Essential oil yield estimation by Gas chromatography-mass spectrometry (GC-MS) after Methyl jasmonate (MeJA) elicitation in in vitro cultivated tissues of Coriandrum sativum L

Studying the impact of titanium dioxide nanoparticles on the expression of pivotal genes related to menthol biosynthesis and certain biochemical parameters in peppermint plants (Mentha Piperita L.)

BACKGROUND

This study examines the impact of titanium dioxide nanoparticles (TiO2NPs) on gene expression associated with menthol biosynthesis and selected biochemical parameters in peppermint plants (Mentha piperita L.). Menthol, the active ingredient in peppermint, is synthesized through various pathways involving key genes like geranyl diphosphate synthase, menthone reductase, and menthofuran synthase. Seedlings were treated with different concentrations of TiO2NPs (50, 100, 200, and 300 ppm) via foliar spray. After three weeks of treatment, leaf samples were gathered and kept at -70 °C for analysis.

RESULTS

According to our findings, there was a significant elevation (P ≤ 0.05) in proline content at concentrations of 200 and 300 ppm in comparison with the control. Specifically, the highest proline level was registered at 200 ppm, reaching 259.64 ± 33.33 µg/g FW. Additionally, hydrogen peroxide and malondialdehyde content exhibited a decreasing trend following nanoparticle treatments. Catalase activity was notably affected by varying TiO2NP concentrations, with a significant decrease observed at 200 and 300 ppm compared to the control (P ≤ 0.05). Conversely, at 100 ppm, catalase activity significantly increased (11.035 ± 1.12 units/mg of protein/min). Guaiacol peroxidase activity decreased across all nanoparticle concentrations. Furthermore, RT-qPCR analysis indicated increased expression of the studied genes at 300 ppm concentration.

CONCLUSIONS

Hence, it can be inferred that at the transcript level, this nanoparticle exhibited efficacy in influencing the biosynthetic pathway of menthol.

Elicitation Induced α-Amyrin Synthesis in Tylophora indica In Vitro Cultures and Comparative Phytochemical Analyses of In Vivo and Micropropagated Plants

Tylophora indica (Burm. f.) Merrill is an endangered medicinal plant that possesses various active agents, such as tylophorinine, kaempferol, quercetin, α-amyrin and beta-sitosterol, with multiple medicinal benefits. α-amyrin, a triterpenoid, is widely known for its antimicrobial, anti-inflammatory, gastroprotective and hepatoprotective properties. In this study, we investigated the metabolite profiling of tissues and the effects of cadmium chloride and chitosan on in vitro accumulation of alkaloids in T. indica. First, the callus was induced from the leaf in 2,4-D-, NAA- and/or BAP-fortified MS medium. Subsequent shoot formation through organogenesis and in vitro roots was later induced. Gas chromatography-mass spectrometry (GC-MS)-based phytochemical profiling of methanolic extracts of in vivo and in vitro regenerated plants was conducted, revealing the presence of the important phytocompounds α-amyrin, lupeol, beta-sitosterol, septicine, tocopherol and several others. Different in vitro grown tissues, like callus, leaf and root, were elicited with cadmium chloride (0.1-0.4 mg L-1) and chitosan (1-50 mg L-1) to evaluate the effect of elicitation on α-amyrin accumulation, measured with high-performance thin layer chromatography (HPTLC). CdCl2 and chitosan showed improved sugar (17.24 and 15.04 mg g-1 FW, respectively), protein (10.76 and 9.99 mg g-1 FW, respectively) and proline (7.46 and 7.12 mg g-1 FW), especially at T3 (0.3 and 25 mg L-1), in the leaf as compared to those of the control and other tissues. The antioxidant enzyme activities were also evaluated under an elicitated stress situation, wherein catalase (CAT), superoxide dismutase (SOD) and ascorbate peroxidase (APX) displayed the highest activities in the leaf at T4 of both of the two elicitors. The α-amyrin yield was quantified with HPTLC in all tested tissues (leaf, callus and root) and had an Rf = 0.62 at 510 nm wavelength. Among all the concentrations tested, the T3 treatment (0.3 mg L-1 of cadmium chloride and 25 mg L-1 of chitosan) had the best influence on accumulation, irrespective of the tissues, with the maximum being in the leaf (2.72 and 2.64 μg g-1 DW, respectively), followed by the callus and root. Therefore, these results suggest future opportunities of elicitors in scaling up the production of important secondary metabolites to meet the requirements of the pharmaceutical industry.

