Hepatoprotective activity of twelve novel 7'-hydroxy lignan glucosides from Arctii Fructus

9,9'-epoxylignans from Syringa pinnatifolia: A typical case of stereochemical assignment by a quantum chemical calculation with MAEΔΔδ parameter

In the current study, twenty-two stereochemical 9,9'-epoxylignans including 19 undescribed ones were isolated from the ethanol extract of Syringa pinnatifolia in our continuing effort to understand the overall chemical spectrum of this species. These isolates were structurally elucidated by extensive spectroscopic data analysis, X-ray diffraction, modified Mosher's method, and quantum chemical calculations. Meanwhile, the utilization of 13C NMR calculation and the MAEΔΔδ parameter facilitated the stereochemical assignment of groups of lignan stereoisomers. The 13C NMR data were corrected by the averaged errors at each corresponding carbon position in groups of lignan stereoisomers, which improved the theoretic 13C NMR calculation. The finding of the stereochemical structures of 9,9'-epoxylignans is significant. It is helpful to determine the absolute configurations of molecules with the similar core. In addition, these lignans exhibited potential cardioprotective activities on H9c2 cardiomyocytes in vitro and presented significant antioxidant effect.

Research progress of chinese herbal medicine compounds and their bioactivities: Fruitful 2020

Traditional Chinese medicines (TCMs) have continued to be a treasure trove. The study of chemodiversity and versatility of bioactivities has always been an important content of pharmacophylogeny. There is amazing progress in the discovery and research of natural components with novel structures and significant bioactivities in 2020. In this paper we review 271 valuable natural products, including terpenoids, steroids, flavonoids, phenylpropanoids, phenolics, nitrogen containing compounds and essential oil, etc., isolated and identified from TCMs published in journals of Chinese Traditional and Herbal Drugs (Zhong Cao Yao) and Chinese Herbal Medicines (CHMs), and focus on their structures, source organisms, and relevant bioactivities, paying special attention to structural characteristics of novel compounds and newly revealed pharmacological properties of known compounds. It is worth noting that natural products with antitumor activity still constitute the primary object of research. Among the reported compounds, two new triterpenoids, i.e., ursolic acid 3-O-β-cis-caffeate and mollugoside E, display remarkable cytotoxicity against PC-9 and HL-60 cell lines, respectively. Three known phenolic compounds, i.e., pyoluteorin, 4-hydroxy-3-methoxy cinnamaldehyde and 3,7-dimethoxy-5-hydroxy-1,4-phenanthrenequinone, exhibit significant cytotoxicity against multiple cell lines. Numerous studies on the free radical scavenging activity of reported compounds are currently underway. In vitro, three known phenolic compounds, i.e., 3,4-O-dicaffeoylquinic acid methyl ester, 3,4,5-O-tricaffeoylquinic acid methyl ester and arbutin, had more considerable antioxidant activities than vitamin C. The anti-inflammatory, anti-diabetic, hypolipidemic, neuroprotective and antimicrobial activities of isolated compounds are also encouraging. The structural characteristics and bioactivities of TCM compounds highlighted here reflect the enormous progress of CHM research in 2020 and will play a positive role in the future drug discovery and development. According to pharmacophylogeny, the phylogenetic distribution of compounds with different natures and flavors can be explored, with view to better mining TCM resources.

Fructus arctii: an overview on its traditional uses, pharmacology and phytochemistry

OBJECTIVES

Fructus arctii (F. arctii) is the dried ripe fruit of Arctium lappa Willd (Asteraceae). It is being used as a traditional medicine in China, Japan, Iran, Europe, Afghanistan, India, etc. for cough, inflammation, clearing the heat, detoxification, cancer and diabetes. This review summarized the botanical description, distribution, ethnopharmacology, bioactive constituents and pharmacological actions of F. arctii including methods to assess its quality. In addition, this review also provides insights into future research directions on F. arctii to further explore its bioactive constituents, mechanism involved in pharmacological activity, and clinical use including the development of new analytical methods for assessing the quality.

