Chemical composition and biological action of the Ruta graveolens L. and Ambrosia arborescens: sociocultural incidence

Plant growth-promoting rhizobacteria (PGPRs) are a specific group of soil microorganisms that aggressively colonize the rhizosphere and rhizoplane, and substantially improve plant growth and efficiency via direct or indirect mechanisms. Moreover, infection by microorganisms as well as physiological and genetic factors and environmental conditions are the main agents affecting the accumulation and composition of secondary metabolites. As an environmentally friendly strategy, PGPRs should be considered to achieve sustainable high yields of industrially important secondary metabolites in plants using minimum chemical inputs. This chapter aims to introduce proven or putative mechanisms by which PGPRs promote seed germination, growth, nutrient acquisition, and production of primary and secondary metabolites in aromatic and medicinal plants.

Carnivorous plants are an ideal model system for evaluating the role of secondary metabolites in plant ecology and evolution. Carnivory is a striking example of convergent evolution to attract, capture and digest prey for nutrients to enhance growth and reproduction and has evolved independently at least ten times. Though the roles of many traits in plant carnivory have been well studied, the role of secondary metabolites in the carnivorous habit is considerably less understood. This review provides the first synthesis of research in which secondary plant metabolites have been demonstrated to have a functional role in plant carnivory. From these studies we identify key metabolites for plant carnivory and their functional role, and highlight biochemical similarities across taxa. From this synthesis we provide new research directions for integrating secondary metabolites into understanding of the ecology and evolution of plant carnivory. Carnivorous plants use secondary metabolites to facilitate prey attraction, capture, digestion and assimilation. We found ~170 metabolites for which a functional role in carnivory has been demonstrated. Of these, 26 compounds are present across genera that independently evolved a carnivorous habit, suggesting convergent evolution. Some secondary metabolites have been co-opted from other processes, such as defence or pollinator attraction. Secondary metabolites in carnivorous plants provide a potentially powerful model system for exploring the role of metabolites in plant evolution. They also show promise for elucidating how the generation of novel compounds, as well as the co-option of pre-existing metabolites, provides a strategy for plants to occupy different environments.

Spices and aromatic herbs have been used since antiquity as preservatives, colorants, and flavor enhancers. Secondary metabolites(SM) are compounds that are not necessary for a cell (organism) to live, but play a role in the interaction of the cell (organism) with its environment. These compounds are often involved in plants protection against biotic or abiotic stresses. Secondary metabolites are mainly responsible for plant defense and have no direct involvement in the growth and development of such plants. Terpenes, alkaloids and phenolics are three main classes of secondary metabolites in plants. Black pepper, cardamom, ginger, turmeric, cinnamon, clove and nutmeg are spices of great commercial importance as it provides flavor and taste to the culinary preparations were it is added. Secondary metabolites of these spices are of great significance in the present era of nutraceuticals as these spices possess antioxidant, anticancerous, numerous other medicinal properties. Detailed information on these spices is very interesting.

Nature, the supreme artist, and scientists have designed almost an infinite range of plant molecular bioactive molecules for drugs operative for the remedy of innumerable human disorders in the biosynthetic laboratory of plants. From 250,000 to 300,000 plant species which exist on Earth, only about 5000 were investigated for chemical compounds with pharmacological and biological activities. More than 25% of pharmaceutical molecules are plant based through sequestration of the novel bioactive compounds. The 200,000 known secondary metabolites with widespread chemical structures are manly categorized into phenolics, terpenoids or terpenes, and steroids and alkaloids. Secondary metabolites perform significant functions in plants including role as signaling molecules, chemical defense mechanism and adaptation, pollination and seed dispersal, protection from predators, herbivores, pathogens, and allelopathic agents. Medicinal and aromatic plants (MAPs) are bestowed with both the aromatic and medicinal properties and contain bioactive secondary metabolites with a broad range of pharmacological and therapeutic potentials such as antioxidant, antitumor, anticancer, antiviral, antimicrobial, anti-inflammatory, antiatherosclerotic, antidepressant, antidiabetic, hepatoprotective, antithrombotic, vasoprotective, and immunoprotective effects, cardiovascular improver, memory enhancer, anti-AIDS, anti-Alzheimer’s, anti-Parkinson’s disease, and anti-cognitive impairment.

