3. Potential Use of Apiaceae Extracts as Agrochemicals
Synthetic agrochemicals are used to manage weeds, pests, and phytopathogens, thus increasing productivity and food safety. However, long-time usage of these synthetic chemicals may lead to environmental contamination, accumulation of toxic residues and biomagnification through the food chain, development of insect resistance, and threats to humans and non-target organisms
[10][11]. These synthetic chemicals produce acute or chronic toxicity in living beings, depending on physicochemical characteristics, concentration and exposure time, route of entry, toxicodynamics and toxicokinetics (absorption, distribution, half-life, metabolism, and elimination), a combination of various pesticides, and the components of their formulation
[10]. Secondary metabolites, including EOs, from aromatic plants, drew much attention due to their low toxicity to animals and non-target insects, fast degradation in the environment, and local availability. Other than the many health benefits, the biocidal potential of Apiaceae has great importance in agriculture for use as a natural pesticide, herbicide or phytotoxin, and antimicrobial
[12].
3.1. Insecticidal Activity for Crops and Stored Producs Protection
3.1.1. Insecticidal Activity to Protect Crops
Several Apiaceae genera are toxic to various insects
[12].
Tuta absoluta, a major pest of tomato cropping, can be controlled by the EO of
Carum capticum (Ajwain)
[13]. Thymol, γ-terpinene, and ρ-cymene are the major components of
C. capticum oil that showed AChE inhibition
[13].
Ammi visnaga (toothpick-plant) seeds possess acaricidal activity against
Tetranychus urticae Koch, which is a polyphagous species causing damage to numerous plants (around 1200 species), including major food crops and ornamental plants
[14].
Cotton leafworm,
Spodoptera littoralis, causes serious damage to important economic crops, such as maize, cotton, cereals, potatoes, tobacco, tomato, vegetables, and ornamental plants
[15][16]. Apiaceae species,
C. carvi,
F. vulgare,
C. cyminum,
C. caraway,
C. sativum,
D. carota [16], Helosciadium nodiflorum (water celery)
[17], and
Crithmum maritimum [15] were demonstrated to possess toxicity against
S. littoralis larvae. Benelli et al.
[18] also suggest that cumin (
C. cyminum) and anise (
P. anisum) EOs can be used to protect crops from pests or to control insect vectors, as they have potential insecticidal activity against the peach-potato aphid (
Myzus persicae) and the tobacco cutworm/cotton leafworm (
S. littoralis), and insect vectors, such as the common housefly (
Musca domestica). The crop pest
Spodoptera litura is a threat to many crops and develops resistance to synthetic pesticides. This pest can be counteracted by sea fennel (
C. maritimum) EOs
[19].
3.1.2. Insecticidal Activity to Protect Stored Products
Several species of storage insect pests infest agricultural products and stored granaries, causing substantial weight losses (around 10%) and quality
[6]. They may carry pathogens and contaminate food
[20].
Sitophilus oryzae (rice weevil),
Sitophilus zeamais (maize weevil),
Tyrophagus putrescentiae (mould or cheese mite),
Tribolium confusum (confused flour beetle),
Callosobruchus maculatus (cowpea weevil),
Periplaneta americana (American cockroach),
Tribolium castaneum (red flour beetle) are some of the pests that affect stored cereals, grains, flour, and other dried products
[20]. Research is focused on producing safe and low-risk natural compounds for pest control
[21]. Several Apiaceae species were reported to carry insecticidal activities and have potential to protect stored grains from insect infestation.
Monoterpenes, such as (S)-(−)-linalool and (S)-(−)-menthone showed the most contact toxicity and fumigant activities, respectively, while α- pinene, menthone, citronellal, and linalool exhibited repellent activities against the rice weevil (
S. oryzae)
[22]. Cuminaldehyde and (S)-carvone showed strong repellent activities, fumigation toxicity, and AChE inhibition
[23].
Apiaceae species were demonstrated to possess insecticidal and repellent activity. EOs from
F. vulgare,
Petroselinum hortense,
C. sativum, and
P. anisum showed stronger fumigant toxicity against the storage pest, red flour beetle (
T. castaneum) than against the rice weevil (
S. oryzae)
[21].
C. carvi EO and two isolated main compounds, (R)-carvone and D-limonene, exhibited strong contact and fumigant toxicity against the maize weevil (
S. zeamais) and the red flour beetle (
T. castaneum)
[24].
A. graveolens (dill),
C. cyminum (cumin), and
P. crispum (parsley) EOs were reported as having contact toxicity, fumigant, and repellent activities against the stored grain pest
S. zeamais. Moreover, AChE inhibition was also reported with
P. crispum and
C. cyminum EOs
[23].
Trachyspermum ammi EO also showed repellent and fumigant activity against the rice weevil (
S. oryzae). In addition,
T. ammi EO showed significant inhibition of AChE activity in rice weevils
[6].
