**4. Conclusion**

Plant extracts represent very interesting source of bioactive compounds which provide unlimited opportunities for new antibacterial agents. The results obtained in this study confirm this statement. Significant activities of ethanol extract from *Aegopodium podagraria*  and ethyl acetate and acetone extract from *Cichorium intybus*, one of insufficiently explored plants, indicate their use as potential, new antibacterial agents. These results, also, offer a scientific basis for the traditional use of extracts of *Salvia officinalis* and *Melissa officinalis*. The extracts from *Clinopodium vulgare*, *Torilis anthriscus*, *Cytisus nigricans*, *Cytisus capitatus* and *Dorycnium pentaphyllum* showed interesting activity against certain pathogenic bacteria. Mostly, the most sensitive bacteria were *B. subtilis* and *S. aureus* ATCC 25923. Susceptibility of *E. cloaceae*, *Ent. faecalis*, *K. pneumoniae*, *S. aureus*, *Ps. aeruginosa* ATCC 27853 was moderate while *Ps. aeruginosa*, *P. mirabilis*, *E. coli* were resistant. This study represents the first preliminary report on antibacterial activity of the extracts from *Cytisus nigricans*, *Cytisus capitatus* and *Dorycnium pentaphyllum* and contributes to overall examine antibacterial activity of plant species. Since, the compounds and mechanisms of action responsible for the antibacterial activities of these extracts are currently unclear; the further work will be performed on the isolation and identification of the active compounds and understanding of mechanisms of action.

#### **5. Acknowledgment**

This work was supported by the Ministry of Science and Education of the Republic of Serbia (grant number OI173032).

#### **6. References**

18 Antimicrobial Agents

*Escherichia coli*, *Proteus mirabilis*, *Salmonella enteritidis*, *Pseudomonas aeruginosa*, *Streptococcushaemoliticus* A, *Staphylococcus aureus* and *Candida albicans*. *Melilotus albus* extracts were less

*Dorycnium penthaphyllum* extracts showed different level of antibacterial activity. Ethanol extract acted in the interval from 2.5 mg/ml tо 20 mg/ml, ethyl acetate from 1.25 mg/ml tо >20 mg/ml, and acetone extract from 1.25 mg/ml tо 20 mg/ml (Figure 11.). Between the

Fig. 11. Antibacterial activity of *Dorycnium penthaphylum* extracts expressed as MIC values

The most significant results were obtained for *Bacillus subtilis, Staphylococcus aureus* ATCC 25923, *Pseudomonas aeruginosa* and *Proteus mirabilis*. MIC values were between 1.25 mg/ml - 10 mg/ml. Other bacteria showed sensitivity at approximately the same concentrations (20 mg/ml). The exception was *Escherichia coli* which was resistant to ethylaacetate extract. Sensitivity of tested bacteria to the extracts of *D. penthaphylum* was presented for the first time in this study. A group of scientists tested anti - *Helicobacter pilory* effect of medicinal plants of Greek traditional medicine, among which is also *D. penthaphylum,* although they

Plant extracts represent very interesting source of bioactive compounds which provide unlimited opportunities for new antibacterial agents. The results obtained in this study

did not note this plant's effect (Stamatis et al., 2003).

efficient than other tested plants.

(mg/ml)

**4. Conclusion** 

**3.10 Antibacterial activity of** *Dorycnium penthaphyllum*

extracts there was no statistically significant difference in action (*p*<0.05).


Antibacterial Activity of Naturally Occurring Compounds from Selected Plants 21

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**1. Introduction** 

on the screening of natural products.

**2. History of antibiotic discovery** 

**2.1 The golden age of antibiotic discovery** 

natural scaffolds to be translated into functional drugs.

**2** 

*Slovenia* 

**Future Antibiotic Agents:** 

Nataša Radić1,2 and Tomaž Bratkovič<sup>1</sup> *1Department of Pharmaceutical Biology,* 

*2AB Inovacije d.o.o., Mirna* 

**Turning to Nature for Inspiration** 

*Faculty of Pharmacy, University of Ljubljana, Ljubljana* 

Few drugs have made such a profound impact on modern medicine as antibiotics. With the discovery of sulfonamides, β-lactams, and subsequent antibiotic classes after World War II, bacterial infections with often fatal outcomes literally became curable overnight. These "magic bullets," however, suffer from a serious drawback; the use (and misuse) of antibiotics induces selection pressure resulting in the development of resistance traits in bacterial populations. The process is augmented by short generation times of bacteria enabling rapid mutation and selection of resistant strains, and a horizontal transfer of resistance genes. Bacterial pathogens resistant to more than one, or even most clinically used antibiotics, have become common (Fischbach & Walsh, 2009). Faced with the fact that a renewed pre-antibiotic era might be just around the corner, the World Health Day 2011 campaign "Antimicrobial resistance and its global spread" launched by the WHO offers a strategy to safeguard existing antibiotics for future generations, and contain the spread of antimicrobial resistance (World Health Organization, 2011). However, taking a more sensible approach in prescribing and using available antibiotic drugs will only help to put off the inevitable. In the battle against the ever-increasing multidrug resistance of pathogenic bacteria, we urgently need new alternatives to the currently available broadspectrum antibiotics. Here we review some current trends in antibiotic discovery focusing

This chapter is composed of four parts. We start by briefly reviewing the history of antibiotic discovery, gradually moving from its most fruitful era in the 1940's and 50's to the unexpected outcome decline in the genomic era. Next, we address two fundamental questions of antibiotic research in the post-genomic age; namely, *where* to look for novel antibiotics and *how*. Finally, we conclude with a concise discussion on the modification of

Before the discovery of prontosil, the forerunner of sulfonamide chemotherapeutics, the only available measures in combating bacterial infections, apart from practicing proper

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