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.

The influence of light quality on the production of bioactive metabolites - verbascoside, isoverbascoside and phenolic acids and the content of photosynthetic pigments in biomass of Verbena officinalis L. cultured in vitro

In vitro callus cultures of Verbena officinalis L. were maintained on solid Murashige and Skoog medium, enriched with 1 mg dm^-3 BA and 1 mg dm^-3 IBA under LED lights (red, blue, red/blue 70%/30%), in darkness and under control fluorescent lamps. The measurements of 2 phenylpropanoid glycosides (verbascoside and isoverbascoside) and 23 phenolic acids were performed in methanolic extracts from the biomass collected after 2-, 3- and 4-week growth cycles using the HPLC-DAD method. The presence of verbascoside, isoverbascoside and additionaly 7 phenolic acids (protocatechuic, chlorogenic, vanillic, caffeic, ferulic, o-coumaric and m-coumaric acids) was confirmed in all extracts. Blue and red/blue lights stimulated the accumulation of verbascoside (max. of 6716 and 6023 mg 100 g^-1 DW after a 4-week growth cycle) and isoverbascoside (max. 333 and 379 mg 100 g^-1 DW also after 4 weeks). The maximum amounts of verbascoside and isoverbascoside were respectively 1.8- and 7.0-fold higher than under the control conditions. Phenolic acids were accumulated in different amounts, and the maximum total amounts ranged from 36 to 65 mg 100 g^-1 DW. LED lights also stimulated their accumulation in comparison with darkness and control. The main phenolic acids included: m-coumaric acid (max. 39 mg 100 g^-1 DW), ferulic acid (max. 12 mg 100 g^-1 DW), and protocatechuic acid (max. 13 mg 100 g^-1 DW). Additionally, the quantities of photosynthetic pigments (chlorophyll a, b and carotenoids) were estimated in acetonic extracts using spectrophotometry. Red/blue light stimulated the biosynthesis of pigments (max. total content 287 μg g^-1 FW after 4-week growth cycles). This is the first study describing the effect of LED lights on the production of phenylpropanoid glycosides and phenolic acids in V. officinalis callus cultures. Very high amounts of verbascoside and isoverbascoside are interesting from a practical point of view.

Strategy for early callus induction and identification of anti-snake venom triterpenoids from plant extracts and suspension culture of Euphorbia hirta L

Euphorbia hirta L. from the family of Euphorbiaceae is an annual herb, which grows as a roadside weed in most tropical countries. It is prominently used by the traditional healers in rural India for the treatment of snakebites. However, the mechanisms and the major bioactive compounds behind its inhibition activity are relatively unknown. From our preliminary in silico studies, it was found that a group of pentacyclic triterpenoids from this plant are playing a major role in inhibiting the snake venom proteins. The present study was aimed at standardizing methods for obtaining callus from this medicinal plant at a much faster rate by hormone pretreatment of explants and, thus, by developing suspension cultures to obtain bioactive secondary metabolites in vitro. The results were promising that longer incubation of explants with hormone treatment showed early induction of callus. The major bioactive compounds responsible for the anti-snake venom activity were characterized from natural plant material as well as from suspension cultures, and the efficiency was found to be relatively high. The secondary metabolite analysis from suspension culture and natural plant extracts revealed that a major compound 'Taraxerol' and its derivatives was found abundant along with few other triterpenoids. This compound showed high inhibitory activity against pit viper snake venoms from our in silico studies with molecular docking tools. Hence, this study with identification of potential bioactive compounds against snake venom with standardization of In vitro culture methods would help in developing natural alternative medicine for snakebites in near future.

New triterpenic acids produced in callus culture from fruit pulp of Acca sellowiana (O. Berg) Burret

The aim of this work was the study of the best conditions for obtaining a callus culture from the pulp of Acca sellowiana, and to perform a quali-quantitative analysis of the secondary metabolites yielded by the in vitro callus culture. To this end, callus was induced on both Murashige and Skoog and Gamborg B5 media containing various combinations of growth regulators. Three previously undescribed ursane-type triterpenoids, 2α,3β,6α,23-tetrahydroxy-18α,19α-urs-20-en-28-oic acid, 2α,3β,23-trihydroxy-18α,19α-urs-20-en-28-oic acid and 2α,3β,6β,23-tetrahydroxy-18α,19α-urs-20-en-28-oic acid were isolated from the methanolic extract of A. sellowiana culture and characterized by 1D and 2D NMR experiments. Moreover, the quali-quantitative analysis (ESI-MSn and GC-MS) also showed the presence of β-sitosterol, phloridzin, oleanolic, ursolic, 3β-hydroxy-18α,19α-urs-20-en-28-oic, maslinic, corosolic, 2α,3β-dihydroxy-18α,19α-urs-20-en-28-oic, and tormentic acid.

