The interplay between light, plant growth regulators and elicitors on growth and secondary metabolism in cell cultures of Fagonia indica

Red light enhances the antibacterial properties, biofabrication, and stability of Fagonia indica callus-based silver nanoparticles

Plant-based nanoparticles can be tuned through the frequency of light for efficient synthesis, structural properties, and antibacterial applications. This research assessed the effect of material type (callus and whole-plant extract) and the interaction with a specific range of light wavelength on AgNP synthesis. All types of AgNPs were characterized by their size, shape, associated functional groups, and surface charge. Interestingly, the size of red light and callus-based AgNPs (RC-AgNPs) was smaller (6.32 nm) compared to 14.59 nm for Ultraviolet light and callus-based AgNPs (UV-C-AgNPs). Zeta potential analysis showed that RC-AgNPs had higher stability (-29.2 mV) compared to UV-C-AgNPs (-16.7 mV). Similarly, red light-based AgNPs had higher Oxidation reduction potential in both whole-plant-based and callus-based AgNPs, indicating a more oxidizing nature compared to those synthesized under UV light. This was confirmed by the lower total phenolic and flavonoid content associated with them and their lower antioxidant activity. The higher antibacterial activities and lower minimum inhibitory concentrations of red light-based AgNPs against highly resistant pathogenic bacteria demonstrated the role of red light in enhancing antibacterial activity. These results indicate that AgNPs synthesized in red light and callus extract are more active compared to those synthesized under other wavelengths and/or in whole-plant extracts.

Co-cultures from Plants and Cyanobacteria: A New Way for Production Systems in Agriculture and Bioprocess Engineering

Due to the global increase in the world population, it is not possible to ensure a sufficient food supply without additional nitrogen input into the soil. About 30-50% of agricultural yields are due to the use of chemical fertilizers in modern times. However, overfertilization threatens biodiversity, such as nitrogen-loving, fast-growing species overgrow others. The production of artificial fertilizers produces nitrogen oxides, which act as greenhouse gases. In addition, overfertilization of fields also releases ammonia, which damages surface waters through acidification and eutrophication. Diazotrophic cyanobacteria, which usually form a natural, stable biofilm, can fix nitrogen from the atmosphere and release it into the environment. Thus, they could provide an alternative to artificial fertilizers. In addition to this, biofilms stabilize soils and thus protect against soil erosion and desiccation. This chapter deals with the potential of cyanobacteria as the use of natural fertilizer is described. Possible partners such as plants and callus cells and the advantages of artificial co-cultivation will be discussed later. In addition, different cultivation systems for studying artificial co-cultures will be presented. Finally, the potential of artificial co-cultures in the agar industry will be discussed.

A Comprehensive Review on the Roles of Metals Mediating Insect-Microbial Pathogen Interactions

Insects and microbial pathogens are ubiquitous and play significant roles in various biological processes, while microbial pathogens are microscopic organisms that can cause diseases in multiple hosts. Insects and microbial pathogens engage in diverse interactions, leveraging each other's presence. Metals are crucial in shaping these interactions between insects and microbial pathogens. However, metals such as Fe, Cu, Zn, Co, Mo, and Ni are integral to various physiological processes in insects, including immune function and resistance against pathogens. Insects have evolved multiple mechanisms to take up, transport, and regulate metal concentrations to fight against pathogenic microbes and act as a vector to transport microbial pathogens to plants and cause various plant diseases. Hence, it is paramount to inhibit insect-microbe interaction to control pathogen transfer from one plant to another or carry pathogens from other sources. This review aims to succinate the role of metals in the interactions between insects and microbial pathogens. It summarizes the significance of metals in the physiology, immune response, and competition for metals between insects, microbial pathogens, and plants. The scope of this review covers these imperative metals and their acquisition, storage, and regulation mechanisms in insect and microbial pathogens. The paper will discuss various scientific studies and sources, including molecular and biochemical studies and genetic and genomic analysis.

Application of Data Modeling, Instrument Engineering and Nanomaterials in Selected Medid the Scientific Recinal Plant Tissue Culture

At present, most precious compounds are still obtained by plant cultivation such as ginsenosides, glycyrrhizic acid, and paclitaxel, which cannot be easily obtained by artificial synthesis. Plant tissue culture technology is the most commonly used biotechnology tool, which can be used for a variety of studies such as the production of natural compounds, functional gene research, plant micropropagation, plant breeding, and crop improvement. Tissue culture material is a basic and important part of this issue. The formation of different plant tissues and natural products is affected by growth conditions and endogenous substances. The accumulation of secondary metabolites are affected by plant tissue type, culture method, and environmental stress. Multi-domain technologies are developing rapidly, and they have made outstanding contributions to the application of plant tissue culture. The modes of action have their own characteristics, covering the whole process of plant tissue from the induction, culture, and production of natural secondary metabolites. This paper reviews the induction mechanism of different plant tissues and the application of multi-domain technologies such as artificial intelligence, biosensors, bioreactors, multi-omics monitoring, and nanomaterials in plant tissue culture and the production of secondary metabolites. This will help to improve the tissue culture technology of medicinal plants and increase the availability and the yield of natural metabolites.