Genome size and gas chromatography-mass spectrometry (GC-MS) analysis of field-grown and in vitro regenerated Pluchea lanceolata plants

Pluchea lanceolata is a threatened pharmacologically important plant from the family Asteraceae. It is a source of immunologically active compounds; large-scale propagation may offer compounds with medicinal benefits. Traditional propagation method is ineffective as the seeds are not viable; and root sprout propagation is a slow process and produces less numbers of plants. Plant tissue culture technique is an alternative, efficient method for increasing mass propagation and it also facilitate genetic improvement. The present study investigated a three-way regeneration system in P. lanceolata using indirect shoot regeneration (ISR), direct shoot regeneration (DSR), and somatic embryo mediated regeneration (SER). Aseptic leaf and nodal explants were inoculated on Murashige and Skoog (MS) medium amended with plant growth regulators (PGRs), 2,4-dichlorophenoxy acetic acid (2,4-D), 1-naphthalene acetic acid (NAA), and 6-benzyl amino purine (BAP) either singly or in combinations. Compact, yellowish green callus was obtained from leaf explants in 1.0 mg/l BAP (89.10%) added medium; ISR percentage was high, i.e., 69.33% in 2.0 mg/l BAP + 0.5 mg/l NAA enriched MS with 4.02 mean number of shoots per callus mass. Highest DSR frequency (67.15%) with an average of 5.62 shoot numbers per explant was noted in 0.5 mg/l BAP added MS medium. Somatic embryos were produced in 1.0 mg/l NAA fortified medium with 4.1 mean numbers of somatic embryos per culture. On BAP (1.0 mg/l) + 0.5 mg/l gibberellic acid (GA₃) amended medium, improved somatic embryo germination frequency (68.14%) was noted showing 12.18 mean numbers of shoots per culture. Histological and scanning electron microscopic (SEM) observation revealed different stages of embryos, confirming somatic embryogenesis in P. lanceolata. Best rooting frequency (83.95%) of in vitro raised shootlets was obtained in 1.0 mg/l IBA supplemented half MS medium with a maximum of 7.83 roots per shoot. The regenerated plantlets were transferred to the field with 87% survival rate. The 2C genome size of ISR, DSR, and SER plants was measured and noted to be 2.24, 2.25, and 2.22 pg respectively, which are similar to field-grown mother plant (2C = 2.26 pg). Oxidative and physiological events suggested upregulation of enzymatic activities in tissue culture regenerated plants compared to mother plants, so were photosynthetic pigments. Implementation of gas chromatography-mass spectrometry (GC-MS) technique on in vivo and in vitro raised plants revealed the presence of diverse phyto-chemicals. The yields of alpha amyrin and lupeol (medicinally important triterpenoids) were quantified using high-performance thin-layer chromatography (HPTLC) method and enhanced level of alpha amyrin (2.129 µg g^-1 dry wt) and lupeol (1.232 µg g^-1 dry wt) was noted in in vitro grown leaf tissues, suggesting in vitro conditions act as a potential trigger for augmenting secondary metabolite synthesis. The present protocol represents a reliable mass propagation technique in producing true-to-type plants of P. lanceolata, conserving 2C DNA and ploidy successfully without affecting genetic homogeneity.

Cryo-derived plants through embryogenesis showed same levels of vinblastine and vincristine (anticancer) in Catharanthus roseus and had normal genome size

Cryopreservation of rare plant materials is an important approach for preserving germplasms and is a good added concept to tissue banking. The preservation of embryogenic cell suspensions is even more valuable as the tissues facilitate in producing millions of embryos, plantlets and generates transgenics en masse. Catharanthus roseus is a medicinally important plant that produces a variety of anticancerous phytocompounds and needs conservation of alkaloid producing cell lines. In this study, embryogenic tissue banking has been attempted in C. roseus by the two-step cryopreservation method combining cryoprotection and dehydration. Prior to plunging into liquid nitrogen (LN), the tissues were exposed to osmotic—and cryoprotective agents. Two osmotic agents (sugar and sorbitol) and three cryoprotective compounds, polyethylene glycol (PEG), dimethyl sulfoxide (DMSO) and glycerol were used at varying concentrations to protect cells from freezing damages. Both sucrose and sorbitol increased callus biomass post-cryopreservation; the influence of sucrose was however, more prominent. Embryogenic tissue treated in medium with 0.4 M sucrose for 2 days followed by 5% PEG for 2 h showed maximum viability before (83%) and after (55%) cryopreservation, high regrowth percentage (77%) and produced an average 9 cell colonies per Petri dish. Additionally, dehydration (1–5 h) was tested to reduce water content for improving viability and regrowth of cryopreserved embryogenic cells. Among the various tested cryoprotective conditions, the highest (72%) viability was observed following the combination of treatments with 0.4 M sucrose (2 days),10% PEG (2 h) and dehydration (2 h). Maximum regrowth percentage (88%) and 12 colonies/petri dish was noted in combination of 0.4 M sucrose + 5% PEG. The cryopreserved calli differentiated into somatic embryos (52.78–54.33 globular embryos/callus mass) in NAA (0.5 mg/l) and BAP (0.5–1.0 mg/l) added media. Plantlets were successfully regenerated from cryopreserved tissue and the 2C DNA was estimated through flow cytometry. The genome size of cryopreserved regenerant was 1.51 pg/2C, which is similar to field-grown Catharanthus plants. Vinblastine and vincristine levels were nearly the same in mother plant’s and frozen (cryopreserved) leaf tissue. The post cryopreservation embryogenesis protocol may be used for continuous production of plants for future applications.