Melissa officinalis (lemon balm) presents essential oils and poliphenols with reported biological activity. Micropropagation represents an important tool for the standardization and selection of elite plants. Production of secondary metabolites in plants depends on the biotic and abiotic conditions of the culture environment. Plants induced to produce specific biologically active compounds by exogenous molecules may have their nutraceutical value increased. Salicylic acid acts in plants as an inducer of the expression of protective protein and it can be thus included into biotic elicitors. The present paper examined the effects of salicylic acid (1.5mM) aqueous solution on the essential oil composition of M. officinalis in vitro plants. The maximal content of neral/nerol (twice as large as the control content) detected by GC/ME was demonstrated after 24 hours. In vitro plants, showed an increase of 2.2 times in geranial / geraniol proportion and 1.6% of neral / nerol, after 24 hours of exposure to SA, when compared to control plants (MS0).

Chapter 4 - Medicinal Activities of Essential Oils: Role in Disease Prevention

Intoduction Essential oils (EOs) are important aromatic components of herbs and spices which are complex mixtures of secondary plant metabolites consisting of low-boiling-phenylpropenes and terpenes. Their biological activities have been known and utilized since ancient times in perfumery, food preservation, flavoring, and medicine. Some of their biological activities include antibacterial, antifungal, anti-oxidant and anti-inflammatory effects. The ban on the use of antibiotics as growth promoters has stimulated the search for alternative feed supplements in animal production. EOs have received attention in recent years as potential ‘natural’ alternatives for replacing antibiotic growth promoters (AGPs) in animal diets due to their positive impact on growth performance and welfare. A number of studies have been carried out to investigate the effects of EOs on broiler performance rather than the physiological effects, but the results have not been consistent (or constant). The purpose of this study was to investigate the effects of four essential oils (Thymus vulgaris, Mentha piperita, Citrus lemon, Carum copticom) on growth performance, some of the serum biochemistry parameters and lipogenic gene expression in broiler chickens. Materials and Methods A total of 312, 1-day-old broiler chicks were allocated in completely randomized design to 13 groups with 6 replicate cages per treatment. After 2-day adjustment with the basal diet, the birds were randomly assigned to the corresponding experimental diets supplemented with 0 (Control), 50, 100 and 150 mg/kg diet essential oils extracted from Crum capticum, Thymus vulgaris, Mentha piperita and Cirtus lemon. The basal diet composed of maize–soybean meal prepared in our laboratory and all birds had free access to water for the entire period. Food intake and BW were recorded to determine growth performance and feed: gain ratio. At the end of the experiment (42 day) blood samples (6 samples per treatment) were taken for measuring biochemical analysis including total protein, triglyceride, total cholesterol, HDL-c and LDL-c by commercial kits. Samples of the liver were collected on day 42 after slaughter (6 samples per treatment) and the hepatic expression of the genes encoding malic enzyme (ME), fatty acid synthase (FAS) were determined with reverse transcription-polymerase chain reaction (RT-PCR) using SYBR green as a flourophore monitored in a real time mode. Results and discussion The results showed that the body weight, feed intake and feed conversion ratio of broilers at day 42 were not affected by supplementing EOs to the basal diet. However, daily body weight gain of broilers at 21 day decreased significantly (P<0.05) by dietary supplementation of 150 ppm Mentha piperita essential oil compared to control and some of the treatment groups. In the previous studies, variable effects of EOs on performance have been reported. The variability in the efficacy of EOs on animal performance could be attributed to the composition of the basal diet (less digestible diet), level of feed intake, hygienic standards and environmental conditions. Other factors that could affect the results of in vivo experiments are: harvesting time and state of maturity of plants, extraction methods of plants, method and duration of conservation and storing and possible synergistic or antagonistic effect of the bioactive compounds. The concentrations of serum cholesterol, total protein, triglyceride, total cholesterol, HDL-c and LDL-c were not affected by treatments. The absence of hypochlosrtrolemic and hypolipidemic effects of applied essential oils in the present study may be attributed to rapid urinary excretion of essential oil metabolites and composition of the basal feed. Treatments had no significant effect on the expression of mRNA for fatty acid synthase compared to control. In chicks fed the diet supplemented with 150 ppm mint essential oil, malic enzyme mRNA expression was significantly (P≤0.05) enhanced compared with chicks fed the basal diet. The reason for this effect is unknown, but it may be attributed to Stress-Induced Metabolic or metabolic stress inducing by upper dose of mint EO that may predispose broilers to hepatic steatosis.In general, results of the present study propose a possible role for some herbal essential oils in the regulation of broiler metabolism. However, contrary to our previous assumption, this role may not be antilypogenic. Moreover, according to the results it could be claimed that EOs may have differential and dose response effects on lipid metabolism in broilers. In conclusion, supplementation of Mint EO at upper levels (150 ppm) in not recommended as feed additive in broiler diets.

