The term ‘antimicrobial agent’ refers to specific synthetic or natural substances such as drugs, chemicals, or extracts that have the ability to either kill or inhibit the growth of microbes, including bacteria, fungi and algae [1]. Antibiotics have played a tremendous role in attenuating mortality and morbidity of humans since the antibiotic era started at the early of the last century [2,3]. The introduction of antibiotics into therapeutics has extended the average human life expectancy by around 23 years in just 100 years [4]. However, because of widespread misuse of antibiotics, bacteria have developed mechanisms to escape from antimicrobial agents. Although antibiotic resistance is a natural phenomenon [5] (it was observed before the extensive use of penicillin [6]), its pace has been accelerated due to overuse, inappropriate prescribing and extensive agricultural use [7]. Today, antimicrobial resistance is one of the greatest challenges for global health, and the World Health Organization (WHO) has declared it one of the top threats for humanity [8]. In the United States, more than 2.8 million people are infected by antibiotic-resistant bacteria, with over 35,000 deaths every year. An estimated USD $4.6 billion is spent to fight only six multidrug-resistant pathogens [9]. Globally, drug resistant infections cause half a million deaths each year, and the toll is suspected to exceed 10 million by 2050 [10]. Many first-line antibiotics are predicted to be ineffective by 2025 and, consequently, the ‘post antibiotic era’ will start soon, or may already has started [9,11]. Though the discovery of new antibiotics is critical, concerning the pace of antibiotic resistance, unfortunately, a huge innovation gap has been created in antibiotic drug discovery after the end of its ‘golden era’ between 1950 and 1970 [12]. It is almost 50 years since the last new antibiotic was discovered, and research funding to find new antibiotics has been drastically reduced in both the pharmaceutical and academia domain, which considering such investment nonprofitable during an economic crisis [13,14]. In 2017, the WHO published a global priority pathogen list comprising 12 species of bacteria categorized by critical, high, and medium antibiotic resistance, with the aim of ensuring quick R&D responses, guiding strategic directions and achieving new antibiotics for urgent public health needs (Figure 1) [15]. The United States Centers for Disease Control and Prevention’s (CDC) 2019 AR Threats Report listed 18 germs, including bacteria and fungi, on three levels of human health concern: urgent, serious, and concerning, as a measure of estimation of antibiotic resistance burden in the USA [9]. Today, the world is witnessing how an emerging infectious disease such as the COVID-19 pandemic, caused by Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2), can result from a lack of appropriate medicines, in addition to many other causes. The pandemic led to more than 4.8 million documented deaths globally in the 23 months up to 6 October 2021 [16].

In the history of the treatment of infectious diseases, cannabis has been used for thousands of years without knowledge of the scientific background of its effects [17,18]. A substantial amount of research has documented that C. sativa possesses hundreds of secondary metabolites including cannabinoids, terpenes and phenolic compounds [19] which have pharmacological properties in anticonvulsant therapy, appetite stimulation, neurodegenerative diseases, pain treatment, skin pathologies and infectious diseases [20]. Cannabinoids and terpenes, or essential oils (EO) enriched with these, are well known to confer anti-inflammatory effects in mammals during infectious diseases [21,22,23]. So far, 545–550 known compounds, of which about 177 phytocannabinoids, about 200 terpenes and nearly same number of phenolics, have been identified from C. sativa [20,24,25,26]. Bonini et al. reviewed the pharmacological potential of cannabinoids, stating that preclinical and clinical studies of cannabinoid compounds are beneficial for treatment of pain, colitis, spasticity, nausea and vomiting, anorexia, sleep disorders, anxiety, epilepsy, and Alzheimer’s disease [24]. Since cannabinoids can modulate the immune response through binding CB1 and CB2 receptors (a G-protein-coupled receptor densely located in the immune tissue, nervous tissue and brain), their role in infectious diseases has been discussed critically in many scientific publications [27,28,29,30,31,32]. However, the antimicrobial activity of cannabinoids, extracts and EOs from C. sativa is not unexpected, as many secondary metabolites of plants exhibit bioactivity against numerous pathogenic bacteria and fungi [33,34,35]. There is also fragmentary evidence in the literatures that cannabis compounds have efficacy against some viruses [25,32].