Influence of cold pretreatment on shoot regeneration from callus in date palm (Phoenix dactylifera L.) cv. 'Barhee'

Mass propagation of date palm through indirect somatic embryogenesis or organogenesis has attracted the interest of commercial producers. But, this technique still faces some problems that hindered the production of date palm plantlets in vitro. Tissue browning is one of the serious problems that reduce callus growth and shoot regeneration. So the objective of the present study is to investigate the effect of cold pretreatment on callus growth, shoot regeneration, and polyphenol oxidase (PPO) activity during the callus culture. Results showed that a high survival rate of callus cultures (100%) were obtained when cultures were incubated in low temperature (cold treatment) for 45 and 75 days. On the other hand, total amount on phenolic compounds was also reduced to 0.47 and 0.53 mg GAE/g after same period of incubation (45 and 75 days respectively) at low temperature. In additional, our results showed that the highest frequency of shoot formation (66.67 and 73.34, %) and the highest shoot numbers (7.8 and 8.6 shoots/100 mg) were obtained from callus treated with low temperature for 45 and 75 days, respectively.

Isolation and quantification of antimalarial N-alkylamides from flower-head derived in vitro callus cultures of Spilanthes paniculata

This is the pioneer work reporting on simple procedure for synchronized determination and quantification of two biologically active N-alkylamides, (2E,6Z,8E)-N-isobutyl-2,6,8-decatrienamide (spilanthol) and (2E,4Z)-N-isobutyl-2,4-undecadiene-8,10-diynamide (UDA), using in vitro callus cultures from flower-heads of Spilanthes paniculata. The extracts were purified using preparative thin layer chromatography (TLC) and finest separation of compounds was optimized using high performance liquid chromatography (HPLC). Eventually, N-alkylamides were validated by mass spectrometry. Linearity curve with its regression coefficients (R²) obtained for both these alkylamides was 0.99. While spilanthol was quantified using tentative standard dodeca-2(E),4(E)-dienoic acid due to the non-availability of commercial standard and the precision of a developed method was evaluated in terms of relative standard deviation by measuring inter- and intra-days variation 3.52% and 1.74%, respectively. Similarly, calibration curve was obtained for the compound UDA isolated from flower-head explants from field grown parental plant with its inter- and intra-day RSD values as 4.33% and 3.61%, respectively. With this protocol, a very high yield of 2.23 mg/g of spilanthol and 4.30 mg/g dry weight (DW) of UDA, was obtained, simultaneously, from callus cultures. Flower-heads from parent plants, used as control, showed negligible amount of spilanthol and quantity of UDA was marginally higher than that in callus cultures. The highly stable biotherapeutic spilanthol and UDA with m/z 222 and m/z 230, respectively, showed retardation of malaria parasite development through blockage at ring stage of erythrocytic schizogony and ultimately lead to parasite death. The effect on parasite was additive. This study signifies the utility of in vitro cell cultures for therapeutic compound production, throughout the year, at higher yield for down-stream applications.

Cryopreservation of Chrysanthemum cinerariaefolium Vis. cells and its impact on their pyrethrin biosynthesis ability

An efficient protocol for cryogenic storage of high-pyrethrin-producing cell lines of Chrysanthemum cinerariaefolium is described. Optimal survival (92%) was obtained with cells precultured in 1/2 Murashige and Skoog nutrient medium containing 180 g ⋅ l^-1 sucrose for 30 days, then incubated in the same medium in the presence of 5% DMSO for 1 h in an ice bath, cooled slowly to -20°C and immersed for 30 min in liquid nitrogen. After cryopreservation, the cells conserved the same growth pattern, but displayed different biochemical properties. The subculture derived from the thawed cells was characterized by a lower chlorophyll content and a higher pyrethrin biosynthesis ability.