Effect of Biotic Elicitors on the Growth, Antioxidant Activity and Metabolites Accumulation in In Vitro Propagated Shoots of Pueraria tuberosa

Pueraria tuberosa contains a wide range of bioactive compounds, including polyphenols, alkaloids, and phytosterols, which make it valuable to the pharmaceutical and food industries. Elicitor compounds trigger the defense mechanisms in plants and are widely used to increase the yield of bioactive molecules in in vitro cultures. The present study was conducted to evaluate the effects of different concentrations of biotic elicitors such as yeast extract (YE), pectin (PEC), and alginate (ALG) on growth, antioxidant activity, and metabolite accumulation in in vitro propagated shoots of P. tuberosa. The elicitors applied to shoot cultures of P. tuberosa significantly increased biomass (shoot number, fresh weight, and dry weight), and metabolites such as protein, carbohydrates, chlorophyll, total phenol (TP), and total flavonoid (TF) contents, as well as antioxidant activity compared to untreated control. Biomass, TP, and TF contents, as well as antioxidant activity, were most significant in cultures treated with 100 mg/L PEC. In contrast, chlorophyll, protein, and carbohydrate increased most in cultures treated with 200 mg/L ALG. Application of 100 mg/L of PEC led to the accumulation of high amounts of isoflavonoids including puerarin (220.69 μg/g), daidzin (2935.55 μg/g), genistin (5612 μg/g), daidzein (479.81 μg/g), and biochanin-A (111.511 μg/g) as analyzed by high-performance liquid chromatography (HPLC). Total isoflavonoids content of 100 mg/L PEC treated shoots was obtained as 9359.56 μg/g, 1.68-fold higher than in vitro propagated shoots without elicitors (5573.13 μg/g) and 2.77-fold higher than shoots of the mother plant (3380.17 μg/g). The elicitor concentrations were optimized as 200 mg/L YE, 100 mg/L PEC, and 200 mg/L ALG. Overall, this study showed that the application of different biotic elicitors resulted in better growth, antioxidant activity, and accumulation of metabolites in P. tuberosa, which could lead to obtaining phytopharmaceutical advantages in the future.

Effect of Wide-Spectrum Monochromatic Lights on Growth, Phytochemistry, Nutraceuticals, and Antioxidant Potential of In Vitro Callus Cultures of Moringa oleifera

Moringa oleifera, also called miracle tree, is a pharmaceutically important plant with a multitude of nutritional, medicinal, and therapeutic attributes. In the current study, an in-vitro-based elicitation approach was used to enhance the commercially viable bioactive compounds in an in vitro callus culture of M. oleifera. The callus culture was established and exposed to different monochromatic lights to assess the potentially interactive effects on biomass productions, biosynthesis of pharmaceutically valuable secondary metabolites, and antioxidant activity. Optimum biomass production (16.7 g/L dry weight), total phenolic contents (TPC: 18.03 mg/g), and flavonoid contents (TFC: 15.02 mg/g) were recorded in callus cultures placed under continuous white light (24 h), and of other light treatments. The highest antioxidant activity, i.e., ABTS (550.69 TEAC µM) and FRAP (365.37 TEAC µM), were also noted under white light (24 h). The analysis of phytochemicals confirmed the significant impact of white light exposures on the enhanced biosynthesis of plant secondary metabolites. The enhanced levels of secondary metabolites, i.e., kaempferol (1016.04 µg/g DW), neochlorogenic acid (998.38 µg/g DW), quercetin (959.92 µg/g DW), and minor compounds including luteolin, apigenin, and p-coumaric acid were observed as being highest in continuous white light (24 h with respect to the control (photoperiod). Similarly, blue light enhanced the chlorogenic acid accumulation. This study shows that differential spectral lights demonstrate a good approach for the enhancement of nutraceuticals along with novel pharmacologically important metabolites and antioxidants in the in vitro callus culture of M. oleifera.

Obtaining 2,3-Dihydrobenzofuran and 3-Epilupeol from Ageratina pichinchensis (Kunth) R.King & Ho.Rob. Cell Cultures Grown in Shake Flasks under Photoperiod and Darkness, and Its Scale-Up to an Airlift Bioreactor for Enhanced Production

Ageratina pichinchensis (Kunth) R.King & Ho.Rob. is a plant used in traditional Mexican medicine, and some biotechnological studies have shown that its calluses and cell suspension cultures can produce important anti-inflammatory compounds. In this study, we established a cell culture of A. pichinchensis in a 2 L airlift bioreactor and evaluated the production of the anti-inflammatory compounds 2,3-dihydrobenzofuran (1) and 3-epilupeol (2). The maximum biomass production (11.90 ± 2.48 g/L) was reached at 11 days of culture and cell viability was between 80% and 90%. Among kinetic parameters, the specific growth rate (µ) was 0.2216 days^-1 and doubling time (td) was 3.13 days. Gas chromatography coupled with mass spectrometry (GC-MS) analysis of extracts showed the maximum production of compound 1 (903.02 ± 41.06 µg/g extract) and compound 2 (561.63 ± 10.63 µg/g extract) at 7 and 14 days, respectively. This study stands out for the significant production of 2,3-dihydrobenzofuran and 3-epilupeol and by the significant reduction in production time compared to callus and cell suspension cultures, previously reported. To date, these compounds have not been found in the wild plant, i.e., its production has only been reported in cell cultures of A. pichinchensis. Therefore, plant cell cultured in an airlift reactor can be an alternative for the improved production of these anti-inflammatory compounds.