Secondary metabolites in plants having aromatic and medicinal properties are commercially usable and are being used for health protection in different forms such as in drugs, pheromones, flavors, antioxidants, fragrances, insecticides, and dyes. About 25% of the legal drugs have been synthesized directly from natural substances obtained from plants, and 40% involve chemically modified natural substances. Owing to immense demand of these secondary metabolites, the deficient production capacity of plants must be overcomed. Plant breeding is a traditional, time-consuming, and limited way of improving the secondary metabolites production capacity of medicinal plants. Metabolic engineering in this regard can be a helpful and economical method which involves insertion of genes of interest into other cells and modify target pathways, allowing for improved processing of usable natural substances as well as the development of novel compounds. This review illustrates the importance of medicinal plants in producing secondary metabolites. Here we discussed the pathways involved in producing secondary metabolites and the role of metabolic engineering in manipulating these pathways to get the required results. Additionally, we explained how RNAi-mediated gene silencing helps to regulate different genes involved in synthesizing useful natural substances.KeywordsSecondary metabolitesMedicinal plantsMetabolic engineeringNovel compoundsRNAi-mediated gene silencing

Introduction: Basil genus (Ocimum) contains 30 to 150 species which grown in tropical and subtropical regions of Asia, Africa, Central and South America and found as a wild plant in these areas. In India, around 25,000 ha is under cultivation of Ocimum spp., with an annual production of about 250–300 tonnes of essential oil. Ocimum gratissimum L., a dicotyledonous shrub plant, which belongs to the Lamiaceae family, stands out for the quality, quantity and chemical diversity of the essential oils. These oils have been used in the pharmaceutical, cosmetic and food industries. Some of the essential oil compounds have antibacterial, insecticidal and antioxidant properties with high demand on the international market of the fine perfumery industry. It is also popularly used in herbal medicine for treating several diseases, such as upper respiratory tract infection, fever, cough, diarrhea and pneumonia. Being a short-duration economically viable medicinal and aromatic crop, clove basil has huge potential for large scale cultivation. Plant genetic has an important role in determining the type and amount of secondary metabolites of medicinal plants. Moreover, the recognition of species and genotypes with high genetic capability in the production of desired metabolites has been at the top of the plant breeding plans of medicinal plants. In addition, essential oil composition of plants may be affected by harvest time which is due to the impact of weather conditions on plant growth and development. The present study was aimed to evaluate the oil composition of two genotypes in two harvests. Materials and Methods: The research was conducted in the research farm of the college of agriculture, shahid Chamran University, Ahvaz, Iran during 2019. Two valuable genotypes of Ocimum gratissimum L. (278 and 296), with two different essential oil profiles, were investigated in two harvests; spring and autumn seasons. The aboveground parts of the plants were collected on June and November and dried on shade at room temperature. The essential oils of the plants were extracted by water distillation through Clevenger apparatus and the quantity and quality of the essential oils were analyzed by GC and GC-MS. Results and Discussion: The results of present study showed that the essential oil content of two genotypes was not affected by the harvest season while its amount was different in two genotypes. The essential oil content of genotype 296 was 2-fold of 278. According to the qualitative analysis of the essential oils, fifty compounds were identified in the essential oils of 278 and 296 genotypes. More than 98% of the identified compounds (in the essential oils of these two genotypes) were classified into five chemical classes; including hydrocarbon and oxygenated monoterpens, and hydrocarbon and oxygenated sesquiterpene and phenylpropanoids. The major constituent of the essential oil of genotype 278 was oxygenated monoterpene, thymol, on June (35.48 %) and November (45.85 %), which was not found in genotype 296. Gamma-terpinene was also significantly increased from June (13.15 %) to November (25.80 %). P-cymene (11.31-3.56 %), alpha- thujone (4.76-2.94 %), Germacrene D (3.73-2.76 %), caryophyllene E (3.66-1.51 %), myrcene (2.93-3.01 %), alpha-terpinene (2.63-3.38 %) and bourneol (2.28-0.71 %) were the remains of oil composition. Dihydro eugenol, which belongs to the chemical class of phenylpropanoids, was identified as the main essential oil components of genotype 296 which its amount was not affected by the harvest time. The other oil constituents were Beta (Z)-Ocimene (11.89-3.40 %), Germacrene D (3.58-2.80 %), and caryophyllene E (0.52-2.68 %). Conclusion: Terpenoids such as thymol are synthesized via the mevalonic acid pathway, and phenylpropanoid compounds such as dihydroeugenol and eugenol are synthesized via the shikimic acid pathway. The metabolite diversity across different species could be explained by the differential gene expression pattern. According to the results of the present study, thymol was identified as the main oil components of genotype 278. This may be due to the increased expression of mevalonate enzymes. The monoterpene was replaced by phenylpropanoid; dihydrogenugenol, in the oil of genotype 296 which might be due to more expression of the enzymes of the phenylpropanoid pathway. In the other hand, Thymol, P-cymene and gamma-terpinene in genotype 278 varied significantly in different harvesting times, indicating the effect of temperature on the activity of enzymes involved in the synthesis of essential oil components. On the contrary, the amount of dihydrogenugenol in genotype 278 on June and November is not affected by the environmental conditions in two seasons. With regard to the conclusions to the proper growth of genotype 278 and 296, as well several harvests annually, essential oil content and thymol and dihydrogenugenol, therefore, it is suggested that further research should be carried out for developing plant cultivation in Khuzestan and southern provinces which is not suitable for basil growth.

