Sesamum indicum L. commonly called Beniseed in the country and international circle is one of the oldest oilseeds cultivated in Nigeria [1] . Beniseed has been reported to be an excellent source of high quality oil and protein [1] . The seed contains about 50% edible semi-drying oils and also is rich in protein, carbohydrate, calcium and phosphorus [1] . Based on its chemical composition, Beniseed therefore is a crop of considerable value. However, Sesame seed has the risk of contamination during storage by mycotoxins, especially the ubiquitous and hepatotoxic aflatoxins which are produced when seeds are kept under conditions that favour the development of these fungi [2] . Aflatoxins are potent toxic, carcinogenic, mutagenic, immunosuppressive and teratogenic agents produced as secondary metabolites by Aspergillus flavus [3] . A study on the nature of the toxin suggested its origin from the fungus Aspergillus flavus and thus, the toxin was named “aflatoxin” by virtue of its origin from A. flavus [4] . Aflatoxins have been reported to be highly toxic to humans and animals, causing liver diseases and cancer, and chronic exposure to aflatoxins is also associated with stunting and immune system suppression [5] [6] .

Chemical and physical approaches are widely used to minimize the risk of aflatoxin contamination in food [7] . These strategies are usually expensive, time-consuming, inefficient and also reported to cause serious environmental and health problems [8] . The most promising strategy currently being used to reduce pre-harvest contamination of crops with aflatoxin is to introduce non-aflatoxin (biocontrol) A. flavus into the crop environment. There are many challenges facing this strategy. First, the population biology of A. flavus is not well understood due to A. flavus’s diversity, its ability to form heterokaryotic reproductive forms, and its unknown ability to survive for prolonged periods after application. Secondly, biocontrol strains must be selected that are suitable for the environment, the type of crop, and the soil into which they will be introduced.

The African continent holds an enormous resource in terms of floral biodiversity and its medicinal plants have remained a main reservoir of phytochemicals for pharmaceutical drug development [9] . Plants produce secondary metabolites that can inhibit bacteria, fungi, viruses and pests [10] . All parts or any single part of the plant, such as bark, leaves, peel, seed, and stem, may possess antimicrobial properties. Plants produce secondary metabolites that can inhibit bacteria, fungi, viruses and pests [10] . This justifies the search for an alternative source of control which could inhibit the establishment of aflatoxin, producing potential fungi, the plant derived extracts. Research results on the efficacy of plant extracts to control toxigenic strains of A. flavus are scanty and several plants exist in North-Central Nigeria whose extracts with antifungal activity have been reported [11] .

The medicinal plants used for this study are: Prosopis africana, Psorospermum febrifugum and Curcuma longa L. Almost all parts of the tree of Prosopis africana are used in medicine; the leaves in particular are used for the treatment of headache and toothache as well as various other head ailments [12] . The roots are a diuretic and are used to treat gonorrhea, tooth and stomach-ache, dysentery and bronchitis [12] . Psorospermum febrifugum is widely used in traditional medicine in Africa, being employed in the treatment of a wide range of conditions but especially those related to fevers and skin problems. This species has been used as a febrifuge, a leprosy treatment, a poison antetode, a purgative [13] . The Roots bark decoction is also recorded to be effective for the treatment of Syphilis [14] .

Curcuma longa L. is a rhizomatous herbaceous evergreen plant. The rhizome, the portion of the plant used medicinally, is usually boiled, cleaned, and dried, yielding a yellow powder. Dried Curcuma longa is the source of the spice turmeric, the ingredient that gives curry powder its characteristic yellow colour. Apart from its culinary uses, turmeric has been used widely in the traditional medicine in India, Pakistan, and Bangladesh because of its several beneficial properties [15] . Turmeric is anti-inflammatory to the mucous membrane which coats the throat, lungs, stomach and intestine [16] . The objective of the present investigation is therefore to screen these plants for fungicidal activity against aflatoxin producing fungi in Sesame in Makurdi, Benue State, North Central Nigeria.

Effects of methanolic extract on the isolates shows that Curcuma longa L. has reputed value for its antifungal properties. Among the different plant extracts, Curcuma longa extract brought about the lowest radial growth of all the organisms evaluated and it was significantly different from the growth observed on samples treated with P. africana (leaf), P. febrifugum (leaf), P. africana (stem bark) and P. febrifugum (stem bark) extracts showing highly statistical significant level (P < 0.01) Curcuma longa has the lowest mean of (10.00), P.africana leaf (12.50) P. africana stem bark (11.83), P. febrifugum (Leaf) (16.33), P. febrifugum (Stem bark) (15.50) respectively (Plate 6 (a-f)).

NB: += positive; = Negative.

Plate 1. Raw Sesame samples.

Plate 2. Innoculation of sesame seeds for fungi growth.

Plate 3. (a), (b). Growth of Fungi colonies.

Many researches have been conducted to demonstrate the effects of different plants against pathogenic fungi. In this present investigation, the anti aflatoxigenic activity of the methanolic plant extracts of Curcuma longa L. (Turmeric), stem bark of Prosopis africana, leaf of P. africana, Stem bark of Psorospermum febrifugum and leaf of Psorospermum febrifugum were assayed against toxigenic

Plate 4. Pure culture of Aspergillus flavus.

Plate 5. Pure culture of Aspergillus niger.

A. flavus and A. niger in sesame production. All the methanolic extracts of the plants showed promising activity against the test fungi. This indicates their broad range of activity (Plate 6 (a-f)). This is consistent with the earlier reports that many plant products contain fungitoxic constituents that have the potential to control plant diseases [25] [26] [27] . It was reported that Curcuma longa has anti-inflammatory, choleretic, antimicrobial, and carminative actions [28] . Similarly, Paramasivan et al., [29] reported that in vitro studies with Turmeric showed that it has strong antimicrobial properties.

Kisangau [30] observed that series of xanthones were isolated from P. febrifugum and are responsible for its antiviral activities and other constituents from the extracts were proven to be effective as antimicrobial agents. Methanol extracts of P. africana leaves were reported to have substantial antifungal activity against mycelia growth of the fungus Colletotrichum musae, causing the most serious post harvest fungal diseases of banana [31] . Many studies have demonstrated a strong correlation between the phenolic/antioxidant compounds of plants and their antifungal/antiaflatoxigenic activities [32] . Consequently, plants

Plate 6. Inhibitory effect of plant extracts on mycelia growth of aflatoxigenic fungi.

extracts could potentially provide protection against aflatoxigenic fungus and aflatoxins. Previously, many plant extracts have been investigated for their capacity to inhibit aflatoxin production not only in culture medium conditions but also in food commodities [11] [33] . Particularly, Equisetum arvense, Stevia rebaudiana, Zingiber officinalis, Oxalis corniculata and Trigonella foenum-graecum have been reported to have antifungal and antiaflatoxigenic properties [11] [33] .

It is suggested that more and more indigenous plants should be exploited for the prevention of aflatoxin because of its concern all over the world. This present study is significant in identification of indigenous plant extracts as possible detoxifier and biocontrol for aflatoxigenic fungi. These findings can be exploited for the prevention of aflatoxin contamination in sesame. Further works are needed to investigate the biologically active ingredients of these plants.

The authors declare no conflicts of interest regarding the publication of this paper.

Elaigwu, M., Oluma, H.O.A., Aguoru, C.U. and Onekutu, A. (2020) Screening and Phytochemical Analysis of Some Plants Extracts against Aflatoxin Producing Fungi in Sesame, Benue State, Nigeria. American Journal of Plant Sciences, 11, 344-353. https://doi.org/10.4236/ajps.2020.113025