LED-enhanced biosynthesis of biologically active ingredients in callus cultures of Ocimum basilicum

Influence of light-emitting diodes (LEDs) on the 2,4-diclorophenoxyacetic acid phytoremediation by plectranthus neochilus

2,4-Dichlorophenoxyacetic acid (2,4-D) is an herbicide widely used in crops against broadleaf weeds. However, 2,4-D residues are considered an environmental pollutant in bodies of water. Phytoremediation with Plectranthus neochilus is a substantial strategy to remove 2,4-D from the aquatic environment. The objective of this study was to verify the efficiency of the association of the photostimulus by Light Emitting Diodes (LED) with P. neochilus to improve phytoremediation of 2,4-D in water. Phytoremediation was evaluated with the following samples: natural light, white LED, blue LED, and red LED, with and without the plant as controls. The data corresponding to the validation of the method were in accordance with the required parameters: R2: 0.9926; RSD: 1.74%; LOD: 0.075 mg.L-1; LOQ: 0.227 mg.L-1 and recovery by SPE was 76.57%. The efficiency of the association of LED with P. neochilus in the 28 days was: ambient light + plant (47.0%); white light + plant (37.10%); blue light + plant (26.80%); red light + plant (3.32%). This study demonstrated, for the first time, the efficiency of using LEDs light in association with P. neochilus for the phytoremediation of 2,4-D in water.

Effect of LED Lights on Secondary Metabolites and Antioxidant Activities in Red Pakchoi Baby Leaves

Pakchoi (Brassica rapa subsp. chinensis) is one of the most widely consumed vegetables in Asian countries, and it is high in secondary metabolites. The availability, quantity, and quality of light play a critical role in the growth and development of plants. In this study, we investigated the effect of LEDs (light-emitting diodes; white, blue, red, and red + blue) on anthocyanin, glucosinolates, and phenolic levels in red pakchoi baby leaves. On the 24th day after sowing (DAS), red baby pakchoi leaves were harvested, and shoot length, root length, and fresh weight were measured. Among the different LED treatments, there was no significant difference in shoot length, whereas the highest root length was achieved in the red + blue LED treatment (23.8 cm). The fresh weight also showed a significant difference among the different LED treatments. In total, 12 phenolic and 7 glucosinolate individual compounds were identified using high-performance liquid chromatography (HPLC) analysis. The highest total glucosinolate (2937 μg/g dry wt) and phenolic (1589 μg/g dry wt) contents were achieved in baby leaves exposed to red + blue light. Similarly, the highest contents of total anthocyanins (1726 μg/g dry wt), flavonoids (4920 μg/g dry wt), and phenolics (5900 μg/g dry wt) were achieved in the red + blue treatment. Plants exposed to red + blue LED light showed the highest accumulation of anthocyanin, glucosinolates, and phenolic compounds. For antioxidant activity, DPPH (2,2-diphenyl-1-picrylhydrazylradical) free radical scavenging, ABTS (2,2-azinobis (3-ethylbenzothiazoline)-6-sulfonic acid) radical scavenging, and reducing power assays were performed, and the antioxidant activity of red pakchoi baby leaves grown under red + blue LED light was found to be the best. The metabolic profiling of the identified metabolites revealed distinct separation based on the secondary metabolites. This research will be helpful for farmers to choose the best LED light combination to increase the secondary metabolic content in pakchoi plants.

Improvement of Bioactive Polyphenol Accumulation in Callus of Salvia atropatana Bunge

Callus cultures of the Iranian medicinal plant Salvia atropatana were initiated from three-week-old seedlings on Murashige and Skoog (MS) medium supplemented with α-naphthaleneacetic acid (NAA) and various cytokinins. Although all tested hormonal variants of the medium and explant enabled callus induction, the most promising growth was noted for N-(2-chloro-4-pyridyl)-N'-phenylurea (CPPU)-induced calli. Three lines obtained on this medium (cotyledon line-CL, hypocotyl line-HL, and root line-RL) were preselected for further studies. Phenolic compounds in the callus tissues were identified using UPLC-MS (ultra-performance liquid chromatography-mass spectrometry) and quantified with HPLC (high-performance liquid chromatography). All lines exhibited intensive growth and contained twelve phenolic acid derivatives, with rosmarinic acid predominating. The cotyledon-derived callus line displayed the highest growth index values and polyphenol content; this was exposed to different light-emitting diodes (LED) for improving biomass accumulation and secondary metabolite yield. Under LED treatments, all callus lines exhibited enhanced RA and total phenolic content compared to fluorescent light, with the highest levels observed for white (48.5-50.2 mg/g dry weight) and blue (51.4-53.9 mg/g dry weight) LEDs. The selected callus demonstrated strong antioxidant potential in vitro based on the 2,2'-azino-bis(3-ethylbenzthiazoline-6-sulfonic acid) (ABTS), 2,2-diphenyl-1-picrylhydrazyl (DPPH), and ferric reducing antioxidant power (FRAP) tests. Our findings confirm that the S. atropatana callus system is suitable for enhanced rosmarinic acid production; the selected optimized culture provide high-quality plant-derived products.

Untargeted metabolomic in basil cell cultures - a case study of Ocimum basilicum L. var. minimum Alef

AIMS

Due to the lack of experimental databases, together with the chemical complexity and the dynamic nature of plants' metabolome, most of the metabolites in complex biological materials (like plant in vitro tissue cultures) are not-annotated, unidentified metabolites. In this study, a method for further metabolite characterization and classification based on the UPLC-HESI-HRMS/MS approach for small-leaved basil (Ocimum basilicum L. var. minimum Alef.) callus and cell suspension culture is presented.

