Effects and mechanism of extracts rich in phenylpropanoids-polyacetylenes and polysaccharides from Codonopsis Radix on improving scopolamine-induced memory impairment of mice

ETHNOPHARMACOLOGICAL RELEVANCE

Alzheimer's disease (AD) is a progressive developmental neurodegenerative disease that primarily develops in old age. Memory impairment is an important manifestation of AD. It has been demonstrated that inflammation and oxidative stress are important mediators in the development and progression of AD. Codonopsis Radix (CR) has a long history of consumption, exhibiting lots of beneficial health effects, including anti-ageing, antioxidant, and anti-inflammatory properties. However, studies on the effects of CR on scopolamine-induced amnesia have rarely been reported.

AIM OF THE STUDY

The aim of this study was to investigate the ameliorative effect of macromolecular portion (polysaccharides, POL) and small molecule portion (fine extract rich in phenylpropanoids-polyacetylenes, EPP) from CR on improving scopolamine-induced memory impairment and to elucidate the potential mechanism of action.

MATERIALS AND METHODS

C57BL/6 mice were pretreated with EPP (0.2, 0.4, and 0.6 g/kg), POL (0.3, 0.6, and 0.9 g/kg), and donepezil (5 mg/kg) by gavage for 7 days, followed by intraperitoneal injection of scopolamine (1 mg/kg) to induce memory impairment. The 16S rRNA gene sequencing, histopathological, western blotting, and biochemical analysis (various biochemical markers and protein expressions related to cholinergic system, oxidative stress, and neuroinflammation) were performed to further elucidate the mechanism of action. Moreover, the acetylcholinesterase (AChE) inhibitory activities of POL, EPP, and its main compounds tangshenoside I, lobetyol, lobetyolin, and lobetyolinin were evaluated.

RESULTS

Experiments have confirmed that both POL and EPP from CR could improve scopolamine-induced spatial learning memory deficits. Both of them could regulate cholinergic function by inhibiting AChE and activating choline acetyltransferase (ChAT) activities. They also could enhance antioxidant defense via increasing the activities of superoxide dismutase and glutathione peroxidase, and anti-inflammatory function through suppressing inflammatory factors (nitric oxide, TNF-α, and IL-6) and regulating gut flora. Besides, in vitro experiments demonstrated that four monomeric compounds and EPP, except POL, exhibited inhibition of AChE activity.

CONCLUSION

EPP and POL from CR exert a beneficial effect on learning and memory processes in mice with scopolamine-induced memory impairment. CR may be a promising medicine for preventing and improving learning memory.

Integrative analysis of transcriptome and metabolome reveals the sesquiterpenoids and polyacetylenes biosynthesis regulation in Atractylodes lancea (Thunb.) DC

Atractylodes lancea (Thunb.) is a perennial medicinal herb, with its dry rhizomes are rich in various sesquiterpenoids and polyacetylenes components (including atractylodin, atractylon and β-eudesmol). However, the contents of these compounds are various and germplasms specific, and the mechanisms of biosynthesis in A. lancea are still unknown. In this study, we identified the differentially expressed candidate genes and metabolites involved in the biosynthesis of sesquiterpenoids and polyacetylenes, and speculated the anabolic pathways of these pharmaceutical components by transcriptome and metabolomic analysis. In the sesquiterpenoids biosynthesis, a total of 28 differentially expressed genes (DEGs) and 6 differentially expressed metabolites (DEMs) were identified. The beta-Selinene is likely to play a role in the synthesis of atractylon and β-eudesmol. Additionally, the polyacetylenes biosynthesis showed the presence of 3 DEGs and 4 DEMs. Notably, some fatty acid desaturase (FAB2 and FAD2) significantly down-regulated in polyacetylenes biosynthesis. The gamma-Linolenic acid is likely involved in the biosynthesis of polyacetylenes and thus further synthesis of atractylodin. Overall, these studies have investigated the biosynthetic pathways of atractylodin, atractylon and β-eudesmol in A. lancea for the first time, and present potential new anchor points for further exploration of sesquiterpenoids and polyacetylenes compound biosynthesis pathways in A. lancea.

The genetic control of polyacetylenes involved in bitterness of carrots (Daucus carota L.): Identification of QTLs and candidate genes from the plant fatty acid metabolism

BACKGROUND

Falcarinol-type polyacetylenes (PAs) such as falcarinol (FaOH) and falcarindiol (FaDOH) are produced by several Apiaceae vegetables such as carrot, parsnip, celeriac and parsley. They are known for numerous biological functions and contribute to the undesirable bitter off-taste of carrots and their products. Despite their interesting biological functions, the genetic basis of their structural diversity and function is widely unknown. A better understanding of the genetics of the PA levels present in carrot roots might support breeding of carrot cultivars with tailored PA levels for food production or nutraceuticals.

RESULTS

A large carrot F₂ progeny derived from a cross of a cultivated inbred line with an inbred line derived from a Daucus carota ssp. commutatus accession rich in PAs was used for linkage mapping and quantitative trait locus (QTL) analysis. Ten QTLs for FaOH and FaDOH levels in roots were identified in the carrot genome. Major QTLs for FaOH and FaDOH with high LOD values of up to 40 were identified on chromosomes 4 and 9. To discover putative candidate genes from the plant fatty acid metabolism, we examined an extended version of the inventory of the carrot FATTY ACID DESATURASE2 (FAD2) gene family. Additionally, we used the carrot genome sequence for a first inventory of ECERIFERUM1 (CER1) genes possibly involved in PA biosynthesis. We identified genomic regions on different carrot chromosomes around the found QTLs that contain several FAD2 and CER1 genes within their 2-LOD confidence intervals. With regard to the major QTLs on chromosome 9 three putative CER1 decarbonylase gene models are proposed as candidate genes.

