The increase in demand for agricultural produce necessitates the continuous search for affordable, ecofriendly, readily available crop protectors, and food preservatives. Historically, the use of various chemicals was employed in controlling plant diseases and to maintain food quality. In the past few decades, several natural product-based alternatives have been discovered and projected as better alternatives to synthetic pesticides and other synthetic agrochemicals. Recent studies focusing on the application of different botanicals in crop protection and food preservation were carefully selected and reviewed. The application of plant extract in the biogenic preparation of nanoparticles was also reviewed. This review confirms that several natural products can be used as a safe replacement for synthetic agrochemicals. Different plant extracts have also served as feed for the synthesis of nanoparticle, which is increasingly applicable in crop protection and food preservation.
The ever increasing population of man has continued to fuel the global urge for producing cash and food crops. The recent breakthrough in food production is partly due to the discovery and usage of synthetic agrochemicals and food preservatives, which significantly resolved several issues [
The innovative approach to enhance global food productivity is achievable through applications of sustainability channels. In advanced countries, agrochemicals are applied not only to preserve foods but also to mitigate pest invasion leading to unbroken food supply [
Maximum residues’ limits of pesticides in fruits and vegetables.
Maximum residue limit (MRL) in mg/kg | |||||||
---|---|---|---|---|---|---|---|
Class of pesticides | Carbamate | Dithiocarbamates | Pyrethroid | ||||
Examples | Benomyl | Carbaryl | Carbosulfan | Mancozebthiram | Cypermethrin | Deltamethrin | Fenvalerate |
Sweet corn | 1.0 | 0.05 | 0.1 | ||||
Cucumber | 3.0 | 0.5 | 2.0 | ||||
Watermelon | 1.0 | 0.2 | 1.0 | ||||
Brassica vegetables | 1.0 | 0.5 | 1.0 | 0.1 | 2.0 | ||
Peppers chili | 2.0 | 0.5 | 0.5 | 2.0 | 2.0 | 0.1 | |
Mango | 2.0 | 1.0 | 2.0 | 0.7 | 0.2 | 1.5 | |
Potato | 0.2 | 0.05 | 0.2 | 0.05 | |||
Citrus fruits | 3.0 | 7.0 | 0.1 | 2.0 | 0.3 | ||
Grapes | 3.0 | 5.0 | 5.0 | 0.5 | |||
Spring onion | 0.5 | 0.3 | 2.0 | ||||
Tomato | 3.0 | 10.0 | 0.2 | 0.1 | |||
Shallot | 2.0 | 0.5 | 0.5 | 0.1 | 0.05 | ||
Onion, bulb | 0.5 | 0.01 | |||||
Okra | 0.5 | 0.2 | 0.5 | ||||
Egg plant | 0.03 | 0.2 | 0.03 | 2.0 | |||
Kale | 15.0 | ||||||
Pumpkins | 0.2 | 2.0 | |||||
Cabbage | 3.0 | ||||||
Papaya | 0.5 | ||||||
Class of pesticides | Organophosphate | Organochlorine | Bipyridyliums | Triazine | |||
Examples | Chlorpyrifos | Dimethoate | Malathion | DDD | Paraquat | Atrazine | Ametryn |
Cabbages | 1.0 | 8.0 | 0.02 | 0.07 | |||
Sweet corn | 0.02 | 0.1 | |||||
Spinach | 0.5 | 0.2 | 0.07 | ||||
Banana | 2.0 | ||||||
Okra | 0.5 | ||||||
Cauliflower | 0.2 | 0.5 | |||||
Spring onion | 5.0 | 0.05 | |||||
Broccoli | 5.0 | 0.07 | |||||
Kale | 1.0 | 0.07 | |||||
Peppers chili | 3.0 | 0.1 | |||||
Tomato | 2.0 | 0.5 | 0.05 | ||||
Citrus fruits | 5.0 | 7.0 | 0.02 | ||||
Shallot | 0.2 | 0.5 | 1.0 | ||||
Onion, bulb | 0.2 | 0.5 | 1.0 | 0.05 | |||
Potatoes | 3.0 | 0.05 | |||||
Cucumber | 1.0 | 0.02 | |||||
Pineapple | 0.1 | 0.1 |
The table was developed from FAO and WHO data [
The intake of organophosphate residue in food was found to cause antiandrogenic effects and interfere with semen production, ejaculation, and total sperm count in male organisms [
Crop protection and food preservation are indispensable entities in global food sustainability. Several methods of preservation have effectively prevented food spoilage caused by insect infestation, climatic conditions, and microbial attacks [
In the past two decades, the production and distribution of crop and food products have been severely affected due to the invasion of drug resistance microbes, pests, and other external influences [
Over the years, herbicides have been seen as an agent, which control the growth of unwanted plants in a sustainable way. Synthetic herbicides are widely engaged and are made available to farmers at cheaper prices [
Fungal growth (spores), which affect the growth and well-being of plants, can be successfully inhibited by the utilization of fungicides [
Insecticides are applied to depopulate or eliminate the pests, which cause qualitative and quantitative damages to plants and farm produce [