KEY RESULTS

A total of 2168 metabolic features were detected, out of which the database for exact mass metabolic profiling for 1949 metabolites is presented here since there is no available database dedicated to O. basilicum. We further focused on secondary metabolites (particularly phenolic compounds). The presence of 60 different phenolic compounds belonging mainly to the groups of flavonoids, glycosides, terpenoids, and phenolic acids is confirmed. By comparing relative abundances of phenolic compounds from callus culture and cell suspension culture, both grown on two types of media, via svd-PCА, univariate analysis, post-hoc tests, and heatmapping of metabolites, we provided a practical example of how resources presented here can be further applied in tissue culture-based basil metabolomics studies.

UTILITY

This study represents the first approach toward routine targeted investigation of secondary metabolites in basil in vitro cultures and provides various opportunities for new-generation analyses.

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.

Trends in the Tissue Culture Techniques and the Synthesis of Bioactive Compounds in Eurycoma longifolia Jack-Current Status and Future Perspectives

Over the last two decades, there has been a concerted effort by researchers to mass propagate Eurycoma longifolia and improve the yield of its very important and sought-after anti-cancer and aphrodisiac bioactive compounds. To achieve this, various techniques have been used to mass propagate and improve the yield of these bioactive compounds in tissue cultures. These techniques include the optimization of media conditions and application of various types and combinations of plant growth regulators (PGRs). In addition, some elicitation techniques have been used to improve the synthesis of these bioactive compounds. However, in comparison with other herbal species with similar economic importance, many techniques have not been applied to E. longifolia. Adopting the most recent methodologies would ensure efficiency and sustainability in the in vitro production of bioactive compounds in E. longifolia. Therefore, in this review, we present an up-to-date record on the success stories in the tissue culture techniques and synthesis of bioactive compounds. In addition, we attempted to identify some of the missing links on the road to the effective and sustainable biotechnological utilization of this super important biological resource.

Improvement in Yield of Extracellular Vesicles Derived from Edelweiss Callus Treated with LED Light and Enhancement of Skin Anti-Aging Indicators

The process of skin aging is currently recognized as a disease, and extracellular vesicles (EVs) are being used to care for it. While various EVs are present in the market, there is a growing need for research on improving skin conditions through microbial and plant-derived EVs. Edelweiss is a medicinal plant and is currently an endangered species. Callus culture is a method used to protect rare medicinal plants, and recently, research on EVs using callus culture has been underway. In this study, the researchers used LED light to increase the productivity of Edelweiss EVs and confirmed that productivity was enhanced by LED exposure. Additionally, improvements in skin anti-aging indicators were observed. Notably, M-LED significantly elevated callus fresh and dry weight, with a DW/FW ratio of 4.11%, indicating enhanced proliferation. Furthermore, M-LED boosted secondary metabolite production, including a 20% increase in total flavonoids and phenolics. The study explores the influence of M-LED on EV production, revealing a 2.6-fold increase in concentration compared to darkness. This effect is consistent across different plant species (Centella asiatica, Panax ginseng), demonstrating the universality of the phenomenon. M-LED-treated EVs exhibit a concentration-dependent inhibition of reactive oxygen species (ROS) production, surpassing dark-cultured EVs. Extracellular melanin content analysis reveals M-LED-cultured EVs' efficacy in reducing melanin production. Additionally, the expression of key skin proteins (FLG, AQP3, COL1) is significantly higher in fibroblasts treated with M-LED-cultured EVs. These results are expected to provide valuable insights into research on improving the productivity of plant-derived EVs and enhancing skin treatment using plant-derived EVs.

Rosmarinic Acid and Flavonoids of the Seagrass Zostera noltei: New Aspects on Their Quantification and Their Correlation with Sunlight Exposure

Seagrasses are plants adapted to the marine environment that inhabit shallow coastal waters, where they may be exposed to direct sunlight during low tides. These plants have photoprotection mechanisms, which could include the use of phenolic secondary metabolites. In this study, rosmarinic acid (RA) and the flavonoids of Zostera noltei from the Bay of Cadiz (Spain) have been analyzed, first to define suitable conditions of leaves (i.e., fresh, dried, or frozen) for quantitative analysis, and then to explore the potential correlation between the phenolic profile of the leaves and sunlight exposure using an in situ experimental approach. Compared with fresh leaves, the contents of RA and flavonoids were significantly lower in air-dried and freeze-dried leaves. Freezing caused highly variable effects on RA and did not affect to flavonoid levels. On the other hand, the content of RA was significantly higher in plants that emerged during low tides than in plants permanently submerged, while plants underneath an artificial UV filter experienced a progressive reduction in RA content. However, the major flavonoids did not show a clear response to sunlight exposure and were unresponsive to diminished UV incidence. The results showed a positive correlation of RA with direct sunlight and UV exposure of leaves, suggesting that this compound contributes to the photoprotection of Z. noltei.

Integrated metabolome and transcriptome analyses provide insight into the effect of red and blue LEDs on the quality of sweet potato leaves

Red and blue light-emitting diodes (LEDs) affect the quality of sweet potato leaves and their nutritional profile. Vines cultivated under blue LEDs had higher soluble protein contents, total phenolic compounds, flavonoids, and total antioxidant activity. Conversely, chlorophyll, soluble sugar, protein, and vitamin C contents were higher in leaves grown under red LEDs. Red and blue light increased the accumulation of 77 and 18 metabolites, respectively. Alpha-linoleic and linolenic acid metabolism were the most significantly enriched pathways based on Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analyses. A total of 615 genes were differentially expressed between sweet potato leaves exposed to red and blue LEDs. Among these, 510 differentially expressed genes were upregulated in leaves grown under blue light compared with those grown under red light, while the remaining 105 genes were expressed at higher levels in the latter than in the former. Among the KEGG enrichment pathways, blue light significantly induced anthocyanin and carotenoid biosynthesis structural genes. This study provides a scientific reference basis for using light to alter metabolites to improve the quality of edible sweet potato leaves.

