Morus alba L. Leaves - Integration of Their Transcriptome and Metabolomics Dataset: Investigating Potential Genes Involved in Flavonoid Biosynthesis at Different Harvest Times

Structures, activities, and putative biosynthetic pathways of characteristic polyphenolic compounds from Morus plants: A review

Morus plants played a pivotal role in ancient Chinese sericulture and silk production, which served as critical components of economy and culture. Besides, many parts of mulberry trees, including roots, leaves, stems, and fruits, hold various medicinal value, and have been utilized in traditional medicine for thousands of years. The chemical composition of mulberry has been reported in many literatures, while the characteristic compounds have not been systematically summarized. In this review, we focused on the polyphenolic compounds in mulberry, including flavonoids, 2-arylbenzofurans, and Diels-Alder (D-A) adducts, and summarized their structural features, structure-activity relationships, and potential biosynthetic pathways. The results revealed a characteristic class of 2'-hydroxylated flavonoids and stilbenes which played an important role in the biosynthesis of downstream 2-arylbenzofurans and D-A adducts in mulberry but had been overlooked by most studies. The prenylated modifications of different compounds were also discussed and their function as precursors of D-A adducts was emphasized. We also describe the effects of different modifications on biological activities. Besides, the chemical composition of Morus was most similar to that of Artocarpus in the Moraceae family in that they had almost identical characteristic compounds. Finally, a putative total biosynthetic pathway of D-A adducts in mulberry was proposed based on structure derivation and combination of verified reactions. This review contributes to the understanding of the biological activity and biosynthesis of the characteristic components of Morus plants.

Differences in the flavonoid composition of the leaves, fruits, and branches of mulberry are distinguished based on a plant metabolomics approach

Mulberry is a common crop rich in flavonoids, and its leaves (ML), fruits (M), and branches (Ramulus Mori, RM) have medicinal value. In the present study, a total of 118 flavonoid metabolites (47 flavone, 23 flavonol, 16 flavonoid, 8 anthocyanins, 8 isoflavone, 14 flavanone, and 2 proanthocyanidins) and 12 polyphenols were identified by ultra-performance liquid chromatography-electrospray ionization-tandem mass spectrometry. The most abundant in ML were 8-C-hexosyl-hesperetin O-hexoside and astragalin, the most abundant in M were 8-C-hexosyl-hesperetin O-hexoside and naringenin, and the most abundant in RM were cyanidin 3-O-galactoside and gallocatechin-gallocatechin. The total flavonoid compositions of ML and RM were essentially the same, but the contents of flavonoid metabolite in more than half of them were higher than those in M. Compared with ML, the contents of flavone and flavonoid in RM and M were generally down-regulated. Each tissue part had a unique flavonoid, which could be used as a marker to distinguish different tissue parts. In this study, the differences between flavonoid metabolite among RM, ML, and M were studied, which provided a theoretical basis for making full use of mulberry resources.

Transcriptome, Plant Hormone, and Metabolome Analysis Reveals the Mechanism of Purple Pericarp Formation in 'Zihui' Papaya (Carica papaya L.)

The color of the pericarp is a crucial characteristic that influences the marketability of papaya fruit. Prior to ripening, normal papaya exhibits a green pericarp, whereas the cultivar 'Zihui' displays purple ring spots on the fruit tip, which significantly affects the fruit's visual appeal. To understand the mechanism behind the formation of purple pericarp, this study performed a thorough examination of the transcriptome, plant hormone, and metabolome. Based on the UPLC-ESI-MS/MS system, a total of 35 anthocyanins and 11 plant hormones were identified, with 27 anthocyanins and two plant hormones exhibiting higher levels of abundance in the purple pericarp. In the purple pericarp, 14 anthocyanin synthesis genes were up-regulated, including CHS, CHI, F3H, F3'5'H, F3'H, ANS, OMT, and CYP73A. Additionally, through co-expression network analysis, three MYBs were identified as potential key regulators of anthocyanin synthesis by controlling genes encoding anthocyanin biosynthesis. As a result, we have identified numerous key genes involved in anthocyanin synthesis and developed new insights into how the purple pericarp of papaya is formed.

