SIMULTANEOUS SEPARATION AND QUANTIFICATION OF TARGETED GROUP OF COMPOUNDS IN PSORALEA CORYLIFOLIA L. USING HPLC-PDA-MS-MS

Genus Psoralea: A review of the traditional and modern uses, phytochemistry and pharmacology

ETHNOPHARMACOLOGICAL RELEVANCE

The genus Psoralea (Fabaceae) harbours 105 accepted species that are extensively used by local peoples and medicinal practitioners of China, India, and other countries for treatment of tooth decay, psoriasis, leucoderma, leprosy, kidney problems, tuberculosis, indigestion, constipation and impotence. Presently, pharmacological research reports are available on only few species namely Bituminaria bituminosa (Syn: P. bituminosa), P. canescens, P. corylifolia, P. esculenta, P. plicata and P. glandulosa which are valued for their chemical constituents and traditional uses.

AIM OF THE REVIEW

This review article provides explicit information on traditional uses, phytochemistry, and pharmacological activities of selected Psoralea species. The possible trends and perspectives for future research on these plants are also discussed.

MATERIALS AND METHODS

An extensive and systematic review of the extant literature was carried out, and the data under various sections were identified using a computerized bibliographic search via the PubMed, Web of Science and Google Scholar, CAB Abstracts, MEDLINE, EMBASE, INMEDPLAN, NATTS as well as several websites.

KEY FINDINGS

A total of 291 bioactive compounds from 06 species of genus Psoralea have been isolated and characterized. However, P. bituminosa alone possess nearly 150 compounds. These bioactive compounds belong to different chemical classes, including flavonoids, coumarins, furanocoumarins, chalcones, quinines, terpenoids and some others due to which these species exhibit significant anti-oxidant, anti-bacterial, anti-fungal, anti-viral, anti-helmintic, anti-diabetic, diuretic, hepatoprotective, anti-cancer and anti-tumor activities. P. corylifolia L. (Babchi), a Chinese traditional medicinal plant has been used in traditional medicine for many decades for its healing properties against numerous skin diseases such as leprosy, psoriasis and leucoderma.

CONCLUSIONS

The in vitro studies and in vivo models have provided a simple bio-scientific justification for various ethnopharmacological uses of Psoralea species. From the toxicological perspective, the root, leaf, and seed extracts and their preparations have been proven to be safe when consumed in the recommended doses. But, meticulous studies on the pharmaceutical standardization, mode of action of the active constituents, and sustainable conservation of Psoralea species are needed, to meet the growing demands of the pharmaceutical industries, and to fully exploit their preventive and therapeutic potentials.

General survey of Fructus Psoraleae from the different origins and chemical identification of the roasted from raw Fructus Psoraleae

Fructus Psoraleae, a traditional Chinese medicine, is widely used for preventing and treating various diseases such as vitiligo, osteoporosis and psoriasis. Coumarin, such as psoralenoside, isopsoralenoside, psoralen and isopsoralen, are important compounds in Fructus Psoraleae. In our study, ultra performance liquid chromatography coupled with diode array detector was employed for an excellent method validation for simultaneous quantification of psoralenoside, isopsoralenoside, psoralen and isopsoralen, which was further applied in performing general survey of Fructus Psoraleae from the different origins and chemical identification of the roasted from raw Fructus Psoraleae in the light of illuminating the transformed rule of psoralenoside and isopsoralenoside. There is a reciprocal relationship between (iso)psoralenoside and (iso)psoralen, and the total content remains balance in Fructus Psoraleae from the different origins. In addition, we found that (iso)psoralenoside in the powder of the raw Fructus Psoraleae could be easily transformed into (iso)psoralen in methanol aqueous solution, especially above 50% water, rather than the roasted one. Thus, we proposed a hypothesis that transformation between (iso)psoralenoside and (iso)psoralen was hindered by inactivation of β-glucosidase in the process of roasting Fructus Psoraleae, which was further verified by observing transformation of (iso)psoralenoside under the different conditions, such as temperature, pH and β-glucosidase. Therefore, we developed a feasible method to distinguish the roasted from raw Fructus Psoraleae by observing conversion from (iso)psoralenoside to (iso)psoralen in 50% methanol aqueous solution. In summary, these results pave the way for elevating quality standard for Fructus Psoraleae and distinguishing the salt-processed from raw Fructus Psoraleae.