Neuroprotective Effect of a Nutritional Supplement Containing Spearmint Extract, Forskolin, Homotaurine and Group B Vitamins in a Mouse Model of Transient Ocular Hypertension

Glaucoma is one of the most common sight-threatening eye disorders and one of the main causes of irreversible blindness worldwide. The current therapies focusing on reducing intraocular pressure (IOP) are often insufficient to prevent the progression of the disease, so the therapeutic management of glaucoma remains a challenge. The aim of this study was to evaluate the neuroprotective, IOP-lowering independent effects of a nutritional supplement containing forskolin, homotaurine, spearmint extract and vitamins of the B group in a model of acute glaucoma developed in mice. Glaucoma was induced in adult wild-type C57BL/6J mice by transient elevation of IOP. The dietary supplement, branded as Gangliomix® (125 mg/kg/day), was administered by oral gavage for 17 days and ocular hypertension was induced on the 10th day of treatment. A histological analysis of the retinas was performed and RGC survival was evaluated with fluorogold labeling and Brn3a immunostaining on wholemount and retinal sections. Expression of alpha-spectrin, caspase-3, PARP-1 and GFAP was studied with western blotting or immunofluorescence. A significant increase in RGC survival was reported in the retina of mice treated with the dietary supplement as compared to vehicle-treated animals. The observed neuroprotection was associated with a calpain activity decrease, reduction in caspase-3 and PARP-1 activation, and prevention of GFAP upregulation. These effects were independent from the hypotensive effects of the supplement. Altogether, our data suggest that the dietary supplementation with forskolin, homotaurine, spearmint extract and vitamins of the B group supports RGC survival and may offer beneficial effects in glaucoma patients in combination with the currently used IOP-lowering therapy.

Precursors and elicitor induced enhancement of cell biomass and phenolic compounds in cell suspensions of Indian basil-Ocimum basilicum (CIM-Saumya)

CIM-Saumya is an improved, methyl chavicol rich variety of Ocimum basilicum (Family-Lamiaceae), developed by Council of Scientific and Industrial Research-Central Institute of Medicinal and Aromatic Plants. This plant possesses analgesic, anti-ulcerogenic, anti-inflammatory, anti-oxidant, cardiac stimulant, Central Nervous System depressant, hepatoprotective and immunomodulator activities due to the presence of various phytoconstituents. Among them rosmarinic acid, caffeic acid and ferulic acid are the three major phenolic compounds responsible for its therapeutic utility. These compounds are produced in very low amounts in the in vivo plants. Therefore, the present study has been conducted for establishment of cell suspensions, optimization of inoculums size, growth kinetics and screening of elicitor and precursors for the accumulation of cell biomass and the production of the three important phenolic compounds in cell suspension of O. basilicum (CIM-Saumya). Leaf derived friable callus was used for establishing the cell suspension in liquid Murashige and Skoog's medium fortified with 1 g/L casein hydrolysate + 2.26 µM 2,4-dichlorophenoxyacetic acid + 0.465 µM kinetin + 2.68 µM naphthalene acetic acid. The growth kinetic analysis pattern of cell suspension revealed the maximum biomass increments (% BI = 486.7) and production of RA 8.086 mg/g dry weight was found in 30th day harvested cells. Whereas, the other two phenolic compounds i.e. ferulic acid (0.0125 mg/g dry weight) and caffeic acid (0.38 mg/g dry weight) was recorded highest on 25th day of growth cycle. In the present study, one biotic elicitor i.e. yeast extract and three precursors [peptone, tryptone and lactalbumin hydrolysate] were tested, among them, lactalbumin hydrolysate (100 mg/L; added at 16th day) treated cells recorded highest estimated phenolic compounds yield (251.5 mg/L; 6.81 fold compared to the control) and biomass increments i.e. % BI = 1207 with 1.85 fold compared to the control. The highest rosmarinic acid content i.e. 25.47 mg/g DW (4.4 fold compared to the control) and 24.42 mg/g dry weight (4.1 folds compared to the control) was noticed in 30th day harvested cells treated with yeast extract (1 g/L on 0 day) and lactalbumin hydrolysate (100 mg/L added on 16th day), respectively. While caffeic acid content (0.91 mg/g dry weight) showed 2.9 folds higher compared to the control in cells treated with peptone 200 mg/L added on 16th day of culture cycle. All the treated cells showed enhanced phenylalanine ammonia-lyase enzyme activity with highest specific activity in lactalbumin hydrolysate followed by tryptone, peptone, and yeast extract.

Supplementary Information

The online version contains supplementary material available at 10.1007/s12298-023-01316-6.