Viruses are infectious agents that can only replicate in living cells of a particular host such as plants, and they are linked to several damages and wastage of crop produce [
Other methods include the use of natural predators or parasites such as lacewings, lady beetles, wasps, and hoverfly larvae, which feeds on a wide range of insects such as aphids, scale insects, spider mites, whiteflies, and many others [
Inappropriate use of synthetic pesticides has led to pollution of a diverse kind in the environment, which is detrimental to man and his environment. The chemicals are applied directly to crops to protect them from attacks by insects, and this has been known to cause unsolicited problems [
The environmental effects of pesticides have been studied and found to be caused by the percolation of pesticide constituents into water bodies via mechanical media such as wind or rain. Over time, the accumulation of pesticide residue in water bodies can threaten the growth, survival, and reproduction of aquatic organisms [
Different methods have been engaged in the control of the pest attack. However, there are some setbacks associated with their uses. For example, making use of natural predators does not ascertain complete eradication of the target pest, and the absence of target pest when natural predators are introduced can cause damages to crops. Likewise, the introduction of these natural predators can be time-consuming, especially if the farm is large [
Negative effects of current methods of crop protection.
Methods | Examples | Disadvantages | References |
---|---|---|---|
Herbicides | Dimethylarsinic acid diuron, imazapyr, and picloram | Dizziness, headache, vomiting, fall in blood pressure, convulsions, and general paralysis | [ |
Cancer | [ | ||
Fungicides | Mancozeb, malathion thirame, and fenarimol | Inhibition of hormone synthesis, developmental defects, menstrual cycle irregularities, impaired fertility, and spontaneous abortion/stillbirths | [ |
Insecticides | Spinetoram | Minimal or mild eye irritation | [ |
Diazinon | Lymphoma | [ | |
Aldrin | Liver diseases and lung cancer | [ | |
DDT | Chronic liver damage, reproductive disorders, cytogenic effects, and breast cancer | [ | |
Genetically modified species | GM maize and soybean | Higher level of severe inflammation in stomach and lower glucose levels | [ |
Use of cover crops | Common vetch, daikon radish, and sweet clover | Soil water depletion | [ |
Natural predators | Lacewings, lady beetles, and trichodrema | The introduction of predators at the wrong time causes more damage to the plants | [ |
Use of scare crows | Mannequin or decoy | Not always effective in scaring birds and animals away | [ |
Several studies have examined the application and efficacy of plant extracts in the fight against various diseases affecting plants. Solvent extracts from various plants have exhibited great potential in combating weeds invasion and microbial attacks.
Weeds are becoming resistant to conventional herbicides such as glyphosate, and natural products are serving as good alternatives [
Asides from plants, several organisms such as bacteria, fungi, and viruses have also been known to produce phytotoxic substances. For instance, certain microorganisms have been established as sources of bioactive secondary metabolites. An example is the new strain of
Relevant natural herbicidal molecules.
Several plant extracts have been successfully employed as fungicides. Examples include
The direct application of pure organic compounds has similarly been reported. Five phenolic compounds namely alkylresorcinols (AR), ferulic acid, quercetin, phlorizin, and resveratrol were directly used against the phytopathogenic fungi
In the same vein, certain microbes have been found to produce secondary metabolites that have been successfully applied in crop protection. For instance, alteramide B, which has a broad spectrum against phytopathogenic fungi such as
Relevant natural fungicidal molecules.
In the search for safe, cheap, and sustainable means to control insect infestation, some selected botanicals have been successfully investigated. Crude extracts from different plant parts have displayed notable insecticidal properties. These include
Another example is
Furthermore, certain microbes have also demonstrated insecticidal potential in recent times. An emulsifiable concentrate of fungus
Natural insecticidal molecules.