Phytotherapeutic potential of compounds identified from fractionated extracts of Morus alba L., as an inhibitor of interleukin-6 in the treatment of rheumatoid arthritis: computational approach

The presence of HLA-DRB1 alleles that encode critical points associated with environmental interactions is associated with increased risk of rheumatoid arthritis caused by anti-citrullinated protein antibodies. Therefore, interleukin-6 (IL-6), a multifunctional cytokine that controls both local and systemic acute inflammatory responses through its ability to induce a phase response, plays a serious role. Its overexpression leads to pathological challenges such as rheumatoid arthritis and menopausal osteoporosis. However, targeting the IL-6 receptor and its region could be the major step in controlling the overexpression of this cytokine for therapeutic importance. Therefore, our research explored the computational insight needed to investigate the anti-RFA potential of phytochemicals from fractionated extracts of Morus alba L. against receptors, which have been implicated as druggable targets for the treatment of rheumatoid arthritis. In this study, fifty-nine (59) previously isolated and characterized phytochemicals from M. alba L. were identified from the literature and retrieved from the PubChem database. In silico screening was used to assess the mode of action of these phytochemicals from M. alba L. against receptors that may serve as therapeutic targets for rheumatoid arthritis. Molecular docking studies, toxicity prediction, drug visualization and molecular dynamics simulation (MD) of the ligands together with the receptor-identified target were carried out using the Schrodinger Molecular Drug Discovery Suite. The findings indicated that a selected group of ligands displayed significant binding strength to specific amino acid residues, revealing an important link between the building blocks of proteins (amino acids) and ligands at the inhibitor binding site through traditional chemical interactions, such as interactions between hydrophobic and hydrogen bonds. The binding affinities of the receptors were carefully checked via comparison with those of the approved ligands, and the results suggested structural and functional changes in the lead compounds. Therefore, the bioactive component from M. alba L. could be a lead foot interleukin-6 (IL-6) inhibitor and could be a promising lead compound for the treatment of rheumatoid arthritis and related challenges.Communicated by Ramaswamy H. Sarma.

Soil Application of Bacillus subtilis Regulates Flavonoid and Alkaloids Biosynthesis in Mulberry Leaves

Flavonoids and alkaloids are the major active ingredients in mulberry leaves that have outstanding medicinal value. Bacillus subtilis can effectively activate the plants defense response and regulate the plant secondary metabolism. In this study, we explored the effects of soil application of B. subtilis on the content of flavonoids and the most important alkaloids (1-deoxynojirimycin, DNJ) in mulberry leaves. Significant decreases in flavonoid content were observed in tender leaves and mature leaves after treatment with B. subtilis; at the same time, significant increases in DNJ content were observed in tender leaves. Based on widely targeted LC-MS/MS and high-throughput approaches, we screened out 904 differentially synthesized metabolites (DSMs) and 9715 differentially expressed genes (DEGs). KEGG analyses showed that these DSMs and DEGs were both significantly enriched in the biosynthesis of secondary metabolites, flavonoid synthesis and plant hormone signal transduction. Further correlation analysis of DEMs and DEGs showed that 40 key genes were involved in flavonoid biosynthesis, with 6 key genes involved in DNJ biosynthesis. The expression of CHS, CHI, F3H, F3'H, FLS, UGT and AOC significantly responded to B. subtilis soil application. This study broadens our understanding of the molecular mechanisms underlying the accumulation of flavonoids and alkaloids in mulberry leaves.

Exploring Antioxidant and α-Glucosidase Inhibitory Activities in Mulberry Leaves (Morus alba L.) across Growth Stages: A Comprehensive Metabolomic Analysis with Chemometrics

Metabolic product accumulation exhibited variations among mulberry (Morus alba L.) leaves (MLs) at distinct growth stages, and this assessment was conducted using a combination of analytical techniques including high-performance liquid chromatography (HPLC), gas chromatography-mass spectrometry (GC-MS), and liquid chromatography-mass spectrometry (LC-MS). Multivariate analysis was applied to the data, and the findings were correlated with antioxidant activity and α-glucosidase inhibitory effects in vitro. Statistical analyses divided the 27 batches of MLs at different growth stages into three distinct groups. In vitro assays for antioxidant activity and α-glucosidase inhibition revealed that IC50 values were highest at the Y23 stage, which corresponds to the 'Frost Descends' solar term. In summary, the results of this study indicate that MLs at different growth stages throughout the year can be categorized into three primary growth stages using traditional Chinese solar terms as reference points, based on the observed variations in metabolite content.

Multi-omics analysis reveals the molecular basis of flavonoid accumulation in fructus of Gardenia (Gardenia jasminoides Ellis)

BACKGROUND

The fruits of Gardenia are rich in flavonoids and geniposides, which have various pharmacological effects such as antioxidant, anti-inflammatory and anticancer. In this study, we analyzed the transcriptome and metabolome of gardenia peel and kernel at different growth stages, revealed the regulatory network related to flavonoid synthesis, and identified the key regulatory genes.