Jasmonates in plant growth and development and elicitation of secondary metabolites: An updated overview

Secondary metabolites are incontestably key specialized molecules with proven health-promoting effects on human beings. Naturally synthesized secondary metabolites are considered an important source of pharmaceuticals, food additives, cosmetics, flavors, etc., Therefore, enhancing the biosynthesis of these relevant metabolites by maintaining natural authenticity is getting more attention. The application of exogenous jasmonates (JAs) is well recognized for its ability to trigger plant growth and development. JAs have a large spectrum of action that covers seed germination, hypocotyl growth regulation, root elongation, petal expansion, and apical hook growth. This hormone is considered as one of the key regulators of the plant's growth and development when the plant is under biotic or abiotic stress. The JAs regulate signal transduction through cross-talking with other genes in plants and thereby deploy an appropriate metabolism in the normal or stressed conditions. It has also been found to be an effective chemical elicitor for the synthesis of naturally occurring secondary metabolites. This review discusses the significance of JAs in the growth and development of plants and the successful outcomes of jasmonate-driven elicitation of secondary metabolites including flavonoids, anthraquinones, anthocyanin, xanthonoid, and more from various plant species. However, as the enhancement of these metabolites is essentially measured via in vitro cell culture or foliar spray, the large-scale production is significantly limited. Recent advancements in the plant cell culture technology lay the possibilities for the large-scale manufacturing of plant-derived secondary metabolites. With the insights about the genetic background of the metabolite biosynthetic pathway, synthetic biology also appears to be a potential avenue for accelerating their production. This review, therefore, also discussed the potential manoeuvres that can be deployed to synthesis plant secondary metabolites at the large-scale using plant cell, tissue, and organ cultures.

Gamma ray-induced tissue responses and improved secondary metabolites accumulation in Catharanthus roseus

The present study investigated the impact of gamma ray irradiation on callus biomass growth and the yield of vincristine and vinblastine of in vitro grown tissues of Catharanthus roseus. The biochemical alteration underlying the synthesis of secondary metabolites has also been studied and a comparison of yield was prepared. The embryogenic tissues were exposed to 20, 40, 60, 80, and 100 Gy gamma ray doses and the callus biomass fresh weight, the embryogenesis (the embryo numbers, germination, plant regeneration), the alteration of protein, proline, and sugar attributes at different morphogenetic stages were monitored. The callus biomass growth was maximum (1.65 g) in 20 Gy exposed tissues and was less in 100 Gy treatment (0.33 g). The gamma-irradiated embryogenic tissues differentiated into embryos but the embryogenesis % and somatic embryo number per culture reduced with increasing doses. It was least in 80 Gy where very low numbers of embryos were formed (3.45 and 3.30 mean torpedo and cotyledonary embryo numbers per callus mass, respectively) which later germinated into plantlets. Protein, proline, sugar, and different antioxidant enzymes, i.e., superoxide dismutase (SOD), ascorbate peroxidase (APX), and catalase (CAT) activities, were investigated as the tissues were exposed to gamma ray elicitation/signaling, evoking cellular stress. Increased 80 Gy gamma dose inhibited a 42.73% decrease in protein accumulation at initiation stages of embryogenic tissue. Soluble sugar level also declined gradually being least in 80 Gy treated tissues (14.51 mg gm^-1 FW) compared to control (20.2 mg gm^-1 FW). Proline content, however, increased with increasing gamma doses, maximum at 80 Gy (8.28 mg gm^-1 FW). The SOD, APX, and CAT activity increased linearly with enhanced level of gamma doses and maximum, i.e., 3.91 EU min^-1 mg^-1, 1.71 EU min^-1 mg^-1, and 4.89 EU min^-1 mg^-1, protein activity was noted for SOD, APX, and CAT, respectively, at 80 Gy gamma rays treated tissues. The quantification of vinblastine and vincristine in gamma ray elicitated tissues was made by using high-pressure thin layer chromatography (HPTLC). Somatic embryo-regenerated plant's leaves had the maximum yield of vinblastine (15.13 µgm gm^-1 DW) at 40 Gy irradiation dose compared to control (13.30 µgm gm^-1 DW)-the increased yield % is 13.75. The stem is also rich source producing 11.98 µgm gm^-1 DW of vinblastine. Among the various developmental stages of embryos, vinblastine content was highest in germinating stage of embryos (10.14 µgm gm^-1 DW) compared to other three, i.e., initiation, proliferation, and maturation embryo stages. Similarly, highest accumulation of vincristine (6.32 µg gm^-1 DW) was noted at low gamma irradiation dose (20 Gy) in leaf tissues. The present study indicates that the synthesis of vinblastine and vincristine was growth- and development-specific and the lower 20-40 Gy gamma levels were more effective in enriching alkaloids while higher doses declined yield. KEY POINTS: • Vinblastine and vincristine yield was quantified in in vitro grown tissues and leaves of embryo regenerated Catharanthus roseus after gamma ray treatment. • The accumulation of vinblastine and vincristine was maximum in regenerated leaves; low doses were more efficient in improving yield. • Gamma ray irradiation impacted biochemical profiles, caused cellular stress, and perhaps responsible for improved alkaloid yield.