Insecticidal activity of EO derived from
A. graveolens (dill) seeds was reported against
T. confusum (confused flour beetle),
C. maculatus (cowpea weevils),
M. domestica,
P. americana (American cockroach), and
T. castaneum (red flour beetles)]
[25].
Plodia interpunctella (Indian meal moth),
Sitotroga cerealella (grain moth), and
T. putrescentiae (mould or cheese mite) affecting stored products, such as grains, flours, feeds, dried nuts, and fruits, globally.
P. interpunctella moth continuously produces a silken web on the food;
S. cerealella larvae invade grains and complete the larval and pupal stages within the grains, thus decreasing grain weight and nutritional value; and
T. putrescentiae mites disseminate toxic fungi and induce allergic reactions among workers engaged in agriculture and food industries. Camphor and linalool found in
C. sativum EO, extracted by steam distillation, exhibited acaricidal and insecticidal properties against
P. interpunctella,
S. cerealella, and
T. putrescentiae [26].
3.2. Herbicidal/Phytotoxic Activity against Weeds
Many studies were undertaken to investigate the herbicidal potential of Apiaceae species against weeds. Enzymes such as α- amylase, catalase, and peroxidase enzymes play a key role in the physiological functions of the seeds and plants. Application of EOs increases oxidative stress in plant cells, which inhibits these enzymes and causes subsequent cell death. Moreover, the detrimental effect on the DNA and RNA of the cell results in decreased cell division, growth, and elongation
[27].
Herbicidal effects of EOs derived from
C. sativum,
C. carvi,
F. vulgare, and
P. anisum were reported against various weeds
[28].
Eryngium triquetrum EO and its major constituent falcarinol showed strong herbicidal activity against
Lepidium, while
Smyrnium olusatrum EO showed moderate herbicidal activity. Therefore,
E. triquetrum and
S. olusatrum EOs can be used in crop protection to inhibit photosynthesis in weeds
[29].
Caraway (
C. carvi) EO (oil in water emulsion) are rich in oxygenated monoterpenes and exhibited herbicidal activity against
Echinochloa crus-galli (barnyard grass, a typical maize weed)
[30].
C. carvi EO was found to inhibit the germination of seeds of common weeds, including
Amaranthus retroflexus,
Centaurea salsotitialis,
Raphanus raphanistrum,
Rumex nepalensis,
Sonchus oleraceus, and
Sinapis arvensis [31].
Fennel (
F. vulgare) EO strongly inhibited the seed germination and seedling growth of grass weeds,
Phalaris minor,
Avena ludoviciana, broad-leaved weeds,
Rumex dentatus and
Medicago denticulate, and can, therefore, be used in the biological management of weeds in wheat (
Triticum aestivum) crops
[27]. Fennel (
F. vulgare) EO was also reported for its phytotoxic activity against field bindweed (
Convolvulus arvensis) with significant inhibition of germination and early growth in field bindweed seedlings
[32].
3.3. Antimicrobial Activity against Phytopathogens
Plant pathogens, including fungi, bacteria, viruses, oomycetes, and nematodes, can cause diseases or damage to plants and result in significant crop yield and quality losses, of which fungi are the predominant pathogens, causing almost 30% of crop diseases during their cultivation or after harvest. Fungal disease symptoms on fruits, leaves, stems, and other plant parts include scabs, mouldy coatings, rust, smuts, powdery mildew, blotches, and rotted tissues. Plant diseases caused by phytopathogenic bacteria and fungi threaten human health and food security
[33][34][35][36].
Various phytopathogenic bacteria, including
Xanthomonas spp. (bacterial spots and blights),
Erwinia spp. (soft rot, fire blight),
Pseudomonas spp. (soft rot, bacterial canker),
Agrobacterium spp. (crown gall), as well as
Ralstonia solanacearum (bacterial wilt in banana), affect various agricultural plants
[37].
Moreover,
Fusarium oxysporum (vascular wilt of the banana tree),
Macrophomina phaseolina (damping-off, seedling blight, and rot in peanuts, cabbage, pepper, chickpeas, soybeans, sweet potatoes, sesame, potatoes, sorghum, wheat, corn, etc.),
Alternaria alternata (rot),
Penicillium digitatum (green mould in citrus), and
Aspergillus flavus (damping-off in peanut) are some of the fungi responsible for many diseases in various plants
[36][38].
Apiaceae family plants were widely investigated for their potential biocidal activity against phytopathogens.
Apiaceae, such as Torilis anthriscus, Aegopodium podagraria, D. carota, Heracleum sphondyilium, Pimpinella saxifrage, P. sativa, Angelica silvestris, and F. vulgare exhibited antimicrobial activity against phytopathogenic bacteria Agrobacterium radiobacter pv tumefaciens, Erwinia carotowora, Pseudomonas fluorescens, and Pseudomonas glycinea
[33]. The EO of C. maculatum (poison hemlock), a poisonous Apiaceae species, has antibacterial activity against Pseudomonas aeruginosa
[39].
