Cannabis sativa L. and its antimicrobial properties – A review

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11. Cannabis sativa L. and its antimicrobial properties – A review
Martyna Głodowska, Malgorzata Łyszcz
Institute of Soil Science and Plant Cultivation – State Research Institute, Pulawy, Poland
Supervisor: dr. Anna Gałązka
Martyna Głodowska: mglodowska@iung.pulawy.pl
Key words: hemp, cannabis, metabolites, THC, CBD,
Abstract
Cannabis sativa L. is a very potent plant that exhibit many interesting features. Although,
presently it is mainly perceived as a narcotic, not many knows that it is also a great source of fiber
and a powerful medicinal plant. The metabolic profile of the cannabis is extremely rich. More than
480 active compounds have already been isolated, among which 180 belong to the cannabinoids
family. The most studied secondary metabolites are the delta-9-tetrahydrocannabinol (Δ9-THC) which
is known to have psychoactive properties, and the cannabidiol (CBD) known for its medicinal
potential. Antimicrobial properties are attributed mostly to some of these active compounds. Several
studies investigated these properties. Therefore, the goal of this paper is to review available scientific
data about the antibacterial and antifungal properties of the cannabis extracts.
Introduction
Cannabis sativa L. is an annual herbaceous plant that belongs to the Cannabis genus,
a species of the Cannabaceae family. Originating from Central Asia cannabis is one of the oldest
psychoactive plant known to man But also it has been used all over the world either as a medicinal
plant or as a source of food and fibers (Jiang 2006). One of the first use of this plant was reported in
China: archeological findings pointed out that cannabis was cultivated for fibers and further used in
textiles, ropes and paper production, since 4000 B.C. (Zuardi 2006). In Europe, cannabis was
introduced by Muslims in paper manufacture techniques, first in 1150 in Spain and later in Italy
(Aldrich 1997). Although cannabis is presently perceived mostly as a recreational drug, the plant has
been appreciated and applied in ancient medicine since centuries. The first written information about
the medicinal use of cannabis comes from ancient China, in the oldest pharmacopoeia dated from the
first century of this Era. At the time cannabis was used in the treatment of rheumatic pain, intestinal
constipation, disorders of the female reproductive system, malaria, and other health problems (Touwn
1981). Some sources reports that cannabis was used in the twentieth century B.C in Egypt to treat
sore eyes. In India, before the tenth century B.C., bhang, (edible preparation of cannabis, traditionally
used in food and drink for centuries) was used as an anesthetic and anti- phlegmatic (Sachindra and
Pradhan 1977). It is still used among Hindu and Muslims as spasmolytic, analgesic in mental
conditions and to increase resistance to severe physical stress (Mechoulam and Lander 1980). It is not
uncommon that cannabis is recommended to patients suffering from rabies, cholera, rheumatism, and
tetanus. In the middle of 19th century in Western Europe, cannabis gained some attention in the
medical science. Later, in 1860, the first clinical conference about cannabis took place in the United
States and afterwards many scientific papers have been published (Zuardi 2006). The situation
changed when in 1942 cannabis was removed from United States Pharmacopoeia and lost its medical
statute due to its potential to lead to” insanity” (Fankhauser 2002). Following the US, most of
European countries adapted in 1971 the Convention on Psychotropic Substances instituted by United
Nations by which cannabis became illegal (Amar 2006). It is the main reason why cannabis gained a
bad reputation, interest in this plant drastically decreased and the access became limited to the black-
market. Since a few years however, an increasing number of scientific evidences demonstrate the
efficiency of cannabinoids in the treatment of epilepsy, Parkinson disease, analgesia, antiemetic
effect, appetite disorders, multiple sclerosis, Tourette’s syndrome and other neurological diseases,
carefully reviewed by Amar (2006) in “Cannabinoids in medicine: A review of their therapeutic
potential”. Nowadays, many countries cultivate cannabis for the fiber and seeds production.

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Furthermore, an increasing number of countries have legalized the medicinal use and cultivation of
plants with an increased THC and CBD content. New varieties with desired characteristics and
suitable for certain climate conditions are constantly being developed. Therefore, cannabis becomes
a very important crop of great potential and economical value. Most of the available literature
concerning cannabis rather describes its medical properties and its use in clinical research. Similarly,
an important number of studies focus on psychological effects for humans. Besides that there is quite
a lot known about its antimicrobial activity against human pathogens but only little is known about
its antimicrobial properties against crop pathogens. Therefore the main goal of this review is to gather
scientific data about the inhibitory effect of cannabis and some of its secondary metabolites on the
microorganisms that cause some of the crop diseases. Although cannabis is mostly know for it
medicinal and psychoactive properties it is widely used as a source of fibers in textile productions.
