2.2. Bacterial and fungi strains tested

biological or pharmacological screening is even smaller [2]; approximately 20% of the plant species in the world have been investigated for these properties [3]. In this context, dandelion serves as an interesting species with which to unify decades-old information regarding its biological potential against diverse microorganisms. This review gathers the existing results to advance the search for products that could strengthen the domestication and mass produc-

The Taraxacum spp. commonly called dandelion is an herbaceous perennial plant of the Asteraceae (Compositae) family. This common weed is found worldwide, though originally introduced from Eurasia, and can be found growing in parks, gardens, pastures, orchards, roadsides, vegetable gardens, and among agricultural and horticultural crops [4]. Primarily used as food, the role of Taraxacum in traditional medicine was mentioned during ancient times by the Greek physician Dioscorides in the first century and during the renaissance by monks in Cyprus [5]. This plant has been used to treat cystitis, liver and gastric ailments, hepatic and renal detoxification, diabetes, as an anti-inflammatory and anticarcinogenic agent, and, to a lesser extent, as an antimicrobial and antiviral agent, as described in several reviews [6, 7]. Ethnopharmacologically, its use as an antimicrobial agent has been known worldwide among varying cultures, though it has always been administered as a cataplasm (poultice) or infusion.

The traditional antimicrobial uses of Taraxacum worldwide are displayed in Table 1.

avoiding misinterpretation and myths regarding Taraxacum or any other plant.

Asia and Europe have an important historical background regarding the traditional uses of Taraxacum, primarily T. officinale, T. mongolicum, and T. coreanum. This traditional knowledge has been the principal reason for studying the potential uses and crop requirements of Taraxacum; studies in America remain scarce [18]. Due to the unscientific approach often present in oral traditions, uncertainty surrounds whether Taraxacum use effectively treats microbial infection or, instead, treats only the symptoms. Therefore, scientific research is extremely important in

The first antibacterial scientific study for Taraxacum was reported a mere 35 years ago [19]. More than a decade later, studies related to Taraxacum antimicrobial activity gained significant

Species Common use Country Part used Consumption References

Tuberculosis Italy — — [10] Cough Italy — — [11] Bacterial infection Mexico — — [12] Diuretic Chikar Roots Tonico [13]

Brewing

[16, 17]

T. cyprium Catarrh and common cold, cough Greece Roots, leaves — [5] T. mongolicum Urinary tract infections China Leaf Infusion [8] T. officinale Malaria Venezuela Roots, leaves Decoction [9]

T. panalpinum Malaria Portugal Roots, leaves, juice — [14, 15]

Table 1. Ethnopharmacological information of Taraxacum genus used as an antimicrobial traditional medicine.

T. platycarpum Pleurodynia Korea Leaf, stem Infusion

tion of this plant.

248 Herbal Medicine

Taraxacum extracts have been tested on different bacterial and fungal strains affecting humans, animals, and plants to determine its antimicrobial profile, confirm its traditional usage, and expand its known uses. Antimicrobial agents are categorized based on the spectrum of action, namely "narrow" and "broad" spectrum, which indicates whether its use is specific for certain bacterial strains or active on a wider range. Bacterial infections can result in mild to lifethreatening illnesses that require immediate antibiotic intervention. Alternatively, a superficial fungal infection is rarely life-threatening but can have debilitating effects and may spread to other people or become invasive or systemic, resulting in a life-threatening infection. The widespread, and sometimes inappropriate, use of chemical compounds can create antibiotic


T. officinale T. officinale

No/No

C

Yes NI

 Aerial Air-dried a 40C

(36–48 h) and

1:5

 Methanol 80%

 1 h

 100C Reflux

 +

[35]

grounded

Weber

T. officinale

No/Yes

 NI

NI

 NI

 Leaves NI

1:4

 Methanol

 5 days

 RT

 NI

 +

[36]

Weber ex. F.

H. Wigg T. officinale

No/No

C

NI

 NI

 Aerial Dry under shade

and ground

1:10 Methanol

 3 weeks

 25C

 Homog.

 +

[37]

Weber

T.

No/No

NI

NI

 NI

 NI

 Dried

NI

 Methanol

 3 h

 80C

 NI

 +

[38]

platycarpum

T.

No/No

NI

NI

 NI

 NI NI

NI

 Methanol 1:2.5 Methanol

 16 h

 24 h

 37C

 120 rpm

 +

[41]

 50C

+

[40]

 Dried

NI

 Methanol

 3 h

 80C

 NI

 +

[39]

platycarpum

T. officinale T. officinale

T.