Blue LED light promoting the growth, accumulation of high-value isoflavonoids and astragalosides, antioxidant response, and biosynthesis gene expression in Astragalus membranaceus (Fisch.) Bunge hairy root cultures

The root of Astragalus membranaceus (Fisch.) Bunge is one of the most frequently used herbs in traditional Chinese medicine (TCM) formulae for fighting COVID-19 infections, due to the presence of isoflavonoids and astragalosides associated with antiviral and immune-enhancing activities. For the first time, the exposure of A. membranaceus hairy root cultures (AMHRCs) to different colors of LED lights i.e., red, green, blue, red/green/blue (1/1/1, RGB), and white, was conducted to promote the root growth and accumulation of isoflavonoids and astragalosides. LED light treatment regardless of colors was found beneficial for root growth, which might be a result of the formation of more root hairs upon light stimulation. Blue LED light was found most effective for enhancing phytochemical accumulation. Results showed that the productivity of root biomass in blue-light grown AMHRCs with an initial inoculum size of 0.6% for 55 days was 1.40-fold higher than that in dark (control), and yields of high-value isoflavonoids and astragalosides including calycosin, formononetin, astragaloside IV, and astragaloside I increased by 3.17-fold, 2.66-fold, 1.78-fold, and 1.52-fold relative to control, respectively. Moreover, the photooxidative stress together with transcriptional activation of biosynthesis genes might contribute to the enhanced accumulation of isoflavonoids and astragalosides in blue-light grown AMHRCs. Overall, this work offered a feasible approach for obtaining higher yields of root biomass and medicinally important compounds in AMHRCs via the simple supplementation of blue LED light, which made blue-light grown AMHRCs industrially attractive as plant factory in controlled growing systems.

Graphical abstract

Supplementary Information

The online version contains supplementary material available at 10.1007/s11240-023-02486-7.

Metabolic Profiling of Primary and Secondary Metabolites in Kohlrabi (Brassica oleracea var. gongylodes) Sprouts Exposed to Different Light-Emitting Diodes

Light-emitting diode (LED) technology is one of the most important light sources in the plant industry for enhancing growth and specific metabolites in plants. In this study, we analyzed the growth, primary and secondary metabolites of 10 days old kohlrabi (Brassica oleracea var. gongylodes) sprouts exposed to different LED light conditions. The results showed that the highest fresh weight was achieved under red LED light, whereas the highest shoot and root lengths were recorded below the blue LED light. Furthermore, high-performance liquid chromatography (HPLC) analysis revealed the presence of 13 phenylpropanoid compounds, 8 glucosinolates (GSLs), and 5 different carotenoids. The phenylpropanoid and GSL contents were highest under blue LED light. In contrast, the carotenoid content was found to be maximum beneath white LED light. Principal component analysis (PCA) and partial least-squares discriminant analysis (PLS-DA) of the 71 identified metabolites using HPLC and gas chromatography-time-of-flight mass spectrometry (GC-TOF-MS) showed a clear separation, indicating that different LEDs exhibited variation in the accumulation of primary and secondary metabolites. A heat map and hierarchical clustering analysis revealed that blue LED light accumulated the highest amount of primary and secondary metabolites. Overall, our results demonstrate that exposure of kohlrabi sprouts to blue LED light is the most suitable condition for the highest growth and is effective in increasing the phenylpropanoid and GSL content, whereas white light might be used to enhance carotenoid compounds in kohlrabi sprouts.

Phenolic Acids and Amaryllidaceae Alkaloids Profiles in Leucojum aestivum L. In Vitro Plants Grown under Different Light Conditions

Light-emitting diodes (LEDs) have emerged as efficient light sources for promoting in vitro plant growth and primary and secondary metabolite biosynthesis. This study investigated the effects of blue, red, and white-red LED lights on plant biomass growth, photosynthetic pigments, soluble sugars, phenolic compounds, the production of Amaryllidaceae alkaloids, and the activities of antioxidant enzymes in Leucojum aestivum L. cultures. A white fluorescent light was used as a control. The plants that were grown under white-red and red light showed the highest fresh biomass increments. The blue light stimulated chlorophyll a, carotenoid, and flavonoid production. The white-red and blue lights were favourable for phenolic acid biosynthesis. Chlorogenic, p-hydroxybenzoic, caffeic, syringic, p-coumaric, ferulic, sinapic, and benzoic acids were identified in plant materials, with ferulic acid dominating. The blue light had a significant beneficial effect both on galanthamine (4.67 µg/g of dry weight (DW)) and lycorine (115 µg/g DW) biosynthesis. Red light treatment increased catalase and superoxide dismutase activities, and high catalase activity was also observed in plants treated with white-red and blue light. This is the first report to provide evidence of the effects of LED light on the biosynthesis of phenolic acid and Amaryllidaceae alkaloids in L. aestivum cultures, which is of pharmacological importance and can propose new strategies for their production.

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.

Light Quality Modulates Growth, Triggers Differential Accumulation of Phenolic Compounds, and Changes the Total Antioxidant Capacity in the Red Callus of Vitis davidii

Light quality is one of the key elicitors that directly affect plant cell growth and biosynthesis of secondary metabolites. In this study, the red callus of spine grape was cultured under nine light qualities (namely, dark, white, red, yellow, blue, green, purple, warm-yellow, and warm-white light). The effects of different light qualities were studied on callus growth, accumulation of phenolic compounds, and total antioxidant capacity of the red callus of spine grape. The results showed that blue and purple light induced increased red coloration in the callus, whereas yellow light induced the greatest callus proliferation. Among all of the light quality treatments, darkness treatment downregulated the contents of phenolic compounds, whereas blue light was the treatment most conducive to the accumulation of total phenolics. White, blue, and purple light induced increased anthocyanin accumulation. Mixed-wavelength light was beneficial to the accumulation of flavonoids. Blue and purple light were conducive to the accumulation of proanthocyanidins. A further study showed that cyanidin 3-glucoside (Cy3G) and peonidin 3-glucoside (P3G) were the main anthocyanin components in the callus, and blue, purple, and white light treatments promoted their accumulation, whereas flavan-3-ols and flavonols were the main components of non-anthocyanin phenolics, and their accumulation changed in response to not only light quality but also culture duration. The total antioxidant capacity of the callus cultures changed significantly in response to different light qualities. These results will provide evidence for an abiotic elicitor strategy to stimulate callus growth and enhance the accumulation of the main phenolic compounds in the red callus of spine grape.

