Antimicrobial Activity of Plant Extracts

Dear Colleagues,

Traditional medicine summarizes the millenary knowledge based on the customs, rituals, and activities of indigenous peoples and civilizations around the world; part of this knowledge lies in the use of plants, which are a potential source of leading compounds or molecules. A high percentage of drugs for clinical use approved in the last 40 years have been developed from products of natural origin or their semi-synthetic derivatives, and a significant number of them come from plants. In this way, plants have represented a rich source of compounds with diverse activities that promote human health, among which are anti-inflammatory, anti-cancer, or anti-infectious activities. The development of pharmaceutical products from plants requires a long and extensive research, which begins with the selection of the plant, often based on ethnomedical knowledge of its use. Under ethnomedical or non-ethnomedical criteria, the plant is selected, then it is collected, its taxonomic identity is confirmed and later it is processed for the extraction of its ctivee principles, obtaining the respective plant extract, which can be polar or non-polar. The most commonly solvents used in the preparation of plant extracts are of different polarity, the most polar are water, ethanol, or methanol; those of intermediate polarity are dichloromethane, chloroform, and ethyl acetate, and those of low polarity or non-polar are benzene, n-hexane, or ether. The extraction process is complemented by using, in addition to solvents, different extraction procedures, such as maceration, digestion, decoction, infusion, percolation, distillation, or extractions assisted with ultrasound, microwave, or Soxhlet. The studies of the biological properties of these extracts are generally carried out in a bioguided way. The isolation of the active compounds is performed through chromatographic techniques, such as High Pressure Liquid Chromatography (HPLC), these procedures have accelerated and facilitated the isolation of the active principles. The final part of this process involves the chemical characterization of the isolated active ingredients, where various spectroscopic techniques are fundamental, including UV-visible, infrared, nuclear magnetic resonance, and mass spectroscopy. 

A current global health problem is antimicrobial resistance caused by microorganisms responsible for the infectious diseases that afflict humanity today. Antimicrobial resistance occurs when different types of microorganisms from viruses, bacteria, fungi, and parasites are no longer susceptible to antimicrobials in such a way that neither antibiotics nor other drugs are effective for the control of pathogens, with the consequent worsening of the disease that can lead not only to the death of the patient but also to the transmission of the pathogenic agent with such antimicrobial resistance, becoming a public health problem.

Diseases that were thought to be under control have re-emerged, antibiotic resistance being one of the main factors responsible of the re-emergency. WHO considers antimicrobial resistance as one of the top 10 global public health threats facing humanity. Without decisive actions driven to address antimicrobial resistance, it is estimated that by 2050 the leading cause of death worldwide will be from antimicrobial-resistant infectious diseases. Ten fundamental actions have been proposed to contain antimicrobial resistance in the medium term, including the search for and optimization of new drugs, as well as the rational use of existing drugs. Thus, plants remain an unsurpassed source of leading compounds or molecules with potential antimicrobial activity.

The present Special Issue aims to gather current information on the antimicrobial activity of plant extracts; papers on the activity of extracts against bacteria, fungi, and parasites are welcome. Preferably, the studies should present the total or partial characterization of the extracts and ideally describe, identify, or characterize the compound(s) responsible for the antimicrobial activity; additionally, we welcome studies describing the antimicrobial activity of standardized or characterized plant extracts. It is recommended that the studies describe the selection of the plant or plants used, especially if they were selected for their ethnomedical utility.

Dr. Julieta Luna-Herrera
Dr. María Adelina Jimenez Arellanes
Guest Editors

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• traditional medicine
• medicinal plants
• Plant extracts
• antimicrobial activity
• drug resistance
• phytotherapy
• standardized plant extracts
• bioactive compounds or extracts