RESULTS

The results showed that in terms of flavonoid metabolic pathways, gardenia fruits mainly synthesized cinnamic acid through the phenylpropanoid pathway, and then synthesized flavonoids through the action of catalytic enzymes such as 4-coumaroyl-CoA ligase, chalcone synthase, chalcone isomerase and flavanol synthase, respectively. In addition, we found that the metabolomics data showed a certain spatial and temporal pattern in the expression of genes related to the flavonoid metabolism pathway and the relative content of metabolites, which was related to the development and ripening process of the fruit.

CONCLUSIONS

In summary, this study successfully screened out the key genes related to the biosynthesis metabolism of flavonoids in gardenia through the joint analysis of transcriptome and metabolome. This is of certain significance to the in-depth study of the formation mechanism of gardenia efficacy components and the improvement of quality.

Effects and Mechanistic Role of Mulberry Leaves in Treating Diabetes and its Complications

Diabetes mellitus (DM) has become a surge burden worldwide owing to its high prevalence and range of associated complications such as coronary artery disease, blindness, stroke, and renal failure. Accordingly, the treatment and management of DM have become a research hotspot. Mulberry leaves (Morus alba L.) have been used in Traditional Chinese Medicine for a long time, with the first record of its use published in Shennong Bencao Jing (Shennong's Classic of Materia Medica). Mulberry leaves (MLs) are considered highly valuable medicinal food homologs that contain polysaccharides, flavonoids, alkaloids, and other bioactive substances. Modern pharmacological studies have shown that MLs have multiple bioactive effects, including hypolipidemic, hypoglycemic, antioxidation, and anti-inflammatory properties, with the ability to protect islet [Formula: see text]-cells, alleviate insulin resistance, and regulate intestinal flora. However, the pharmacological mechanisms of MLs in DM have not been fully elucidated. In this review, we summarize the botanical characterization, traditional use, chemical constituents, pharmacokinetics, and toxicology of MLs, and highlight the mechanisms involved in treating DM and its complications. This review can provide a valuable reference for the further development and utilization of MLs in the prevention and treatment of DM.

Pharmacological and Pathological Effects of Mulberry Leaf Extract on the Treatment of Type 1 Diabetes Mellitus Mice

This study investigated the pharmacological and pathological effects of aqueous mulberry leaf extract on type 1 diabetes mellitus mice induced with an intraperitoneal injection of streptozotocin (STZ). Diabetic mice were randomized into six groups: control (normal group), model, metformin-treated mice, and high-dose, medium-dose, and low-dose mulberry. The mulberry-treated mice were divided into high-, medium-, and low-dose groups based on the various doses of aqueous mulberry leaf extract during gavage. The efficacy of the six-week intervention was evaluated by measuring levels of fasting plasma glucose, alkaline phosphatase, alanine aminotransferase, aspartate transaminase, blood urea nitrogen, gamma-glutamyl transferase, glucose, high-density lipoprotein cholesterol, lactate dehydrogenase, and low-density lipoprotein cholesterol and recording body weight. Results revealed that mulberry leaf extract exhibited an ideal hypoglycemic effect, and the high-dose group was the most affected. Histology analysis, glycogen staining and apoptosis detection were used to study the extract's effects on the liver, kidney, and pancreatic cells of diabetic mice, enabling the assessment of its effectiveness and complications on a clinical and theoretical basis. It was shown that a certain concentration of aqueous mulberry leaf extract repaired the islet cells of type 1 diabetes mellitus mice, promoting normal insulin secretion. Herein, it was confirmed that mulberry leaf could be used to develop new hypoglycemic drugs or functional health food with broad applicability.

Metabolome and Transcriptome Integrated Analysis of Mulberry Leaves for Insight into the Formation of Bitter Taste

Mulberry leaves are excellent for health care, confirmed as a 'drug homologous food' by the Ministry of Health, China. The bitter taste of mulberry leaves is one of the main problems that hinders the development of the mulberry food industry. The bitter, unique taste of mulberry leaves is difficult to eliminate by post-processing. In this study, the bitter metabolites in mulberry leaves were identified as flavonoids, phenolic acids, alkaloids, coumarins and L-amino acids by a combined analysis of the metabolome and transcriptome of mulberry leaves. The analysis of the differential metabolites showed that the bitter metabolites were diverse and the sugar metabolites were down-regulated, indicating that the bitter taste of mulberry leaves was a comprehensive reflection of various bitter-related metabolites. Multi-omics analysis showed that the main metabolic pathway related to bitter taste in mulberry leaves was galactose metabolism, indicating that soluble sugar was one of the main factors of bitter taste difference in mulberry leaves. Bitter metabolites play a great role in the medicinal and functional food of mulberry leaves, but the saccharides in mulberry leaves have a great influence on the bitter taste of mulberry. Therefore, we propose to retain bitter metabolites with drug activity in mulberry leaves and increase the content of sugars to improve the bitter taste of mulberry leaves as strategies for mulberry leaf food processing and mulberry breeding for vegetable use.