Several studies have shown that there are thousands of plant viruses, but the available treatment is not sufficient in eradicating these infections. This has led to a continuous search for sustainable alternatives. Interestingly, some plants naturally resist virus replication in their cells, while some natural extracts resist virus replication when applied to other plants [
Different classes of phytochemicals have been implicated in the foregoing antiviral activities of plant extracts. These include alkaloids, coumarins, flavonoids, phenolics, and terpenoids amongst others. Alkaloids: 1-methoxycarbonyl-
The use of microbes as effective producers of antiviral agents has also been exploited in the eradication of plant viruses. An example is the application of
Natural virucidal molecules.
The need to maintain dietary value, composition, flavor, colour, pH, and texture of a particular food product over long time is the reason behind food preservation [
The pitfalls observed in the current methods of preservation include a reduction in nutritional quality, unpleasant side effects, and diseases such as cancer in extreme cases. Prolonged drying/smoking and irradiation lead to loss of colour, flavor, aroma, texture, and vitamins [
Pitfalls of the current methods in food preservation.
Methods | Examples of food preserved | Disadvantages | References |
---|---|---|---|
Drying, smoking, freezing irradiation, boiling | Fish, tobacco leaves, and various products | After a long period time, the food starts losing its colour, flavor, aroma, and vitamins | [ |
Fermentation | Dairy products and wine | Increased risk of gastric cancer | [ |
Salting | Meat and fish products | When in excess, it causes high blood pressure and kidney stone | [ |
Artificial food additives, e.g., sodium bisulfite, | Fruits, vegetables | They cause side reactions such as headaches and allergies | [ |
Sodium benzoate | Carbonated drinks, fruit juice, and pickles | Hyperactivity, leukemia, and other cancers | [ |
Potassium sorbate | Flavoured drinks, fine bakery wares, bread, and rolls | Not yet established | [ |
Nitrite or nitrate | Meat products | Suspected to cause stomach cancer, brain tumors, and leukemia | [ |
The nature of food usually determines the kind of preservative to be employed [
Several plant extracts have been investigated for their ability to serve as preservatives agents against foodborne pathogens. Recently, the antibacterial activity of pure compounds isolated from plant extracts has been reported. The potency of stigmasterol, an isolate of ethyl acetate fraction of
Second, several extracts have been proven as potent against the activity of
Although the active antimicrobial agents in these natural sources were not isolated before use, the activity of the extracts is a result of the inherent phytochemicals, which may be working together in synergy. The antimicrobial, antioxidant, and cytotoxic properties of the extracts have been attributed to phytochemicals such as citral, aspilactonol B, and 8-methyl-6-prenylquercetin (found in
Some food products require preservatives because they are fragile and more susceptible to spoilage caused by microorganisms. Tomato fruit, an important example, was preserved using aqueous extracts of
The foregoing extracts exhibited both antimicrobial/antioxidant properties due to the presence of certain alkaloids and carpaine in
Apart from the use of plant extracts and phytochemicals, microbes have found increasing applications in the food industry. An active compound reuteri was isolated and purified from
Natural antimicrobial–preservative molecules.
Polyphenols make use of their hydroxyl group to attack the phospholipid bilayer of bacterial cell membranes, disrupting enzyme systems, which result in a limited supply of essential iron required for the growth of the microbes [
Phytosterols such as stigmasterol have been known to mimic endogenous sterols based on their structural similarity. This gives them the ability to replace the hormone, thus disrupting the cell membrane. In the same vein, certain steroids suppress the ability of certain microbes to resist antibiotics by disrupting the multiple drug efflux pump proteins in multidrug-resistant microbes [
Furthermore, a variety of plant extracts have been found to successfully inhibit biofilm formation from various microbes mentioned earlier; such extracts which can be used as preventive coatings include
Natural extracts with antioxidant capacity have been employed in different food products ranging from meat, fruits, yogurt, and biscuits. Apart from microbial suppression/elimination, parameters that are used to assess the efficacy of preservatives include antioxidant capacity, external appearance, nutritional profile, pH, and individual fatty acids. Various crude extracts have been applied to some of these examples. In meat preservation, extracts from
Similarly, a natural pigment found in tomatoes, “anthocyanin,” whose production is usually enhanced by contaminations from pathogens and stress conditions were augmented in purple tomatoes to slow down ripening and vulnerability to
Natural antioxidant-preservative molecules.
The benefits associated with the use of natural extract cannot be overestimated. However, some demerits are involved in the use of botanicals for food preservation.