Chemical characterization and the intrusion through elicitation and Agrobacterium rhizogenes mediated hairy root transformation in Saussurea costus C.B. Clarke

Saussurea costus (Asteraceae) commonly known as kuth, is an important medicinal plant with a rich repository of medicinally valuable compounds. During the present study, pharmacologically important sesquiterpene lactones namely costunolide, dehydrocostus lactone, betulinic acid and syringin were isolated from different plant extracts. Furthermore, the elicitation effect of jasmonic acid (JA) and different light regiments on the accumulation of secondary metabolites (costunolide and dehydrocostus lactone) was evaluated using HPLC. There was an increase in amount of costunolide and dehydrocostus lactone compared to control after 96 h of treatment with JA and continuous light. The amount of costunolide after 96 h was maximum 6.47 mg/g DW in response to JA as compared to control which was found to be 1.7 mg/g DW. Similarly, the concentration of dehydrocostus lactone after 96 h showed maximum accumulation of compound 4.7 mg/g DW in response to continuous light. The in vitro response in MS medium augmented with BAP (4 mg/l) produces friable and creamish coloured callus, however, number of days increased from 10 to 22 days with 70% culture response. Also, Agrobacterium rhizogenes strain LBA9402 was found to be most effective strain for the establishment of hairy root cultures among all the strains used. The genomic DNA was used as template in PCR to amplify rolB gene which confirmed the efficient transformation of the roots. Additionally, total metabolite content of in vitro raised hairy roots of S. costus was significantly higher than the field grown plants. The production of secondary metabolites through elicitation and hairy roots can serve as a potential tool for the conservation action programme in S. costus.

Supplementary Information

The online version contains supplementary material available at 10.1007/s12298-022-01270-9.

Gene expression pattern and taxane biosynthesis in a cell suspension culture of Taxus baccata L. subjected to light and a phenylalanine ammonia lyase (PAL) inhibitor

Taxus baccata L. cell culture is a promising commercial method for the production of taxanes with anti-cancer activities. In the present study, a T. baccata cell suspension culture was exposed to white light and 2-aminoindan-2-phosphonic acid (AIP), a phenylalanine ammonia lyase (PAL) inhibitor, and the effects of this treatment on cell growth, PAL activity, total phenol content (TPC), total flavonoid content (TFC), taxane production and the expression of some key taxane biosynthetic genes (DXS, GGPPS, T13OH, BAPT, DBTNBT) as well as the PAL were studied. Light reduced cell growth, whereas AIP slightly improved it. Light increased PAL activity up to 2.7-fold relative to darkness. The highest TPC (24.89 mg GAE/g DW) and TFC (66.94 mg RUE/g DW) were observed in cultures treated with light and AIP. Light treatment also resulted in the maximum content of total taxanes (154.78 μg/g DW), increasing extracellular paclitaxel and cephalomannin (3.3-fold) and intracellular 10-deacetyl paclitaxel (2.5-fold). Light significantly increased the expression level of PAL, DBTNBT, BAPT, and T13αOH genes, whereas it had no effect on the expression of DXS, a gene active at the beginning of the taxane biosynthetic pathway. AIP had no significant effect on the expression of the target genes. In conclusion, the light-induced activation of PAL transcription and altered expression of relevant biosynthetic genes reduced cell growth and increased the content of total phenolic compounds and taxanes. These findings can be applied to improve taxane production in controlled cultures and bioreactors.

Enhanced Production of Phenylethanoids Mediated Through Synergistic Approach of Precursor Feeding and Light Regime in Cell Suspension Culture of Rhodiola imbricata (Edgew.)

Precursor feeding is a potential strategy for increasing specialized metabolite production in plant cell culture systems. In the present study, cell suspension cultures were developed and subsequently evaluated for precursor feeding investigations. Cell suspension cultures were established in Murashige and Skoog (MS) medium containing 0.5 mg/L thidiazuron (TDZ) + 1 mg/L α-naphthalene acetic acid (NAA). The growth biomass and metabolite pattern were analyzed to identify specific culture days required for prolific biomass production. The maximum cell dry weight (DW) was observed in leaf cell suspension (1.22 g/100 mL) and root cell suspension culture (1.12 g/100 mL) on day 21. Afterward, the effect of precursor concentrations (tyrosol; 0.5, 1, 2, and 3 mM) along with two light regimes, photoperiod (16L/8D h, 70 µmol/m²/s) and dark (24 h), was evaluated for cell growth and metabolite accumulation. The results revealed that leaf cell suspension treated with 3 mM tyrosol concentration detected maximum salidroside content (26.05 mg/g DW) on day 15, incubated under photoperiod (16L/8D h) condition. Similarly, under photoperiod (16L/8D h), root cell suspension treated with 3 mM tyrosol produced maximum salidroside content (26.62 mg/g DW) on day 12. Moreover, the total phenolics content increased significantly (44.21 mg/g DW) on day 12 in 3 mM tyrosol treatment under photoperiod (16L/8D h). However, precursor concentrations did not influence the total flavonoids content. The present investigation suggests that the immediate pathway precursor, tyrosol, has a strong effect on enhanced production of salidroside, irrespective of explant type and light regimes.

