Ning Yan

Solanesol: a review of its resources, derivatives, bioactivities, medicinal applications, and biosynthesis

Solanesol, which mainly accumulates in solanaceous crops, including tobacco, tomato, potato, eggplant, and pepper plants, is a long-chain polyisoprenoid alcohol compound with nine isoprene units. Chemical synthesis of solanesol is difficult; therefore, solanesol is primarily extracted from solanaceous crops, particularly tobacco leaves. In plants, solanesol exists in both free and esterified forms, and its accumulation is influenced by genetic and environmental factors. Solanesol is widely used in the pharmaceutical industry as an intermediate for the synthesis of ubiquinone drugs, such as coenzyme Q10 and vitamin K2. Solanesol possesses antibacterial, antifungal, antiviral, anticancer, anti-inflammatory, and anti-ulcer activities, and solanesol derivatives also have anti-oxidant and antitumour activities, in addition to other bioactivities. Solanesol derivatives can also be used for the treatment of cardiovascular disease, osteoporosis, acquired immune deficiency syndrome, and wound healing. Solanesol biosynthesis occurs in plastids of higher plants via the 2-C-methyl-d-erythritol-4-phosphate (MEP) pathway. The key enzymes in solanesol biosynthesis, including 1-deoxy-d-xylulose-5-phosphate synthase, 1-deoxy-d-xylulose-5-phosphate-reductoisomerase, isopentenyl pyrophosphate isomerase, and solanesyl diphosphate synthase, are also important regulators of the MEP pathway, and their overexpression is favourable for downstream metabolic flow, further promoting the synthesis of downstream metabolites, such as solanesol. Future studies should determine the pharmacokinetic properties of solanesol and its derivatives and investigate the metabolic pathways and regulatory mechanisms mediating solanesol biosynthesis, metabolic and genetic engineering of solanesol, the synthetic biology of solanesol, and the physiological role of solanesol. In the present review, we systematically summarise current knowledge on solanesol resources, derivatives, bioactivities and medicinal applications, metabolic pathways, and key biosynthetic enzymes.

Morphological Characteristics, Nutrients, and Bioactive Compounds of Zizania latifolia, and Health Benefits of Its Seeds

Zizania latifolia (tribe Oryzeae Dum., subfamily Oryzoideae Care, family Gramineae) is native to East Asian countries. The seeds of Z. latifolia (Chinese wild rice) have been consumed as a cereal in China for >3000 years. Z. latifolia forms swollen culms when infected with Ustilago esculenta, which is the second most-cultivated aquatic vegetable in China. The current review summarizes the nutrients and bioactive compounds of Z. latifolia, and health benefits of its seeds. The seeds of Z. latifolia contain proteins, minerals, vitamins, and bioactive compounds, the activities of which—for example, antioxidant activity—have been characterized. Various health benefits are associated with their consumption, such as alleviation of insulin resistance and lipotoxicity, and protection against cardiovascular disease. Chinese wild rice may be used to prevent and treat metabolic disease, such as diabetes, obesity, and cardiovascular diseases. Various compounds were isolated from the swollen culm, and aerial parts of Z. latifolia. The former suppresses osteoclast formation, inhibits growth of rat glioma cells, and may act as antioxidants and immunomodulators in drugs or foods. The latter exerts anti-fatigue, anti-inflammatory, and anti-allergic effects. Thus, Z. latifolia may be used to produce nutraceuticals and functional foods.

Chemical Basis of the Fungicidal Activity of Tobacco Extracts against Valsa mali

Under pressure from social criticism and an unclear future, tobacco researchers have begun to seek alternative uses for the product. Here, we present our study on isolating tobacco compounds with fungicidal activity, which could be used as plant-derived pesticides. Using Valsa mali as the target fungus, agar plate tests were conducted to evaluate the fungicidal activity of various tobacco extracts, including tobacco leaves extracts prepared with different solvents, extracts of different tobacco cultivars, and samples from different tobacco organs. Fungal growth morphology was used as the criterion to evaluate the fungicidal activity of tobacco extracts. Correlation analyses between the fungicidal activities and the chemical components of tobacco extracts indicated the major chemical constituents with fungicidal activity. Then, the active compounds were isolated and their effects on the ultra-microstructures of V. mali was analyzed using scanning- and transmission-electron microscopy. The results suggested that tobacco extracts prepared with solvents of weaker polarity had higher fungicidal activity, and the inhibitory activity of tobacco extracts against V. mali was also cultivar dependent. Furthermore, the fungicidal effects of tobacco flower extracts were higher than those of the leaf extracts. Chemical analysis indicated that cembranoids were the main fungicidal substances, which act by destroying the endometrial structure of the fungus. Tobacco cembranoids at 80 μg/mL could completely inhibit the growth of V. mali, with an EC50 value of 13.18 μg/mL. Our study therefore suggests that tobacco leaves and inflorescences are excellent plant resources for the biological control of V. mali.