Furthermore, hemp (cannabis grown for industrial purposes) gain recently some importance as a bio-
composite material used for construction and insulation (National Non-Food Crops Centre). Whole
seeds and seed oil are consumed by human, seeds and leaves are frequently used as a feed to animals.
Moreover, seed oil and stalks can be burned as fuel (Clark 2002).
Cannabis active compounds
Cannabis sativa L. is known to have numerous active compounds representing different
chemical classes. Some of them belong to primary metabolites, for example, amino acids, fatty acids
and steroids, while cannabinoids, stilbenoids, flavonoids, lignans, terpenoids, and alkaloids belongs
to secondary metabolites. Generally, the metabolic profile of this plant is extremely rich, more than
480 compounds have been discovered, from which 180 belong to cannabinoids family (Fischedick et
al. 2010). Cannabinoids are usually a group of compounds build of 21 carbons (C21) and they are in
the form of carboxylic acids. The cannabinoids are the most known among secondary metabolites of
cannabis (Amer 2006). The classical cannabinoids are usually concentrated in the viscous resin
produced in structures known as glandular trichomes (Figure 2).
Tetrahydrocannabinol (Δ9-THC) (Figure 1a) is the most studied among them and it attracts
lot of attention due to its psychoactive properties. On the other hand cannabidiol (CBD) (Figure 1b)
is a non-psychoactive cannabinoid that gained lot of interest in recent years due to the increasing
number of evidences demonstrating its efficiency in the treatment of several neurological diseases.
The concentration of active compounds depends on many factors such as variety, age, tissue type,
growing conditions, harvest time as well as storage conditions. Hemphill et al. (1980) found that the
quality as well as quantity of cannabinoids varies importantly between organs of geographically
distinct hemp plants. It the analysis of the leaves of different ages it was demonstrated that the
youngest leaves from the upper part of the flowering plant contained the highest concentrations of
cannabinoid. Some study report that the production of cannabinoids increases in plants under stress
conditions (Pate 1999). Also, it was reported that hemp grown in the northern latitudes has usually
higher concentration of Δ9-THC and CBD (Leizer et al. 2000). Cannabinoids are found in all parts of
hemp organs, however the highest concentrations are found in the resinous exudate of flowering tops
(Figure 2).
Theoretically all genotypes of industrial hemp contain Δ9-THC. Nonetheless, unlike
marijuana (cannabis with the high content of THC, used as a recreational drug), industrial cultivars
contain minimal amount of THC, usually not exceeding 0.2% (w/v), which is about 50 times lower
than that of marijuana (Nissen et al. 2010). Most of available studies assessing antimicrobial
properties of plant extracts, based on the high-THC varieties, which are known to have powerful
antimicrobial characteristics (Appendino et al. 2008). Nevertheless, remarkably little studies focus on
the antimicrobial features of compounds isolated from low-THC varieties, which are much more
common and can be cultivated without any legal restrictions.

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Figure 1. Two most important compound from cannabinoid family
a) cannabidiol (CBD) and b) tetrahydrocannabinol (Δ9-THC)
Figure 2. Phenology of Cannabis plant and its inflorescence

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Cannabis and its antibacterial activity
For a long time cannabis has been regarded as possessing an antibacterial activity against
a wide range of pathogenic bacteria as well as against some fungi. The antibacterial character is
contributed mainly from Δ9-THC and CBD. However number of studies demonstrated that plant
extracts or essential oils also present this activity. Wasim and coworkers (1995) tested ethanol and
petroleum cannabis extracts prepared out of leaves against different microorganisms. The results
showed that the extracts have strong inhibitory effects on both Gram positive (Baccilus subtilus,
Baccilus pumilus, Staphlococcus aureus, Micrococcus flavus) and Gram negative bacteria (Proteus
vlugaris, Bordetella bronchioseptica). The antibacterial activity of extracts was compare with the
effect of the common antibiotic Celphalexin. The results were comparable, however the concentration
of leaf extract was 250 times higher than the concentration of the antibiotic. It can be explain in two
ways. First of all the plants that were used for this study were wiled varieties with unknown content
of cannabinoids, therefore the concentration of active compounds could be very low. Second of all
the extracts were prepared out of leaves. Although cannabis leaves can contain some cannabinoids,
it is well known that the highest concentration of these substances are usually found in the
inflorescences. Nissen et al. (2010) assessed the in-vitro antimicrobial activity of the essential oils
extracted from the inflorescence of three hemp varieties of low-THC content. The antimicrobial
activity was tested against Gram (+), opportunistic and moderate pathogenic bacteria such as
Clostridium spp. and Enterococcus spp., and against Gram (−), phytopathogens bacteria including
Pseudomonas spp. and Pectobacterium spp. Results showed that oil made of the Futura variety was
the only oil that was able to inhibit all Garam (+) and Gram (-) bacteria, as well as yeasts.