Using the Strategy of Inducing and Genetically Transforming Plant Suspension Cells to Produce High Value-Added Bioactive Substances

Plants can produce many functional bioactive substances. The suspension cell system of plants can be constructed based on its characteristics to realize the large-scale production of valuable products. In this review, we mainly talk about the main strategies, elicitation, and genetic transformation to improve the yield of active substances by using this system. Meanwhile, we focus on the challenges hiding in the practical application and the future prospects and provide new ideas and the theoretical basis for obtaining numerous bioactive substances from plants.

Traditional in vitro strategies for sustainable production of bioactive compounds and manipulation of metabolomic profile in medicinal, aromatic and ornamental plants

Precursor feeding, elicitation and culture medium parameters are traditional in vitro strategies to enhance bioactive compounds of medicinal, aromatic, and ornamental plants (MAOPs). Machine learning can help researchers find the best combination of these strategies to increase the secondary metabolites content of MAOPs. Many requirements for human life, from food, pharmaceuticals and cosmetics to clothes, fuel and building materials depend on plant-derived natural products. Essential oils, methanolic and ethanolic extracts of in vitro undifferentiated callus and organogenic cultures of medicinal, aromatic, and ornamental plants (MAOPs) contain bioactive compounds that have several applications for various industries, including food and pharmaceutical. In vitro culture systems provide opportunities to manipulate the metabolomic profile of MAOPs. Precursors feeding, elicitation and culture media optimization are the traditional strategies to enhance in vitro accumulation of favorable bioactive compounds. The stimulation of plant defense mechanisms through biotic and abiotic elicitors is a simple way to increase the production of secondary metabolites in different in vitro culture systems. Different elicitors have been applied to stimulate defense machinery and change the metabolomic profile of MAOPs in in vitro cultures. Plant growth regulators (PGRs), stress hormones, chitosan, microbial extracts and physical stresses are the most applied elicitors in this regard. Many other chemical tolerance-enhancer additives, such as melatonin and proline, have been applied along with stress response-inducing elicitors. The use of stress-inducing materials such as PEG and NaCl activates stress tolerance elicitors with the potential of increasing secondary metabolites content of MAOPs. The present study reviewed the state-of-the-art traditional in vitro strategies to manipulate bioactive compounds of MAOPs. The objective is to provide insights to researchers involved in in vitro production of plant-derived natural compounds. The present review provided a wide range of traditional strategies to increase the accumulation of valuable bioactive compounds of MAOPs in different in vitro systems. Traditional strategies are faster, simpler, and cost-effective than other biotechnology-based breeding methods such as genetic transformation, genome editing, metabolic pathways engineering, and synthetic biology. The integrate application of precursors and elicitors along with culture media optimization and the interpretation of their interactions through machine learning algorithms could provide an excellent opportunity for large-scale in vitro production of pharmaceutical bioactive compounds.

Enhanced Accumulation of Betulinic Acid in Transgenic Hairy Roots of Senna obtusifolia Growing in the Sprinkle Bioreactor and Evaluation of Their Biological Properties in Various Biological Models

Betulinic acid, which is found in transgenic roots of Senna obtusifolia (L.) H.S.Irwin & Barneby, is a pentacyclic triterpene with distinctive pharmacological activities. In this study, we report the differences in the content of betulinic acid and selected anthraquinones in transgenic S. obtusifolia hairy roots with overexpression of the PgSS1 gene (SOPSS2 line) and in transformed hairy roots without this genetic construct (SOA41 line). Both hairy root lines grew in 10 L sprinkle bioreactor. Additionally, the extracts obtained from this plant material were used for biological tests. Our results demonstrated that the SOPSS2 hairy root cultures from the bioreactor showed an increase in the content of betulinic acid (38.125 mg/g DW), compared to the SOA41 hairy root line (4.213 mg/g DW). Biological studies have shown a cytotoxic and antiproliferative effect on U-87MG glioblastoma cells, and altering the level of apoptotic proteins (Bax, p53, Puma and Noxa). Antimicrobial properties were demonstrated for both tested extracts, with a stronger effect of SOPSS2 extract. Moreover, both extracts showed moderate antiviral properties on norovirus surrogates.

UV-C mediated accumulation of pharmacologically significant phytochemicals under light regimes in in vitro culture of Fagonia indica (L.)

