Enhancing hypericin production of Hypericum perforatum cell suspension culture by ozone exposure

Optimizing elicitation strategy of salicylic acid for flavonoid and phenolic production of fed-batch cultured Oplopanax elatus adventitious roots

Oplopanax elatus is a valuable medicinal plant, but its plant resource is lacking. Adventitious root (AR) culture of O. elatus is an effective way for the production of plant materials. Salicylic acid (SA) exerts enhancement effect on metabolite synthesis in some plant cell/organ culture systems. To clarify the elicitation effect of SA on fed-batch cultured O. elatus ARs, this study investigated the effects of SA concentration, and elicitation time and duration. Results showed that flavonoid and phenolic contents, and antioxidant enzyme activity obviously increased when the fed-batch cultured ARs were treated with 100 μM SA for 4 days starting on day 35. Under this elicitation condition, total flavonoid and phenolic contents reached 387 rutin mg/g DW and 128 gallic acid mg/g DW, respectively, which were significantly (p < 0.05) higher than those in the SA-untreated control. In addition, DPPH scavenging and ABTS⁺ scavenging rates, and Fe²⁺ chelating rate also greatly increased after SA treatment, and their EC₅₀ values were 0.0117, 0.61, and 3.34mg/L, respectively, indicating the high antioxidant activity. The findings of the present study revealed that SA could be used as an elicitor to improve the flavonoid and phenolic production in fed-batch O. elatus AR culture.

Signalling molecules responsive to ozone-induced oxidative stress in Salvia officinalis

Tropospheric ozone (O₃) is the most important gaseous pollutant and induces a mass of negative impacts on vegetation at functional and genic levels. The aim of the present study was to investigate the role of reactive oxygen species and signalling molecules in sage plants exposed to O₃ (200 ppb, 5 h). Ozone exposure induced only a transient oxidative burst, as confirmed by the rapid peak of anion superoxide during the first hours of exposure (+16% compared to controls). The spontaneous reaction of O₃ with membrane fatty acids stimulates peroxidative processes, as demonstrated by the rise of thiobarbituric acid reactive substances concentration starting after 1 h of exposure (+25%). The formation of lipid-based signalling molecules (e.g. jasmonic acid) may be regarded as a sort of O₃-perception. The concomitant accumulation of salicylic acid suggests that sage responds early to O₃ by inducing cellular antioxidants mechanisms in order to minimize O₃-oxidative burst. The transient increase of abscisic acid (+25% at the end of the treatment) twinned with the maximal ethylene emission (about two-fold higher than controls) could be interpreted as a first attempt by plants to regulate the signalling responses induced by O₃. In order to investigate the involvement of transcription factors in managing oxidative protection, BLASTX analysis against the Salvia miltiorrhiza sequence genome was carried out using Arabidopsis thaliana WRKY sequences as queries. Six gene sequences were identified for sage WRKYs and their relative gene expression analyses were characterized. WRKY4, WRKY5, WRKY11 and WRKY46 were up-regulated by O₃ at 2 and 5 h of exposure and they showed similarity with AtWRKY48, AtWRKY22 and AtWRKY53 in A. thaliana. These results suggest that WRKYs could play a pivotal role in the signalling mechanisms during the responses of plants to O₃.

Enhanced expression of ginsenoside biosynthetic genes and in vitro ginsenoside production in elicited Panax sikkimensis (Ban) cell suspensions

