Secondary plant metabolities as antimicrobial agents

One of the oldest achievements of the human thought is the use of plants and plant extracts in therapeutics. Drugs of a plant origin are characterized by multieffects. In recent years, much interest was directed at medicinal plants containing a mixture of biologically active substances with antimicrobial properties. In medicine, for many years have been used substances extracted from plants and their secondary metabolites and plant extracts, but now due to the development of organic chemistry, pharmacology and medicine, we can determine which biologically active substances produced by these plants are useful. Antimicrobial activity were described for selected groups of plant secondary metabolites, which potentially would allow their use as antimicrobial substances in medicines. These substances can be complementary to basic medical treatment, because their main advantage is a lower incidence of side effects. This paper presents an overview of research on antimicrobial properties of alkaloids, coumarins, flavonoids, terpenoids and essential oils, phytosterols, and tannins and phenolic compounds. Examples of alkaloids active against strains of S. aureus, E. faecalis and E. coli are quindoline (1) and cryptolepine (2) which are components of an extract of Sida acuta [7]. Saal et al. described the effect of 7-amino-4-methylcoumarin (8) and daphnetin (9) isolated from Gingo biloba. These compounds are characterized by activity against strains of the genus S. aureus, E. coli and Salmonella entertidis [5]. Apigenin (15) and amentoflavone (16) have a strong activity against pathogenic fungi Candida albicans, S. cerevisiae, and T. beigelii. Terpenoids are potent phorbol esters (21-26), dustanine (27), 15-acetoxydustaine (28), cycloartenole (29) [14]. Several phytosterols has antibacterial activity [2, 5, 48]. The examples might be: stigmasterol (36), β-sitosterol (37), epidoxysterol (38) isolated from Morinda citrifolia (Rubiaceae), which were characterized by strong activity against Mycobacterium intracellulare [5]. Many authors reported that the tannins and phenolic compounds were characterized by antimicrobial activity [49-53]. Natural substances that inhibit the growth of microorganisms are becoming an alternative to synthetic compounds, as this literature review confirms it