Fagonia indica (L.) is an important medicinal plant with multitude of therapeutic potentials. Such application has been attributed to the presence of various pharmacological important phytochemicals. However, the inadequate biosynthesis of such metabolites in intact plants has hampered scalable production. Thus, herein, we have established an in vitro based elicitation strategy to enhance such metabolites in callus culture of F. indica. Cultures were exposed to various doses of UV radiation (UV-C) and grown in different photoperiod regimes and their impact was evaluated on biomass accumulation, biosynthesis of phytochemicals along antioxidant expression. Cultures grown under photoperiod (16L/8D h) after exposure to UV-C (5.4 kJ/m²) accumulated optimal biomass (438.3 g/L FW; 16.4 g/L DW), phenolics contents (TPC: 11.8 μgGAE/mg) and flavonoids contents (TFC: 4.05 μgQE/mg). Similarly, HPLC quantification revealed that total production (6.967 μg/mg DW) of phytochemicals wherein kaempferol (1.377 μg/mg DW), apigenin (1.057 μg/mg DW), myricetin (1.022 μg/mg DW) and isorhamnetin (1.022 μg/mg DW) were recorded highly accumulated compounds in cultures at UV-C (5.4 kJ/m²) dose than other UV-C radiations and light regimes.. The antioxidants activities examined as DPPH (92.8%), FRAP (182.3 µM TEAC) and ABTS (489.1 µM TEAC) were also recorded highly expressed by cultures under photoperiod after treatment with UV-C dose 5.4 kJ/m². Moreover, same cultures also expressed maximum % inhibition towards phospholipase A2 (sPLA2: 35.8%), lipoxygenase (15-LOX: 43.3%) and cyclooxygenases (COX-1: 55.3% and COX-2: 39.9%) with 1.0-, 1.3-, 1.3- and 2.8-fold increased levels as compared with control, respectively. Hence, findings suggest that light and UV can synergistically improve the metabolism of F. indica and could be used to produce such valuable metabolites on commercial scale.

Effect of red light on photosynthetic acclimation and the gene expression of certain light signalling components involved in the microRNA biogenesis in the extremophile Eutrema salsugineum

The photosynthetic acclimation of extremophile Eutrema salsugineum plants to red light (RL) (14 days, 150 μmol photons m^-2 s^-1, 660 nm) and the expression of the key photoreceptor apoprotein genes, transcription factors (TFs) and associated with phytochrome system MIR (microRNA) genes were studied. RL exposure induced an increase in the content of anthocyanin and total phenolic compounds and the level of Chls was decreased. The photosystem 2 electron transport rate and the number of open reaction centres (q_L) were not changed in RL plants, however, the levels of non-photochemical quenching (NPQ) and the regulated quantum yield of non-photochemical quenching Y(NPQ) were significantly higher in the RL plants. The rate of CO₂ uptake was decreased by almost 1.4-fold but the respiration and transpiration rates, as well as the stomatal conductance were not changed in the RL plants. An increase in the expression of the photoreceptor apoprotein genes PHYA, PHYB and PHYC, the TF genes PIF4, PIF5 and miR395, miR408, miR165 and decreases in the levels of the transcripts of the TF gene HY5 and miR171, miR157, and miR827 were detected. The acclimation effect of photosynthetic apparatus to RL was accompanied by an increase of pigment content such as total phenolic compounds and carotenoids and it is due to the changes in the expression of the apoprotein phytochrome genes PHYA, PHYB, PHYC and phytochrome signalling TFs (PIF4, PIF5 and HY5) as well as MIR genes associated with phytochrome system.

Comparative analysis of the effects of chemically and biologically synthesized silver nanoparticles on biomass accumulation and secondary metabolism in callus cultures of Fagonia indica

Biotechnological strategies are needed to produce larger quantities of biomass and phytochemicals. In this study, callus cultures of Fagonia indica were elicited with different concentrations of chemically and biologically synthesized silver nanoparticles (chem- and bioAgNPs) to compare their effects on biomass, total phenolic content (TPC), total flavonoid content (TFC) and antioxidant activity of the extracts from callus. The results revealed that bioAgNPs being more biocompatible produced the highest biomass initially on day 10 (FW = 4.2152 ± 0.13 g; DW = 0.18527 ± 0.01 g) and day 20 (FW = 7.6558 ± 0.10 g; DW = 0.3489 ± 0.01 g) when supplemented in media as 62.5 µg/mL and 250 µg/mL, respectively. Initially, the highest TPC (319.32 ± 8.28 µg GAE/g of DW) was recorded on day 20 in chemAgNPs (31.25 µg/mL) induced callus as compared to TPC = 302.85 ± 3.002 µg GAE/g of DW in bioAgNPs-induced callus. Compared to the highest values of TFC (108.15 ± 2.10 µg QE/g of DW) produced in 15.6 µg/mL chemAgNPs-induced callus on day 20, TFC produced in bioAgNPs (62.5 µg/mL) was 168.61 ± 3.17 µg GAE/g of DW on day 10. Similarly, chemAgNPs-induced callus (62.5 µg/mL) showed the highest free radical scavenging activity (FRSA) i.e. 87.18% on day 20 while bioAgNPs (125 µg/mL) showed 81.69% FRSA on day 20 compared to highest among control callus (63.98% on day 40). The highest total antioxidant capacity of chemAgNPs-(125 µg/mL) induced callus was 330.42 ± 13.65 µg AAE/g of DW on day 20 compared to bioAgNPs-(62.5 µg/mL) induced callus (312.96 ± 1.73 µg AAE/g of DW) on day 10. Conclusively, bioAgNPs are potent elicitors of callus cultures of F. indica.