2. Antibacterial Activity of Cannabinoids and C. sativa

2.1. Historical Overview

The antibacterial efficacy of C. sativa was scientifically revealed in a dissertation by Krejci in 1950 [36] and preliminary results were published later stating that extracts were effective against only Gram-positive bacteria (GPB) [37,38]. Independently, the microbial inhibitory property of seeds of hemp was observed by Ferenczy in 1956. The diffused compounds from whole seeds produced an inhibitory zone against GPB in culture medium [39]. Later, resinous organs of the plant, such as the seeds and leaves, exhibited a considerable amount of antibacterial activity against GPB in an acidic culture medium, but were found ineffective against gram negative bacteria (GNB), yeasts and molds [40]. It was observed that the antibacterial activity depended on the intensity of the hashish reaction, which indicated the activity might come from psychoactive Δ⁹-tetrahydrocannabinol (THC), though other cannabinoids from C. sativa had not been identified at that time [40]. The following sections include some subsections of the WHO priority list, as well as some non-listed pathogenic bacteria.

2.2. Antibacterial Activities of Cannabinoids against Pathogens in the WHO’s Priority List

Cannabinoids and C. sativa extracts have substantial activity against several resistant bacteria in the WHO’s current priority list (Table 1). All major cannabinoids, including cannabidiol (CBD), THC, cannabigerol (CBG), cannabichromene (CBC), cannabinol (CBN), their derivatives like cannabidiolic acid (CBDA), cannabichromenic acid (CBCA), and even extracts and EOs, inhibit MRSA including the epidemic-causing EMRSA 15 and EMRSA 16. Methicillin-resistant Staphylococcus aureus (MRSA) are resistant to all known beta-lactam antibiotics [41], and even to linezolid, daptomycin and vancomycin [42]. Extensive work has been published recently by Farha et al., enlightening the antibiotic potency of major cannabinoids against MRSA regarding their efficacy to inhibit biofilms and persister cells [43]. Biofilms represent a subpopulation of bacteria that secure themselves against adverse situations, and persister cells, which are dormant and non-dividing, are common sources of antibiotic tolerance to MRSA [44,45]. When a biofilm forms, bacterial cells acquire 10–1000 times more resistance to antibiotics [46]. Biofilms and persisters of MRSA are considered important virulence factors, especially when formed on necrotic tissues and medical devices [43]. All five major cannabinoids can obstruct the formation of biofilms, destroy preformed biofilms and eradicate stationary phase cells of MRSA. MRSA persisters, which are highly resistant to gentamicin, ciprofloxacin, and vancomycin [47] can be killed by cannabinoids, and notably by CBG, at a concentration of 5 µg/mL [43], whereas oxacillin and vancomycin are ineffective [48]. The MIC₉₀ of CBG against MRSA strains is favorable compared to conventional antibiotics [43]. The efficacy of CBG against biofilms and persisters of MRSA was found to be MIC 2 µg/mL in vivo, in a murine systemic infection model. CBG was found to be hemolytic at only 32 µg/mL, many-fold higher than MIC [43].

Table 1. Activity of cannabinoids and C. sativa against the resistant pathogens enlisted in WHO’s current priority list.