CONCLUSION

The present study increases the current knowledge on the genetics of PA accumulation in carrot roots. Our finding that carrot candidate genes from the fatty acid metabolism are significantly associated with major QTLs for both major PAs, will facilitate future functional gene studies and a further dissection of the genetic factors controlling PA accumulation. Characterization of such candidate genes will have a positive impact on carrot breeding programs aimed at both lowering or increasing PA concentrations in carrot roots.

Inducing Intermediates in Biotransformation of Natural Polyacetylene and A Novel Spiro-γ-Lactone from Red Ginseng by Solid Co-Culture of Two Gut Chaetomium globosum and The Potential Bioactivity Modification by Oxidative Metabolism

The ω-hydroxyl-panaxytriol (1) and ω-hydroxyl-dihydropanaxytriol (2)-are rare examples of polyacetylene metabolism by microbial transformation, and these new metabolites (1, 2) from fermented red ginseng (FRG) by solid co-culture induction of two Chaetomium globosum should be the intermediates of biotransformation of panaxylactone (metabolite A). The metabolic pathway of panaxylactone was also exhibited. The ingredients of red ginseng (RG) also induced the production of rare 6/5/5 tricyclic ring spiro-γ-lactone skeleton (3). The ω-hydroxylation of new intermediates (1, 2) decreases cytotoxicity and antifungal activity against C. globosum compared with that of its bioprecursor panaxytriol. Additionally, compounds 1 and 2 indicated obvious inhibition against nitric oxide (NO) production, with ratios of 44.80 ± 1.37 and 23.10 ± 1.00% at 50 μM. 1 has an equivalent inhibition of NO production compared with the positive drug. So, the microbial biotransformation that occurred in FRG fermented by gut C. globosum can change the original bioactivity of polyacetylene, which gave a basis about the metabolic modification of red ginseng by intestinal fungus fermentation.

FAD2 Gene Radiation and Positive Selection Contributed to Polyacetylene Metabolism Evolution in Campanulids

Polyacetylenes (PAs) are bioactive, specialized plant defense compounds produced by some species in the eudicot clade campanulids. Early steps of PA biosynthesis are catalyzed by Fatty Acid Desaturase 2 (FAD2). Canonical FAD2s catalyze desaturation, but divergent forms can catalyze hydroxylation, conjugation, acetylenation, and epoxygenation. These alternate reactions give rise to valuable unusual fatty acids, including the precursors to PAs. The extreme functional diversity of FAD2 enzymes and the origin of PA biosynthesis are poorly understood from an evolutionary perspective. We focus here on the evolution of the FAD2 gene family. We uncovered a core eudicot-wide gene duplication event giving rise to two lineages: FAD2-α and FAD2-β. Independent neofunctionalizations in both lineages have resulted in functionally diverse FAD2-LIKEs involved in unusual fatty acid biosynthesis. We found significantly accelerated rates of molecular evolution in FAD2-LIKEs and use this metric to provide a list of uncharacterized candidates for further exploration of FAD2 functional diversity. FAD2-α has expanded extensively in Asterales and Apiales, two main clades of campanulids, by ancient gene duplications. Here, we detected positive selection in both Asterales and Apiales lineages, which may have enabled the evolution of PA metabolism in campanulids. Together, these findings also imply that yet uncharacterized FAD2-α copies are involved in later steps of PA biosynthesis. This work establishes a robust phylogenetic framework in which to interpret functional data and to direct future research into the origin and evolution of PA metabolism.

Identification of Genes Encoding Enzymes Catalyzing the Early Steps of Carrot Polyacetylene Biosynthesis

Polyacetylenic lipids accumulate in various Apiaceae species after pathogen attack, suggesting that these compounds are naturally occurring pesticides and potentially valuable resources for crop improvement. These compounds also promote human health and slow tumor growth. Even though polyacetylenic lipids were discovered decades ago, the biosynthetic pathway underlying their production is largely unknown. To begin filling this gap and ultimately enable polyacetylene engineering, we studied polyacetylenes and their biosynthesis in the major Apiaceae crop carrot (Daucus carota subsp. sativus). Using gas chromatography and mass spectrometry, we identified three known polyacetylenes and assigned provisional structures to two novel polyacetylenes. We also quantified these compounds in carrot leaf, petiole, root xylem, root phloem, and root periderm extracts. Falcarindiol and falcarinol predominated and accumulated primarily in the root periderm. Since the multiple double and triple carbon-carbon bonds that distinguish polyacetylenes from ubiquitous fatty acids are often introduced by Δ12 oleic acid desaturase (FAD2)-type enzymes, we mined the carrot genome for FAD2 genes. We identified a FAD2 family with an unprecedented 24 members and analyzed public, tissue-specific carrot RNA-Seq data to identify coexpressed members with root periderm-enhanced expression. Six candidate genes were heterologously expressed individually and in combination in yeast and Arabidopsis (Arabidopsis thaliana), resulting in the identification of one canonical FAD2 that converts oleic to linoleic acid, three divergent FAD2-like acetylenases that convert linoleic into crepenynic acid, and two bifunctional FAD2s with Δ12 and Δ14 desaturase activity that convert crepenynic into the further desaturated dehydrocrepenynic acid, a polyacetylene pathway intermediate. These genes can now be used as a basis for discovering other steps of falcarin-type polyacetylene biosynthesis, to modulate polyacetylene levels in plants, and to test the in planta function of these molecules.