Influence of photoperiod on growth, bioactive compounds and antioxidant activity in callus cultures of Basella rubra L

Basella rubra L. is an important green leafy vegetable vine and is known for its health benefits in traditional medicine. Light is a basic physical factor essential to the development and bioactive secondary metabolite production in in vitro callus cultures. The present study researched the impact of different photoperiods on biomass, bioactive compounds, and antioxidant activity in callus cultures of B. rubra. The in vitro seedling based cotyledonary leaf explants responded differently, when cultured on Murashige and Skoog (MS) medium with varying concentrations and combination of auxins and cytokinins. The best callus proliferation was found in MS medium with 0.1 mg.L^-1 1-naphthaleneacetic acid (NAA) and 6 mg.L^-1 6-benzylaminopurine (BAP), with greenish callus inception by about 2 weeks. The growth curve recorded for 6 weeks of culturing revealed that the photoperiod effect was found to be pivotal for acquiring biomass. At the fifth week, the continuous light supported maximum biomass (12.42 g) production followed by the 16:8 h photoperiod (9.02 g) and continuous darkness (4.28 g). The 80% ethanol extract of 1-week-old callus that grows under the 16:8 h photoperiod showed the highest total phenolic content (TPC) (74 mg.100 g^-1 fresh weight, FW) when compared to all other extracts at different stages. The ferric reducing antioxidant power assay showed the highest (336.23 mg.100 g^-1 FW) activity in methanol extractions of first-week callus cultures maintained in the continuous light condition. HPLC-UV identification and quantification of individual phenolics and flavonoids, such as gallic, trans-cinnamic, quercetin, protocatechuic and rutin, were highest in the callus cultures. The outcome of this study is significant to this plant, as B. rubra is familiar for its important health constituents with high-value bioactives and applications in the pharma and nutraceutical industries.

Spectral quality as an elicitor of bioactive compound production in Solanum aculeatissimum JACQ cell suspension

Solanum aculeatissimum Jacq. is a common plant in much of Brazil. Despite containing metabolites with a wide range of pharmacological applications, there are few tissue culture reports for this plant. The possibility of large-scale in vitro production of this material has significant biotechnological potential. Therefore, the objective of this study was to investigate the effect of light conditions on the growth of cells in suspension, observing the production and yield of biomass and bioactive compounds and the enzymatic behavior. Calli obtained from leaf segments were cultured in solid medium supplemented with 1 mg L^-1 of 2,4-D, 2.5 mg L^-1 kinetin, pH 5.7, in the dark. After 110 days of subculture, the calli were transferred to liquid medium. Cells were kept in the dark under agitation at 110 rpm and 25 °C and subcultured every 30 days. After 90 days of culture, 20 mL aliquots of cell suspension were added to flasks containing approximately 20 mL of medium (1:1) and cultured at different wavelengths (white, green, blue, red, and blue/red) under a photoperiod of 16 h with irradiance of 50 μmol m^-2 s^-1) and in the absence of light. The experiment was performed in a 6 × 6 factorial design (light condition × culture time). The cell cultures showed viability throughout the entire cycle, and chlorogenic and ferulic acids, orientin, quercitrin and, in higher amounts, quercetin, were detected in the first 7 days of culture. There was an increase in superoxide dismutase and catalase and a decrease in ascorbate peroxidase after exposure to different light conditions; for phenylalanine ammonia lyase, no differences were observed. The different light conditions were not sufficient to trigger responses in the concentrations of bioactive compounds, despite the detection of increased levels of the enzymes involved in cellular homeostasis.

Variation in surface properties, metabolic capping, and antibacterial activity of biosynthesized silver nanoparticles: comparison of bio-fabrication potential in phytohormone-regulated cell cultures and naturally grown plants

We compared surface properties, metabolic capping and antibacterial activity of silver nanoparticles, synthesized through extracts of cell cultures of Fagonia indica and its naturally grown form. Extracts from cell cultures (produced with thidiazuron (TDZ) or melatonin (MLN)) were compared to the naturally grown whole plant extracts (WPEs) for their reducing potential, and their effects on physical and biochemical properties of the biosynthesized silver nanoparticles. UV-Vis spectroscopy revealed that the surface plasmon resonance peaked at λ = 415 nm for MLN-AgNPs, λ = 430 nm for TDZ-AgNPs and λ = 460–465 nm for WPE-AgNPs. Transmission electron microscopy and energy dispersive X-rays of AgNPs showed that compared to WPE-AgNPs (mean diameter = 22 nm), extracts from MLN- and TDZ-induced cell cultures produced particles with spherical shapes and smaller diameters (i.e. mean diameter = 15 nm and 19 nm, respectively). Size distribution analysis also showed that TDZ-AgNPs were nearer to a symmetric distribution in terms of diameter (skewness = 0.80) as compared to WPE-AgNPs (skewness = 0.9) and MLN-AgNPs (skewness = 1.4). Furthermore, MLN-induced cell culture extracts produced AgNPs in higher concentration (210 μg mL⁻¹) compared to AgNPs from TDZ-induced cell culture extracts (160 μg mL⁻¹) and WPE (138 μg mL⁻¹). Two-way comparisons of LC-MS/MS profiles of TDZ-AgNPs, MLN-AgNPs, and WPE-AgNPs revealed differences in their secondary metabolite profiles, which might account for differences in their differential response in bio-fabrication, and size distribution. Activity against different pathogenic bacterial strains, Escherichia coli, Bacillus cereus, Xanthomonas citri, Agrobacterium tumefaciens, Streptomyces griseus, and Erwinia carotovora suggested that MLN-AgNPs were more effective compared to TDZ- and WPE-AgNPs. These results indicated that phytohormones induced cell cultures can enhance the production, physical and biochemical properties of AgNPs.