During extraction, the use of hot extraction techniques is expected to facilitate extracts production. However, this leads to thermal decomposition of vital phytochemicals responsible for the antimicrobial activity and antioxidant activity, thus rendering the extract impotent and forcing industrialists to source for sustainable alternatives [
Most crude extracts obtained from plants contain a mixture of compounds, which are used directly without any further purification. Thus, the active compounds are not separated from the inactive/toxic ones, which are responsible for crude extract toxicity [
After extraction, quantification of the resulting natural product isolates usually reveals a low percentage yield. Hence, synthesizing these components becomes crucial. During synthesis, the stereochemistry of the compounds to be synthesized is very important because a wrong configuration can give rise to unsolicited outcomes. Apart from synthesizing natural products, there are various avenues via which the yield of natural products can be enhanced. Chromatographic methods such as countercurrent chromatography can give a reasonable amount of bioactive compounds [
In addition to the foregoing, some crude extracts may sometimes have a particular odor, taste, colour, flavor, which affect the sensory properties of food even at low concentrations [
Apart from the direct application of plant extracts in crop protection and food preservatives, several plant extracts, fractions, and isolates have served as reducing agents and stabilizers in the preparation of nanoparticles [
Green synthesized silver nanoparticles from plant and their applications in crop protection and food preservation.
Plants material | Extracts | Possible applications | References |
---|---|---|---|
Aqueous | As an antimicrobial agent in the pharmaceutical and food industries | [ | |
” | Nano-ice for the preservation of fish and other food products | [ | |
Oolong tea | ” | As a fruit coating to preserve postharvest qualities of fruits, e.g., cherry tomatoes | [ |
” | As an antifungal agent against | [ | |
” | For cancer treatment and radical scavenging agent | [ | |
” | As an antibacterial and antitumor agent | [ | |
Belladonna mother tincture | ” | Antimicrobial agent and anti-inflammatory agent | [ |
” | As a fruit coating, antioxidant, and good antifungal agent. | [ | |
” | As an antimicrobial agent against | [ | |
” | As larvicidal agent against dengue vector (Aedes aegypti) and antimicrobial activity | [ | |
” | As an antimicrobial agent against food pathogens | [ | |
Grape pomace and orange peels | ” | ” | [ |
” | ” | [ | |
Cocoa pod | ” | Growth enhancer for root and shoot elongation for more nutrient absorption, a good antioxidant, prolongs shelf life, high tolerance level against fungi, and nematodes | [ |
” | As nematicides against | [ | |
Ethanol | As biopesticides to fight against | [ | |
Aqueous and ethanol | Antioxidants wound healing and anticancer agents | [ |
As nanoparticles application continues to expand, concerns have begun to emerge about the possible toxicity of the materials [
The foregoing review shows that natural product has gained reasonable ground in crop protection and food preservation. Various extracts from different plant sources execute protective and preventive properties via known classes of secondary metabolites that they contain. Several studies directly employed crude extracts, while some studies fractionated the extract into less complex forms before application. A few in-depth studies, however, isolated the active constituents, which were responsible for the activities under review. Although the active natural molecules are usually present in little quantities, they have proven to be better alternatives compared to their synthetic counterparts, which have been hitherto employed. There is a widely spread notion that natural remedies are safer than synthetic chemicals. Hence, the growing interest of scientists in authenticating the efficiency of natural products in crop protection, food preservation, and other medicinal applications. Although various crude extract have given impressive results in this direction, isolating the phytochemicals such as flavonoids, alkaloids, tannins, and saponins could provide better solutions to various agro-related challenges. This approach deserves more scientific attention in the future. An interesting development is the application of plant extract for the green synthesis of nanoparticles, which tend to proffer impressive results. Particularly, silver nanoparticles (AgNPs) have been applied in crop protection and food preservation. However, the rising toxicity and environmental concerns about AgNPs are also worthy of further research [
Acetohydroxyacid synthase
Alkylresorcinols
Clove and cinnamon
Cucumber mosaic virus
Environmental Protection Agency
Fall armyworm
Food and Agriculture Organization
Genetically modified
High-performance liquid chromatography
Lemon grass
Silver nanoparticles
Tobacco mosaic virus
World Health Organization.
The data used to support this review article are available in major scientific databases such as Scopus, Google scholar, PubMed, Science Direct, and other relevant sources. Keywords such as crop protection, food protection, natural products, pesticides, insecticides, herbicides, and natural food preservative will assist in obtaining these articles.
The authors declare that they have no conflicts of interest.