Here is a list of six main antimicrobial spices.
1. Ajwain (Carum Copticum/Trachyspermum Ammi):
The essential oil of ajwain exhibited a broad spectrum of fungi toxic behavior against all tested fungi such as A. niger, A. flavus, A. oryzae, A. ochraceus, F. monoliforme, F. graminearum, P. citrium, P. viridicatum, P. madriti, and C. lunata through absolute mycelial zone inhibition that was obtained at a 6-micro dose of the oil. The essential oil has some use in the treatment of intestinal dysbiosis. Its benefit comes from being able to inhibit the growth of undesired pathogens while not adversely affecting the beneficial flora.
Anti-bacterial efficacy of ajwain shown by Kaur and Arora (2009) provided a scientific basis and thus, validated their traditional uses as home-made remedies. Isolation and purification of different phytochemicals form ajwain may further yield significant anti-bacterial agents.
Lymphatic filariasis is caused by infection with the parasitic filarial nematodes Wuchereria bancrofti, Brugia malayi and B. timori, transmitted by mosquitoes. The lack of an adulticidal drug poses a challenge to filariasis elimination, hence it is essential to develop an effective anti-filarial drug which could either kill or permanently sterilize the adult worms.
Mathew et al. (2008) found that the crude extract of ajwain showed significant activity against the adult S. digitata by both a worm motility and MTT [3- (4, 5-dimethylthiazol-2-yl)-2, 5-diphenyltetrazolium bromide] reduction assays. The isolated active principle was chemically characterized by IR, (1) H-NMR and MS analysis and identified as a phenolic monoterpene. It was screened for in vivo anti- filarial activity against the human filarial worm B. malayi in Mastomys coucha rats. The findings thus provide a new lead for development of a macrofilaricidal drug from ajwain.
The emerging trends of multidrug resistance among several groups of microorganisms against different classes of antibiotics led different researchers to develop efficient drugs from plant sources to counter multidrug resistant strains. Khan et al (2010c) investigated different solvent extracts of ajwain to determine the efficacy against multidrug resistant microbes.
The petroleum ether fraction (least MIC- 625 micro g/ml) showed best activity against multidrug resistant strains of C. glabrata, E. coli and reference strains of S. mutans and S. bovis when compared to its other fractions. Khan et al. (2010 d) reported a novel compound, a naphthalene derivative, isolated first time from ajwain seeds with anti-biofilm activity against S. mutans.
2. Asafoetida (Ferula Assafoetida):
Asafoetida has a broad range of uses in traditional medicine as an antimicrobial agent with well documented uses for treating chronic bronchitis and whooping cough, as well as reducing flatulence.
Asafoetida was used in 1918 to fight the Spanish influenza pandemic. In 2009, scientists at the Kaohsiung Medical University in Taiwan reported that the roots of Asafoetida produce natural antiviral drug compounds that kill the swine flu virus, H1N1. In an article published in the American Chemical Society’s Journal of Natural Products, the researchers said that the compounds “may serve as promising lead components for new drug development” against this type of flu.
The oleo-gum-resin from asafetida has been known to possess antifungal, antidiabetic, anti-inflammatory, anti-mutagenic and anti-viral activities. Asafoetida decreased counts and viability of all tested isolates of Blastocystis sp. subtype 3 which was confirmed by microscopy.
The degree of the inhibitory effect was dependent on the concentration, form, as well as the time of incubation with asafetida extracts. The lowest concentrations of 16 and 40 mg/ml, of asafetida powder and oil respectively caused 100 per cent inhibition of Blastocystis growth and 100 per cent inhibition of multiplication.
Asafoetida had a potent anti-parasitic effect on T. vaginalis compared to metronidazole, thus, worth further investigation on its applicability in treatment of parasitic infections.
A highly significant statistical difference was noticed in the antimicrobial effect of different forms of asafoetida (oil-form and a powder-form in different concentrations) administered to experimentally infected mice with S. mansoni, with regard to the mean worm burden and tissue egg count as confirmed histo-pathologically and by ultra-structural profile alteration.