We compared surface properties, metabolic capping and antibacterial activity of biosynthesized silver nanoparticles, synthesized through extracts of cell cultures of Fagonia indica and its naturally grown form.

The effect of light, phenylalanine and methyl jasmonate, alone or in combination, on growth and secondary metabolism in cell suspension cultures of Vitis vinifera

The cultivated grapevine V. vinifera is a rich source of stilbene compounds such as resveratrol, which are widely believed to provide dietary protection against the development of cardiovascular disease and some forms of cancer. Elicitation is a well-known strategy to increase commercial production of natural products in plant cell suspension culture systems. Callus tissues obtained from berry slices of V. vinifera cv. Shahani grown on an optimized medium were used to develop cell suspension cultures used to study the effects of elicitation on stilbene synthesis. The effect of two light regimes (135.1 μmol. s^-1 m^-2 radiation, and dark), the concentration of phenylalanine (Phe; 0, 0.1, 0.5 and 1 mM) and of methyl jasmonate elicitor (MeJA; 0 and 25 μM), alone or in combination, were tested. The results showed that cultures grown in darkness resulted in significantly higher levels of the accumulation of total stilbenes (resveratrol + piceid) compared with the high light condition. The combined treatments of dark +1 mM Phe and dark +25 μM MeJA induced the synthesis of high levels of total phenolics, total flavonoids and total stilbenes. Finally, the combined elicitation of dark +1 mM Phe + 25 μM MeJA gave the highest synergistic coefficient (1.24) and proved to be the most effective treatment for the production of total phenolics, total flavonoids, and total stilbenes with mean contents of 384.80 mg GA/g DW, 527.62 mg catechin/g DW and 188.34 μg/g DW, respectively. The results of our study suggest that the combinations of dark together with MeJA and/or Phe can be used as an efficient method for the future scale-up of V. vinifera cell cultures for the production of high value stilbene compounds in a bioreactor system.

Recent advances in allelopathy for weed control: from knowledge to applications

Allelopathy is the biological phenomenon of chemical interactions between living organisms in the ecosystem, and must be taken into account in addressing pest and weed problems in future sustainable agriculture. Allelopathy is a multidisciplinary science, but in some cases, aspects of its chemistry are overlooked, despite the need for a deep knowledge of the chemical structural characteristics of allelochemicals to facilitate the design of new herbicides. This review is focused on the most important advances in allelopathy, paying particular attention to the design and development of phenolic compounds, terpenoids and alkaloids as herbicides. The isolation of allelochemicals is mainly addressed, but other aspects such as the analysis and activities of derivatives or analogs are also covered. Furthermore, the use of allelopathy in the fight against parasitic plants is included. The past 12 years have been a prolific period for publications on allelopathy. This critical review discusses future research areas in this field and the state of the art is analyzed from the chemist's perspective. © 2019 Society of Chemical Industry.

Light elicited growth, antioxidant enzymes activities and production of medicinal compounds in callus culture of Cnidium officinale Makino

Cnidium officinale Makino is an important medicinal plant of oriental clinics and is considered as the main source of phthalides, polyphenols, and flavonoids. However, there is no available report regarding the effect of different light colors on the secondary metabolites composition of C. officinale. In this study different light (dark, white, blue, red and red: blue) conditions were arranged to raise callus on MS medium containing 0.5 mg·L^-1 of each 2,4-D and BAP. Callus grown in dark condition showed maximum (2.0 g) fresh weight with lower total phenolic and flavonoids contents. Also, in dark condition callus faced higher catalase (CAT) and guaiacol peroxidase (GPX) activities to avoid free radicals. Mix (red: blue) light condition favored the synthesis of phenolics and flavonoids in callus at the cost of higher ascorbate peroxidase (APX) and superoxide dismutase (SOD) enzymes expression. However, DPPH free radical scavenging activity was less variable among the samples from the different light conditions. Interestingly, the HPLC profile showed higher (28.3 μg·g^-1 DW) phthalide accumulation in dark grown-cultures. Compared to other light conditions, 3-butyledinephthalide accumulation was higher (0.43 μg·g^-1 DW) in white light-grown callus. These findings suggest that light conditions play an important role in the regulation of in vitro callus growth and synthesis of important medicinal compounds of C. officinale.