Yes/Yes

 C

Yes Yes

 NI NI

1:05 Water 1:20 Water

NI

24 h

 35C

 Shaking

 +

[43]

http://dx.doi.org/10.5772/intechopen.71619

 NI

 Homog.

 +

[42]

*Taraxacum* Genus: Potential Antibacterial and Antifungal Activity

 Air-dried and

NI

 Water

3 h

 100C By boiling

 +

[36]

grounded

mongolicum

Hand-Mazz T. officinale T. officinale T. officinale

No/No

C/P

 NI

 NI

 Root

 Cleaning prior

1:10 Water

3 h

 RT

 170 rpm

 +

[44]

251

freeze-dried,

grounded

F.H. (Webb)

No/No

NI

NI

 NI

 NI

 Dried at 25–

30C for 1 week.,

ground with a

mortar

No/No

C

NI

 NI

 Leaves Dried under

shade and grounded

No/No

NI

NI

 NI

 Leaves Air-dried

1:1.4 Methanol 75%

 NI

 NI

 NI

 +

[34]

1 month and

grounded

Autentification/

C: Collected

Zone Season Plant

part

manipulation

\*

Sample

Ratio Solvent

 Extraction

Temp. Agitation

 Inhibition

Ref.

activity\*\*

time

P: Purchase

Voucher


T. officinale

No/No

NI

NI

 NI

 Flower NI

1:10 Acetic acid 10% 1 h

Wigg.

T. officinale

No/No

C

NI

 Yes

 Seeds

 Grounded

 1:10 Acetic acid 10% 1 h

Wigg.

T. officinale

Yes/No

 C

Yes Yes

 NI

 Dried

NI

 Water, ethanol

1 h

 80C

 Maceration

 +

[24]

and ethyl acetate

Weber

T. officinale Taraxacum

No/No

C

Yes NI

 NI

 NI

spp.

T. officinale T. coreanum

T.

No/No

C

NI

 NI

 Aerial

Frezee-dried

1:5

 Ethanol 75%

 2 days

 NI

 Soaked

 +

[29]

and grounded

20-mesh

mongolicum

T. officinale

No/Yes

 C

Yes Yes

 Root

 Dried and

NI

 Ethanol 80%

 NI

 NI

 Reflux

 +

[20]

grounded

Weber

T. officinale

Yes/Yes

 C

NI

 NI

 Aerial Air-dried and

NI

1:10 Ethanol 95%

 3 h

 80C

+

[31]

crushed

1:1

 Ethanol 90%

 2 days

 RT

 Intermitent

+

[30]

shaking

F. H. Wigg

T.

mongolicum

H.

T.

No/No

NI

NI

 NI

 NI

air-dried (40C, 24 h), grounded

24-mesh

Freeze-dried,

1:16 Ethanol 95%

 24 h

 RT

Shaking

 +

[32]

(23C)

ohwianum

T. officinale T. officinale

Yes/Yes

 P

NI

 NI

 Root

and blended

Freeze-dried

1:10 Hexane

> F.H. Wigg.

Yes/No

 NI

NI

 NI

 Leaves Air-dried

 1:5

Ethylacetate

 24 h Overnight

 RT

 70 rpm

 +

[33]

 RT

 150 rpm

 +

[22]

No/No

NI

NI

 NI

 NI

 NI

No/Yes

 C

Yes Yes

 NI

 NI

NI

1:3.3 Ethanol 75%

Dichloromethane

 3 days

 9 h

 60C

 Reflux

 +

[28]

 NI

 Homog.

 +

[27]

Yes/Yes

 C

Yes NI

 NI

 Air-dried

 1:14 Acetone

1:10

Dichloromethane

 3 h

 20C

 Homog.

 +

[26]

 30 min

 NI

 NI

 +

[25]

Autentification/

C: Collected

Zone Season Plant

part\*

manipulation

Sample

Ratio Solvent

 Extraction

Temp. Agitation

 Inhibition

Ref.

activity\*\*

250 Herbal Medicine

time

 RT

 RT

 NI

 +

[23]

 Homog.

 +

[22]

P: Purchase

Voucher



T. officinale

T.

Yes/Yes

 C

Yes NI

 Aerial Air-dried and

grounded

phaleratum

G. Hagl et

Rech

T. officinale

No/No

P

NI

 NI

 Root

 Dried

1:04 Ethanol

24 h

 NI

[61]

Cass.