Pathogen	Compound/Extract/EO	Activity	Reference Antibiotic		Ref
			Antibiotic	Activity
Gram+ve
Enterococcus faecium	EO, α-humulene, α-pinene, β-pinene, myrcene	MIC 0.75–1.87 (%v/v) MBC 1.39–2.83 (%v/v)			[93]
E. faecium	EO, α-humulene, α-pinene, β-pinene, myrcene	MIC 1–4 µg/mL	Ciprofloxacin	MIC 8 µg/mL	[94]
EMRSA 15 and EMRSA 16	CBD, THC, CBG, CBC, CBN	MIC 0.5–2.0 µg/mL			[95]
MRSA	4-acetoxy-2-geranyl-5-hydroxy-3-n-pentylphenol and 8-hydroxycannabinolic acid A	IC50 6.7 µM	Ciprofloxacin	IC50 0.4 µM	[96]
MRSA	CVDVM	MIC 15.6 µM			[52]
MRSA	CBCA	MIC 3.9 µM			[52]
MRSA	CBD	MIC 1 µg/mL	Tobramycin, Meropenem, Ofloxacin	MIC 1, 16, 64 µg/mL (respectively)	[50]
MRSA	CBD	MBEC 2–4 µg/mL			[49]
MRSA	CBD analogs	MIC 0.25–64.0 µg/mL	Vancomycin, Daptomycin, Mupirocin	MIC 0.125–2.0 µg/mL	[49]
MRSA	CBD, CBN, CBC, CBDV and Δ1 & 9-THC	IC50 5.8–10.6 µM	Ciprofloxacin	IC50 9.33 µM	[97]
MRSA	CBDA	MIC 4 µg/mL	Tobramycin, Meropenem, Ofloxacin	MIC 1, 16, 64 µg/mL (respectively)	[50]
MRSA	CBG	MIC 2 µg/mL and MBEC 4 µg/mL			[43]
MRSA	EO	IC50 0.82–4.22 µg/mL			[98]
MRSA, VISA, VRSA, E. faecium	CBD	MIC 1–2 µg/mL	Vancomycin, Daptomycin, Trimethoprim, Mupirocin, Clindamycin	MIC 0.125 to >64 µg/mL	[49]
Streptococcus pneumoniae	CBD	MIC 1–4 µg/mL	Vancomycin, Daptomycin, Trimethoprim, Mupirocin, Clindamycin	MIC 0.25 to >64 µg/mL	[49]
VRE	CBCA	MIC 7.8 µM			[52]
Gram -ve
Escherichia coli	Aqueous extract	MIC 7.14 mg/mL	Ciprofloxacin	MIC < 0.12 mg/mL	[99]
E. coli	N-p-trans-coumaroyl-tyramine	IC50 0.8 µg/mL	Ciprofloxacin	IC50 0.01 µg/mL	[100]
E. coli	Seed extract	MIC 25 µg/mL			[67]
E. coli and Salmonella typhimurium	Seed extract	Growth inhibition at 1 mg/mL			[101]
E. coli, and Pseudomonas aeruginosa	EO	MIC 1.2 mg/mL		MIC 0.062–1.0 mg/mL	[60]
Enterobacter aerogenes	Seed extract	MIC 2.5 mg/mL			[101]
Neisseria gonorrhoeae	CBD	MIC 1–2 µg/mL	Vancomycin, Levofloxacin, Meropenem, Gentamicin	MIC 0.002–4.0 µg/mL	[49]
N. gonorrhoeae	CBD analogs	MIC 0.03–16.0 µg/mL	Mupirocin Colistin	MIC 1–32 µg/mL	[49]
P. aeruginosa	Aqueous extract	MIC 7.14 mg/mL	Ciprofloxacin	MIC 1.23 mg/mL	[99]
P. aeruginosa	Whole plant extract	MIC 12.5 µg/mL			[67]

The rapid bactericidal activity of CBD was observed (<3 h) at 2 µg/mL [49], and the effect resembled that of the natural nonionic detergents, saponins [50]. CBD and CBDA showed no toxicity to human keratinocyte cells at up to seven and four-fold higher concentration of their respective MIC against MRSA (Table 1) [50]. CBD could potentiate bacitracin activity, reducing its MIC 64-fold against resistant bacteria, including MRSA [51]. The combination affected morphological changes of the pathogen, impaired cell division and induced membrane irregularities. No synergistic or antagonist effect was seen on MRSA resulting from CBD with conventional antibiotics including vancomycin, methicillin, clindamycin, tobramycin, teicoplanin, ofloxacin and meropenem [50]. Because of the hydrophobic nature of CBD, it cannot attack enough of the bacterial membrane to enhance the uptake of antibiotic drugs and does not interfere the mechanism of action of last-resort antibiotics.

