While we may not be able to conclusively state that all plant-derived terpenes can fight all antibiotic-resistant infections, the current evidence allows us to wonder whether these plant compounds are the future of antibiotic treatment?
The first antibiotic, penicillin, was discovered by Sir Alexander Fleming in 1928. This discovery marked the beginning of “the antibiotic golden age” which was the period from the 1940s-1970s. All was fine and dandy until antibiotic resistance became a thing due to the misuse and overuse of antibiotics.
The antimicrobial potential of terpenes has been highlighted in several studies. [1] For example, in one study, it was shown that the hydroxyl group found in phenols and alcohols offers this antibiotic property to terpenes. [2] A different study demonstrated the synergistic benefits that occur when terpenes are combined with antibiotics, such as rifampicin which is used to treat bacterial infections such as tuberculosis, Mycobacterium avium complex, leprosy, and Legionnaires’ disease. [3]
A group of researchers in Rome reviewed available studies to understand the unique role that terpenes play in fighting antibiotic resistance. [1] The researchers found that plant-derived terpenes can reduce antibiotic resistance through different mechanisms. Here are a few highlights from the study:
The terpene geraniol has activity against a gram-negative bacteria called Enterobacter aerogenes. By acting as an efflux pump inhibitor, this terpenoid reverses chloramphenicol resistance. [4]
The terpenoid camphor has activity against several bacteria such as Staphylococcus aureus, Escherichia coli, and Klesiella pneumoniae. It acts as a growth inhibitor and is able to reverse antibiotic resistance against these microorganisms. [5]
Other terpenoids including linalool, terpinen-4-ol, and borneol have synergistic benefits that inhibit the growth of E. coli and Salmonella species. [5]
Other terpenes groups, including sesquiterpenes, diterpenes, and triterpenes, have demonstrated antibiotic activity against Streptococcus species. This reduces resistance to β-lactam antibiotics. [6]
The diterpene vitexolide that is found in the chaste tree has activity against the gram-positive bacteria, S. aureus. It is useful in combating multi-drug resistance to this bacterium.
This review highlighted the potential of plant-derived terpenes in combating antibiotic resistance which is now in crisis levels. The study authors highlighted the need for further studies.
Image Source
https://commons.wikimedia.org/wiki/File:Antibiotic_resistance_mechanisms.jpg
References
[1] Cappiello F, Loffredo MR, Del Plato C, et al. The revaluation of plant-derived terpenes to fight antibiotic-resistant infections. Antibiotics (Basel). 2020; 9(6):325. Doi:10.3390/antibiotics9060325. Journal Impact Factor: 2.921, Times Cited: 14 (PubMed)
[2] Guimarães AC, et al. Antibacterial activity of terpenes and terpenoids present in essential oils. Molecules (Basel, Switzerland). 2019; 24(13):2471. Journal Impact Factor: 3.267, Times Cited: 182 (PubMed)
[3] Sieniawska E, et al. Natural terpenes influence the activity of antibiotics against isolated mycobacterium tuberculosis. Medical Principles & Practice. 2017; 26:108-112. Journal Impact Factor: 1.295, Times Cited: 11 (PubMed)
[4] Lorenzi V, al. Geraniol restores antibiotic activities against multidrug-resistant isolates from gram-negative species. Antimicrob. Agents Chemother. 2009; 53:2209–2211. Journal Impact Factor: 4.715, Times Cited: 264 (PubMed)
[5] Sayout A, et al. Evaluation of antibacterial activity of Lavandulapedunculata subsp. atlantica (braun-blanq.) romo essential oil and selected terpenoids against resistant bacteria strains-structure-activity relationships. Chem Biodivers. 2020: 17(e1900496). Journal Impact Factor: 2.039, Times Cited: 10 (Semantic Scholar)
[6] Brilhante RS, et al. Sesquiterpene farnesol contributes to increased susceptibility to beta-lactams in strains of Burkholderia pseudomallei. Antimicrob Agents Chemother. 2012; 56: 2198–2200. Journal Impact Factor: 4.715, Times Cited: 27 (PubMed)