KEY FINDINGS

The comprehensive analysis of the literature revealed that F. arctii contains lignans, volatile oil, flavonoids, sesquiterpenoids, triterpenes, phenolic acids, etc. Experimental studies on various extracts and drug formulations showed that it has antioxidant, antimicrobial, hypoglycaemic, lipid-lowering, anti-inflammatory, analgesic, antiviral, anti-tumour activity, etc.

SUMMARY

The pharmacological activity of a few major constituents in F. arctii have been identified. However, there are still need more studies and more new technologies to prove the pharmacological activity and the effective mechanism of the other constituents that undergoing uncertain. Except for the animal experiments, clinical studies should be carried out to provide the evidence for clinical application.

Lignan Constituents from the Fruits of Viburnum macrocephalum f. keteleeri and Their α-Amylase, α-Glucosidase, and Protein Tyrosine Phosphatase 1B Inhibitory Activities

Eight previously undescribed lignan glycosides, viburmacrosides A-H (1-8), and seven known analogues (9-15) were isolated from Viburnum macrocephalum f. keteleeri fruits through bioactivity-guided fractionation. Their structures and absolute configurations were elucidated by extensive spectroscopic analyses and chemical evidence. Using the well-recognized carbohydrate-hydrolyzing enzymes α-amylase and α-glucosidase, as well as the promising protein tyrosine phosphatase 1B (PTP1B), as inhibitory targets, all isolated compounds were tested for their antidiabetic potential in vitro. Compound 4 displayed potent inhibitory activities with IC₅₀ values of 9.9 ± 0.6 and 8.9 ± 0.5 μM against α-glucosidase and PTP1B, respectively. The enzymatic kinetics results suggested that compound 4 competitively inhibited α-glucosidase while it suppressed α-amylase and PTP1B in the mixed-type manner. These findings supported that V. macrocephalum f. keteleeri fruits may be a new functional food resource with antidiabetic potential.

Lignans from linseed (Linum usitatissimum L.) and its allied species: Retrospect, introspect and prospect

Lignans are complex diphenolic compounds representing phytoestrogens and occur widely across the plant kingdom. Formed by the coupling of two coniferyl alcohol residues, lignans constitute major plant "specialized metabolites" with exceptional biological attributes that aid in plant defence and provide health benefits in humans by reducing the risk of ailments such as cancer, diabetes etc. Linseed (Linum usitatissimum L.) is one of the richest sources of lignans followed by cereals and legumes. Among the various types of lignans, secoisolariciresinol diglucoside (SDG) is considered as the essential and nutrient rich lignan in linseed. Lignans exhibit established antimitotic, antiviral and anti-tumor properties that contribute to their medicinal value. The present review seeks to provide a holistic view of research in the past and present times revolving around lignans from linseed and its allied species. This review attempts to elucidate sources, structures and functional properties of lignans, along with detailed biosynthetic mechanisms operating in plants. It summarizes various methods for the determination of lignan content in plants. Biotechnological interventions (in planta and in vitro) aimed at enriching lignan content and adoption of integrative approaches that might further enhance lignan content and medicinal and nutraceutical value of Linum spp. have also been discussed.

Suppressive Effect of Arctium Lappa L. Leaves on Retinal Damage Against A2E-Induced ARPE-19 Cells and Mice