Plant elicitation and TiO2 nanoparticles application as an effective strategy for improving the growth, biochemical properties, and essential oil of peppermint

Mentha piperita L., which is an abundant source of essential oils (EO) and phenolic acids, is well known for its medicinal significance. The present research aimed to evaluate the impact of various concentrations of methyl jasmonate (MeJA; 0, 0.1, and 0.5 mM), titanium dioxide nanoparticles (TiO₂ NPs; 0 and 150 mg L^-1), and salicylic acid (SA; 0, 0.1, and 1 mM) on growth, EOs, and phenolic compounds of M. piperita L. The results demonstrated that the simultaneous application of SA (0.1 mM) and TiO₂ NPs (150 mg L^-1) enhanced shoot dry weight, the shoot length, and membrane stability index of peppermint by 56.17, 19.52, and 36%, respectively, compared to control. Moreover, phenolic content (76%), caffeic acid content (78%), rosmarinic acid content (87%), 2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging ability (78%), and catalase (155%), ascorbate peroxidase activities (95%) were further improved by simultaneously applying MeJA (0.1 mM) and TiO₂ NPs (150 mg L^-1) compared to control. The highest menthol production (44.51%) was obtained with exogenous application of MeJA (0.1 mM) with 150 mg L^-1 TiO₂ NPs. The findings of the current study presented an ideal combination of TiO₂ NPs with plant growth regulators for promoting antioxidant activities and increasing major components of EO in peppermint plants.

Cadmium chloride (CdCl2) elicitation improves reserpine and ajmalicine yield in Rauvolfia serpentina as revealed by high-performance thin-layer chromatography (HPTLC)

In vitro cultures play a promising role for production of pharmaceutically important plant secondary metabolites and the use of elicitation can mitigate the low productivity of active compounds. In the present study, the influence of cadmium chloride (CdCl₂) elicitation on alkaloid yield was investigated in Rauvolfia serpentina. This heavy metal was employed to enhance the yield of reserpine and ajmalicine in leaf derived callus, leaves, stems and roots of in vitro grown cultures. Different concentrations [0.05 mM (C1), 0.10 mM (C2), 0.15 mM (C3) and 0.20 mM (C4)] of CdCl₂ were added to the MS medium. The elicitor's influence on callus biomass, biochemical attributes and the yield of alkaloids was monitored at regular intervals. The amendment of CdCl₂ improved growth and maximum callus biomass (1.29 g fresh weight and 0.16 g dry weight) was noted at 0.15 mM (C3) after 6 days of elicitation. The addition of elicitor in medium caused cellular stress and to analyse the role of CdCl₂ in plant defence responses various antioxidant enzymes, i.e., superoxide dismutase (SOD), catalase (CAT) and ascorbate peroxidase (APX) activities were measured in treated and non-treated cultures. The antioxidant enzyme activity increased linearly with elevated levels of CdCl₂ in medium; highest APX (0.88 EU min^-1 mg^-1protein), SOD (5.40 EU min^-1 mg^-1protein) and CAT (4.21 EU min^-1 mg^-1protein) activity were observed in leaves of in vitro regenerated plants at C4. The quantitative analyses of reserpine and ajmalicine were conducted in different elicitated tissues using high-performance thin-layer chromatography (HPTLC) method. The study reveals enriched level of reserpine and ajmalicine in cultivated tissues and the enhancement was noted up to C3 (0.15 mM) elicitor level. Reserpine yield was maximum (0.191 mg g^-1 DW) in roots of in vitro regenerated plants. The accumulation of ajmalicine was, however, better in leaf derived callus at C3 (0.131 mg g^-1 DW). Higher elicitor dose (0.20 mM) inhibited callus biomass growth and subsequent alkaloid accumulation. The present study indicates the use of CdCl₂ as a propitious method in enhancing reserpine and ajmalicine yield in R. serpentina.