Characterization of essential oils revealed that this variety had a significantly higher concentration of
terpinolene compare to the three others. Therefore, it was assumed that the antimicrobial activity was
attributed to this compound. The results suggest that although Δ9-THC and CBD are the most studied
compounds, there are still many compounds out of 480 already discovered in the cannabis plant that
have not yet been tested for antimicrobial properties. It is possible that some of these substances are
even more efficient in antibacterial agents. Furthermore, the interactions between compounds of
essential oils are still not clear. It is highly probable that the synergic and antagonistic effects of oil
compounds exist and are the cause of different activities of the oils. Indeed, the synergistic activity of
some monoterpens, such as terpinolene and pinenes, have been already reported (Gallucci et al. 2009).
Ali et al. (2011) studied the effect of Cannabis sativa L. seed oil as well as petroleum ether and
methanol extracts of the whole plant on two Gram (+) organisms (Bacillus subtilis, Staphylococcus
aureus), and two Gram (-) organisms (Escherichia coli, Pseudomonas aeruginosa). The Cannabis
sativa seed oil demonstrated a strong antibacterial activity (21 - 28 mm) against Bacillus subtilis and
Staphylococcus aureus, and moderate activity (15 mm) against Escherichia coli and Pseudomonas
aeruginosa (16 mm). These results are similar to those reported by Wasim et al. (1995), although the
extracts were prepared from different plant materials. Cannabis seeds are known for their nutritional
values and they are being considered as a great source of fatty acids, however the concentration of
secondary metabolites is rather low. Whole plant extracts based on methanol and petroleum ether
showed a slightly higher antimicrobial activity, particularly in the case of Bacillus subtilis where the
inhibition zone was 29 and 28 mm respectively.
Antifungal properties of cannabis
Few researchers investigated antifungal properties of the cannabis and its secondary
metabolites. Although this effect is not as extensively studied and as strongly pronounced as in the
case of antibacterial activities, some papers report that plant extracts can be successfully used in the
control of pathogenic fungi. Wasim and coworkers (1995) demonstrated that the ethanol and
petroleum extract of cannabis leaves are effectively inhibiting the growth and development of the
common human pathogenic fungi Candida albicans and Aspergillus niger, responsible for the black
mould in fruits and vegetables. The zone of inhibition in both cases was significantly higher compare

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to antifungal antibiotic (Nystatin), however the concentration of the leave extract was 10 times higher
compare to antibiotic. Similarly, Ali and coworkers (2011) studied the effect of Cannabis sativa L.
seed oil as well as petroleum ether and methanol extracts of the whole plant on two fungi Aspergillus
niger and Candida albicans. The seed extract as well as the whole plant methanol extract turned out
to be inactive against the two fungi tested, but the whole plant petroleum ether extract showed a
modest activity against Candida albicans. Pal and coworkers (2013) tested the extracts of eleven weed
plants for their antifungal activity against seed-borne phytopathogenic fungi Alternaria SPP. All
plants demonstrated antifungal properties, some performed significantly better than others. Although
Cannabis sativa L. was not the most efficient among studied plants, it did show quit height percentage
of mycelial growth inhibition. Among 5 different types of extracts, the acetone based extract turned
out to be the most powerful antifungal agent.
Conclusion
Cannabis sativa L. is a very powerful plant which present many interesting properties due
to its rich metabolic profile. Although most people associate it with drugs, many scientific data
showed that its medicinal features should not be neglected. Number of studies showed its potential as
an antimicrobial agent. An important amount of them focus on antibacterial properties, however there
is less studies analyzing antifungal properties. The physiology of cannabis is already well understood.
It is know that the highest concentration of active compounds is concentrated in inflorescent, therefore
it is surprising that in most studies assessing antimicrobial properties of cannabis, leaves and seeds
are usually used to prepare extracts. Furthermore, many of the studies look at the response of the same
pathogenic fungi such as Aspergillus and Candida, or bacteria such as Baccilus or Staphlococcus.