Rosmarinic Acid and Related Dietary Supplements: Potential Applications in the Prevention and Treatment of Cancer

Cancer constitutes a severe threat to human health and quality of life and is one of the most significant causes of morbidity and mortality worldwide. Natural dietary products have drawn substantial attention in cancer treatment and prevention due to their availability and absence of toxicity. Rosmarinic acid (RA) is known for its excellent antioxidant properties and is safe and effective in preventing and inhibiting tumors. This review summarizes recent publications on culture techniques, extraction processes, and anti-tumor applications of RA-enriched dietary supplements. We discuss techniques to improve RA bioavailability and provide a mechanistic discussion of RA regarding tumor prevention, treatment, and adjuvant therapy. RA exhibits anticancer activity by regulating oxidative stress, chronic inflammation, cell cycle, apoptosis, and metastasis. These data suggest that daily use of RA-enriched dietary supplements can contribute to tumor prevention and treatment. RA has the potential for application in anti-tumor drug development.

Comparative Analysis of Various Plant-Growth-Regulator Treatments on Biomass Accumulation, Bioactive Phytochemical Production, and Biological Activity of Solanum virginianum L. Callus Culture Extracts

Solanum virginianum L. (Solanum xanthocarpum) is an important therapeutic plant due to the presence of medicinally useful plant-derived compounds. S. virginianum has been shown to have anticancer, antioxidant, antibacterial, antiaging, and anti-inflammatory properties. This plant is becoming endangered due to overexploitation and the loss of its native habitat. The purpose of this research is to develop an ideal technique for the maximum biomass and phytochemical accumulation in S. virginianum leaf-induced in vitro cultures, as well as to evaluate their potential antiaging, anti-inflammatory, and antioxidant abilities. Leaf explants were grown on media (Murashige and Skoog (MS)) that were supplemented with various concentrations and combinations of plant hormones (TDZ, BAP, NAA, and TDZ + NAA) for this purpose. When compared with the other hormones, TDZ demonstrated the best response for callus induction, biomass accumulation, phytochemical synthesis, and biological activities. However, with 5 mg/L of TDZ, the optimal biomass production (FW: 251.48 g/L and DW: 13.59 g/L) was estimated. The highest total phenolic level (10.22 ± 0.44 mg/g DW) was found in 5 mg/L of TDZ, whereas the highest flavonoid contents (1.65 ± 0.11 mg/g DW) were found in 10 mg/L of TDZ. The results of the HPLC revealed that the highest production of coumarins (scopoletin: 4.34 ± 0.20 mg/g DW and esculetin: 0.87 ± 0.040 mg/g DW) was determined for 10 mg/L of TDZ, whereas the highest accumulations of caffeic acid (0.56 ± 0.021 mg/g DW) and methyl caffeate (18.62 ± 0.60 mg/g DW) were shown by 5 mg/L of TDZ. The determination of these phytochemicals (phenolics and coumarins) estimates that the results of our study on biological assays, such as antioxidant, anti-inflammatory, and antiaging assays, are useful for future cosmetic applications.

Enhanced Accumulation of Biologically Active Coumarin and Furanocoumarins in Callus Culture and Field-grown Plants of Ruta chalepensis Through LED Light-treatment

Ruta chalepensis, a medicinal plant, produces biologically active coumarins (CRs) and furanocoumarins (FCRs). However, their yield is quite low in cultivated plants. In this work, the influence of light emitting diodes (LEDs) was investigated on the accumulation of CRs and FCRs in the callus cultures and field-grown plants of R. chalepensis. Among the various tested wavelengths of LED lights, maximum accumulation of CR and FCRs was recorded under blue LED treatment in both the callus cultures as well as field-grown plants as compared to respective controls treated with white LED. Metabolite analyses of LED-treated field-grown plants showed that highest concentrations of CR (umbelliferone, 2.8-fold), and FCRs (psoralen, 2.3-fold; xanthotoxin, 3.8-fold; bergapten, 1.16-fold) were accumulated upon blue LED-treatment for six days. CR and FCRs contents were also analyzed in the blue- and red-LED-treated in vitro callus tissue. Upon blue LED-treatment, callus accumulated significantly high levels of umbelliferone (48.6 ± 1.2 µg/g DW), psoralen (370.12 ± 10.6 µg/g DW) and xanthotoxin (10.16 ± 0.48 µg/g DW). These findings imply that blue LED-treatment is a viable option as a non-invasive and low-cost elicitation technology for the enhanced production of biologically active CR and FCRs in field-grown plants and callus cultures of R. chalepensis.

Effect of LED Lighting on Physical Environment and Microenvironment on In Vitro Plant Growth and Morphogenesis: The Need to Standardize Lighting Conditions and Their Description

In the last decades, lighting installations in plant tissue culture have generally been renewed or designed based on LED technology. Thanks to this, many different light quality advances are available but, with their massive implementation, the same issue is occurring as in the 1960s with the appearance of the Grolux (Sylvania) fluorescent tubes: there is a lack of a methodological standardization of lighting. This review analyzes the main parameters and variables that must be taken into account in the design of LED-based systems, and how these need to be described and quantified in order to homogenize and standardize the experimental conditions to obtain reproducible and comparable results and conclusions. We have designed an experimental system in which the values of the physical environment and microenvironment conditions and the behavior of plant tissue cultures maintained in cabins illuminated with two lighting designs can be compared. Grolux tubes are compared with a combination of monochromatic LED lamps calibrated to provide a spectral emission, and light irradiance values similar to those generated by the previous discharge lamps, achieving in both cases wide uniformity of radiation conditions on the shelves of the culture cabins. This study can help to understand whether it is possible to use LEDs as one standard lighting source in plant tissue culture without affecting the development of the cultures maintained with the previously regulated protocols in the different laboratories. Finally, the results presented from this caparison indicate how temperature is one of the main factors that is affected by the chosen light source.