T. officinale T. officinale

Yes/Yes

 NI

NI

 NI

 NI

 Dried and

1:40 Methanol

 Overnight

 RT

 NI

[63]

grounded

Weber

T.

No/Yes

 C

NI

 NI

 Whole NI

1:10 Water

Overnight

 NI

 Homog.

[64]

mongolicum

Hand-Mazz

T. officinale T. officinale \*NI, No indicated.

Table 2.

Physical parameters

 on

Taraxacum

extracts for testing

antimicrobial

 activity.

No/No

C

Yes Yes

 Leafs,

NI

1:03 Water

roots

No/No

P

NI

 NI

 Root

 Grounded

 1:8.3 Water

30 min

 100C By boiling 

RT

 Homog.

[66]

*Taraxacum* Genus: Potential Antibacterial and Antifungal Activity

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253

[65]

No/No

C

Yes NI

 flower Chopped and

frozen

NI

 Methanol 90%

 30 min

 4C

 Homog.

[62]

No/No

Extract (P) NI

 NI

 NI

 Diluted

 NI NI

 Ethanol 70%

 NI

 RT

 NI

[60]

 ethanol 45%

 NI

 NI

 NI

[59]

Autentification/

C: Collected

Zone Season Plant

part

manipulation

\*

Sample

Ratio Solvent

 Extraction

Temp. Agitation

 Inhibition

Ref.

activity\*\*

time

P: Purchase

Voucher


T. officinale T. officinale

No/No

NI

NI

 NI

 leaves Grounded

 1:01 Water

> Weber ex

Wigger

T.

No/No

NI

NI

 NI

 NI

 Grounded

 NI

 Water

1 h

 100C By boiling

 +

[47]

mongolicum

T. officinale T. officinale

NI/NI

NI

NI

 NI

 NI

 NI

H.

T. officinale

NI/NI

C

Yes Yes

 Honey NI

NI

 NI

NI

 NI

 NI

 +

[50]

F.H. Wigg

T. farinosum

NI/NI

C

NI

 Yes

 Root

 NI

NI

 NI

NI

 NI

 NI

 +

[51]

Hausskn. &

Bornm

T. officinale T. officinale T. officinale

T.

No/No

P

NI

 NI

 NI

 Grounded 50-

mesh

platycarpum

Taraxacum

No/No

NI

NI

 NI

 Aerial Grounded

 1:10 Water

4 h

 100C By boiling

 +W

 [56]

sp.

T. officinale

No/No

C

Yes Yes

 Aerial Frozen, cut and

grounded

1:01 Ethanol 20%

 24 h

 RT

 NI

[57]

F.H. Wigg. T. officinale

No/No

NI

NI

 NI

 Leaves Dried

NI

 Ethanol 40%

 NI

 NI

 NI

[58]

No/No

P

NI

 NI

 NI

 NI

NI/NI

NI

NI

 NI

 NI

 NI

NI

NI

1:10 Ethanol

 Ethanol 35%

 NI

24 h

 RT

 Homog.

 +W

 [55]

 NI

 NI

 +W

 [54]

 NI

NI

 NI

 NI

 +W

 [53]

Yes/No

 C

Yes Yes

 NI

 Dried 40C 5

NI

 NI

NI

 NI

 Reflux

 +

[52]

days and

grounded

No/No

NI

NI

 NI

 NI

 Dried at 60C 

1:10 Water

NI

 NI

 NI

 + +

[49]

[48]

2 h and grounded 60-

mesh

No/No

NI

NI

 NI

 NI

 NI

1:04 Water

45 min

5 min

 NI

 NI

 +

[46]

 100C NI

 +

[45]

Autentification/

C: Collected

Zone Season Plant

part\*

manipulation

Sample

Ratio Solvent

 Extraction

Temp. Agitation

 Inhibition

Ref.

activity\*\*

252 Herbal Medicine

time

P: Purchase

Voucher

Table 2. Physical parameters on Taraxacum extracts for testing antimicrobial activity. resistance. Due to this issue, the potential of Taraxacum as a useful, broad-spectrum antimicrobial and antifungal agent that can be "easily and worldwide grown," is highly valuable. A list of the strains against which Taraxacum's antimicrobial activity has been tested is displayed in Table 3.