3. Coriander Leaves/Seeds (Coriandrum Sativum):
Chemicals derived from coriander leaves were found to have antibacterial activity against S. choleraesuis. Coriander essential oil also showed a delay in E. coli growth, suggesting possible agricultural anti-bacterial applications.
4. Cumin Seeds (Cuminum Cyminum):
It is encouraging that there is currently a quest for safe and effective antimicrobial agents.
The anti-bacterial activity of C. cyminum essential oil is perhaps attributable to the high levels of cuminaldehyde (16.1 per cent), followed by a-pinene (11.4 per cent). Fabio et al (2007) reported the zone diameter of inhibition (ZDI) of 24 and 18 mm, respectively for C. zeylanicum and S. aromaticum against S. aureus. Agaoglu et al. (2007) also reported C. zeylanicum as the most effective spice against S. aureus.
Cumin seeds showed excellent in vitro anti-bacterial activity against methicillin- resistant S. aureus (MRSA). The C. cyminum exhibited bactericidal activity at a concentration of 300 μg/ml, hence, could be a potential anti- MRSA agent. It will also be of great benefit in combating antibiotic resistance of S. aureus.
Recently, many antimicrobial/resistant organisms such as K. pneumoniae are emerging. K. pneumonia is an important Gram-negative pathogen, usually associated with nosocomial acquired infections in addition to its involvement in urinary tract infections, pneumonia, bacteremia, septicemia, and infections of surgical wounds. Biofilm growth enhances its resistance to antibiotic therapies, as well as host defense mechanisms.
Derakhshan et al. (2008) reported that the essential oil of cumin seeds has a significant anti-bacterial activity against K. pneumoniae in vitro. The essential oil decreased biofilm formation and enhanced the activity of the ciprofloxacin disk. The incubation of the R-plasmid DNA with essential oil could not induce plasmid DNA degradation. The results of this study by Derakhshan et al. (2010) suggest the potential use of cumin seed essential oil against K. pneumoniae in vitro while suggesting its potential contribution to the in vivo efficacy.
The mechanism by which the cumin seed essential oil acts to enhance the activity of ciprofloxacin against K. pneumoniae, as indicated by an increased inhibition zone diameter, is not known; but some cell wall damage or alteration in the outer membrane proteins may be caused by the cumin seed essential oil, which sensitizes cells to ciprofloxacin as well as resists cells to trimethoprim- sulfamethoxazole. The enhancement of antibacterial efficacy of ciprofloxacin by the essential oil is significant.
C. cyminum essential oil may be considered as an interesting source of antibacterial, anti-fungal and anti-oxidant components used as potent agents in food preservation and for therapeutic or nutraceutical industries. The seed essential oil in combination with nisin can inhibit growth of food-borne pathogens in food. Cumin seed showed the most bactericidal effects on B. cereus at 8°C.
Ultra structural studies of vegetative cells confirmed the synergistic destructive effects of the essential oil and nisin on membrane and utilization of cell wall of the bacteria. The cumin seed oil exhibited anti-bacterial and antifungal activities with a high effectiveness against Vibrio spp. strains with a diameter of inhibition zones growth ranging from 11 to 23 mm, and MIC and MBC values ranging from (0.078-0.31 mg/ml) to (0.31-1.25mg/ml), respectively.
Keskin and Toroglu (2011) studied the antimicrobial activity of cumin seed and the inhibition zone was found to be 7-15 mm 30microl (-1). All cumin oils and cuminic aldehyde exhibited a considerable inhibitory effect against all the organisms tested, Gram-positive and Gram-negative bacteria isolated from different sources of food (pork fillet, minced meat and sausages) except Pseudomonas spp. According to Khosravi et al. (2011) the essential oil of C. cyminum, could be used as natural inhibitor in foods at low concentrations to protect from fungal and toxin contaminations by A. parasiticus.