Copper oxide (CuO) and manganese oxide (MnO) nanoparticles induced biomass accumulation, antioxidants biosynthesis and abiotic elicitation of bioactive compounds in callus cultures of Ocimum basilicum (Thai basil)

Nano-elicitation is one among the prioritised strategies considered globally for sustainable and uniform production of industrially important medicinal compounds. Ocimum basilicum (Thai basil), a renowned medicinal species is a reservoir of commercially vital metabolites and proved for its health assuring effects in cancer, diabetes, microbial and cardiovascular diseases. However, its consumption and industrial demand raised intent to divert towards better alternates for ensuring sustainable production of medicinal compounds. Herein, we investigated the comparative potential of metal oxide [copper oxide (CuO) and manganese oxide (MnO)] nanoparticles to elicit the biosynthesis of bioactive metabolites and antioxidative capacity of O.basilicum callus cultures. Results showed that callus grown on MS media supplemented with 10 mg/L CuO-NPs resulted in the highest biomass accumulation (FW: 172.8 g/L, DW: 16.7 g/L), phenolic contents (TPC: 27.5 mg/g DW), and flavonoid contents (TFC: 9.1 mg/g DW) along with antioxidant activities (DPPH: 94%, ABTS: 881 μM TEAC, FRAP: 386 μM TEAC) compared with MnO-NPs and control. Likewise, the Superoxide dismutase (SOD: 1.28 nM/min/mg FW) and Peroxidase (POD: 0.48 nM/min/mg FW) activities were also recorded maximum in CuO-NPs elicited cultures than MnO-NPs and control. Moreover, the HPLC results showed that rosmarinic acid (11.4 mg/g DW), chicoric acid (16.6 mg/g DW), eugenol (0.21 mg/g DW) was found optimum in cultures at 10 mg/L CuO-NPs. Overall, it can be concluded that CuO nanoparticles can be effectively used as a elicitor for biosynthesis of metabolites in callus cultures of O. basilicum (Thai basil). The study is indeed a contribution to the field that will help decoding the mechanism of action of CuO NPs. However, further molecular investigations are needed to fully develop understanding about the metabolic potential of O. bascillicum and scalling up this protocol for bulkup production of bioactive compounds.

A glance at the chemodiversity of Ocimum species: Trends, implications, and strategies for the quality and yield improvement of essential oil

Ocimum species represent commercially important medicinal and aromatic plants. The essential oil biosynthesized by Ocimum species is enriched with specialized metabolites specifically, terpenoids and phenylpropanoids. Interestingly, various Ocimum species are known to exhibit diverse chemical profiles, and this chemical diversity has been at the center of many studies to identify commercially important chemotypes. Here, we present various chemotypes from the Ocimum species and emphasize trends, implications, and strategies for the quality and yield improvement of essential oil. Globally, many Ocimum species have been analyzed for their essential oil composition in over 50 countries. Asia represents the highest number of chemotypes, followed by Africa, South America, and Europe. Ocimum basilicum L. has been the most widespread and well-studied species, followed by O. gratissimum L., O. tenuiflorum L., O. canum Sims, O. americanum and O. kilimandscharicum Gürke. Moreover, various molecular reasons, benefits, adverse health effects and mechanisms behind this vast chemodiversity have been discussed. Different strategies of plant breeding, metabolic engineering, transgenic, and tissue-culture, along with anatomical modifications, are surveyed to enhance specific chemotypic profiles and essential oil yield in numerous Ocimum species. Consequently, chemical characterization of the essential oil obtained from Ocimum species has become indispensable for its proper utilization. The present chemodiversity knowledge from Ocimum species will help to exploit various applications in the industrial, agriculture, biopharmaceutical, and food sectors.

SUPPLEMENTARY INFORMATION

The online version contains supplementary material available at 10.1007/s11101-021-09767-z.

Comparative Effects of Different Light Sources on the Production of Key Secondary Metabolites in Plants In Vitro Cultures

Plant secondary metabolites are known to have a variety of biological activities beneficial to human health. They are becoming more popular as a result of their unique features and account for a major portion of the pharmacological industry. However, obtaining secondary metabolites directly from wild plants has substantial drawbacks, such as taking a long time, posing a risk of species extinction owing to over-exploitation, and producing a limited quantity. Thus, there is a paradigm shift towards the employment of plant tissue culture techniques for the production of key secondary metabolites in vitro. Elicitation appears to be a viable method for increasing phytochemical content and improving the quality of medicinal plants and fruits and vegetables. In vitro culture elicitation activates the plant's defense response and increases the synthesis of secondary metabolites in larger proportions, which are helpful for therapeutic purposes. In this respect, light has emerged as a unique and efficient elicitor for enhancing the in vitro production of pharmacologically important secondary metabolites. Various types of light (UV, fluorescent, and LEDs) have been found as elicitors of secondary metabolites, which are described in this review.