2.2.1. Human pathogens

V. parahaemolyticus (+) [38, 39] Xanthomonas campestris (+) [69]

[20, 27, 37, 57, 58, 62, 64, 66] S. epidermidis (+) [28] () [66] Streptococcus haemolyticus (+) [20]

S. agalactiae (+) [47] S. dysgalactiae (+) [47] Vibrio cholerae (+) [37]

In the study of antibacterial properties of these plants, most attention has been focused on human pathogenic strains, including S. aureus, E. faecalis, V. cholerae, B. subtilis, P. aeruginosa, K. pneumonia, and E. coli. These are the pathogens commonly responsible for infections in gastrointestinal and massive organ systems such as the lungs and skin. Taraxacum officinale is the species generally studied to combat these pathogens, but it has demonstrated diverse results depending on the extraction characteristics or the bioassay performed. For instance, a methanolic extract of T. officinale at 0.2 mg/mL was as effective as an antibacterial agent against M. luteus and V. cholera with minimum inhibitory concentration (MIC) values of 1.0 and 12.5 mg/mL, respectively, but displayed no activity against S. aureus, E. faecalis, E. bacter, V. cholerae, B. subtilis, P. aeruginosa, K. pneumonia, or E. coli [37]. In the same study, the inhibition percentages achieved for mycelial growth of A. niger, A. flavus, A. fumigatus, and R. solani were 37, 71, 85, and 78%, respectively. Other works indicate that methanolic T. officinale leaf extracts ranging from 0.003 to 0.5 mg/mL were active against S. aureus, P. aeruginosa, B. cereus, S. sonnei,

(+) Extracts of Taraxacum active against the pathogen; () extracts of Taraxacum inactive against the pathogen.

Bacterial strains Fungi strains P. fluorescens (+) [24] Ph. betae (+) [23, 68]

P. syringae (+) [69] Phytophthora infestans (+) [69] Serratia/Rahnella sp. () [66] Pityrosporum ovale (+) [49] Salmonella typhimurium (+) [36] () [33, 44] Pythium debaryanum (+) [69] S. abony enterica (+) [58] Rhizoctonia solani (+) [37, 56] S. poona () [66] Saccharomyces cereviseae (+) [34] S. typhi (+) [44, 51] () [20] Saprolegnia australis () [61] Sarcina lutea (+) [24] Scedosporium apiospermum () [66] Serratia marcescens (+) [25] () [66] Trichophyton longifusus (+) [51] Shigella fiexeri () [70] T. mentagrophytes (+) [27]

S. sonnei (+) [36] Verticillium albo-atrum (+) [23] ()

Staphylococcus aureus (+) [22, 24, 25, 28, 29, 32–34, 36, 38, 39, 41, 43–45, 48–52, 70] ()

Table 3. Bacterial and fungal strains on which Taraxacum extracts have been tested.

[68]

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255


(+) Extracts of Taraxacum active against the pathogen; () extracts of Taraxacum inactive against the pathogen.

Table 3. Bacterial and fungal strains on which Taraxacum extracts have been tested.

#### 2.2.1. Human pathogens

resistance. Due to this issue, the potential of Taraxacum as a useful, broad-spectrum antimicrobial and antifungal agent that can be "easily and worldwide grown," is highly valuable. A list of the strains against which Taraxacum's antimicrobial activity has been tested is displayed in

Bacterial strains Fungi strains

Aeromonas hydrophila () [22] Alternaria alternata (+) [46, 68] Agrobacterium tumefaciens (+) [24] Aspergillus carbonarius (+) [35] Bacillus cereus (+) [22, 33, 36, 44] () [66] A. niger (+) [23, 35, 37, 68, 69] ()

B. pumilus () [66] A. flavus (+) [37] () [66] B. subtilis (+) [20, 24, 25, 27, 29, 34, 38, 39, 41, 48, 69] () [37, 64, 66] A. fumigatus (+) [37]() [66] Campylobacter jejuni (+) [54, 59] Bipolaris sorokiniana (+) [23, 67] ()

Chromobacterium violaceum (+) [66] () [65] Botrytis cinerea (+) [23, 35, 67] Clavibacter michiganense (+) [69] Candida albicans (+) [27, 34, 36, 52]

Cupriavidus sp. () [66] C. glabrata () [55, 66] Enterobacter coccus () [37] C. krusei () [66]

Enterococcus faecalis (+) [53] () [37, 66] C. parapsilesis () [55, 66]

Helicobacter pylori (+) [31, 54] Cochliobolus sativus (+) [68]