In an in vivo study, CBCA showed more potent and faster bactericidal activity than vancomycin with lower a toxicity level to the mammalian cell lines A549 and HepG2. CBCA and cannabidivarin methyl ester (CBDVM) rendered minimum toxicity concentration (MTC), greater than 100 µM on both cell lines, which is far higher than their respective MIC against MRSA (Table 1). Additionally, compared to vancomycin, the compound exhibited more biocidal activity with higher a bacterial load. Rapid bactericidal activity of CBCA could reduce treatment time and provide less opportunity for emergence of bacterial resistance. A time-kill assay showed considerable reduction of CBCA activity after 8 h of exposition to MRSA. The activity of CBCA was observed against both the exponential and stationary phases of MRSA and was independent of their cellular metabolism [52]. The killing activity of many antibiotics is attributed to their effect on dividing bacteria cells, which is crucially interrupted by the stationary phase of MRSA, resulting in higher morbidity in nosocomial infections [53]. Synergistic effects of phytocannabinoids and terpenoids are reported in the treatment of infections related to MRSA and fungi [54]. The penetration of bacteria cell membranes differs among cannabinoids, which results in the non-identical effects of these compounds [50].

In contrast to pure active compounds, C. sativa extracts and EOs sometimes have even greater activity against resistant pathogens as a result of probable synergism. Drug-resistant clinical isolates, including MRSA, vancomycin-resistant Staphylococcus aureus (VRSA) and vancomycin-intermediate Staphylococcus aureus (VISA) demonstrated susceptibility to alcoholic C. sativa extracts [55,56]. A profound inhibitory efficacy was achieved when an ethanolic extract of C. sativa leaves was combined with a Thuja orientalis leaf extract in a 1:1 ratio. The synergism was obtained due to the antibacterial effect of the phenolic compounds quercetin, gallic acid and catechin present in the leaf extract [55].

Gram-negative organisms generally exhibit more resistance to antibiotics due to their distinctive structure. They are dominant killers in intensive care units showing resistance to wide-spectrum antibiotics including third-generation cephalosporins and carbapenems [57]. They differ in structure from GPB since they have an outer membrane containing lipopolysaccharide (LPS)/endotoxin, which provides the pathogen intrinsic resistance against antibacterial agents [58]. This acts as an important barrier and provides protection by resisting the penetration of toxic antibiotics and innate host immune molecules [59].

However, GNB, whose outer membrane is permeable, are susceptible to cannabinoids [43]. All the five major cannabinoids showed synergism against clinically isolated multidrug-resistant GNB, including Klebsiella pneumoniae, Acinetobacter baumannii, Pseudomonas aeruginosa and Escherichia coli when used with polymyxin B at sublethal concentration [43,49]. The activity against K. pneumoniae was increased for EO exhibiting full synergism with addition of ciprofloxacin [60]. Naringenin with EO was found to be bactericidal against drug resistant Helicobacter pylori [61]. Aqueous and solvent extracts of leaf, stem and roots also displayed substantial activity against K. pneumoniae, A. baumannii and Haemophilus influenzae [62].

CBD has strong inhibitory efficacy on release of membrane vesicles (MV) from E. coli VCS257 and can boost bactericidal power of vancomycin against E. coli, to which it shows resistance [63]. MVs are nanosized spheres composed of lipid membranes derived from the outer membrane of bacteria that can cause an extra layer of protection against antibiotics [64,65]. EO exhibits synergistic effect against E. coli, and P. aeruginosa in combination with ciprofloxacin [60]. P. aeruginosa is resistant to antibiotics including beta-lactams, aminoglycosides and quinolones [66]. The efficacy of solvent extracts of C. sativa against P. aeruginosa in terms of inhibitory zone is comparable with gentamicin [67], ampicillin [68] and ciprofloxacin [60]. Notably, the level of sensitivity of the extracts in qualitative tests is not equipollent since their polarity and solubility change their diffusivity through media [69,70]. However, in many other investigations, the activity of C. sativa was shown against P. aeruginosa [62,71,72,73,74,75], E. coli [62,67,68,72,76,77,78,79,80,81,82], Salmonella species [76,80,83,84], Shigella species [76,82], K. pneumoniae [82], Acinetobacter calcoaceticus [79], Morganella morganii [62] and Serratia marcescens [84].

