This study highlights that various field and storage fungi are associated with medicinal plants in SA, with the lowest fungal load of 1.8 × 104 CFU/g recorded in Acacia karoo, whereas the highest contamination level of 2×107 CFU/g of sample was each found in Putranjiva roxburgii, Schotia brachypetata and Elephantorriza elephantine. According to WHO [53], a maximum contamination limit regulated for fungi and yeasts in medicinal plants has been set to be 1 x 103 CFU/g. It was found in this study that all the plant samples analyzed contained fungal load that exceeded this limit, demonstrating how highly contaminated these samples were that could pose some health implications amongst consumers. The elevated fungal load observed in the medicinal plants may be attributed to various factors, including climatic patterns, improper handling during harvesting, poor storage facilities and conditions (Ashiq et al., 2014; Fontana et al., 2021).
We employed both conventional and molecular techniques to confirm the identity of fungal spp. recovered from the medicinal plants. Approximately 164 fungal isolates were identified, representing 10 fungal genera. Among these, Aspergillus, Penicillium, and Fusarium were found to be the most predominant. The aforementioned fungal genera are important from the mycological point of view, since they are capable of producing mycotoxins, chemical compounds which can cause a range of adverse health effects such as acute poisoning, immune suppression, carcinogenicity, and reproductive disorders in humans and animals [54]. Consequently, the presence of these fungal isolates in medicinal plants raises significant health concerns, particularly considering that none of the analyzed samples were found to be free from these isolates. The incidence of fungal spp. in medicinal plants have been reported in other countries like Portugal, China, and Poland (Ałtyn and Twarużek, 2020; Rocha-Miranda and Venâncio, 2019; Zheng et al., 2017).The results from the current study are in agreement with the study of [55], who reported Aspergillus (43.77%), followed by Fusarium (5.17%), Cladosporium (4.46%), Alternaria (3.69%), Penicillium (2.85%), and Xeromyces (2.46%), as the predominant fungal genera contaminating Chinese herbal medicines. Similar, Zheng et al. (2017) reported Aspergillus (28 isolates) and Penicillium (35 isolates) as the prevalent fungal genera detected in medicinal plants from China. [56] study on the identification of mycoflora in forty medicinal plants revealed that 83.3% of the samples were contaminated with one or more fungal species, which aligns with our present findings. The authors further confirmed that of the 69 strains recovered, Trichoderma (11.6%), Rhizopus (14.5%), Penicillium (24.6%), and Aspergillus (26.1%) were the most prevalent.
Among the nine Aspergillus spp. recovered from the medicinal plants in this present research, A. niger, A. flavus, A. ochraceous, and A. fumigatus were the most prevalent. These results concur with the studies conducted by Kortei et al. [57] who documented 12 species belonging to 7 genera, Aspergillus (niger, flavus, fumigatus, and ochraceus), Penicillium (digitatum, expansum), Fusarium (oxysporum, verticillioides), Mucor (racemosus), Rhizopus (stolonifer), Rhodotorula sp., and Trichoderma harzianum, were identified as fungal contaminants in spices and herbs samples. More so in China, [56] reported 18 strains of Aspergillus, 17 strains of Penicillium, 10 strains of Rhizopus, 8 strains of Trichoderma, 4 strains of Mucor, 5 strains of yeast, 2 strains of Byssochlamys, 2 strains of Chaetomium, 1 strain of Alternaria, 1 strain of Mycosis, and 1 strain of Neurospora in 13 different medicinal herbs from the country. In another study conducted by [58] to investigate the presence of potential mycotoxin-producing fungi in selected herbal medicines from Nigeria, a range of fungal isolates were obtained from the plants, with Aspergillus and Penicillium genera being the most prevalence. Consistent with our findings, A. niger, A. flavus, P. limosum, and P. chrysogenum emerged as the predominant species.
The presence of fungal species in medicinal plants in the present study can be ascribed to climatic factors, poor handling, inadequate storage facilities, as well as poor storage conditions (Ashiq et al., 2014; Fontana et al., 2021). This was clearly evident during the sampling process, where the plant materials were exposed to environmental conditions conducive to microbial contamination. The contamination of medicinal plants with fungi not only leads to a reduction in quality, decreased market value, and diminished healing potential, but it can also pose a health risk if the fungal spp. are toxigenic [38, 59, 60]. Some of the fungal spp. reported in this study, including A. fumigatus, A. flavus, A. niger, A. paraciticus, F. graminearum, F. oxysporum, F. proliferatum, P. expanusm, and P. citrinum have been reported to cause acute and chronic mycotoxicoses, resulting in significant morbidity and mortality among animals and humans (Person et al., 2010; Rana et al., 2020; Stemler et al., 2023). This group of fungi holds great significance, particularly in sub-Saharan Africa, where favorable conditions exist for their proliferation and mycotoxin production [40, 61]. Fungal-contaminated medicinal plants are frequently used worldwide in the treatment of various diseases and for improving human health [33, 62]. Unfortunately, the increased consumption of fungal-contaminated medicinal plants has significantly contributed to public health issues arising from the inadequate examination of their quality and safety.
As previously mentioned, the invasion of fungi on plants is a common occurrence throughout various stages of agricultural practice, including handling, harvesting, and storage processing. It is obvious that many users of medicinal plants often purchase them from markets without inspecting them for visible signs of fungal contamination. Furthermore, there is a lack of awareness and knowledge regarding the potential presence of fungi and their attendant mycotoxins in medicinal plants, as well as the associated adverse effects on human health (Areo et al., 2020). This is a significant issue as contaminated herbs can greatly compromise the expected health benefits and instead lead to unexpected health implications. Therefore, it is imperative to provide education on the health consequences of consuming medicinal plants that have been infested with fungi to traditional healers, individuals involved in cultivation, handling, and the sale of these plants (from field to market), as well as the final consumers.