K. penumoniae (+) [29, 36] () [20, 37, 45, 66] C. lagenarium (+) [42]

Klebsiella aerogenes () [66] Colletotrichium gloesporoides () [68]

Listeria monocytogenes (+) [38, 39] () [66] Cryptococcus neoformans (+) [36] Micrococcus kristinae (+) [25] Exophiala (Wangiella) dermatitidis ()

M. luteus (+) [37, 41] Fusarium avenaceum (+) [68] Mycobacterium aurum () [63] F. graminearum () [69] M. bovis () [63] F. oxysporum (+) [23, 56, 69] M. smegmatis () [63] Microsporum canis (+) [51] M. tuberculosis () [60] Monilinia laxa (+) [35] Propionihacterium acnes (+) [49] Mucor piriformis (+) [46] Proteus mirabilis (+) [43] () [20] Penicillium sp. () [66] P. vulgaris (+) [25, 29] () [70] P. digitatum (+) [35]

Pseudomonas sp. () [50] P. expansum (+) [26, 46] () [35]

P. aeruginosa (+) [24, 27, 29, 36, 41, 49, 70] () [20, 37, 57, 64, 66] P. italicum (+) [35]

Erwinia carotovora (+) [24] C. utils () [55]

Escherichia coli (+) [22, 24, 25, 27, 29, 34, 36, 38, 39, 41, 43, 45, 47, 48, 58, 70]

() [20, 32, 33, 37, 44, 57, 62, 64, 66]

[27, 66]

[68]

[66]

() [55, 57, 66]

C. tropicalis (+) [55]

Cladosporium herbarum (+) [71]

Table 3.

254 Herbal Medicine

In the study of antibacterial properties of these plants, most attention has been focused on human pathogenic strains, including S. aureus, E. faecalis, V. cholerae, B. subtilis, P. aeruginosa, K. pneumonia, and E. coli. These are the pathogens commonly responsible for infections in gastrointestinal and massive organ systems such as the lungs and skin. Taraxacum officinale is the species generally studied to combat these pathogens, but it has demonstrated diverse results depending on the extraction characteristics or the bioassay performed. For instance, a methanolic extract of T. officinale at 0.2 mg/mL was as effective as an antibacterial agent against M. luteus and V. cholera with minimum inhibitory concentration (MIC) values of 1.0 and 12.5 mg/mL, respectively, but displayed no activity against S. aureus, E. faecalis, E. bacter, V. cholerae, B. subtilis, P. aeruginosa, K. pneumonia, or E. coli [37]. In the same study, the inhibition percentages achieved for mycelial growth of A. niger, A. flavus, A. fumigatus, and R. solani were 37, 71, 85, and 78%, respectively. Other works indicate that methanolic T. officinale leaf extracts ranging from 0.003 to 0.5 mg/mL were active against S. aureus, P. aeruginosa, B. cereus, S. sonnei, S. enterica serovar typhimurium, E. coli, K. pneumonia, C. albicans, and C. neoformans with MIC values ranging from 0.04 to 5.0 mg/mL [36]. A similar extract at 10 mg/mL displayed moderate growth diameter inhibition for S. typhi, but was highly active for S. aureus, B. cereus, and E. coli, even when no activity was observed for A. hydrophila [22]. Ethanolic extracts of 2.0 mg/mL were active against A. aureus, MRSA clinical, and B. cereus, with MIC values between 0.38 and 0.5 mg/mL, but were not effective against E. coli or S. typhi. In the same work, a water extract at the same concentration showed no activity against any strain tested [33]. Moreover, 21 ethanolic extracts from various plants were tested against 20 Salmonella serovars. Taraxacum inhibited only 5% of these, and was therefore not considered for additional antimicrobial studies [72].

ethyl acetate, and butanol fractions were active on E. coli, S. aureus, B. subtilis, C. albicans, and S. cerevisiae at 50 mg/mL, with inhibition percentages ranging from 13 to 76%. The water fraction showed moderate inhibition via the broth dilution method (10 and 14% for E. coli and B. subtilis, respectively) but no effect on the disc diffusion assay [34]. The only report in which a Taraxacum extract was compared to another natural antibacterial substance besides other plants extracts evaluated the use of T. officinale extract as an irrigation agent in endodontic treatments against E. faecalis in root canal infections. Leaf and root extracts at 0.7% were slightly active but propolis was more effective for this purpose [53]. In the case of commercial preparations, high activity has been reported for a commercial T. officinale ethanolic extract, showing antibacterial activity against H. pylori at 20 mg/mL with 26% inhibition but no