Genome-wide Expression Analysis and Metabolite Profiling Elucidate Transcriptional Regulation of Flavonoid Biosynthesis and Modulation under Abiotic Stresses in Banana

Flavonoid biosynthesis is largely regulated at the transcriptional level due to the modulated expression of genes related to the phenylpropanoid pathway in plants. Although accumulation of different flavonoids has been reported in banana, a staple fruit crop, no detailed information is available on regulation of the biosynthesis in this important plant. We carried out genome-wide analysis of banana (Musa acuminata, AAA genome) and identified 28 genes belonging to 9 gene families associated with flavonoid biosynthesis. Expression analysis suggested spatial and temporal regulation of the identified genes in different tissues of banana. Analysis revealed enhanced expression of genes related to flavonol and proanthocyanidin (PA) biosynthesis in peel and pulp at the early developmental stages of fruit. Genes involved in anthocyanin biosynthesis were highly expressed during banana fruit ripening. In general, higher accumulation of metabolites was observed in the peel as compared to pulp tissue. A correlation between expression of genes and metabolite content was observed at the early stage of fruit development. Furthermore, this study also suggests regulation of flavonoid biosynthesis, at transcriptional level, under light and dark exposures as well as methyl jasmonate (MJ) treatment in banana.

Constitutive expression of Arabidopsis MYB transcription factor, AtMYB11, in tobacco modulates flavonoid biosynthesis in favor of flavonol accumulation

KEY MESSAGE

Heterologous expression of AtMYB11 , a flavonol-specific transcription factor from Arabidopsis , in tobacco modulates flavonoid biosynthesis, however, with a lower efficiency as compared to its paralogs AtMYB12 and AtMYB111. Transcriptional regulation is the most important means for controlling flavonoid biosynthesis under temporal and spatial cues. In Arabidopsis, three functionally redundant MYB transcription factors (AtMYB11, AtMYB111 and AtMYB12) have been characterized as flavonol-specific regulators which positively modulate expression of biosynthetic genes involved in flavonol biosynthesis. Based on expression of AtMYB111 and AtMYB12 in heterologous systems, studies suggest that these transcription factors can be used to develop plants with enhanced flavonol biosynthesis. The potential of AtMYB11 to activate flavonol biosynthesis in a heterologous system has not yet been studied. In this study, the regulatory potential of AtMYB11 has been studied in Nicotiana tabacum by developing transgenic plants constitutively expressing AtMYB11. Our analysis using leaf and petal tissues of the transgenic plants indicates that AtMYB11 enhances flavonol and chlorogenic acid (CGA) biosynthesis in tobacco through up-regulation of the biosynthetic genes. Activation of flavonol biosynthesis in tobacco by AtMYB11 is not as pronounced as with AtMYB12 or AtMYB111. Taken together, these results reveal a differential regulatory mechanism in plants for modulating flavonol biosynthesis. This study demonstrated that AtMYB11 can be strategically used for enhancing the health beneficial flavonols in species other than Arabidopsis.

AtMYB12 expression in tomato leads to large scale differential modulation in transcriptome and flavonoid content in leaf and fruit tissues

Plants synthesize secondary metabolites, including flavonoids, which play important role during various stresses for their survival. These metabolites are also considered as health-protective components in functional foods. Flavonols, one of the important groups of flavonoids, apart from performing several roles in plants have been recognized as potent phytoceuticals for human health. Tomato fruits are deficient in this group of flavonoids and have been an important target for enhancing the accumulation of flavonols through genetic manipulations. In the present study, AtMYB12 transcription factor of the Arabidopsis has been expressed under constitutive promoter in tomato. Transgenic tomato lines exhibited enhanced accumulation of flavonols and chlorogenic acid (CGA) in leaf and fruit accompanied with elevated expression of phenylpropanoid pathway genes involved in flavonol biosynthesis. In addition, global gene expression analysis in leaf and fruit suggested that AtMYB12 modulates number of molecular processes including aromatic amino acid biosynthesis, phytohormone signaling and stress responses. Besides this, a differential modulation of the genes in fruits and leaves is reported in this study. Taken together, results demonstrate that modulation of primary carbon metabolism and other pathways by AtMYB12 in tomato may lead to sufficient substrate supply for enhanced content of phenolics in general and flavonols in particular.

Expression of Arabidopsis MYB transcription factor, AtMYB111, in tobacco requires light to modulate flavonol content

Flavonoids, due to their pharmacological attributes, have recently become target molecules for metabolic engineering in commonly consumed food crops. Strategies including expression of single genes and gene pyramiding have provided only limited success, due principally to the highly branched and complex biosynthetic pathway of the flavonoids. Transcription factors have been demonstrated as an efficient tool for metabolic engineering of this pathway, but often exhibit variation in heterologous systems relative to that in the homologous system. In the present work, Arabidopsis MYB transcription factor, AtMYB111, has been expressed in tobacco to study whether this can enhance flavonoid biosynthesis in heterologous system. The results suggest that AtMYB111 expression in transgenic tobacco enhances expression of genes of the phenylpropanoid pathway leading to an elevated content of flavonols. However, dark incubation of transgenic and wild type (WT) plants down-regulated both the expression of genes as well as flavonoid content as compared to light grown plants. The study concludes that AtMYB111 can be effectively used in heterologous systems, however, light is required for its action in modulating biosynthetic pathway.