Solanesol Biosynthesis in Plants

Solanesol is a non-cyclic terpene alcohol composed of nine isoprene units that mainly accumulates in solanaceous plants. Solanesol plays an important role in the interactions between plants and environmental factors such as pathogen infections and moderate-to-high temperatures. Additionally, it is a key intermediate for the pharmaceutical synthesis of ubiquinone-based drugs such as coenzyme Q10 and vitamin K2, and anti-cancer agent synergizers such as N-solanesyl-N,N′-bis(3,4-dimethoxybenzyl) ethylenediamine (SDB). In plants, solanesol is formed by the 2-C-methyl-d-erythritol 4-phosphate (MEP) pathway within plastids. Solanesol’s biosynthetic pathway involves the generation of C5 precursors, followed by the generation of direct precursors, and then the biosynthesis and modification of terpenoids; the first two stages of this pathway are well understood. Based on the current understanding of solanesol biosynthesis, we here review the key enzymes involved, including 1-deoxy-d-xylulose 5-phosphate synthase (DXS), 1-deoxy-d-xylulose 5-phosphate reductoisomerase (DXR), isopentenyl diphosphate isomerase (IPI), geranyl geranyl diphosphate synthase (GGPPS), and solanesyl diphosphate synthase (SPS), as well as their biological functions. Notably, studies on microbial heterologous expression and overexpression of key enzymatic genes in tobacco solanesol biosynthesis are of significant importance for medical uses of tobacco.

Genome-Wide Analysis of Long Non-Coding RNAs in Potato and Their Potential Role in Tuber Sprouting Process

Sprouting is a key factor affecting the quality of potato tubers. The present study aimed to compare the differential expression of long non-coding RNAs (lncRNAs) in the apical meristem during the dormancy release and sprouting stages by using lncRNA sequencing. Microscopic observations and Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analyses revealed the changes in the morphology and expression of lncRNAs in potato tubers during sprouting. Meristematic cells of potato tuber apical buds divided continuously and exhibited vegetative cone bulging and vascularisation. In all, 3175 lncRNAs were identified from the apical buds of potato tubers, among which 383 lncRNAs were up-regulated and 340 were down-regulated during sprouting. The GO enrichment analysis revealed that sprouting mainly influenced the expression of lncRNAs related to the cellular components of potato apical buds (e.g., cytoplasm and organelles) and cellular metabolic processes. The KEGG enrichment analysis also showed significant enrichment of specific metabolic pathways. In addition, 386 differentially expressed lncRNAs during sprouting were identified as putative targets of 235 potato miRNAs. Quantitative real-time polymerase chain reaction results agreed with the sequencing data. Our study provides the first systematic study of numerous lncRNAs involved in the potato tuber sprouting process and lays the foundation for further studies to elucidate their precise functions.

Organ- and Growing Stage-Specific Expression of Solanesol Biosynthesis Genes in Nicotiana tabacum Reveals Their Association with Solanesol Content

Solanesol is a noncyclic terpene alcohol that is composed of nine isoprene units and mainly accumulates in solanaceous plants, especially tobacco (Nicotiana tabacum L.). In the present study, RNA-seq analyses of tobacco leaves, stems, and roots were used to identify putative solanesol biosynthesis genes. Six 1-deoxy-d-xylulose 5-phosphate synthase (DXS), two 1-deoxy-d-xylulose 5-phosphate reductoisomerase (DXR), two 2-C-methyl-d-erythritol 4-phosphate cytidylyltransferase (IspD), four 4-diphosphocytidyl-2-C-methyl-d-erythritol kinase (IspE), two 2-C-methyl-d-erythritol 2,4-cyclo-diphosphate synthase (IspF), four 1-hydroxy-2-methyl-2-(E)-butenyl 4-diphosphate synthase (IspG), two 1-hydroxy-2-methyl-2-(E)-butenyl 4-diphosphate reductase (IspH), six isopentenyl diphosphate isomerase (IPI), and two solanesyl diphosphate synthase (SPS) candidate genes were identified in the solanesol biosynthetic pathway. Furthermore, the two N. tabacum SPS proteins (NtSPS1 and NtSPS2), which possessed two conserved aspartate-rich DDxxD domains, were highly homologous with SPS enzymes from other solanaceous plant species. In addition, the solanesol contents of three organs and of leaves from four growing stages of tobacco plants corresponded with the distribution of chlorophyll. Our findings provide a comprehensive evaluation of the correlation between the expression of different biosynthesis genes and the accumulation of solanesol, thus providing valuable insight into the regulation of solanesol biosynthesis in tobacco.

