Effect of drought stress on essential oil composition of Thymus vulgaris L. (Chemotype 1, 8-cineole) from wild populations of Eastern Iberian Peninsula

How climate change-related abiotic factors affect the production of industrial valuable compounds in Lamiaceae plant species: a review

The interest in medicinal and aromatic plants (MAPs) has increased significantly in recent years, driven by the growing demand for natural products. MAPs are a valuable source of secondary metabolites, which renders them useful to a number of industries, including cosmetics, pharmaceuticals, and food. The Lamiaceae family includes economically important MAPs that produce valuable secondary metabolites such as essential oils (EOs) and phenolic compounds (PCs). The quantity and quality of these secondary metabolites are affected by abiotic stress factors. In a climate change scenario, the Lamiaceae is one of the most affected families, especially due to its wide distribution in the Mediterranean region. In the present study, the most common climate-related environmental stress factors, namely, drought, salinity, temperature, light, and heavy metals, were reviewed and discussed in order to assess their impact on the chemical profiles of EOs and PCs, as well as on the biological properties (antioxidant, antibacterial, antimelanogenic, pest-repellent, and UV-protective) of Lamiaceae species. It can be posited that these stresses typically act as a catalyst for the secondary metabolism of these plants, resulting in increased production of EO compounds (e.g., 1,8-cineole, linalool, camphor, borneol, and limonene) and PCs (e.g., rosmarinic, caffeic, and salvianolic acids) and subsequent enhancement of their biological activities. In view of the industrial applications of these bioactive compounds, it is of interest to explore the changes in secondary metabolism induced by environmental factors as it is possible to increase the accumulation of valuable secondary metabolites.

Exploring Chemical Variability in the Essential Oils of the Thymus Genus

Thyme remains an indispensable herb today, finding its place in gastronomy, medicine, cosmetics, and gardens worldwide. It is highly valued in herbal remedies and pharmaceutical formulations for its antibacterial, antifungal, and antioxidant properties derived from the richness of its essential oil, which comprises various volatile components. However, climate change poses a significant challenge today, potentially affecting the quality of thyme, particularly the extracted essential oil, along with other factors such as biotic influences and the plant's geographical distribution. Consequently, complex diversity in essential oil composition was observed, also influenced by genetic diversity within the same species, resulting in distinct chemotypes. Other factors contributing to this chemodiversity include the chosen agrotechnology and processing methods of thyme, the extraction of the essential oil, and storage conditions. In this review, we provide the latest findings on the factors contributing to the chemovariability of thyme essential oil.

Harnessing Plant's Arsenal: Essential Oils as Promising Tools for Sustainable Management of Potato Late Blight Disease Caused by Phytophthora infestans-A Comprehensive Review

Potato late blight disease is caused by the oomycete Phytophthora infestans and is listed as one of the most severe phytopathologies on Earth. The current environmental issues require new methods of pest management. For that reason, plant secondary metabolites and, in particular, essential oils (EOs) have demonstrated promising potential as pesticide alternatives. This review presents the up-to-date work accomplished using EOs against P. infestans at various experimental scales, from in vitro to in vivo. Additionally, some cellular mechanisms of action on Phytophthora spp., especially towards cell membranes, are also presented for a better understanding of anti-oomycete activities. Finally, some challenges and constraints encountered for the development of EOs-based biopesticides are highlighted.

Methyl jasmonate and salicylic acid as powerful elicitors for enhancing the production of secondary metabolites in medicinal plants: an updated review

Plant secondary metabolites are bioactive scaffolds that are crucial for plant survival in the environment and to maintain a defense mechanism from predators. These compounds are generally present in plants at a minimal level and interestingly, they are found to have a wide variety of therapeutic values for humans. Several medicinal plants are used for pharmaceutical purposes due to their affordability, fewer adverse effects, and vital role in traditional remedies. Owing to this reason, these plants are exploited at a high range worldwide and therefore many medicinal plants are on the threatened list. There is a need of the hour to tackle this major problem, one effective approach called elicitation can be used to enhance the level of existing and novel plant bioactive compounds using different types of elicitors namely biotic and abiotic. This process can be generally achieved by in vitro and in vivo experiments. The current comprehensive review provides an overview of biotic and abiotic elicitation strategies used in medicinal plants, as well as their effects on secondary metabolites enhancement. Further, this review mainly deals with the enhancement of biomass and biosynthesis of different bioactive compounds by methyl jasmonate (MeJA) and salicylic acid (SA) as elicitors of wide medicinal plants in in vitro by using different cultures. The present review was suggested as a significant groundwork for peers working with medicinal plants by applying elicitation strategies along with advanced biotechnological approaches.

