Two new quinones from the roots of Juglans mandshurica

Plant anthraquinones: Classification, distribution, biosynthesis, and regulation

Anthraquinones are polycyclic compounds with an unsaturated diketone structure (quinoid moiety). As important secondary metabolites of plants, anthraquinones play an important role in the response of many biological processes and environmental factors. Anthraquinones are common in the human diet and have a variety of biological activities including anticancer, antibacterial, and antioxidant activities that reduce disease risk. The biological activity of anthraquinones depends on the substitution pattern of their hydroxyl groups on the anthraquinone ring structure. However, there is still a lack of systematic summary on the distribution, classification, and biosynthesis of plant anthraquinones. Therefore, this paper systematically reviews the research progress of the distribution, classification, biosynthesis, and regulation of plant anthraquinones. Additionally, we discuss future opportunities in anthraquinone research, including biotechnology, therapeutic products, and dietary anthraquinones.

Juglans mandshurica Maximowicz as a traditional medicine: review of its phytochemistry and pharmacological activity in East Asia

OBJECTIVES

The conducted search reveals that Juglans mandshurica Maximowicz, called Manchuria walnuts, had many local uses that can be categorized into cancer, dermatosis and acesodyne.

KEY FINDINGS

Various metabolites including diarylheptanoids, naphthoquinones, and flavonoids (also their glycosides) were reported as bioactive metabolites. The isolated metabolites and extracts from J. mandshurica showed different biological activity including cytotoxicity, anti-inflammation, antimelanotic, anticomplement, anti-HIV, antimicrobial and anti-obesity activity.

SUMMARY

It is indicated that this review will add value to more scientific research on J. mandshurica and enhance the increased interest in the sustainable commercialization of J. mandshurica. It also leads to the validation of unverified ethnobotanical claims. Future studies on J. mandshurica would be focused to establish the links between the pharmacological activity, bioactive metabolites, and traditional uses.

Biosynthesis of Novel Naphthoquinone Derivatives in the Commonly-used Chassis Cells Saccharomyces cerevisiae and Escherichia coli

Naphthoquinones harboring 1,4-naphthoquinone pharmacophore are considered as privileged structures in medicinal chemistry. In pharmaceutical industry and fundamental research, polyketide naphthoquinones were widely produced by heterologous expression of polyketide synthases in microbial chassis cells, such as Saccharomyces cerevisiae and Escherichia coli. Nevertheless, these cell factories still remain, to a great degree, black boxes that often exceed engineers’ expectations. In this work, the biotransformation of juglone or 1,4-naphthoquinone was conducted to generate novel derivatives and it was revealed that these two naphthoquinones can indeed be modified by the chassis cells. Seventeen derivatives, including 6 novel compounds, were isolated and their structural characterizations indicated the attachment of certain metabolites of chassis cells to naphthoquinones. Some of these biosynthesized derivatives were reported as potent antimicrobial agents with reduced cytotoxic activities. Additionally, molecular docking as simple and quick in silico approach was performed to screen the biosynthesized compounds for their potential antiviral activity. It was found that compound 11 and 17 showed the most promising binding affinities against Nsp9 of SARS-CoV-2, demonstrating their potential antiviral activities. Overall, this work provides a new approach to generate novel molecules in the commonly used chassis cells, which would expand the chemical diversity for the drug development pipeline. It also reveals a novel insight into the potential of the catalytic power of the most widely used chassis cells.

Flower Development of Heterodichogamous Juglans mandshurica (Juglandaceae)

Juglans mandshurica is a monoecious heterodichogamous species with protogynous and protandrous mating strategies that occur at a 1:1 ratio and are randomly distributed in the population. The inconsistent male and female flowering periods of the same mating type result in an imbalance of the ratio of male and female flowers, contributing to the low yield of this species. However, little more is known about its floral development. Following three consecutive years of observations, histological analysis, and scanning electron microscopy, we found that the morphological and anatomical development of the male and female flowers were synchronous. The male floral morphological development of J. mandshurica was divided into seven phases, while that of the female flower was nine. Four stages were shared between the male and female flower's anatomical development. Our findings indicate that there was minimal overlap between sexual functions within the same mating type, guaranteeing synchronization, mutual non-interference, outcrossing, and avoidance of self-fertilization. These results provide a theoretical basis for the improvement of fruit yield and quality through the reasonable allocation of protogynous and protandrous individuals in a population, and for artificial pollination control. Further, these findings lay a foundation for further research on the genetic mechanisms and environmental effects on flower development of heterodichogamous J. mandshurica.

Juglans mandshurica Maxim.: A Review of Its Traditional Usages, Phytochemical Constituents, and Pharmacological Properties

