# _Helichrysum arenarium_: From Cultivation to Application
## 6 Pharmacological Properties
### Antimicrobial Activities  
Since prehistoric times, different parts of plants have been used in traditional medicine to prevent or cure infectious diseases. Recently, the crisis of antimicrobial resistance has become an important reason for the discovery of new antimicrobials of plant origin, with compounds different from synthetic therapeutic substances that could act alone or improve the efficiency of drugs. A number of these phytocompounds seem to have structures and modes of action distinct from those of currently used antibiotics, and therefore the search for potentially new and useful substances is important [82; 83]. Antibacterial, antiviral, and antifungal properties of the _Helichrysum_ species have been investigated in several Euroasia countries. Moreover, the European Medicine Agency published a report in 2015 on the pharmacological effects, clinical efficacy and safety, and antimicrobial properties of _H. arenarium_ (L.) [PERSON] [19]. The first investigation of the antibacterial activity of the everlasting flower flavonoid compounds was performed in the former Soviet Union by [PERSON] and concluded that the preparations in the concentration of 20-40 \(\upmu\)g/mL were active against two important Gram-positive species (_Staphylococcus_ sp. and _Streptococcus_ sp.) [84]. Later, aerial parts of the plant or the whole overground plant were used to prepare infusions, decoctions, essential oils, and extracts with different qualitative content. It is well known in the literature that variability in the chemical composition of the plants is linked to the part of the plant used (roots, stems, leaves, flowers) and the extraction method, but genetic, geographic, and climatic factors also play important roles. Major antimicrobial constituents in _Helichrysum_ species are polyphenols, especially flavonoids and volatile compounds in essential oils [22; 76; 85]. Studies on the antimicrobial properties of _H. arenarium_ strongly suggested that essential oils or extracts from the whole dried plant have different effects than when infloresence was used. The antimicrobial activity of essential oils of _H. arenarium_ has been investigated on different test microorganisms, clinical isolates, and food contamination microbes. [PERSON] et al., 2005 tested the antibacterial activity of 1-5 \(\upmu\)L of everlasting flower essential oil on _Escherichia coli_ ATCC 35,218, _Microococcus luteus_ ATCC 9341, _Pseudomonas tolaasii_ isolated from _Agaricus bisporus_, _Salmonella enteritidis_ ATCC 13,076, _S. Typhimurium_ ATCC 13,311, _Staphylococcus aureus_ ATCC 6538, and _S. epidermidis_ ATCC 12,228 and concluded that at the minimum volume (1 \(\upmu\)L) the oil had activity against all bacterial species tested [45]. Moreover, the inhibition zones (mm) of 5 \(\upmu\)L essential oil preparation were higher than the results obtained for antibiotic streptomycin used as a control. Clinical isolates of _Candidia albicans_ and fungi _Apergillus niger_ ATCC 6275, _A. flavus_ ATCC 9170, _Cladosporium cladosporioides_ ATCC 13,276, _Penicillium funticulosum_ ATCC 10,509, and _Trichoderma viride_ IAM 5061 were tested, and the minimum inhibitory concentration (MIC) detected was between 10 and 30 \(\upmu\)g/mL, while the minimum fungicidal concentration (MFC) ranged from 15 to 60 \(\upmu\)g/mL [45]. Similar antimicrobial activities were obtained in experiments that tested seven species of food contamination microbes and a different method to prepare steam-distilled essential oil [84]. In this case, _Bacillus subtilis_ ATCC 6633 (MIC = 781.25 \(\upmu\)g/mL) showed more resistance than _E. coli_ 0157 NTCC 12,900 and _S. aureus_ ATCC 6538, both with MIC = 97.65 \(\upmu\)g/mL. Yeast _Saccharomyces cerevisiae_ 5052 PTCC, fungi _Candidia albicans_ ATCC 10,231, and two _Aspregillus_ species (_A. flavus_ PTCC and _A. parasiticus_ PTCC 5018) were tested, and minimal bactericidal concentrations (MBC) and MFC were in a range of 390.625-6250 \(\upmu\)g/mL [86].