Dual metabolite, i.e., ginsenoside and anthocyanin, co-accumulating cell suspensions of Panax sikkimensis were subjected to elicitation with culture filtrates of Serratia marcescens (SD 21), Bacillus subtilis (FL11), Trichoderma atroviridae (TA), and T. harzianum (TH) at 1.25% and 2.5% v/v for 1- and 3-week duration. The fungal-derived elicitors (TA and TH) did not significantly affect biomass accumulation; however, bacterial elicitors (SD 21 and FL11), especially SD 21, led to comparable loss in biomass growth. In terms of ginsenoside content, differential responses were observed. A maximum of 3.2-fold increase (222.2 mg/L) in total ginsenoside content was observed with the use of 2.5% v/v TH culture filtrate for 1 week. Similar ginsenoside accumulation was observed with the use of 1-week treatment with 2.5% v/v SD 21 culture filtrate (189.3 mg/L) with a 10-fold increase in intracellular Rg2 biosynthesis (31 mg/L). Real-time PCR analysis of key ginsenoside biosynthesis genes, i.e., FPS, SQS, DDS, PPDS, and PPTS, revealed prominent upregulation of particularly PPTS expression (20-23-fold), accounting for the observed enhancement in protopanaxatriol ginsenosides. However, none of the elicitors led to successful enhancement in in vitro anthocyanin accumulation as compared to control values.

Biotechnological production of hyperforin for pharmaceutical formulation

Hyperforin is a major active constituent of Hypericum perforatum (St. John's wort). It has amazing pharmacological activities, such as antidepressant properties, but it is labile and difficult to synthesize. Its sensitivity and lipophilicity are challenges for processing and formulation. Its chemical complexity provokes approaches of biotechnological production and modification. Dedifferentiated H. perforatum cell cultures lack appropriate storage sites and hence appreciable hyperforin levels. Shoot cultures are capable of forming hyperforin but less suitable for biomass up-scaling in bioreactors. Roots commonly lack hyperforin but a recently established adventitious root line has been demonstrated to produce hyperforin and derivatives at promising levels. The roots also contained lupulones, the typical constituents of hop (Humulus lupulus). Although shear-sensitive, these root cultures provide a potential production platform for both individual compounds and extracts with novel combinations of constituents and pharmacological activities. Besides in vitro cultivation techniques, the reconstruction of hyperforin biosynthesis in microorganisms is a promising alternative for biotechnological production. The biosynthetic pathway is under study, with omics-technologies being increasingly implemented. These biotechnological approaches may not only yield hyperforin at reasonable productivity but also allow for modifications of its chemical structure and pharmacological profile.

Enhanced production of flavonoids by methyl jasmonate elicitation in cell suspension culture of Hypericum perforatum

Background

Flavonoids of Hypericum perforatum are important secondary metabolites which have been widely utilized in medicine for a range of purposes. The use of methyl jasmonate (MeJA) elicitation for the enhancement of flavonoid production in cell suspension culture of H. perforatum would be an efficient alternative method for the flavonoid production.

Results

MeJA influenced the cells growth and flavonoid production. The optimal elicitation strategy was treatment of the cell cultures with 100 μmol/L MeJA on day 15, which resulted in the highest flavonoid production (280 mg/L) and 2.7 times of control cultures. The activities of catalase (CAT) were inhibited after MeJA treatment in the cell cultures, while the activities of phenylalanine ammonia lyase (PAL) increased, which led to the enhancement of flavonoid production.

Conclusion

MeJA elicitation is a useful method for the enhancement of flavonoid production in cell suspension culture of H. perforatum.

Exudation: an expanding technique for continuous production and release of secondary metabolites from plant cell suspension and hairy root cultures

This review addresses methods of obtaining secondary metabolites from plant cell suspension and hairy root cultures and their exudates, particularly the physiological mechanisms of secondary metabolites release and trafficking. The efficiency for product recovery of metabolites can be increased by various methods, based on the principle of continuous product release into the cultivation medium. The most common methods for metabolite recovery are elicitation, influencing membrane permeability, and in situ product removal. The biosynthetic pathways can be influenced by cultivation conditions, transformation, or application of elicitors. The membrane permeability can be altered through the application of chemical or physical treatments. Product removal can be greatly increased through a two-phase system and the introduction of absorbents into the cultivation medium. In this review, we describe some improved approaches that have proven useful in these efforts.