Due to environmental issues associated with pesticides use, many studies nowadays focus on finding
alternatives to synthetic disease control chemicals. Natural plant extracts might be one of them.
Therefore, future studies should search for cannabis use against plant pathogenic bacteria and fungi
instead of focusing on the same model organisms.
References:
Aldrich M. (1997) History of therapeutic cannabis. In: Mathre ML, eds. Cannabis in medical practice.
Jefferson, NC: Mc Farland: 35-55.
Ali EM, Almagboul AZ, Khogali SM, et al. (2012) Antimicrobial Activity of Cannabis sativa
L. Chinese Medicine. 1;3(1):61.
Amar MB (2006) Cannabinoids in medicine: A review of their therapeutic potential. Journal of
Ethnopharmacology 105: 1–25.
Appendino G, Gibbons S, Giana A, et al. (2008) Antibacterial Cannabinoids from Cannabis sativa:
a structure–activity study. J Nat Prod. 71:1427–30.
Clarke RC (2002 )Filed Interview Schedule and Questionnaire for Investigating Cannabis Use,
Rockville National Institute on Drug Abuse,” Journal Indian Hemp, Vol. 7, No. 1, 83-88.
Fankhauser, M (2002) Chapter 4: history of cannabis in Western medicine. In: Grotenhermen, F.,
Russo, R. (Eds.), Cannabis and Cannabinoids: Pharmacology, Toxicology and Therapeutic
Potential. The Haworth Integrative Healing Press, New York, 37–51.
Fischedick JT, Hazekamp A, Erkelens T et al. (2010) Metabolic fingerprinting of Cannabis sativa L.,
cannabinoids and terpenoids for chemotaxonomic and drug standardization purposes.
Phytochemistry 71:2058–2073.
Gallucci MN, Oliva M, Casero C, et al. (2009) Antimicrobial combined action of terpenes against the
food-borne microorganisms Escherichia coli, Staphylococcus aureus and Bacillus cereus. Flavour
and Fragrance J, Vol. 24(6): 348–54.
Hemphill JK, Turner JC, Mahlberg PG (1980) Cannabinoid content of individual plant organs from
different geographical strains of Cannabis sativa L. Journal of Natural Products, 43(1), 112-122.
Jiang HE, Li X, Zhao YX et al. (2006) A new insight into Cannabis sativa (Cannabaceae) utilization
from 2500- year-old Yanghai Tombs, Xinjiang, China. J Ethnopharmacol 108:414–422.

Badania i Rozwój Młodych Naukowców w Polsce – Agronomia i ochrona roślin
82 | S t r o n a
Leizer C, Ribnicky D, Poulev A. et al. (2000) The composition of hemp seed oil and its potential as
an important source of nutrition. Journal of Nutraceuticals, functional & medical foods, 2(4), 35-
53.
Mechoulam R, Lander N (1980) Cannabis a Possible Source of New Drugs. Journal Pharmacy
International, Vol. 1, 1980, 19-21.
Nissen L, Zatta A, Stefanini I, et al. (2010) Characterization and antimicrobial activity of essential
oils of industrial hemp varieties (Cannabis sativa L.). Fitoterapia. 31;81(5):413-9.
NNFCC Renewable Building Materials Factsheet (2008) An Introduction". National Non-Food Crops
Centre. February 21, Retrieved 2011-02-16.
Pal GK, Kumar B, Shahi SK. (2013) Antifungal activity of some common weed extracts against
phytopathogenic fungi Alternaria spp. International journal of universal pharmacy and life
sciences. 24;3(2):6-14.
Pate DW (1999) The phytochemistry of Cannabis: its ecological and evolutionary implications. In:
Ranalli P (ed) Advances in hemp research. Haworth Press, NY, 21–42
Sachindra N, Pradhan A (1977) Marijuana Drug Abuse Clinical and Basic Aspects. The C.V. Mosby
Company, Saint Louis, pp. 148-173.
Touwn M. (1981) The religious and medicinal uses of Cannabis in China, India and Tibet.
J Psychoactive Drugs: 13: 23-34.
Wasim K, Haq IU, Ashraf M (1995) Antimicrobial Studies of the Leaf of Cannabis sativa L.,”
Pakistan Journal of Pharmaceutical Sciences, Vol. 8, 22- 38.
Zuardi AW (2006) History of cannabis as a medicine: a review. Rev Bras Psiquiatr. 28:153-157.