - aflatoxin producer - under in vitro conditions, checking their ability to inhibit fungal growth and aflatoxin biosynthesis. Moreover, a solvent free method implying the adoption of supercritical CO 2 as solvent was set up to extract lipophilic molecules from the buckwheat’ hulls. Positive results in controlling fungal growth and aflatoxin biosynthesis let infer that the extracts could be further tested also under in vivo conditions.

Naturally occurring phenolic compounds as promising antimycotoxin agents: Where are we now?

“…The activity of these extracts to counteract mycotoxin production was determined by in vitro culture of mycotoxigenic fungi in liquid or solid medias (Boonmee et al., 2020; Christ‐Ribeiro et al., 2019). The effect on fungal growth is evaluated by measuring fungal radial growth or weighing fungal biomass after drying (Atanasova‐Pénichon et al., 2014; Nobili et al., 2019). The activity of plant extracts is either expressed as a percentage of fungal growth inhibited (Montibus et al., 2021), minimum inhibitory concentration (Heidtmann‐Bemvenuti et al., 2016), or minimum fungicidal concentration (Abdel‐Razek et al., 2017) (see Table 1).…”

“…Buckwheat hull extract was found to be rich in flavonoids (e.g., hyperoside, vitexin, and rutin). Low concentrations of buckwheat hull extracts (0.1 $$\umu$$g/ml) effectively inhibited AFB1 production up to 93% (Nobili et al., 2019). Another example is the use of maritime pine sawdust extract that efficiently reduced DON production by F. graminearum .…”

The Potential of Fatty Acids and Their Derivatives as Antifungal Agents: A Review

“…They are natural and environmental friendly; fulfil consumer’s expectation for the use of less synthetic chemicals as food preservatives; can be used to control plant disease, reducing chemicals that negatively affect the environment; and are less likely to promote resistance in fungi [ 37 ]. They can also be recovered from waste materials, thus favoring sustainability by promoting a circular economy [ 38 ].…”

“…Lipophilic extract showed at 10 μg/mL and average inhibition of over 80% of aflatoxin production and 74% of mycelial growth. However, no study was conducted to evaluate which component of the lipophilic fraction was responsible for the inhibitory activity [ 38 ].…”

Buckwheat Secondary Metabolites: Potential Antifungal Agents

“…Some of the beneficial effects of phenolic compounds are possibly related to their antioxidant activities. − The latest advances in research on buckwheat health-promoting effects are well described in the work of Zhu et al (2020) or Yılmaz et al (2020) . Among the buckwheat secondary metabolites with antioxidant properties, lipophilic compounds such as tocopherols must also be mentioned …”