Essential oils are secondary metabolites in plants with a variety of biological activities. The flavor and quality of Zanthoxylum armatum DC. are mainly determined by the essential oil components in the Chinese prickly ash peels. In this study, the correlation between climate change in different regions and the content of essential oils of Z. armatum was investigated using gas chromatography-mass spectrometry (GC/MS) and multivariate statistical analysis. The Z1-24 refers to 24 batches of samples from different habitats. A total of 145 essential oils were detected in 24 batches of samples, with the highest number of terpene species and the highest content of alcohol. The relative odor activity (ROAV) values identified nine main flavor compounds affecting the odor of Z. armatum. Linalool, decanal, and d-limonene were the most critical main flavor compounds, giving Z. armatum a spicy, floral, oily, and fruity odor. The results of hierarchical cluster analysis (HCA) and principal component analysis (PCA) classified Z5 into a separate group, Z2 and Z7 were clustered into one group, and the rest of the samples were classified into another group. Correlation analysis and path analysis showed that temperature and precipitation were the main climatic factors affecting essential oils. Comparisons can be made with other plants in the genus Zanthoxylum to analyze differences in essential oil type and content. This study contributes to the identification of Z. armatum quality, promotes the accumulation of theories on the effects of climatic factors on essential oils, and enriches the site selection and breeding of Z. armatum under similar climatic conditions.

Context: Essential oil Olea europaea was investigated for its antibacterial and antifungal activities. Aim: To evaluate antimicrobial activity of O. europaea essential oil against infectious microbial pathogens. Settings and Design: Seeds of O. europaea were grounded by using domestic mixer and powdered material was hydro‑distilled in Clevenger apparatus continuously for 5 hrs to yield essential oil. Essential oil was analysed on Gas‑Chromatography‑Mass spectrometry (GC‑MS) from which 24 components were identified, representing total 99.98% of the oil. Extracted oil was evaluated for their antibacterial and antifungal activities. Materials and Methods: Paper disc diffusion and serial micro‑dilution assays were performed for the determination of inhibition zone diameters and minimal inhibitory concentration, respectively. Results: The O. europaea essential oil showed the diameter of inhibition zone (DIZ) ranging from 19.4 ± 0.07‑26.4 ± 0.09 mm at a concentration level of 28 μg/disc (W/V) separately in all the ten strains tested. The minimum inhibitory concentration of essential oil against bacterial strains was obtained in a range of 7.0-56.0 μg/ml while in and fungal strains it was in a range of 7.0‑28 μg/ml. Statistical analysis: All statistical calculations are expressed as mean ± SE of three replicates. Data were analyzed by one‑way Analysis of Variance (ANOVA) to locate significant variations in oil activity in various bacterial and fungal strains followed by the Duncan’s multiple range tests. Conclusions: Antibacterial and antifungal activities of O. europaea essential oil are due to the presence of certain secondary plant metabolites such as terpenoids, steroids and flavonoids, esters, and acids, which were identified in the essential oil. The oil components can be further investigated for their biological activities and study to overcome the problem of drug resistance in microbes. Key words: Antimicrobial activity, essential oil, gas-chromatography-mass spectrometry analysis, inhibition zone diameters, minimum bacterial concentration, minimum fungicidal concentration, minimum inhibitory concentration, Olea europaea