The ability of cannabinoids to modulate physiological and pathophysiological activities can hinder bacterial conjugation by targeting plasmid DNA [85]. Conjugation is one of the major processes of acquiring antibiotic resistance and involves replication and transfer of an extra piece of bacterial DNA plasmid into a recipient bacterium [86]. Plasmids contain genes to express resistance to antibiotics. Δ⁹-THC, CBN and CBD impaired plasmid transfer activity near to zero for pKM 101 and TP 114 [85]. Tetrahydrocannabinolic acid (THCA) reduced plasmid curing activity by 30% in E. coli K12 F’lac strain [87]. Plasmid curing is a process by which the plasmid is eliminated, and the bacteria become susceptible. THCA and some cannabispiro compounds were inhibited transformation of plasmid DNA (pBR322), elimination (F’lac) and transfer (R144) of plasmid from E. coli to E. coli, and even killing plasmid carrying bacteria despite possessing a higher MIC value [88].

Apart from phytocannabinoids, some endocannabinoids (EC) and endocannabinoid-like (EC-like) natural endogenous compounds have good potency against MRSA biofilms. Anamide and arachidonoyl serine, an EC and EC-like natural endogenous compound respectively, did not kill the bacteria in vitro, but inhibited biofilm formation and preformed biofilms of MRSA, altered biofilm-associated virulence factors, and could modify MRSA cell surface characteristics [89]. The compounds also exhibited synergy with different antibiotics including ampicillin, methicillin and gentamicin under both planktonic growth conditions and biofilm formation [90]. Besides, their combination with methicillin impaired slime formation of MRSA [90]. The slime layer is not easily be washed off and can be expressed as a virulence factor [91,92].

2.3. Antibacterial Activities of Cannabinoids against Pathogenic Bacteria Not on the WHO Priority List

C. sativa has broad-spectrum antibacterial efficacy against a number of pathogenic bacteria (Table 2) that are not listed in WHO’s current priority list.

Table 2. Activity of cannabinoids and C. sativa against pathogens other than those on the WHO’s priority list (* collected from foods or food environments).