E. triquetrum EO exhibited strong antibacterial activities against potato blackleg disease,
Pectobacterium atrosepticum, and the soil bacterium
Pseudomonas cichorii, which is responsible for disease in lettuce, celery, and chrysanthemum, while
S. olusatrum EO showed moderate antibacterial activity
[29].
The Apiaceae Ferulago angulate exhibited toxicity in variable degrees against phytopathogenic bacteria (Erwinia amylovora, Xanthomonas oryzae, Pseudomonas syringae, Pectobacterium carotovorum, R. solanacearum, Bacillus thuringiensis), and fungi (A. alternata, Culvularia fallax, M. phaseolina, F. oxysporum, Cytospora sacchari, Colletotrichum tricbellum)
[40].
A. alternata and
P. digitatum are two postharvest pathogens in tomato fruits. Based on in vivo studies,
Carum copticum and
F. vulgare EOs have the potential to control postharvest decay in tomatoes caused by
A. alternata and
P. digitatum [41].
E. triquetrum and
S. olusatrum EOs have potent antifungal and fumigant activity against
Fusarium graminearum (cereal fusarium) and moderate activity against
Botrytis cinerea (grey rot on tomatoes, strawberries)
. S. olusatrum EO showed strong antifungal activity against
F. graminearum and
Zymoseptoria tritici, which are responsible for the septoria blight
[29].
A. graveolens (dill) seeds EO mainly consists of carvone, limonene, α-phellandrene, β-phellandrene and p-cymene and were proved to have antifungal (
Aspergillus niger,
Aspergillus oryzae,
A. flavus,
A. alternata) and antibacterial (
Escherichia coli,
P. aeruginosa,
Bacillus subtilis,
Staphylococcus aureus) activities
[25].
Food poisoning is the most common cause of illness and death in both developed and developing countries. Most food poisoning diseases are caused by bacterial contamination. Pathogenic and food spoilage bacteria, such as
Salmonella typhi,
E. coli,
P. aeruginosa,
S. aureus,
Listeria monocytogenes, and
Bacillus cereus are the causal agents of foodborne diseases or food spoilage. Plant extracts are a good source of antimicrobial agents that can be used as food preservatives
[42][43].
Apiaceae
C. cyminum was reported to be effective against
S. aureus [43]. Coriander (
C. sativum) EO and its major compound linalool showed antibacterial activity against
Campylobacter jejuni and
Campylobacter coli, pathogens that cause foodborne diseases
[44].
Coriander (
C. sativum) was also reported to have strong antimicrobial activity against bacteria,
B. subtilis, followed by
Stenotropomonas maltophilia, and
Penicillium expansum (fungi producing mycotoxin). Moreover, the strongest antibiofilm activity of coriander EO was also reported against
S. maltophilia [45].
Carum nigrum (black caraway) seed EO has antibacterial activity against foodborne bacteria,
B. cereus and
P. aeruginosa, and antifungal activity against foodborne fungi, such as
P. purpurogenum,
Acrophialophora fusispora,
A. flavus, and
A. niger [46].
The antimicrobial activity of
T. ammi (Ajwain) EO was demonstrated against various food spoilage and foodborne bacteria (
B. cereus,
S. aureus,
L. monocytogenes,
Salmonella typhimurium,
E. coli) and fungi (
Penicillium citrinum,
Penicillium chrysogenum,
A. flavus,
A. niger,
Aspergillus parasiticus)
[47].
Moreover, certain fungi, including
Aspergillus spp.,
Fusarium spp., and
Alternaria spp., produce mycotoxins that can be harmful to human health due to hepatotoxic, nephrotoxic, and carcinogenic effects, or even cause death
[34]. Mycotoxins are toxic secondary metabolites produced by certain fungal species in various agricultural and other food products, either in the field or during storage. Mycotoxin contamination in crops is potentially harmful to animals and human health. Aflatoxins B1, B2, G1, and G2 are the four major toxins generated in foods, of which the aflatoxin B1, secreted by
A. flavus,
A. parasiticus and
Aspergillus nomius, is the most toxic and has potent teratogenic, mutagenic, hepatotoxic, and immune suppressive activities
[48][49][50].
Apiaceae,
F. vulgare EO extracted from flowers and roots, significantly inhibited the growth of
A. parasiticus and the production of aflatoxins B1 and G1
[51]. Carvone and linalool compounds found in
C. carvi and
C. sativum seed EOs, respectively, showed an antifungal and aflatoxin-inhibition ability against
A. flavus. Thus, they can be used as a preservative, particularly in post-harvest processing and the storage of agricultural products that are susceptible to aflatoxin contamination, such as cereals, dried fruits, and spices
[50]. EOs of other Apiaceae plants, including
C.
cyminum [52],
C. carvi [53][54],
C. sativum [53], and
C.
copticum (
T. ammi) were also reported to inhibit both growth and/or mycotoxin production.