Drought stress modifies the community structure of root-associated microbes that improve Atractylodes lancea growth and medicinal compound accumulation

Atractylodes lancea is an important medicinal plant in traditional Chinese medicine, its rhizome is rich of volatile secondary metabolites with medicinal values and is largely demanded in modern markets. Currently, supply of high-yield, high-quality A. lancea is mainly achieved via cultivation. Certain soil microbes can benefit plant growth, secondary metabolism and induce resistance to environmental stresses. Hence, studies on the effects of soil microbe communities and isolates microorganisms on A. lancea is extremely meaningful for future application of microbes on cultivation. Here we investigated the effects of the inoculation with an entire soil microbial community on the growth, resistance to drought, and accumulation of major medicinal compounds (hinesol, β-eudesmol, atractylon and atractylodin) of A. lancea. We analyzed the interaction between A. lancea and the soil microbes at the phylum and genus levels under drought stress of different severities (inflicted by 0%, 10% and 25% PEG6000 treatments). Our results showed that inoculation with soil microbes promoted the growth, root biomass yield, medicinal compound accumulation, and rendered drought-resistant traits of A. lancea, including relatively high root:shoot ratio and high root water content under drought. Moreover, our results suggested drought stress was more powerful than the selectivity of A. lancea in shaping the root-associated microbial communities; also, the fungal communities had a stronger role than the bacterial communities in protecting A. lancea from drought. Specific microbial clades that might have a role in protecting A. lancea from drought stress were identified: at the genus level, the rhizospheric bacteria Bacillus, Dylla and Actinomadura, and rhizospheric fungi Chaetomium, Acrophialophora, Trichoderma and Thielava, the root endophytic bacteria Burkholderia-Caballeronia-Paraburkholderia, Allorhizobium-Neorhizobium-Pararhizobium-Rhizobium, Dylla and Actinomadura, and the root endophytic fungus Fusarium were closely associated with A. lancea under drought stress. Additionally, we acquired several endophytic Paenibacillus, Paraburkholderia and Fusarium strains and verified they had differential promoting effects on the medicinal compound accumulation in A. lancea root. This study reports the interaction between A. lancea and soil microbe communities under drought stress, and provides insights for improving the outcomes in A. lancea farming via applying microbe inoculation.

In-Depth Study of Thymus vulgaris Essential Oil: Towards Understanding the Antibacterial Target Mechanism and Toxicological and Pharmacological Aspects

Questions have been raised apropos the emerging problem of microbial resistance, which may pose a great hazard to the human health. Among biosafe compounds are essential oils which captured consumer draw due to their multifunctional properties compared to chemical medication drugs. Here, we examined the chemical profile and the mechanism(s) of action of the Thymus vulgaris essential oil (TVEO) against a Gram-negative bacterium Salmonella enterica Typhimurium ATTCC 10028 (S. enterica Typhimurium ATTCC 10028) and two Gram-positive bacteria Staphyloccocus aureus ATCC 6538 (S. aureus ATCC 6538) and Listeria monocytogenes ATCC 19117 (L. monocytogenes ATCC 19117). Findings showed that TVEO was principally composed of thymol, o-cymene, and γ-terpinene with 47.44, 16.55, and 7.80%, respectively. Molecular docking simulations stipulated that thymol and β-sesquiphellandrene (a minor compound at 1.37%) could target multiple bacterial pathways including topoisomerase II and DNA and RNA polymerases of the three tested bacteria. This result pointed plausible impairments of the pathogenic bacteria cell replication and transcription processes. Through computational approach, the VEGA quantitative structure–activity relationship (QSAR) model, we revealed that among twenty-six TVEO compounds, sixteen had no toxic effects and could be safe for human consumption as compared to the Food and Drug Administration (FDA) approved drugs (ciprofloxacin and rifamycin SV). Assessed by the SwissADME server, the pharmacokinetic profile of all identified TVEO compounds define their absorption, distribution, metabolism, and excretion (ADME) properties and were assessed. In order to predict their biological activity spectrum based on their chemical structure, all TVEO compounds were subjected to PASS (Prediction of Activity Spectra for Substances) online tool. Results indicated that the tested compounds could have multiple biological activities and various enzymatic targets. Findings of our study support that identified compounds of TVEO can be a safe and effective alternative to synthetic drugs and can easily combats hazardous multidrug-resistant bacteria.

Altered Antimicrobial and Anti-biofilm Forming Effect of Thyme Essential Oil due to Changes in Composition

The antimicrobial and anti-biofilm forming effect of thyme (Thymus vulgaris) essential oil (TEO) with different compositions was evaluated. Normally the main component in this TEO is thymol, but in 2014 we found that the proportions of γ-terpinene and p-cymene (the precursors in thymol biosynthesis) increased and that of thymol decreased. This altered composition led to changes in the antimicrobial and anti-biofilm forming capacity of the essential oil depending also on the type of microorganisms. In the case of bacteria, minimal inhibitory (MIC) and minimal bactericidal (MBC) concentrations either decreased or increased. In the case of yeasts, minimal fungicidal concentrations (MFC) increased 4- and 8-fold for TEO containing p-cymene as the main component. On the contrary, MIC values decreased for all the tested moulds. Anti-biofilm forming activity of TEO containing p-cymene as its main component decreased in almost all cases and P. fluorescens biofilm forming capacity was even enhanced.