Partial Purification, Identification, and Quantitation of Antioxidants from Wild Rice (Zizania latifolia)

To provide further insights into the potential health-promoting antioxidants from wild rice (Zizania latifolia), which is an abundant but underutilized whole grain resource in East Asia, a partial purification based on D101 macroporous resin was carried out for the purification and enrichment of the antioxidants from the bioactive ethanol extracts of wild rice. On that basis, 34 phenolic compounds in the antioxidant fractions were identified by a high-performance liquid chromatography-linear ion trap quadrupole-Orbitrap-mass spectrometry (HPLC-LTQ-Orbitrap-MSn). The results suggested that phenolic acids could be enriched in the 10% ethanol-eluted fraction whereas flavonoids (including procyanidins and flavonoid glycosides) could be enriched in 20–30% ethanol-eluted fractions. A quantitative analysis determined by the multiple reaction monitoring mode of the ultra-performance liquid chromatography-triple quadrupole-tandem mass spectrometry (UPLC-QqQ-MS/MS) revealed a high content of procyanidins in wild rice. Compared with phenolic acids, flavonoids may contribute more to the potent antioxidant activity of wild rice. This is the first study on the antioxidants from wild rice Z. latifolia. These findings provide novel information on the functional components of wild rice, and will be of value to further research and development on Z. latifolia.

Chemical Composition, Antioxidant Activity and α-Glucosidase Inhibitory Activity of Chaenomeles Speciosa from Four Production Areas in China

Chaenomeles speciosa (Sweet) Nakai is a medicinal plant. Until date, there are no studies focusing on comparing the chemical profiles, antioxidant activity and α-glucosidase inhibitory activity of the dried fruits of C. speciosa from different production regions. In the study, we investigated the chemical components of dried fruits of C. speciosa from Yunnan, Chongqing, Zhejiang and Anhui provinces in China in relation to the antioxidant activity and α-glucosidase inhibitory activity. C. speciosa from Yunnan had higher total flavonoid (47.92 ± 3.79 mg/g), total polyphenol (29.15 ± 0.29 mg/g) and polysaccharide (27.60 ± 1.56 mg/g) contents than plants from other production areas. Samples from Yunnan, Zhejiang and Anhui (all > 3200 mg/kg) had higher free amino acid contents than those from Chongqing (2286.66 mg/kg). Oleanolic acid and ursolic acid levels were highest in samples from Zhejiang (555.98 ± 20.88 μg/g) and Anhui (321.06 ± 14.64 μg/g), respectively. C. speciosa from Chongqing had low total flavonoid, total polyphenol, polysaccharide, free amino acid, oleanolic acid and ursolic acid contents but high levels of palmitic acid (12.04 ± 0.02 mg/g) and stearic acid (2.23 ± 0.08 mg/g). Among four production areas, Yunnan represented the highest antioxidant activity and α-glucosidase inhibitory activity. In addition, correlation analysis revealed that total flavonoid, total polyphenol, polysaccharide and ursolic acid were the major components responsible for the antioxidant activity of C. speciosa, while total flavonoid and polysaccharide were the main contributors for α-glucosidase inhibitory activity of the plant. These results would be helpful for evaluating the quality of C. speciosa in the different production areas.

Formation of α- and β-Cembratriene-Diols in Tobacco (Nicotiana tabacum L.) Is Regulated by Jasmonate-Signaling Components via Manipulating Multiple Cembranoid Synthetic Genes

Cembranoids are a group of natural diterpenoid compounds with pharmaceutical potentials, and the cembratriene-diols produced by Nicotiana (tobacco) species display activities in anti-nicotine addiction and neuron protection. Although the enzymes catalyzing cembratriene-diols’ formation in tobacco have been investigated, the regulatory mechanism underlying this physiological process remains unknown. This study has investigated the roles of phytohormone jasmonic acid (JA) in regulating cembratriene-diol formation in N. tabacum cv. TN90 and found that JA and COI1, the receptor protein of the bioactive derivative of JA (i.e., JA-Ile), display critical roles in regulating cembratriene-diols’ formation and the expression of cembranoid synthetic genes CBTS, P450 and NtLTP1. Further studies showed that over-expressing either the gene encoding bHLH transcription factor MYC2a or that encoding MYB transcription factor MYB305 could upregulate the cembranoid synthetic genes and enhance the cembranoid production in plants with dysfunction of COI1. Further studies suggest that COI1 and its downstream regulators MYC2a and MYB305 also modulate the trichome secretion, which is correlated with cembranoid formation. Taken together, this study has demonstrated a critical role of JA-signaling components in governing the cembratriene-diol formation and the transcription of cembratriene-diol synthetic genes in tobacco. Findings in this study are of great importance to reveal the molecular regulatory mechanism underlying cembranoid synthesis.