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257

Considering other Taraxacum species, T. platycarpum anticandidal activity was determined against five different Candida sp. by agar diffusion assay. An ethanolic extract at 0.2 mg/mL weakly inhibited C. tropicalis but no other Candida strains [55]. A methanolic extract was active against B. subtilis, S. aureus, L. monocytogenes, E. coli, and V. parahaemolyticus at concentrations ranging from 0.5 to 2.0 mg/mL, with growth inhibition ranging from 5.1 to 100%, correlating to the concentration. In that study, chloroform, butanol, and ethyl acetate fractions were active in the disc diffusion assay for almost every strain tested, but an aqueous extract was inactive [38, 39]. An ethanolic extract of T. mongolicum at 0.2 mg/mL was not able to achieve growth inhibition in a microdilution assay for B. subtilis, S. aureus, E. coli, or P. aeruginosa [64]. In contrast, an ethanolic extract of this species was active for E. coli, S. aureus, and P. aeruginosa in the disc diffusion assay with MIC values between 0.05 and 0.1 mg/mL, which was three times higher than the values obtained for erythromycin. However, no activity was achieved for S. fiexneri or P. vulgaris [75]. Another report indicated that only the butanol fraction of an ethanolic extract of this plant was active on H. pylori, but water and methyl chloride fractions were inactive. Nevertheless, a different report indicated that a butanol fraction exerted higher inhibition (13%) than the aqueous fraction, possibly due to the flavonoid and luteolin content (28 and 1.1%, respectively) [31]. Against S. aureus and S. epidermis, an acetyl acetate fraction of an ethanolic T. coreanum extract was active at 0.5, 1.0, and 3.0 mg/disc, a chloroform fraction was active at 1.0 and 3.0 mg/disc, and a butanol fraction at 1.0 mg/mL, but displayed no activity against MRSA displayed [28]. An ethanolic T. ohwianum extract was active against E. coli at 240 and 320 mg/mL, but not against S. aureus [32]. These authors indicate that the pH and temperature of the bioassay were important parameters in the antimicrobial performance of the extract. An extract of the aerial parts of T. phaleratum was inactive at 0.2 mg/mL against

M. tuberculosis, even when several solvent fractions were tested [60].

Limited studies have been conducted on humans establishing the antimicrobial potential of Taraxacum extracts. Chinese language studies have reported the effects of various formulas containing T. mongolicum for medical treatment. An herbal formula known as "fu zheng qu xie" was just as effective as the antibiotic gentamycin in 75 cases of gastric disease caused by H. pylori. Furthermore, an herbal formula called "jie du yang gan gao," which includes T. mongolicum, was significantly more effective than another botanical formulation in lowering elevated liver

enzymes and curing patients with hepatitis B in a 96-person, double-blind trial [76].

observable activity for C. jejuni [54].

Recently, methanolic and chloroformic leaf extracts of T. officinale were found to be effective against M. luteus, P. aeruginosa, B. subtilis, E. coli, and S. aureus with MIC values of 0.3 mg/mL and no observable activity for water extracts [41]. In this study, the highest impact was noted with methanol and chloroform extracts against S. aureus and E. coli, respectively, and the lowest with both extracts against P. aeruginosa. Furthermore, an ethanolic extract was effective against E. coli and S. aureus, but no activity was observed for either extract against K. pneumonia and P. aeruginosa at 50, 100, and 200 mg/mL. Nevertheless, a water extract was effective only for E. coli at 100 and 200 mg/mL [45]. Water and ethanolic extracts at 1.0 mg/mL exhibit effective inhibition against S. aureus and fewer inhibitory effects were observed for P. mirabilis; against S. aureus, an ethanolic extract was active at 0.5 mg/mL, but a water extract was only active at 1.0 mg/mL; and inhibition was not achieved for either extracts at 0.1 mg/mL [73]. An ethanolic extract was slightly active against B. subtilis and S. haemolyticus, but was inactive against other Gram positive and Gram negative strains, resulting in no further studies with this extract [20]. Furthermore, only weak activity was achieved by methanolic extracts of this plant against P. syringae [74].