Effect of Frost on the Different Metabolites of Two Mulberry (Morus nigra L. and Morus alba L.) Leaves

Mulberry leaves are a well-known traditional Chinese medicine herb, and it has been observed since ancient times that leaves collected after frost have superior medicinal properties. Therefore, understanding the changes in critical metabolic components of mulberry leaves, specifically Morus nigra L., is essential. In this study, we conducted widely targeted metabolic profiling analyses on two types of mulberry leaves, including Morus nigra L. and Morus alba L., harvested at different times. In total, we detected over 100 compounds. After frost, 51 and 58 significantly different metabolites were identified in the leaves of Morus nigra L. and Morus alba L., respectively. Further analysis revealed a significant difference in the effect of defrosting on the accumulation of metabolites in the two mulberries. Specifically, in Morus nigra L., the content of 1-deoxynojirimycin (1-DNJ) in leaves decreased after frost, while flavonoids peaked after the second frost. In Morus alba L., the content of DNJ increased after frost, reaching its peak one day after the second frost, whereas flavonoids primarily peaked one week before frost. In addition, an analysis of the influence of picking time on metabolite accumulation in two types of mulberry leaves demonstrated that leaves collected in the morning contained higher levels of DNJ alkaloids and flavonoids. These findings provide scientific guidance for determining the optimal harvesting time for mulberry leaves.

The impact of boron nutrient supply in mulberry (Morus alba) response to metabolomics, enzyme activities, and physiological parameters

Boron (B) is essential for normal and healthy plant growth. Therefore, Boron stress is a common abiotic stress that limits plant growth and productivity. However, how mulberry copes with boron stress remains unclear. In this study, seedlings of the Morus alba cultivar, Yu-711, were treated with five different concentrations of boric acid (H₃BO₃), including deficient (0 and 0.02 mM), sufficient (0.1 mM) and toxic (0.5 and 1 mM) levels. Physiological parameters, enzymatic activities and non-targeted liquid chromatography-mass spectrometry (LC-MS) technique were employed to evaluate the effects of boron stress on the net photosynthetic rate (Pn), chlorophyll content, stomatal conductance (Gs), transpiration rate (Tr), intercellular CO₂ concentration (Ci) and metabolome signatures. Physiological analysis revealed that Boron deficiency and toxicity induced a decline in P_n, C_i, G_s, T_r, and chlorophyll content. Also, enzymatic activities, including catalase (CAT) and superoxide dismutase (SOD), decreased, while POD activity increased in response to Boron stress. Osmotic substances such as soluble sugars, soluble proteins, and proline (PRO) presented elevated levels under all Boron concentrations. Metabolome analysis indicated that differential metabolites, including amino acids, secondary metabolites, carbohydrates, and lipids, played a key role in Yu-711's response to Boron stress. These metabolites were mainly involved in amino acid metabolism, biosynthesis of other secondary metabolites, lipid metabolism, metabolism of cofactors and vitamins, and metabolism of other amino acids pathways. Our findings reveal the various metabolites pathways in mulberry response to boron nutrient supply and may serve as fundamental knowledge in breeding resistance mulberry plants, so that it can cope with climate changes.

Microneedle-based interstitial fluid extraction for drug analysis: Advances, challenges, and prospects

Similar to blood, interstitial fluid (ISF) contains exogenous drugs and biomarkers and may therefore substitute blood in drug analysis. However, current ISF extraction techniques require bulky instruments and are both time-consuming and complicated, which has inspired the development of viable alternatives such as those relying on skin or tissue puncturing with microneedles. Currently, microneedles are widely employed for transdermal drug delivery and have been successfully used for ISF extraction by different mechanisms to facilitate subsequent analysis. The integration of microneedles with sensors enables in situ ISF analysis and specific compound monitoring, while the integration of monitoring and delivery functions in wearable devices allows real-time dose modification. Herein, we review the progress in drug analysis based on microneedle-assisted ISF extraction and discuss the related future opportunities and challenges.