Monochromatic lights-induced trends in antioxidant and antidiabetic polyphenol accumulation in in vitro callus cultures of Lepidium sativum L

Lepidium sativum L. is an important edible, herbaceous plant with huge medicinal value as cardio-protective, hepatoprotective and antitumor agent. This study was designed and performed to investigate biosynthesis of plant's active ingredients in callus cultures of L. sativum in response to the exposure of multi spectral lights. Optimum biomass accumulation (15.36 g/L DW), total phenolic and flavonoid contents (TPC; 47.43 mg/g; TFC; 9.41 mg/g) were recorded in calli placed under white light (24 h) compared to rest of the treatments. Antioxidant enzymatic activities i.e. superoxide dismutase and peroxidase were found optimum in cultures exposed to green light (SOD; 0.054 nM/min/mg FW, POD; 0.501 nM/min/mg FW). Phytochemical analysis further confirmed the potential influence of white light exposure on enhanced production of plant's metabolites. Significant enhancement level of major metabolic compounds such as chlorogenic acid (7.20 mg/g DW), quercetin (22.08 mg/g DW), kaempferol (7.77 mg/g DW) and minor compounds including ferulic acid, sinapic acid, protocatechuic acid, vanillic acid and caffeic acid were recorded in white light compared to control (photoperiod), whereas blue light increased the p-coumaric acid accumulation. Moreover, callus cultures of this plant under white light (24 h) showed highest in vitro based anti-diabetic and antioxidant activities compared to other conditions. Finding of our current study revealed that multi spectral lights are proved to be an effective strategy for enhancing metabolic quantity of antioxidant and anti-diabetic bioactive compounds in callus cultures of L. sativum L.

Synergistic effects of melatonin and distinct spectral lights for enhanced production of anti-cancerous compounds in callus cultures of Fagonia indica

Fagonia indica is one of the commercially vital medicinal plant species. It is well-known for biosynthesis of anticancer phenolics and flavonoids metabolites. The plant has been exploited for in vitro studies and production of vital phytochemicals, however, the synergistic effects of melatonin and lights remains to be investigated. In current study, we have evaluated the synergistic effects of melatonin and different light emitting diodes (LEDs) in callus cultures of F. indica. Both, light and melatonin play vital role in physiological and biochemical processes of plant cell. The highest Fresh weight (FW: 320 g/L) and Dry weight (DW: 20 g/L) was recorded in cultures under white LEDs. Optimum total phenolics content (11.3 μg GAE/mg), total flavonoids content (4.02 μg QAE/mg) and Free radical scavenging activity (97%) was found in cultures grown under white LED and melatonin. Furthermore, cultures maintained under white light were also found with highest levels of phenolic and flavonoids production (total phenolic production; 226.9 μg GAE/mg, Total flavonoid production; 81 μg QAE/mg) than other LED-grown cultures. However, the antioxidant enzymes; Superoxide dismutase (SOD: 0.53 nM/min/mg FW) and Peroxidase (POD:1.18 nM/min/mg FW) were found optimum in cultures grown under blue LED. The HPLC data showed that enhanced total production of metabolites was recorded in cultures under white LED (6.765 μg/mg DW) than other lights and control. The findings of this study comprehend the role of melatonin and influence of light quality on biomass accumulation and production of phytochemicals in callus cultures of F. indica.

Anticancer potential of rosmarinic acid and its improved production through biotechnological interventions and functional genomics

Rosmarinic acid (RA) is a highly valued natural phenolic compound that is very commonly found in plants of the families Lamiaceae and Boraginaceae, including Coleus blumei, Heliotropium foertherianum, Rosmarinus officinalis, Perilla frutescens, and Salvia officinalis. RA is also found in other members of higher plant families and in some fern and horned liverwort species. The biosynthesis of RA is catalyzed by the enzymes phenylalanine ammonia lyase and cytochrome P450-dependent hydroxylase using the amino acids tyrosine and phenylalanine. Chemically, RA can be produced via methods involving the esterification of 3,4-dihydroxyphenyllactic acid and caffeic acid. Some of the derivatives of RA include melitric acid, salvianolic acid, lithospermic acid, and yunnaneic acid. In plants, RA is known to have growth-promoting and defensive roles. Studies have elucidated the varied pharmacological potential of RA and its derived molecules, including anticancer, antiangiogenic, anti-inflammatory, antioxidant, and antimicrobial activities. The demand for RA is therefore, very high in the pharmaceutical industry, but this demand cannot be met by plants alone because RA content in plant organs is very low. Further, many plants that synthesize RA are under threat and near extinction owing to biodiversity loss caused by unscientific harvesting, over-collection, environmental changes, and other inherent features. Moreover, the chemical synthesis of RA is complicated and expensive. Alternative approaches using biotechnological methodologies could overcome these problems. This review provides the state of the art information on the chemistry, sources, and biosynthetic pathways of RA, as well as its anticancer properties against different cancer types. Biotechnological methods are also discussed for producing RA using plant cell, tissue, and organ cultures and hairy-root cultures using flasks and bioreactors. The recent developments and applications of the functional genomics approach and heterologous production of RA in microbes are also highlighted. This chapter will be of benefit to readers aiming to design studies on RA and its applicability as an anticancer agent.