Juglans mandshurica Maxim., also known as “Manchurian walnut” (Chinese) and “Onigurumi” (Japanese), is a medicinal plant widely distributed in Western and Central Asia, especially in China. It has been traditionally used to treat cancer, gastric ulcers, diarrhea, dysentery, dermatosis, uterine prolapse, and leukopenia. To date, more than 400 constituents including quinones (e.g. naphthoquinones, anthraquinones, naphthalenones, tetralones), phenolics, flavonoids, triterpenoids, coumarins, lignans, phenylpropanoids, diarylheptanoids, and steroids, were isolated and structurally identified from different plant parts of J. mandshurica. Among them, quinones, phenolics, triterpenoids, and diarylheptanoids, as the major bioactive substances, have been extensively studied and displayed significant bioactivity. Previous studies have demonstrated that J. mandshurica and a few of its active components exhibit a wide range of pharmacologically important properties, such as antitumor, immunomodulatory, anti-inflammatory, neuroprotective, anti-diabetic, antiviral, antimicrobial, and anti-melanogenesis activities. However, many investigations on biological activities were mainly based on crude extracts of this plant, and the major bioactive ingredients responsible for these bioactivities have not been well identified. Further in vitro and in vivo studies on the mechanisms of action of the pure bioactive compounds, and more elaborate toxicity studies as well as clinical studies are needed to ensure safety and effectiveness of the plant for human use. Taken together, the present review will provide some specific useful suggestions guide to further investigations and applications of this plant in the preparation of medicines and functional foods.

Two new quinones and six additional metabolites with potential anti-inflammatory activities from the roots of Juglans mandshurica

Two new quinones, 4-(5-hydroxy-1,4-dioxo-1,4-dihydronaphtha-len-3-ylamino)-butyric acid methyl ester (compound 1) and 1,3-dimethoxycarbonyl-8-hydroxy-9,10-anthraquinone (2), and six known compounds (3-8) were isolated from the roots of Juglans mandshurica Maxim., a member of the Juglandaceae family. The chemical structures of the compounds were elucidated by nuclear magnetic resonance spectroscopy and compared with data from the literature. The isolated compounds were evaluated for their ability to inhibit the production of nitric oxide, tumour necrosis factor-α, and interleukin-6 by the mouse macrophage RAW 264.7 cell line after lipopolysaccharide stimulation in vitro. We found that compounds 1-4 exhibited potent anti-inflammatory effects, as indicated by suppression of lipopolysaccharide-stimulated nitric oxide and cytokine production with 50% inhibitory concentrations between 20.09 μM and 27.63 μM. These results identify two novel quinones from J. mandshurica with potential utility as anti-inflammatory compounds.

New α-ditetralonyl glucoside from the green walnut husk of Juglans mandshurica

One new α-ditetralonyl glucoside (1), was isolated from the green walnut husk of Juglans mandshurica (Juglandaceae), together with twelve known compounds (2-13). The structure of the new compound was determined as (2R,4S,10S,12S)-2-[7-(12,13,16-trihydroxy-α-tetralonyl-13-O-β-D-glucopyranoside)]- 4,8-dihydroxy-α-tetralone-4-O-β-D-glucopyranoside (1), on the basis of detailed spectroscopic analyses, and acidic hydrolysis. Compounds 6, 7 and 11 were isolated from the genus Juglans for the first time. Compound 1-13 showed weak cytotoxic against A549 and HeLa cell lines.

A new anti-Helicobacter pylori juglone from Reynoutria japonica

A 70% ethanol extract from the root portion of Reynoutria japonica afforded one new and three known juglone derivatives, namely, 2-methoxy-6-acetyl-7-methyljuglone (1), 2-ethoxy-6-acetyl-7-methyljuglone (2), 2-methoxy-7-acetonyljuglone (3), and 3-acetyl-7-methoxy-2-methyljuglone (4) together with two phenolics (5 and 6), an anthraquinone (7), a stilbene (8) and a phthalide (9). Their structures were elucidated on the basis of comprehensive spectroscopic studies including IR, MS, and ¹H, ¹³C, 2D NMR spectra. Compound 3 is a new compound in nature, and compounds 4-6 have been isolated for the first time from R. japonica. The isolates were evaluated for their antibacterial activity against three strains (43504, 51, and 26695) of Helicobacter pylori. The four isolated juglone derivatives (1-4) showed potent growth inhibitory activity. Among them, compounds 1-3 exhibited stronger inhibitory activity than those of the positive controls, juglone and metronidazole, for the three strains and that of another reference, clarithromycin, for the 43504 and 51 strains. Specifically, the new juglone compound 3 displayed the most potent antibacterial activity against all three strains, 43504, 51, and 26695, with MIC values of 0.06, 0.06 and 0.13 μM, respectively, and MIC₅₀ values of 0.14, 0.11 and 0.15 μM, respectively.

A new diarylheptanoid and a new diarylheptanoid glycoside isolated from the roots of Juglans mandshurica and their anti-inflammatory activities

A new diarylheptanoid, (2S,3S,5S)-2,3,5-trihydroxy-1,7-bis(4-hydroxy- 3-methoxyphenyl)heptane (1), and a new diarylheptanoid glycoside, (2S,3S,5S)-2,3-dihydroxy-5-O-β-d-xylopyranosyl-7-(4-hydroxy-3-methoxyphenyl)-1-(4-hydroxyphenyl)heptane (2), together with three known compounds, rhoiptelol C (3), rhoiptelol B (4) and 3',4″-epoxy-2-O-β-d-glucopyanosyl-1-(4-hydroxyphenyl)- 7-(3-methoxyphenyl)heptan-3-one (5) were isolated from the roots of Juglans mandshurica (Juglandaceae). The structures of compounds 1 and 2 were identified based on HR-ESI-MS, 1D and 2D NMR spectroscopic methods. Compounds 1-5 were assayed for their inhibitory effects on the production of NO, TNF-α and IL-6 in LPS-stimulated RAW264.7 cells.