Application of plant derived compounds to control fungal spoilage and mycotoxin production in foods.

OBJECTIVE: To evaluate the antibacterial potential of aqueous and acetone extracts of galls of Quercus infectoria by determination of Minimum Inhibitory Concentration (MIC) and Minimum Bactericidal Concentration (MBC) values. 
MATERIALS AND METHODS: The extracts from the galls of Q. infectoria at 10 mg/ml were screened against three Gram-positive bacteria (Staphylococcus aureus ATCC 25923, Staphylococcus epidermidis and Bacillus subtilis) and three Gram-negative bacteria (Escherichia coli NCTC 12079 serotype O157:H7, Salmonella typhimurium NCTC 74 and Pseudomonas aeruginosa ATCC 27853). The MIC of the extracts were then determined using the twofold serial microdilution technique at a concentration ranging from 5 mg/ml to 0.0024 mg/ml. The MBC values were finally obtained from the MIC microtiter wells which showed no turbidity after 24 hrs of incubation by subculturing method. 
RESULTS: Out of the six bacterial species tested, S. aureus was the most susceptible. On the other hand, the extracts showed weak inhibitory effect against S. epidermidis, B. subtilis, S. typhimurium and P. aeruginosa while there was no inhibition zone observed for E. coli O157. The MIC values of the extracts ranged from 0.0781 mg/ml to 1.25 mg/ml whereas the MBC values ranged from 0.3125 mg/ml to 2.50 mg/ml. The MBC values of aqueous extract against S. aureus and S. typhimurium were higher than their MIC values. The MBC value of acetone extract against S. aureus was also higher than its MIC value. Interestingly, however, the MIC and MBC values of acetone extract against S. typhimurium were the same (1.25 mg/ml). 
CONCLUSION: The aqueous and acetone extracts displayed similarities in their antimicrobial activity on the bacterial species and as such, the galls of Quercus infectoria are potentially good source of antimicrobial agents.

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Research Paper - The potential of aqueous and acetone extracts of galls of Quercus infectoria as antibacterial agents

Background
The present investigation evaluated 4 different solvent compositions for their relative capacity to extract total phenolic and total flavonoid (TF) components of the leaves, trunks, and stems of Bucida buceras L. (Combretaceae), and the stems of Phoradendron californicum (Viscaceae), plus mesquite and oak species endemic to the Southwestern United States, northern Mexico, and tropical regions of Central and South America, as well as to profile the composition of these plant materials and to measure their antioxidant capacity.

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Solvent effects on phytochemical constituent profiles and antioxidant activities, using four different extraction formulations for analysis of Bucida buceras L. and Phoradendron californicum

Active packaging with antifungal activities

Background: Plant fungal pathogens play a crucial role in the profitability, quality and quantity of plant production. These phytopathogens are persistent in avoiding plant defences causing diseases and quality losses around the world that amount to billions of US dollars annually. To control the scourge of plant fungal diseases, farmers have used fungicides to manage the damage of plant pathogenic fungi. Drawbacks such as development of resistance and environmental toxicity associated with these chemicals have motivated researchers and cultivators to investigate other possibilities.
Materials and Methods: Several databases were accessed to determine work done on protecting plants against plant fungal pathogens with plant extracts using search terms “plant fungal pathogen”, “plant extracts” and “phytopathogens”. Proposals are made on the best extractants and bioassay techniques to be used. 
Results: In addition to chemical fungicides, biological agents have been used to deal with plant fungal diseases. There are many examples where plant extracts or plant derived compounds have been used as commercial deterrents of fungi on a large scale in agricultural and horticultural setups. One advantage of this approach is that plant extracts usually contain more than one antifungal compound. Consequently the development of resistance of pathogens may be lower if the different compounds affect a different metabolic process. Plants cultivated using plants extracts may also be marketed as organically produced. Many papers have been published on effective antimicrobial compounds present in plant extracts focusing on applications in human health. More research is required to develop suitable, sustainable, effective, cheaper botanical products that can be used to help overcome the scourge of plant fungal diseases.
Conclusions: Scientists who have worked only on using plants to control human and animal fungal pathogens should consider the advantages of focusing on plant fungal pathogens. This approach could not only potentially increase food security for rural farmers, lead to commercial rewards, but it is also much easier to test the efficacy in greenhouse or field experiments. Even if extracts are toxic it may still be useful in the floriculture industry.