Pathogen	Compound/Extract/EO	Activity	Reference Antibiotic		Ref
			Antibiotic	Activity
Gram+ve
Bacillus subtilis and Staphylococcus aureus	Leaf extract	MIC 1.56 mg/mL			[81]
B. subtilis, S. aureus and Micrococcus luteus	EO	MIC 1.2–4.7 mg/mL	Ciprofloxacin	MIC 0.015–0.031 mg/mL	[60]
B. subtilis, S. aureus, Mycobacterium smegmatis	CBC, its homologs and isomers	MIC 0.39–3.12 µg/mL			[112]
Clostridium species *, Enterococcus hirae *, Streptococcus salivarius *	EO, α-humulene, α-pinene, β-pinene, myrcene	MIC ≥ 0.8 (%v/v)			[93]
Enterococcus *, Staphylococcus *, and Bacillus species *	EO	MIC ≥ 0.5 µg/mL	Ampicillin, Ciprofloxacin	MIC ≥ 0.25 µg/mL	[94]
Listeria monocytogenes strains *	EO	MIC/MBC 2.5–5.0 μL/mL			[110]
L. monocytogenes *	EO	MIC ≥ 1 µg/mL	Ampicillin	MIC ≥ 0.25 µg/mL	[94]
L. monocytogenes *	EO, α-pinene, Myrcene	MBC ≥ 1024 µg/mL			[111]
Lancefield Group A Streptococcus sp.	Leaf extract	MIC 20 mg/mL MBC 30 mg/mL			[113]
MRSA biofilms *	Seed extract	MIC 1 mg/mL			[101]
MSSA	CBCA	MIC 7.8 µM			[52]
MSSA, VISE, Staphylococcus epidermidis, Staphylococcus pyogenes, Enterococcus faecalis, Cutibacterium acnes, Clostridioides difficile	CBD	MIC 0.5–4.0 µg/mL	Vancomycin, Daptomycin, Trimethoprim, Mupirocin, Clindamycin, Levofloxacin, Meropenem, Gentamicin, Erythromycin, Tetracycline, Mupirocin	MIC 0.03–64.0 µg/mL	[49]
Mycobacterium intracellulare	CBG	IC50 15 µg/mL			[114]
S. aureus	4-acetoxy-2-geranyl-5-hydroxy-3-n-pentylphenol, 8-hydroxycannabinolic acid A	IC50 3.5 µM	Ciprofloxacin	IC50 0.4 µM	[96]
S. aureus	Aqueous extract	MIC 3.57 mg/mL	Ciprofloxacin	MIC 0.62 µg/mL	[99]
S. aureus	Methanol extract	MIC 25 µg/mL			[67]
S. aureus (including multi drug resistant S. aureus 104)	EO	MIC 8 mg/mL			[61]
S. aureus (mature and pre-formed biofilms)	EO	MBEC 24 mg/mL			[61]
S. aureus and E. faecalis	Seed extract	MIC 1 mg/mL			[101]
S. aureus biofilm *	EO	MIC 0.5 mg/mL			[101]
S. aureus planktonic cells *	EO	MIC 1 mg/mL			[101]
S. aureus *	EO	MIC 1.25–5.0 µg/mL			[110]
S. aureus *	EO	MIC 1–4 µg/mL	Ciprofloxacin	MIC 0.5–16.0 µg/mL	[94]
S. aureus, S. epidermidis	CBD, CBDA	MIC 1–4 µg/mL	Torbamycin, Meropenem, Ofloxacin	MIC 0.06–0.5 µg/mL	[50]
SA-1199B (MDR), RN4220 (Macrolide-resistant), XU212 (Tetracycline-resistant)	CBD, CBC, THC, CBG, CBN, Carboxylated versions, Abnormal cannabinoids	MIC 0.5–4.0 µg/mL			[95]
Staphylococcus species	THC, CBD	MIC 1–5 µg/mL			[115]
Staphylococcus, Lactococcus and Bacillus species	CBD, CBN, CBC, CBDV and Δ1 & 9-THC	IC50 2.6–9.2 µM	Ciprofloxacin	IC50 0.003–2.4 µM	[97]
Gram-ve
Moraxella catarrhalis, Neisseria meningitidis and Legionella pneumophila	CBD	MIC 0.25–1.0 µg/mL	Vancomycin, Levofloxacin, Meropenem, Gentamicin	MIC 0.03–32 µg/mL	[49]
Pectobacterium carotovorum subsp. carotovorum *	EO, α-humulene, α-pinene, β-pinene, myrcene	MIC ≥ 1.24 (%v/v)			[93]
Pseudomonas fluorescens and Xanthobacter flavus	CBD, CBN, CBC, CBDV and Δ1 & 9-THC	IC50 3.1–9.3 µM	Ciprofloxacin	IC50 0.15–2.3 µM	[97]
Pseudomonas species	EO(s) and Terpenes	MIC 1.05–1.97 (%v/v)			[93]

CBD has bacitracin activity, reducing its MIC 64-fold against Listeria monocytogenes and Enterococcus faecalis [51]. It can increase the effectiveness of kanamycin against Staphylococcus aureus without affecting MV release [63]. The EO exhibited bactericidal activity against clinically isolated methicillin-resistant Staphylococcus pseudintermedius (MRSP) from dogs suffering from pyoderma [102]. A combination of ciprofloxacin with EO significantly decreased MIC against Bacillus subtilis, S. aureus and Micrococcus luteus due to partial and full synergism [60]. The inhibition pattern of seed extract against S. aureus biofilms is similar to that of vancomycin, and the efficacy was found to be dose-dependent [103]. The bactericidal activity of solvent extracts against penicillin resistant S. aureus was recorded by Kabelik [18,104]. Acidic fractions are responsible for the antimicrobial properties of crude extract of leaves [105]. Leaf extract out-performs chloramphenicol in terms of inhibition zone against the strep-throat-causing Lancefield Group A Streptococcus sp., and its activity is comparable with penicillin and amoxicillin [10], which are commercially used as beta-lactam antibiotics for strep-throat treatment.

Moreover, a considerable number of diffusion tests showed medium to higher activity against S. aureus [67,68,71,74,76,77,79,82,84,105,106], B. subtilis [67,79,80,82,84,105], Bacillus cereus [77,80,84], Bacillus pumilus [105], E. faecalis [77,83,84,107], Micrococcus flavus [105], M. luteus [79,84], Brevibacterium linens, Brochothrix thermosphacta [79] and Methicillin-resistant coagulase-negative Staphylococci (MRCoNS) [56]. The findings indicate that C. sativa can be targeted as a natural source for developing antibacterial drugs.