The Protective Function and Modification of Secondary Metabolite Accumulation in Response to Light Stress in Dracocephalum forrestii Shoots

The aim of this work was to determine the effect of stress conditions caused by different light sources, i.e., blue LED (λ = 430 nm), red LED (λ = 670 nm), blue and red LED (70%:30%) and white LED (430–670 nm) on the growth and morphology of cultivated in vitro Dracocephalum forrestii shoot culture. It also examines the effects on bioactive phenolic compound production and photosynthetic pigment content, as well as on antioxidant enzyme activity (CAT, SOD, POD) and antioxidant properties. The most beneficial proliferation effect was observed under white LEDs (7.1 ± 2.1 shoots per explant). The white and blue lights stimulated the highest fresh weight gain, while red light induced the highest dry weight gain. The total phenolic acid content ranged from 13.824 ± 1.181 to 20.018 ± 801 mg g DW⁻¹ depending on light conditions. The highest content of rosmarinic acid was found in the control shoots (cultivated under fluorescent lamps), followed by culture grown under red light. All LED treatments, especially red and blue, increased salvianolic acid B content, and blue increased apigenin p-coumarylrhamnoside biosynthesis. The greatest ferric reduction activity was observed in shoots cultivated under red light, followed by blue; this is associated with the presence of the highest total phenol content, especially phenolic acids. Similarly, the highest DPPH radical scavenging potential was observed under red light followed by blue. This study proves that LEDs have emerged as significant support for directed in vitro propagation, taking advantage of specific stress responses on various light spectra. This study also showed how stress induced by different LED light spectra increases in Dracocephalum forrestii the synthesis of pharmacologically-active compounds. Hence, light stress may turn out to be a simpler alternative to metabolic engineering for improving the production of secondary metabolites of therapeutic value.

Application of Light-Emitting Diodes for Improving the Nutritional Quality and Bioactive Compound Levels of Some Crops and Medicinal Plants

Light is a key factor that affects phytochemical synthesis and accumulation in plants. Due to limitations of the environment or cultivated land, there is an urgent need to develop indoor cultivation systems to obtain higher yields with increased phytochemical concentrations using convenient light sources. Light-emitting diodes (LEDs) have several advantages, including consumption of lesser power, longer half-life, higher efficacy, and wider variation in the spectral wavelength than traditional light sources; therefore, these devices are preferred for in vitro culture and indoor plant growth. Moreover, LED irradiation of seedlings enhances plant biomass, nutrient and secondary metabolite levels, and antioxidant properties. Specifically, red and blue LED irradiation exerts strong effects on photosynthesis, stomatal functioning, phototropism, photomorphogenesis, and photosynthetic pigment levels. Additionally, ex vitro plantlet development and acclimatization can be enhanced by regulating the spectral properties of LEDs. Applying an appropriate LED spectral wavelength significantly increases antioxidant enzyme activity in plants, thereby enhancing the cell defense system and providing protection from oxidative damage. Since different plant species respond differently to lighting in the cultivation environment, it is necessary to evaluate specific wavebands before large-scale LED application for controlled in vitro plant growth. This review focuses on the most recent advances and applications of LEDs for in vitro culture organogenesis. The mechanisms underlying the production of different phytochemicals, including phenolics, flavonoids, carotenoids, anthocyanins, and antioxidant enzymes, have also been discussed.

Lights triggered differential accumulation of antioxidant and antidiabetic secondary metabolites in callus culture of Eclipta alba L

Eclipta alba L., also known as false daisy, is well known and commercially attractive plant with excellent hepatotoxic and antidiabetic activities. Light is considered a key modulator in plant morphogenesis and survival by regulating important physiological cascades. Current study was carried out to investigate growth and developmental aspects of E. alba under differential effect of multispectral lights. In vitro derived callus culture of E. alba was exposed to multispectral monochromatic lights under controlled aseptic conditions. Maximum dry weight was recorded in culture grown under red light (11.2 g/L) whereas negative effect was observed under exposure of yellow light on callus growth (4.87 g/L). Furthermore, red light significantly enhanced phenolics and flavonoids content (TPC: 57.8 mg/g, TFC: 11.1 mg/g) in callus cultures compared to rest of lights. HPLC analysis further confirmed highest accumulation of four major compounds i.e. coumarin (1.26 mg/g), eclalbatin (5.00 mg/g), wedelolactone (32.54 mg/g) and demethylwedelolactone (23.67 mg/g) and two minor compounds (β-amyrin: 0.38 mg/g, luteolin: 0.39 mg/g) in red light treated culture whereas stigmasterol was found optimum (0.22 mg/g) under blue light. In vitro based biological activities including antioxidant, antidiabetic and lipase inhibitory assays showed optimum values in cultures exposed to red light, suggesting crucial role of these phytochemicals in the enhancement of the therapeutic potential of E. alba. These results clearly revealed that the use of multispectral lights in in vitro cultures could be an effective strategy for enhanced production of phytochemicals.

Plant In Vitro Systems as a Sustainable Source of Active Ingredients for Cosmeceutical Application

Cosmeceuticals are hybrids between cosmetics and pharmaceuticals which are being designed for a dual purpose: (1) To provide desired esthetical effects and (2) simultaneously treat dermatological conditions. The increased demand for natural remedies and the trends to use natural and safe ingredients resulted in intensive cultivation of medicinal plants. However, in many cases the whole process of plant cultivation, complex extraction procedure, and purification of the targeted molecules are not economically feasible. Therefore, the desired production of natural cosmetic products in sustainable and controllable fashion in the last years led to the intensive utilization of plant cell culture technology. The present review aims to highlight examples of biosynthesis of active ingredients derived through plant in vitro systems with potential cosmeceutical application. The exploitation of different type of extracts used in a possible cosmeceutical formulation, as well as, their activity tested in in vitro/in vivo models is thoroughly discussed. Furthermore, opportunities to manipulate the biosynthetic pathway, hence engineering the biosynthesis of some secondary metabolites, such as anthocyanins, have been highlighted.

