Antifungal and anti-mycotoxigenic activity of selected South African medicinal plants species

Abstract

A B S T R A C TAntifungal and anti-mycotoxigenic activity of 25 acetone leaf extracts of South African medicinal plants with potent antioxidant activity were investigated against three phytopathogenic fungal strains. The extracts exhibited varying degrees of in vitro anti-mycotoxigenic effect against Fusarium verticillioides, Aspergillus flavus and Aspergillus ochraceous. Markhamia obtusifolia (Baker) Sprague exhibited the lowest minimum inhibitory concentration (MIC) values as low as 0.08 mg/ml against Aspergillus flavus and Furasium verticilloides at both 24 and 48 hr incubation period, while Curtisia dentata exhibited similar MIC value against Aspergillus ochraceous. Curtisia dentata further yielded the highest total activity of 1583 ml/g against Aspergillus ochraceous at 24 and 48 hr incubation period. In the mycelial growth inhibition (MGI) evaluation, Fusarium verticilloides was more sensitive to plants extracts, while Kirkia wilmsii exhibited highest MGI of 50.08% against Fusarium verticilloides on the 6 th day of incubation. Five acetone extracts from Acokanthora oppositifolia, Bauhinia galpinii, Combretum caffrum, Ricinus communis and Solanum aculeastrum exhibited lowest IC 50 value of 0.01 mg/ml against (2,2'-azinobis-3-ethylbenzthiazoline-6suphonic acid (ABTS). Curtisia dentata and Markhamia obtusifolia extracts were further subjected to gas chromatography mass-spectrophotometry (GC-MS) analysis. Curtisia dentata revealed the presence of triterpenoid compounds, β-amyrin (53.30%) and α-amyrin (6.42%), while Markhamia obtusifolia yielded the presence of neophytadiene (4.38%) and palmitic acid (3.61%) The results suggest that natural products from plants may well be used as possible substitutes for synthetic fungicides. Given the antifungal and antioxidant potential of the selected plants, they may have potential as possible leads for the development of biofungicides that may well prevent oxidation related food spoilage.

The use of plant extracts and their phytochemicals for control of toxigenic fungi and mycotoxins

“…According to the World Health Organization ( WHO, 2001 ), approximately 80% of the population of the world still depend on traditional medicine for primary healthcare ( Prakash et al., 2020 ). Recent studies have also created renewed interest in the use of botanicals and their compounds as nutraceuticals in this regard in both developed and developing countries ( Galvano et al., 2001 ; Reddy et al., 2010 ; Anjorin et al., 2013 ; Dikhoba et al., 2019 ). The advantage of using plants for drug discovery is due to their abundance in nature and wide distribution geographically.…”

“…Fusarium verticillioides, A. flavus and A. ochraceous . The results reported potentials of the selected medicinal plants to be used for the discovery of biofungicides that may prevent oxidative related food spoilage ( Dikhoba et al., 2019 ). A study by Abdel-Fattah et al.…”

“…The most prevalent mycotoxins of agricultural importance include the aflatoxins (AFs), ochratoxins (OTA), fumonisins (FBs), trichothecenes and zearalenone (ZEN). These have been given serious attention due to the health risks that they pose in humans and animals ( Dikhoba et al., 2019 ; Celik, 2020 ).…”

“…They contain various phytochemicals with pharmacological properties against various diseases. Recent studies have been conducted on the possible application of botanicals as bio-fungicides and nutraceuticals to ameliorate the proliferation of toxigenic fungi and mycotoxin contamination in food and feed ( Dikhoba et al., 2019 ; Ponzilacqua et al., 2019 ; Kavitha et al., 2020 ). This review aimed to elucidate the use of botanical extracts and their phytochemical compounds to prevent and detoxify mycotoxins without any adverse effect on the nutritional value of food and feed.…”

Proof of concept: could snake venoms be a potential source of bioactive compounds for control of mould growth and mycotoxin production

“…However, 83/84 fractions were able to reduce mycotoxins production by >90%. Regarding fungal growth, a number of studies have shown a low percentage of extract fractions, especially from natural antifungal sources such as plant extracts or actinobacteria, were effective at controlling growth of fungal pathogens (Lahoum et al 2016;Nalubega et al 2016;Dikhoba et al 2019). However, many of these studies did not examine impacts on mycotoxin production.…”