Like other antibiotics, a plant’s secondary metabolites encounter a barrier at the outer membrane of GNB, and limited efficacy is observed [108]. Nevertheless, many studies show C. sativa having a moderate to large inhibitory zone for Yersinia enterocolitica [79,83,107], Vibrio cholerae [73], Citrobacter freundii CCM 7187 [84], Erwinia carotovora [109], Bordetella bronchioseptica, Proteus vulgaris [105], Aeromonas hydrophyla, Beneckea natriegens, and Flavobacterium suaveolens [79].

It can be assumed that the bioactivity of C. sativa extracts and EOs fundamentally come from compounds such as cannabinoids, phenolics and terpenes [60,101,110]. The anntimicrobial profile of low-level THC content of C. sativa (industrial hemp) is partially related to CBD [94], CBDA [103], phenolics including flavonoids, caffeoyltyramine, cannabisin and polyphenols [99,101] and terpenes including α-pinene, α-humulene, β-pinene, β-caryophyllene, (E) caryophyllene, caryophyllene oxide and myrcene [60,93,94,102,110,111].

3. Antifungal Activity

Both superficial and systemic fungal infections have increased due to the emergence of many immunological dysfunctions in people [116]. The management of fungal infections suffers from the unavailability of drugs, toxicity, resistance and relapse of conditions [117]. Therefore, finding new antifungal drugs to combat fungal infections is a priority. In agreement with the set threshold by Kuete and Dabur to ascribe the antimicrobial and antifungal properties of plant juices [118,119], C. sativa extract, EO and their phytoconstituents possess significant activity against a number of pathogenic fungi and algae (Table 3).

Table 3. Activity of cannabinoids and C. sativa against fungi.

Pathogen	Compound/Extract/EO	Activity	Reference Antibiotic		Ref
			Antibiotic	Activity
Candida albicans	Extract	MIC 0.25 mg/mL			[124]
C. albicans	Extract	MIC 1.42 mg/mL	Fluconazole	MIC 2 mg/mL	[99]
C. albicans	4-terpenyl cannabinolate	MIC 8.5 µg/mL			[125]
C. albicans	8-hydroxycannabinol	IC50 4.6 µM	Amphotericin B	IC50 0.3 µM	[96]
C. albicans	Cannabis and ginger blend	MIC 4.69 mg/mL			[126]
C. albicans	CBDV	IC50 11.9 mM	Nystatin	IC50 1.50 mM	[97]
C. albicans	CBNA	IC50 8.5 µg/mL			[125]
Candida krusei	Cannabinoids	IC50 53.4–60.5 µM	amphotericin B	IC50 0.7 µM	[96]
Candida neoformans	β-caryophyllene/oxide	IC50 1.18–19.4 µg/mL			[98]
Candida species	β-caryophyllene	MIC 1.45–10.0 µg/mL			[98]
Plasmodium falciparum	Cannabinoids	IC50 4.0–6.7 µM	Chloroquine	IC50 0.1–0.5 µM	[96]
P. falciparum	CBNA	IC50 2.4–2.7 µg/mL			[125]
Trichophyton and Arthroderma species	EO	MIC 0.312–6.3 µg/mL	Griseofulvin	MIC 1.26 to >8.0 µg/mL	[123]

Candida albicans, a prevalent opportunistic pathogenic fungus to humans, which is resistant to fluconazole, exhibited higher susceptibility to C. sativa extracts, EO and other compounds. Moreover, EO of C. sativa has a full synergistic effect with fluconazole, resulting in a 16-fold reduction of MIC against Candida spp. [60]. C. albicans is part of a natural microflora that forms asymptomatic colonies on the skin and inside the body and can proliferate if the host has an immunosuppressed condition and cause superficial mucosal and dermal infections [120,121]. Activity against Candida species [67,73,74,105,107] Fusarium spp. [68], Candida neoformans [73] and Aspergillus [68,105,122] are documented. Antifungal activity is cultivar-dependent [123] and also related to the active compounds’ chemical structures [75]. The findings indicate that more intensive study on the fungicidal activity of C. sativa phytoextracts is required for the treatment of fungal infections, especially for external use.