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The use of plants to protect plants and food against fungal pathogens: a review.

https://repository.up.ac.za/bitstream/handle/2263/15448/Mahlo_Antifungal_2010.pdf?sequence=1

Antifungal activity of leaf extracts from South African trees against plant pathogens

Background: Invasive alien plant species (IAPs) are plants that have migrated from one geographical region to non-native region either intentional or unintentional.The general view of IAPs in environment is regarded as destructive to the ecosystem and they pose threat to native vegetation and species. However, some of these IAPs are utilized by local inhabitants as a substitute for scarce indigenous plants. The aim of the study is to conduct ethnobotanical survey on medicinal usage of invasive plant species in Waterberg District, Limpopo Province, South Africa.
Materials and methods: An ethnobotanical survey on invasive plant species was conducted to distinguish species used for the treatment of various ailments in the Waterberg, District in the area dominated by Bapedi traditional healers. About thirty Bapedi traditional healers (30) were randomly selected via the snowball method. A guided field work by traditional healers and a semi-structured questionnaire was used to gather information. The questionnaire was designed to gather information based on the local name of plants, plant parts used and methods of preparation which is administered by the traditional healers.
Results: The study revealed that Schinus molle L., Catharanthus roseus (L.), Datura stramonium L., Opuntia stricta (Haw.) Haw., Opuntia ficus- indica, Sambucus canadensis L., Ricinus communis L., Melia azedarch L., Argemone ochroleuca and Eriobotrya japonica are used for treatment of various diseases such as chest complaint, blood purification, asthma, hypertension and infertility. The most plant parts that were used are 57.6% leaves, followed by 33.3% roots, and whole plant, seeds and bark at 3% each. Noticeably, most of these plants are cultivated (38%), followed by 28% that are common to the study area, 20% abundant, 12% wild, and 3% occasionally. Schinus molle is the most frequently used plant species for the treatment of various ailments in the study area.
National Environmental Management Biodiversity Act (NEMBA) (10/2004) and Conservation of Agricultural Resource Act (CARA) were consulted to confirm the invaders status. Only eight plants (60%) are regulated by CARA (10/2004). Of 10 IAPs, 80% (8 species) are listed in both NEMBA and CARA legislation. Only 20% (2 species) are listed in NEMBA alone.
Conclusion: Invasive alien plants are utilized by communities to combat various ailments in humans and these plants can help to reduce pressure on heavily harvested indigenous plant.

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Invasive alien plant species used for the treatment of various diseases in limpopo province, south africa.

Background: Medicinal plants are used by many ethnic groups as a source of medicine for the treatment of various ailments in both
humans and domestic animals. These plants produce secondary metabolites that have antimicrobial properties, thus screening of
medicinal plants provide another alternative for producing chemical fungicides that are relatively non-toxic and cost-effective.
Materials and methods: Leaf extracts of selected South African plant species (Bucida buceras, Breonadia salicina, Harpephyllum
caffrum, Olinia ventosa, Vangueria infausta and Xylotheca kraussiana) were investigated for activity against selected
phytopathogenic fungi (Aspergillus niger, Aspergillus parasiticus, Colletotricum gloeosporioides, Penicillium janthinellum, P.
expansum, Trichoderma harzianum and Fusarium oxysporum). These plant fungal pathogens causes major economic losses in fruit
industry such as blue rot on nectaries and postharvest disease in citrus. Plant species were selected from 600 evaluated inter alia,
against two animal fungal pathogens (Candida albicans and Cryptococcus neoformans). Antioxidant activity of the selected plant
extracts were investigated using a qualitative assay (2, 2-diphenyl-1-picrylhydrazyl (DPPH)). Bioautography assay was used to
determine the number of antifungal compounds in plant extracts.
Results: All plant extracts were active against the selected plant phytopathogenic fungi. Moreover, Bucida buceras had the best
antifungal activity against four of the fungi, with minimum inhibitory concentration (MIC) values as low as 0.02 mg/ml and 0.08
mg/ml against P. expansum, P. janthinellum, T. harzianum and F. oxysporum. The plant extracts of five plant species did not possess
strong antioxidant activity. However, methanol extract of X. kraussiana was the most active radical scavenger in the DPPH assay
amongst the six medicinal plants screened. No antifungal compounds were observed in some of the plant extracts with good
antifungal activity as shown in the microdilution assay, indicating possible synergism between the separated metabolites.
Conclusion: The results showed that acetone was the best extractant. Furthermore, our findings also confirm the traditional use of
Breonadia salicina and demonstrate the potential value of developing biopesticides from plants.

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S.M. Mahlo

Papers

Antifungal activity of leaf extracts from South African trees against plant pathogens

Invasive alien plant species used for the treatment of various diseases in limpopo province, south africa.

Antioxidant and antifungal activity of selected medicinal plant extracts against phytopathogenic fungi

Antifungal activity and cytotoxicity of isolated compounds from leaves of Breonadia salicina

Acetone leaf extracts of Breonadia salicina (Rubiaceae) and ursolic acid protect oranges against infection by Penicillium species