Both ethanolic and water extracts of T. officinale were active for S. marcescens and M. kristinae. The ethanolic extract alone was active on P. vulgaris, E. coli, B. subtilis, and S. aureus with MIC values ranging from 1.0 to 7.0 mg/mL for all strains tested [25]. Similar extracts had antimicrobial effects on four species that induce acne (P. ovale, P. acnes, P. aeruginosa, and S. aureus) in broth dilution tests with effects depending on the extract concentration, but no further information was available [49]. Moreover, a leaf extract (0.04 mg/well) was reported as a bactericidal agent against S. aureus and fungistatic against C. albicans [52]. Contrarily, extracts of 130 and 200 mg/mL from aerial parts were unable to prevent the growth of 34 microorganisms from genera Bacillus, Enterobacter, Klebsiella, Listeria, Pseudomonas, Salmonella, Staphylococcus, Aspergillus, and Candida, among others; therefore, it was considered inactive at these concentrations in a disc diffusion assay [66]. A methanolic T. officinale flower extract was not active against E. coli or S. aureus at 1.0 mg/mL in a diffusion agar assay [62] and no activity was found on S. aureus, E. coli, P. aeruginosa, or C. albicans using a leaf ethanolic extract when 0.05 mL were placed in sterile discs [57]. Furthermore, an ethanolic extract of leaves displayed no activity against S. aureus, E. coli, or S. abony by the serial dilution method [58], with the same results for root and leaf extracts on M. aurum and M. smegmatis at 0.5 mg/mL [63].

Raw extracts of T. officinale have been widely tested, as well as solvent fractions. In a study in which the methanolic leaf extract was fractioned by different solvents, the methyl chloride, ethyl acetate, and butanol fractions were active on E. coli, S. aureus, B. subtilis, C. albicans, and S. cerevisiae at 50 mg/mL, with inhibition percentages ranging from 13 to 76%. The water fraction showed moderate inhibition via the broth dilution method (10 and 14% for E. coli and B. subtilis, respectively) but no effect on the disc diffusion assay [34]. The only report in which a Taraxacum extract was compared to another natural antibacterial substance besides other plants extracts evaluated the use of T. officinale extract as an irrigation agent in endodontic treatments against E. faecalis in root canal infections. Leaf and root extracts at 0.7% were slightly active but propolis was more effective for this purpose [53]. In the case of commercial preparations, high activity has been reported for a commercial T. officinale ethanolic extract, showing antibacterial activity against H. pylori at 20 mg/mL with 26% inhibition but no observable activity for C. jejuni [54].

S. enterica serovar typhimurium, E. coli, K. pneumonia, C. albicans, and C. neoformans with MIC values ranging from 0.04 to 5.0 mg/mL [36]. A similar extract at 10 mg/mL displayed moderate growth diameter inhibition for S. typhi, but was highly active for S. aureus, B. cereus, and E. coli, even when no activity was observed for A. hydrophila [22]. Ethanolic extracts of 2.0 mg/mL were active against A. aureus, MRSA clinical, and B. cereus, with MIC values between 0.38 and 0.5 mg/mL, but were not effective against E. coli or S. typhi. In the same work, a water extract at the same concentration showed no activity against any strain tested [33]. Moreover, 21 ethanolic extracts from various plants were tested against 20 Salmonella serovars. Taraxacum inhibited only 5% of these, and was therefore not considered for additional antimicrobial

Recently, methanolic and chloroformic leaf extracts of T. officinale were found to be effective against M. luteus, P. aeruginosa, B. subtilis, E. coli, and S. aureus with MIC values of 0.3 mg/mL and no observable activity for water extracts [41]. In this study, the highest impact was noted with methanol and chloroform extracts against S. aureus and E. coli, respectively, and the lowest with both extracts against P. aeruginosa. Furthermore, an ethanolic extract was effective against E. coli and S. aureus, but no activity was observed for either extract against K. pneumonia and P. aeruginosa at 50, 100, and 200 mg/mL. Nevertheless, a water extract was effective only for E. coli at 100 and 200 mg/mL [45]. Water and ethanolic extracts at 1.0 mg/mL exhibit effective inhibition against S. aureus and fewer inhibitory effects were observed for P. mirabilis; against S. aureus, an ethanolic extract was active at 0.5 mg/mL, but a water extract was only active at 1.0 mg/mL; and inhibition was not achieved for either extracts at 0.1 mg/mL [73]. An ethanolic extract was slightly active against B. subtilis and S. haemolyticus, but was inactive against other Gram positive and Gram negative strains, resulting in no further studies with this extract [20]. Furthermore, only weak activity was achieved by methanolic extracts of this plant against P. syringae [74].