The anti-bacterial activity of 1-(2-Ethyl, 6-Heptyl) Phenol (EHP) was studied against four Gram-negative and four Gram-positive bacterial pathogens. It was more effective against the Gram negative than Gram positive bacteria. The most sensitive bacterial strain was S. aureus where an inhibition zone of 0.8, 1.6, 2.8, and 3.5 cm was obtained when applying EHP at concentrations of 1, 2.5, 5.0, and 1.0 µg/ml respectively.
S. aureus was followed by B. subtilis, S. pneumoniae and B. thuringiensis. The largest zone of inhibition in Gram-negative bacteria was observed against E. coli; where, 1.5 and 1.8 cm inhibition diameters were reported at 5 and 10 µg/ml EHP concentration respectively. E. coli was followed by S. typhi, S. marcescens and least for P. aeruginosa. Similar results were seen in another study where cumin was more effective against the Gram positive bacteria as compared to the Gram negative bacteria. Amongst the Gram negative bacteria, the antimicrobial activity of cumin was seen in case of E.coli and not much against any other strain.
In another study carried out by Chaudhary and Tariq (2008) also cumin was found to be more effective against the gram negative bacteria as compared to the Gram positive bacteria and the largest inhibitory zone was found against E. coli (23.8mm ± 1.2SD). The aqueous decoction of cumin also exhibited significant inhibitory activity against M. roseus (20.8mm ± 2.3SD), P. shigelloides (18.5mm ± 8.3SD), Alcaligenes spp. (17.1mm ± 2.9SD), Citrobacter spp. (16.2mm ± 0.5SD), K. pneumoniae (15.9mm ± 0.8SD), A. hydrophila (15.8mm ± 1.3SD), K. ozaenae (15.2mm ± 1.3SD), P. aeruginosa (12.3mm ± 3.3SD), E. aerogenes (12.0mm ± 0.1SD) and S. aureus (8.9mm ± 5.6SD).
Cumin oil was also found to be effective against various fungal organisms such as A. flavus, C. albicans etc. responsible for food spoilage. Hajlaoui et al. (2010) in the light of their findings suggested that C. cyminum essential oil may be considered as a source of anti-bacterial, anti-fungal and anti-oxidant components to be potent agents in food preservation and for therapeutic or nutraceutical industries.
5. Mustard Seeds:
An 18.9 kDa anti-fungal protein designated juncin was isolated from seeds of the Japanese takana (Brassica juncea var. integrifolia) by Ye and Ng (2009). The protein exhibited antifungal activity toward the phyto-pathogens F. oxysporum, H. maydis, and M. arachidicola with IC-50 values of 13.5,27, and 10 µM, respectively.
It inhibited the proliferation of hepatoma (HepG2) and breast cancer (MCF7) cells with IC (50) values of 5.6 and 6.4 µM, respectively, and the activity of HIV-1 reverse transcriptase with an IC(50) of 4.5 µM. Its N-terminal sequence differed from those of anti-fungal proteins of Brassica campestris and Brassica alboglabra.
Luciano et al. (2011) found the autoclaved mustard powder to result in more rapid bactericidal action against E. coli, yielding a > 5 log CFU/g reduction in 18 days. This effect may have been due to the formation and/or release of antimicrobial substances from mustard by the autoclave treatment. Hence, autoclaved mustard powder could potentially solve an important challenge faced by the meat industry in manufacturing safe dry fermented sausages.
Compounds generated by the enzymatic hydrolysis of glucosinolates naturally present in mustard powder are potently bactericidal against E. coli. Because E. coli can survive the dry fermented sausage manufacturing process, 2,4, and 6 per cent (wt/wt) heated mustard powder or 6 per cent (wt/wt) deheated (cold) mustard powder were added to dry sausage batter inoculated with E. coli at about 7 log CFU/ g to evaluate the antimicrobial effectiveness of the powders.
The 6 per cent deheated mustard powder treatment provided the most rapid reductions of E. coli (yielding <0.20 log CFU/g after 24 days) by an unknown mechanism and was the least detrimental (P < 0.05) to sausage texture.
An antimicrobial edible film was developed from defatted mustard meal (Sinapis alba) (DMM), a byproduct from the bio-fuel industry, without incorporating external antimicrobials. The film-coating retarded the growth of L. monocytogenes in smoked salmon at 5, 10, and 15°C and the antimicrobial effect during storage was more noticeable when the coating was applied before inoculation.