Essential oils are hydrophobic liquids produced as secondary metabolites by specialized secretory tissues in the leaves, seeds, flowers, bark and wood of the plant, and they play an important ecological role in plants. Essential oils have been used in various traditional healing systems due to their pharmaceutical properties, and are reported to be a suitable replacement for chemical and synthetic drugs that come with adverse side effects. Thus, currently, various plant sources for essential oil production have been explored. Coriander essential oil, obtained from the leaf and seed oil of Coriandrum sativum, has been reported to have various biological activities. Apart from its application in food preservation, the oil has many pharmacological properties, including allelopathic properties. The present review discusses the phytochemical composition of the seed and leaf oil of coriander and the variation of the essential oil across various germplasms, accessions, at different growth stages and across various regions. Furthermore, the study explores various extraction and quantification methods for coriander essential oils. The study also provides detailed information on various pharmacological properties of essential oils, such as antimicrobial, anthelmintic, insecticidal, allelopathic, antioxidant, antidiabetic, anticonvulsive, antidepressant, and hepatoprotective properties, as well as playing a major role in maintaining good digestive health. Coriander essential oil is one of the most promising alternatives in the food and pharmaceutical industries.

Secondary metabolites, including alkaloids, flavonoids, and tannins, are crucial for human health, agriculture, and ecosystem functioning. Their synthesis is often species-specific, influenced by both genetic and environmental factors. The increasing demand for these compounds across various industries highlights the need for advancements in plant breeding and biotechnological approaches. Transcription activator-like effector nucleases (TALENs) have emerged as a powerful tool for precise genome editing, offering significant potential for enhancing the synthesis of secondary metabolites in plants. However, while plant genome editing technologies have advanced significantly, the application of TALENs in improving secondary metabolite production and expanding genetic diversity remains underexplored. Therefore, this review aims to provide a comprehensive analysis of TALEN-mediated genome editing in plants, focusing on their role in enhancing secondary metabolite biosynthetic pathways and improving genetic diversity. The mechanisms underlying TALENs are examined, including their ability to target specific genes involved in the synthesis of bioactive compounds, highlighting comparisons with other genome editing tools such as CRISPR/Cas9. This review further highlights key applications in medicinal plants, particularly the modification of pathways responsible for alkaloids, flavonoids, terpenoids, and phenolic compounds. Furthermore, the role of TALENs in inducing genetic variation, improving stress tolerance, and facilitating hybridization in plant breeding programs is highlighted. Recent advances, challenges, and limitations associated with using TALENs for enhancing secondary metabolite production are critically evaluated. In this review, gaps in current research are identified, particularly regarding the integration of TALENs with multi-omics technologies and synthetic biology approaches. The findings suggest that while underutilized, TALENs offer sustainable strategies for producing high-value secondary metabolites in medicinal plants. Future research should focus on optimizing TALEN systems for commercial applications and integrating them with advanced biotechnological platforms to enhance the yield and resilience of medicinal plants.

Plant growth-promoting rhizobacteria (PGPRs) are a group of naturally occurring beneficial soil bacteria that colonize with the plant root system and promote growth by triggering the production of growth-regulating substances and facilitate the plants in the uptake of essential nutrients from the surrounding environments. Similarly, arbuscular mycorrhizal (AM) fungi also enhanced the growth, water and nutrient uptake, and especially available phosphate through their specialized hyphae. In addition, PGPR and AM fungi are known to stimulate the accumulation of secondary metabolites in plants. For several years, they are commonly employed to increase the plant yield and productivity especially in agricultural practices. The medicinal and aromatic plants are gaining popularity worldwide due to high therapeutic properties with negligible toxic side effects. To fulfill the global demand and supply gap for medicinal and aromatic plants and their products, farmers are encouraged to cultivate these plants on a large scale. However, there is a need to understand and implement a better cultivation practices in order to improve the quality of medicinal and aromatic plants. In this regard, the utilization of PGPRs and AM fungi as biofertilizers instead of chemical fertilizers could be a promising approach to the development of medicinal and aromatic plants under the sustainable production system. The aim of this chapter is to describe the potentiality of PGPRs and AM fungi to improve growth and development of medicinal and aromatic plants and accumulation of secondary metabolites having high therapeutic worth and also pave a way in the development of new biotechnological products as biofertilizers.

Understanding the consequence of environmental stress for accumulation of secondary metabolites in medicinal and aromatic plants