Both ethanolic and water extracts of T. officinale were active for S. marcescens and M. kristinae. The ethanolic extract alone was active on P. vulgaris, E. coli, B. subtilis, and S. aureus with MIC values ranging from 1.0 to 7.0 mg/mL for all strains tested [25]. Similar extracts had antimicrobial effects on four species that induce acne (P. ovale, P. acnes, P. aeruginosa, and S. aureus) in broth dilution tests with effects depending on the extract concentration, but no further information was available [49]. Moreover, a leaf extract (0.04 mg/well) was reported as a bactericidal agent against S. aureus and fungistatic against C. albicans [52]. Contrarily, extracts of 130 and 200 mg/mL from aerial parts were unable to prevent the growth of 34 microorganisms from genera Bacillus, Enterobacter, Klebsiella, Listeria, Pseudomonas, Salmonella, Staphylococcus, Aspergillus, and Candida, among others; therefore, it was considered inactive at these concentrations in a disc diffusion assay [66]. A methanolic T. officinale flower extract was not active against E. coli or S. aureus at 1.0 mg/mL in a diffusion agar assay [62] and no activity was found on S. aureus, E. coli, P. aeruginosa, or C. albicans using a leaf ethanolic extract when 0.05 mL were placed in sterile discs [57]. Furthermore, an ethanolic extract of leaves displayed no activity against S. aureus, E. coli, or S. abony by the serial dilution method [58], with the same results for

Raw extracts of T. officinale have been widely tested, as well as solvent fractions. In a study in which the methanolic leaf extract was fractioned by different solvents, the methyl chloride,

root and leaf extracts on M. aurum and M. smegmatis at 0.5 mg/mL [63].

studies [72].

256 Herbal Medicine

Considering other Taraxacum species, T. platycarpum anticandidal activity was determined against five different Candida sp. by agar diffusion assay. An ethanolic extract at 0.2 mg/mL weakly inhibited C. tropicalis but no other Candida strains [55]. A methanolic extract was active against B. subtilis, S. aureus, L. monocytogenes, E. coli, and V. parahaemolyticus at concentrations ranging from 0.5 to 2.0 mg/mL, with growth inhibition ranging from 5.1 to 100%, correlating to the concentration. In that study, chloroform, butanol, and ethyl acetate fractions were active in the disc diffusion assay for almost every strain tested, but an aqueous extract was inactive [38, 39].

An ethanolic extract of T. mongolicum at 0.2 mg/mL was not able to achieve growth inhibition in a microdilution assay for B. subtilis, S. aureus, E. coli, or P. aeruginosa [64]. In contrast, an ethanolic extract of this species was active for E. coli, S. aureus, and P. aeruginosa in the disc diffusion assay with MIC values between 0.05 and 0.1 mg/mL, which was three times higher than the values obtained for erythromycin. However, no activity was achieved for S. fiexneri or P. vulgaris [75]. Another report indicated that only the butanol fraction of an ethanolic extract of this plant was active on H. pylori, but water and methyl chloride fractions were inactive. Nevertheless, a different report indicated that a butanol fraction exerted higher inhibition (13%) than the aqueous fraction, possibly due to the flavonoid and luteolin content (28 and 1.1%, respectively) [31]. Against S. aureus and S. epidermis, an acetyl acetate fraction of an ethanolic T. coreanum extract was active at 0.5, 1.0, and 3.0 mg/disc, a chloroform fraction was active at 1.0 and 3.0 mg/disc, and a butanol fraction at 1.0 mg/mL, but displayed no activity against MRSA displayed [28]. An ethanolic T. ohwianum extract was active against E. coli at 240 and 320 mg/mL, but not against S. aureus [32]. These authors indicate that the pH and temperature of the bioassay were important parameters in the antimicrobial performance of the extract. An extract of the aerial parts of T. phaleratum was inactive at 0.2 mg/mL against M. tuberculosis, even when several solvent fractions were tested [60].

Limited studies have been conducted on humans establishing the antimicrobial potential of Taraxacum extracts. Chinese language studies have reported the effects of various formulas containing T. mongolicum for medical treatment. An herbal formula known as "fu zheng qu xie" was just as effective as the antibiotic gentamycin in 75 cases of gastric disease caused by H. pylori. Furthermore, an herbal formula called "jie du yang gan gao," which includes T. mongolicum, was significantly more effective than another botanical formulation in lowering elevated liver enzymes and curing patients with hepatitis B in a 96-person, double-blind trial [76].