Evaluation of total phenolic compounds and insecticidal and antioxidant activities of tomato hairy root extract

Tomatoes are one of the most consumed crops in the whole world because of their versatile importance in dietary food as well as many industrial applications. They are also a rich source of secondary metabolites, such as phenolics and flavonoids. In the present study, we described a method to produce these compounds from hairy roots of tomato (THRs). Agrobacterium rhizogenes strain A4 was used to induce hairy roots in the tomato explants. The Ri T-DNA was confirmed by polymerase chain reaction amplification of the rolC gene. Biomass accumulation of hairy root lines was 1.7-3.7-fold higher compared to in vitro grown roots. Moreover, THRs efficiently produced several phenolic compounds, such as rutin, quercetin, kaempferol, gallic acid, protocatechuic acid, ferulic acid, colorogenic acid, and caffeic acid. Gallic acid [34.02 μg/g of dry weight (DW)] and rutin (20.26 μg/g of DW) were the major phenolic acid and flavonoid produced by THRs, respectively. The activities of reactive oxygen species enzymes (catalase, ascorbate peroxidase, and superoxide dismutase) were quantified. The activity of catalase in THRs was 0.97 ± 0.03 mM H2O2 min(-1) g(-1), which was 1.22-fold (0.79 ± 0.09 mM H2O2 min(-1) g(-1)) and 1.59-fold (0.61 ± 0.06 mM H2O2 min(-1) g(-1)) higher than field grown and in vitro grown roots, respectively. At 100 μL/g concentration, the phenolic compound extract caused 53.34 and 40.00% mortality against Helicoverpa armigera and Spodoptera litura, respectively, after 6 days. Surviving larvae of H. armigera and S. litura on the phenolic compound extract after 6 days showed 85.43 and 86.90% growth retardation, respectively.

Co-expression of Arabidopsis transcription factor, AtMYB12, and soybean isoflavone synthase, GmIFS1, genes in tobacco leads to enhanced biosynthesis of isoflavones and flavonols resulting in osteoprotective activity

Isoflavones, a group of flavonoids, restricted almost exclusively to family Leguminosae are known to exhibit anticancerous and anti-osteoporotic activities in animal systems and have been a target for metabolic engineering in commonly consumed food crops. Earlier efforts based on the expression of legume isoflavone synthase (IFS) genes in nonlegume plant species led to the limited success in terms of isoflavone content in transgenic tissue due to the limitation of substrate for IFS enzyme. In this work to overcome this limitation, the activation of multiple genes of flavonoid pathway using Arabidopsis transcription factor AtMYB12 has been carried out. We developed transgenic tobacco lines constitutively co-expressing AtMYB12 and GmIFS1 (soybean IFS) genes or independently and carried out their phytochemical and molecular analyses. The leaves of co-expressing transgenic lines were found to have elevated flavonol content along with the accumulation of substantial amount of genistein glycoconjugates being at the highest levels that could be engineered in tobacco leaves till date. Oestrogen-deficient (ovariectomized, Ovx) mice fed with leaf extract from transgenic plant co-expressing AtMYB12 and GmIFS1 but not wild-type extract exhibited significant conservation of trabecular microarchitecture, reduced osteoclast number and expression of osteoclastogenic genes, higher total serum antioxidant levels and increased uterine oestrogenicity compared with Ovx mice treated with vehicle (control). The skeletal effect of the transgenic extract was comparable to oestrogen-treated Ovx mice. Together, our results establish an efficient strategy for successful pathway engineering of isoflavones and other flavonoids in crop plants and provide a direct evidence of improved osteoprotective effect of transgenic plant extract.

Development of AtMYB12-expressing transgenic tobacco callus culture for production of rutin with biopesticidal potential

Flavonoids synthesized by the phenylpropanoid pathway participate in a number of physiological and biochemical processes in plants. Flavonols, among flavonoids, are considered as health-protective components in functional foods and they protect plants against certain insect pests. There have been efforts to develop strategies for the enhanced production of flavonols in plants, but limited success was achieved due to complex regulation and poor substrate availability. In the present study, we have developed and optimized method for callus cultures for transgenic tobacco line expressing a flavonol-specific transcription factor, AtMYB12, with an objective to use callus as an alternative source of rutin. Transgenic callus displayed enhanced expression of genes related to biosynthetic pathway leading to increased accumulation of flavonols, especially rutin. At each time point of callus growth, the rutin content of transgenic callus was several folds higher than that of wild-type tobacco callus. Supplementation of semi-synthetic diet with extract from transgenic callus as well as purified rutin led to mortality and growth reduction in the Spodoptera litura and Helicoverpa armigera larvae. This study suggests the biotechnological potential of AtMYB12-expressing callus cultures for the production of rutin, which can be used for biopesticide formulations against insect pests.

KEY MESSAGE

Tobacco callus cultures expressing AtMYB12 accumulate enhanced content of rutin and can be used as a potential alternative source of rutin as well as biopesticides against insect pests.