Plant architecture and phytochemical composition of basil (Ocimum basilicum L.) under the influence of light from microwave plasma and high-pressure sodium lamps

Potted herbs such as basil are in high year-round demand in Central Europe. To ensure good quality in winter, artificial light is required. Many horticulturists, who want to replace their high-pressure‑sodium (HPS) lamps with light-emitting diodes (LEDs) to save electricity energy, struggle with high investment costs. In addition, switching to LEDs can overwhelm many smaller horticultural enterprises since there is a requirement of adjusting individual light recipes and furthermore cultivation problems can occur due to the lack of infrared radiation. In this study, the influence of light from microwave plasma lamps (MPL), acting as alternative light sources, on secondary metabolites and morphology of basil plants (Ocimum basilicum L.) was tested. Basil plants were grown in a climate chamber with MPL with two different light bulbs emitting either artificial sunlight (AS) or broad white light with increased blue and green light content (sulfur plasma light; SPL). The effect of these new lamp types was compared to standard commercial HPS lamps. In addition to morphological parameters such as height, internode length and fresh weight, plant secondary metabolites were examined. Essential oils and monoterpenes were quantified by GC-MS analysis, whereby phenolic compounds were analyzed calorimetrically. Elongation growth and biomass production was increased under the AS spectrum in comparison to HPS-grown plants. Increased stem elongation was attributed to a higher content of far-red light in the AS spectrum. Furthermore, basil plants grown under the AS spectrum contained the highest total phenolic and total flavonoid content compared to plants grown under the SPL and HPS lamps, probably due to the higher content of UV-A radiation. The lowest content of phenolic compounds was observed when HPS light was used, which was assumed to be caused by a low blue light content in the emission spectrum. An impact of the different light spectra on essential oil composition was determined. A significantly increased content of linalool was found in basil leaves developed under both tested MPL spectra compared to HPS-grown plants. The total yield of the four major essential oils was lowest under HPS treatment.

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.

Interactive Effects of Light and Melatonin on Biosynthesis of Silymarin and Anti-Inflammatory Potential in Callus Cultures of Silybum marianum (L.) Gaertn

Silybum marianum (L.) Gaertn. is a well-known medicinal herb, primarily used in liver protection. Light strongly affects several physiological processes along with secondary metabolites biosynthesis in plants. Herein, S. marianum was exploited for in vitro potential under different light regimes in the presence of melatonin. The optimal callogenic response occurred in the combination of 1.0 mg/L α-naphthalene acetic acid and 0.5 mg/L 6-benzylaminopurine under photoperiod. Continuous light associated with melatonin treatment increased total flavonoid content (TFC), total phenolic content (TPC) and antioxidant potential, followed by photoperiod and dark treatments. The increased level of melatonin has a synergistic effect on biomass accumulation under continuous light and photoperiod, while an adverse effect was observed under dark conditions. More detailed phytochemical analysis showed maximum total silymarin content (11.92 mg/g dry weight (DW)) when placed under continuous light + 1.0 mg/L melatonin. Individually, the level of silybins (A and B), silydianin, isolsilychristin and silychristin was found highest under continuous light. Anti-inflammatory activities were also studied and highest percent inhibition was recorded against 15-lipoxygenase (15-LOX) for cultures cultivated under continuous light (42.33%). The current study helps us to better understand the influence of melatonin and different light regimes on silymarin production as well as antioxidant and anti-inflammatory activities in S. marianum callus extracts.

Flavan-3-ols Content in Red Raspberry Leaves Increases under Blue Led-Light Irradiation

Berry fruits are well known to contain large amounts of polyphenol compounds. Among them, flavan-3-ol derivatives are a group of secondary metabolism compounds currently attracting a great deal of attention owing to their health benefits. Not only the fruits, but also the leaves of raspberry plants, are highly esteemed for tea making around the world and are largely used for food. In this report, we discuss the results of our study on the effect of light and temperature on polyphenol accumulation in raspberry leaves. When raspberry was cultivated in a plant factory unit and light intensity, wavelength, and temperature were varied, the amount of total polyphenol increased under blue light. Quantitative determination of (+)-catechin, (⁻)-epicatechin, procyanidin B4, flavan-3-ol trimer, which are flavan-3-ol derivatives, was carried out using HPLC, whereby we confirmed their increase under blue light. Semi-quantitative RT-PCR showed correlation between chalcone synthase (CHS) gene expression and the amounts of the compounds measured in the leaves.

Effects of Light-Emitting Diodes on the Accumulation of Glucosinolates and Phenolic Compounds in Sprouting Canola (Brassica napus L.)

In this study, we investigated optimal light conditions for enhancement of the growth and accumulation of glucosinolates and phenolics in the sprouts of canola (Brassica napus L.). We found that the shoot lengths and fresh weights of red light-irradiated sprouts were higher than those of sprouts exposed to white, blue, and blue + red light, whereas root length was not notably different among red, blue, white, and blue + red light treatments. The accumulations of total glucosinolates in plants irradiated with white, blue, and red lights were not significantly different (19.32 ± 0.13, 20.69 ± 0.05, and 20.65 ± 1.70 mg/g dry weight (wt.), respectively). However, sprouts exposed to blue + red light contained the lowest levels of total glucosinolates (17.08 ± 0.28 mg/g dry wt.). The accumulation of total phenolic compounds was the highest in plants irradiated with blue light (3.81 ± 0.08 mg/g dry wt.), 1.33 times higher than the lowest level in plants irradiated with red light (2.87 ± 0.05 mg/g dry wt.). These results demonstrate that red light-emitting diode (LED) light is suitable for sprout growth and that blue LED light is effective in increasing the accumulation of glucosinolates and phenolics in B. napus sprouts.