5.3. Plant part utilization

Reports indicate that compounds present in Taraxacum vary within parts of the plant, and even though there are common compounds across sections, these concentrations vary as well [54, 55]. A disadvantage that creates further uncertainties when comparing data is that a considerable amount of studies do not indicate which part of the plant was used. In general, aerial parts (leaves, flowers, and seeds), roots, and whole Taraxacum plants have been used in antimicrobial research. Only one Taraxacum study indicated differences between a root extract and a leaf extract, in which the root extract was active against S. aureus and S. typhi. Extracts of plant roots and herbs of different Taraxacum species endemic to Turkey displayed significant activity against M. canis and T. longifusus [44]. Few studies refer to the antimicrobial properties of Taraxacum derivatives. Pseudomona sp., S. aureus, and E. coli were inhibited in a disc diffusion assay, but C. albicans and S. enteriditis were not inhibited by T. officinale honey [24]. The pH of dandelion honey is considered the probable antibacterial component observed against S. aureus [56]. Analyzing the information gathered in this work (also see Table 2), Taraxacum root extracts are less effective at fungal and bacterial inhibition than the aerial parts and seem to be more effective on Gram positive than Gram negative bacteria.

#### 5.4. Sample manipulation

it is collected, as well as other ecological and climate factors. For example, sesquiterpene lactones are noticeable in the roots, particularly when harvested in the spring [51]. Sterols, which are present in the leaves throughout the year, are highest during the winter months, whereas levels of sitosterol and cycloartenol esters are highest during periods of sunshine [52]. Few authors indicated in which period of the year the plant was harvested, collected, purchased, or the collection site, another factor that could influence the final concentration of compounds in the extract, even when the same extraction conditions are applied. No Taraxacum studies have investigated a possible relationship between harvesting time or collecting site and its antimicrobial properties. Only one study indicated the environmental conditions in which the plant was grown and collected before the antimicrobial assay [27].

Figure 1. Reported extraction conditions to achieve positive antimicrobial results.

Generally, there is a lack of taxonomic identification of the species characterized, mentioned occasionally as Taraxi radix, Taraxi folium, Taraxi herba, Taraxacum spp., or dandelion, especially when researchers use commercial preparations or purchase the plant from local markets [29, 33, 46]. Samples are commonly obtained in the wild, but the lack of proper identification makes the comparison for antimicrobial properties imprecise for determining the actual efficacy of Taraxacum extracts; therefore, only partial conclusions can be pursued and not always extrapolated. For instance, dandelion is used as a common name for several species: khur mang, a name for dandelion in Tibet, can be used for T. officinale, T. mongolicum, T. tibetanum, and T. Sikkimense [53]. As previously stated, environmental conditions affect the tissue composition of the plants, but few reports indicate the corresponding information for further

5.2. Species identification

290 Herbal Medicine

Several authors propose that plants need to be dried and chopped before extraction. This is a consensus among researches due to the necessity of storing samples prior to processing; however, it is a central issue when testing biological activities because bioactive compounds are highly sensitive and react quickly to changes in environmental conditions. These types of changes are common: a sample is stored at room temperature, refrigerated, frozen, or freezedried. In rare cases, further sample manipulation has been reported prior to extraction. Specifically, the removal of lipids and proteins with solvents [31] could also affect the compound profile of the extract and the final antimicrobial activity. In one study, a fresh sample was also homogenized before tested [30]. In our research, sample manipulation seems to be just as adequate whether plant parts are dried under the sun or by oven prior to extraction, or used directly as fresh biomass in extract preparation. Due to the possibility that the material used in the extraction may be contaminated, a white control is considered in the activity bioassays, which is the sample not inoculated with the pathogen, to confirm sterility of the stored sample.