The tensile strength, percentage elongation, solubility in water cxu, and water vapor permeability of the antimicrobial film were 2.44 ± 0.19 MPa, 6.40 ± 1.13 per cent, 3.19 ± 0.90 per cent, and 3.18 ± 0.63 gmm/kPa hm(2), respectively. Thus, the antimicrobial DMM films have been shown to have potential as food wraps or coatings to control the growth of L. monocytogenes.
6. Tulasi:
The increasing incidence of drug-resistant pathogens and host toxicity of existing anti-fungals attract attention toward the efficacy of natural anti-fungal products in muco-cutaneous infections and combinational therapies. The leaves of Ocimum sanctum are found to be antiseptic in nature. Basil essential oils and their principal constituents were found to exhibit antimicrobial activity against a wide range of Gram-negative and Gram-positive bacteria, yeast, and mold and also possess anti-viral properties.
It inhibits the growth of E. coli, B. anthracis and M. tuberculosis. Its anti-tubercular activity is one-tenth the potency of streptomycin and one-fourth that of isoniazid. In vitro studies have shown the volatile oil of basil to possess anti-bacterial, antifungal, and antiviral activity. It is also believed to act as a carminative, relieving intestinal gas, and as a mild diuretic, though these actions have yet to be definitively proven. The essential oils of the aerial parts of Ocimum basilicum, an endemic medicinal plant growing in China was found to be of potential use as an antimicrobial agent to control S. Enteritidis in food.
Preparations containing tulsi extract significantly shorten the course of illness, clinical symptoms and the biochemical parameters in patients with viral hepatitis and viral encephalitis. The anti-bacterial action of tulsi on the pathogenic organisms – Streptococcus, Staphylococcus, P. pyrogenes, E.coli and Cornyebacterium has also been proved. It has been mentioned that irrigating the wound with infusion of leaves of Ocimum sanctum destroys the infective organisms in the wound and hastens the healing process. Oil obtained from leaves has a bactericidal property and kills certain maggots.
The leaves of the basil yield an essential oil, which contains eugenol, carvacrol, methyl eugenol and caryophyllene. It has the property of destroying bacteria and insects. Antimicrobial activity of the essential oil has been shown against M. tuberculosis and S. aureus in vitro and other bacteria and fungi. An excellent study of oils from four types of Ocimum species, reported inspite of certain variation, all the oils were found to have antimicrobial activity at fairly low dilutions.
Two concentrations of these extracts (30 mg and 60 mg) were tried against the enteric pathogens and C. albicans by Agar diffusion method. Wide zones of inhibition were observed at 60 mg concentration of extract. Aqeous extract showed wider zone of inhibition for Klebisella, E. coli, Proteus and S. aureus when compared to alcoholic extract which showed wider zone for Vibrio cholerae.
The essential oil obtained from Ocimum sanctum with a high content of methyl chavicol (44.63 per cent) and linalool (21.84 per cent) have significant anti-fungal activity against Candida, including azole-resistant strains, advocating further investigation for clinical applications in the treatment of fungal infections. In another report Khan et al. (2010b) found linalool to be the most active constituent of essential oil of tulasi against two of the most prevalent Candida species causing candidiasis, C. albicans and C. tropicalis.
Inhibition of H+ extrusion appeared to be a synergistic function of the lead molecules. Similarly, at the 4 per cent concentration of tulsi extract, the widest zone of inhibition of 22 mm against S. mutans was observed among all the 15 different concentrations of tulsi that were investigated by Agarwal etal. (2010).
The selection of certain combinations of EOs could help to reduce the required amount of essential oils and consequently reduce any adverse sensory impact in food. Bassole et al. (2010) found that the essential oils from leaves of Lippia multiflora, Mentha x piperita and Ocimum basilicum with high phenolic contents were the most effective antimicrobials.
Suppakul et al. (2003) suggested the possible future use of basil in food preservation as the active slow release antimicrobial coating component of an active package.