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Plant-based antimicrobials

Apr 21, 2020
Categories:  Scientific publication
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Author:  Vita Forest

This article is based on the work: Alviano, D., & Alviano, C. Plant Extracts: Search for New Alternatives to Treat Microbial Diseases. (2009) Current Pharmaceutical Biotechnology, 10 (1), 106–121

In recent years, the use of plant extracts (as well as other alternative treatments) has been very popular all over the world. Clinical microbiologists have two reasons for interest in the topic of antimicrobial plant extracts. First, few antibiotics derived from microorganisms are released every year. Secondly, self-medication with these substances is a common occurrence [1]. Excessive use of antibiotics is the most important factor contributing to the emergence of various types of resistant microbes [2]. Antimicrobial resistance is one of the most serious public health challenges.

The increasing prevalence of multidrug resistance in pathogenic microorganisms, as well as the undesirable side effects of certain antibiotics, have generated great interest in the search for new herbal antimicrobials.

Synthetic antibiotics are allergenic and toxic. Allergic reactions can range from transient dermatitis to anaphylactic shock. Thus, extracts of medicinal plants have significant potential for the development of new drugs that are effective against infections that are currently difficult to treat [3].

Plant screening, which may be the source of alternative antimicrobial agents, is currently being conducted worldwide. The antimicrobial properties of plants are explained by the presence of active compounds, for example quinones, phenols, alkaloids, flavonoids, terpenoids, essential oils, tannins, lignans, glucosinolates and some secondary metabolites. Other antimicrobial agents of plants include peptides that form their protective systems, which are similar in structure and function to human antimicrobial peptides [4].

Table 1. Examples of certain substances with antimicrobial activity and the plants in which they are contained.

Substance class

Examples of substances and plants

Link

Quinone

Hypericin, anthraquinone from Hypericum perforatum, has common antimicrobial properties and is also active against methicillin-resistant and methicillin-sensitive staphylococcus

Dadgar T., Asmar M., Saifi S., Mazandarani M., Bayat H., Moradi A., Bazueri M., Ghaemi F. Antibacterial activity of certain Iranian medicinal plants against methicillin resistant and methicillin sensitive Staphylococcus aureus. Asian J. Plant Sci. 2006;5:861–866.

Alkaloids

Berberine is an example of an alkaloid found in the species Berberis, Cortex phellodendri and Rhizoma coptidis, and has an antimicrobial effect against Streptococcus agalactiae. The mechanism of action of berberine is due to its ability to intercalate with DNA and destroy the membrane structure by increasing the permeability of membranes to bacteria

Peng L., Kang S., Yin Z., Jia R., Song X., Li L., Li Z., Zou Y., Liang X., Li L., et al. Antibacterial activity and mechanism of berberine against Streptococcus agalactiae. Int. J. Clin. Exp. Pathol. 2015;8:5217–5223.

Flavonoids

It is known that these phytochemicals have antimicrobial, antiviral, anti-allergic and anti-inflammatory properties. Flavonoids, such as kempferol, rutin, and quercetin, have antifungal properties [a, b]. Legume plant Lupinus spp. contains dihydrofuranoisoflavones that exhibit antifungal activity against Botrytis cinerea and Aspergillus flavus [c].

a. Gabor M. Anti-inflammatory and anti-allergic properties of flavonoids. Plant Flavonoids in Biology and Medicine: Biochemical, Pharmacological and Structure-Activity Relationships. Alan R. Liss; New York, NY, USA: 1986. pp. 471–480. b. Beschia M., Leonte A., Oancea I. Phenolic compounds with biological activity. Bull. Univ. Galati Faso. 1984;6:23–27. c. Thara S., Ingham J., Nakahara S., Mizutani J., Harborne J.B. Fungitoxic dihydrofuranoisoflavones and related compounds in white lupin, Lupinus albus. Phytochemistry. 1984;23:1889–1900.

Flavones

Antimicrobial activity of six flavonoids isolated from Galium fissurense, Viscum album ssp. album and Cirsium hypoleucum were shown against extended-spectrum β-lactamase producing multidrug-resistant bacteria K. pneumoniae.

Ozcelik B., Deliorman O.D., Ozgen S., Ergun F. Antimicrobial Activity of Flavonoids against Extended-Spectrum Beta Lactamase (ESBL)-Producing Klebsiella pneumoniae. Trop J. Pharm. Res. 2008;7:1151–1157.

Coumarins

The pyranocoumarins isolated from Ferulago campestris showed antibacterial activity against nine bacterial strains of the same clinically isolated gram-positive and gram-negative bacterial strains.

Basile A., Sorbo S., Spadaro V., Bruno M., Maggio A., Faraone N., Rosselli S. Antimicrobial and antioxidant activities of Coumarins from the roots of Ferulago campestris (Apiaceae) Molecules. 2009;14:939–952.

Terpenes and terpenoids

Terpenoids extracted from Acacia nilotica bark have antimicrobial activity against S. viridans, S. aureus, E. coli, B. subtilis and Shigella sonnei.

Banso A. Phytochemical and antibacterial investigation of bark extracts of Acacia nilotica. J. Med. Plants Res. 2009;3:82–85.

Essential oils

Cymbopogon citratus essential oil has moderate activity against C. albicans and low activity against P. aeruginosa, E. coli, S. aureus and T. mentagrophy. Essential oils are more active against gram-positive bacteria than gram-negative bacteria; A possible mechanism of action is membrane permeabilizers.

Ragaso C.Y. Antimicrobial and Cytotoxic terpenoid from Cymbopogon citratus Stapf. Philipp. Sci. 2008;45:111–122.

Tannins

Plant extracts containing tannins cause activation of phagocytic cells and anti-infectious action. Tannins have properties that inhibit the growth and protease activity of bacteria by binding the bacterial cell wall [a]. Sorghum tannin has antimicrobial activity against S. aureus, Salmonella typhimurium, A. niger, A. flavus and Saccharomyces cerevisae [b].

a. Jones S.B., Jr., Luchsinger A.E. Plant Systematics. 2nd ed. McGraw-Hill Book Co.; New York, NY, USA: 1986. b. Moneim A., Suleman E., Issa F.M., Elkhalifa E.A. Quantitative determination of tannin content in some sorghum cultivars and evaluation of its antimicrobial activity. Res. J. Microbiol. 2007;2:284–288

The identification and isolation of active compounds from plants is still a problem in most countries. Continuous efforts are being made to study plants in order to find medicines that could save human life from microbial and viral infections with a minimum of side effects and maximum efficiency.

Herbal extracts are very promising for the development of new drugs that are effective against infections.

References:

  1. Cowan, M.M. (1999) Clin. Microbiol. Rev., 12, 564-582;
  2. Takigawa, K.; Fujita, J. and Negayama, K. (1995) J. Antimicrob. Chemother., 35, 425-427;
  3. Machado, T.B.; Leal, I.C.R.; Kuster, R.M.; Amaral, A.C.F.; Kokis, V.; Silva, M.G., Santos, K.R.N. (2005) Phytother. Res., 19, 519-525;
  4. Chandra, H., Bishnoi, P., Yadav, A., Patni, B., Mishra, A., Nautiyal, A. . Antimicrobial Resistance and the Alternative Resources with Special Emphasis on Plant-Based Antimicrobials—A Review. (2017) Plants, 6(2), 16.