Age-related macular degeneration (AMD) is a major cause of irreversible loss of vision with 80–90% of patients demonstrating dry type AMD. Dry AMD could possibly be prevented by polyphenol-rich medicinal foods by the inhibition of N-retinylidene-N-retinylethanolamine (A2E)-induced oxidative stress and cell damage. Arctium lappa L. (AL) leaves are medicinal and have antioxidant activity. The purpose of this study was to elucidate the protective effects of the extract of AL leaves (ALE) on dry AMD models, including in vitro A2E-induced damage in ARPE-19 cells, a human retinal pigment epithelial cell line, and in vivo light-induced retinal damage in BALB/c mice. According to the total phenolic contents (TPCs), total flavonoid contents (TFCs) and antioxidant activities, ALE was rich in polyphenols and had antioxidant efficacies on 2,2-diphenyl-1-picrylhydrazyl (DPPH), 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS), ferric reducing antioxidant power (FRAP), and 2′,7′-dichlorofluorescin diacetate (DCFDA) assays. The effects of ALE on A2E accumulation and A2E-induced cell death were also monitored. Despite continued exposure to A2E (10 μM), ALE attenuated A2E accumulation in APRE-19 cells with levels similar to lutein. A2E-induced cell death at high concentration (25 μM) was also suppressed by ALE by inhibiting the apoptotic signaling pathway. Furthermore, ALE could protect the outer nuclear layer (ONL) in the retina from light-induced AMD in BALB/c mice. In conclusion, ALE could be considered a potentially valuable medicinal food for dry AMD.

Composition, Antioxidant Potential, and Antimicrobial Activity of Helichrysum plicatum DC. Various Extracts

Helichrysum plicatum DC. is widely used in folk medicine in treating a variety of health disorders. The aim of this study was to examine the influence of different extraction solvents on the chemical composition, antioxidant potential, and antimicrobial activities of H. plicatum. Aerial parts were separately extracted with ethanol, dichloromethane, and sunflower oil. The oil extract (OE) was re-extracted with acetonitrile. A total of 142 compounds were tentatively identified in ethanolic (EE), dichloromethane (DCME), and acetonitrile (ACNE) extracts using HPLC-DAD/ESI-ToF-MS. The dominant compound class in all extracts were α-pyrones, alongside flavonoids in EE, terpenoids in DCME and ACNE, and phloroglucinols in DCME. The antioxidant potential of the extracts was assessed by the 2,2-diphenyl-1-picrylhydrazyl radical (DPPH) assay. EE and DCME possessed the most potent radical scavenging capacity. Antimicrobial activity was investigated on eight bacterial, two yeast, and one fungal species. All extracts exhibited high antifungal and notable antibacterial activities compared to control substances, with DCME being the most potent. DCME exhibited stronger antimicrobial activity against P. aeruginosa than the standard chloramphenicol.

Triterpenoid Saponin and Lignan Glycosides from the Traditional Medicine Elaeagnus angustifolia Flowers and Their Cytotoxic Activities

A new triterpenoid saponin, named terpengustifol A (1), and two new lignan glucosides, phengustifols A and B (2 and 3), were isolated from the flowers of Elaeagnus angustifolia. Their structures were determined by the extensive analysis of the spectroscopic data (including NMR and HRMS) and ECD calculations. Compound 1 possesses an unusual monoterpene (Z)-6-hydroxy-2,6-dimethylocta-2,7-dienoyl unit at C-21. Compounds 2 and 3 are a pair of diastereoisomers, while their aglycones are a pair of enantiomers. Compounds 1 and 2 exhibited moderate cytotoxic activities against A375 cell lines with IC₅₀ values at 12.1 and 15.6 μM, respectively. This is firstly reported the triterpenoid saponin and lignans isolated from the Elaeagnus angustifolia flowers.

Isolation, Structure Elucidation, and Antiproliferative Activity of Butanolides and Lignan Glycosides from the Fruit of Hernandia nymphaeifolia

Seven new butanolides, peltanolides A–G (1–7), and two lignan glucosides, peltasides A (8) and B (9), along with eleven known compounds, 10–20, were isolated from a crude CH₃OH/CH₂Cl₂ (1:1) extract of the fruit of Hernandia nymphaeifolia (Hernandiaceae). The structures of 1–9 were characterized by extensive 1D and 2D NMR spectroscopic and HRMS analysis. The absolute configurations of newly isolated compounds 1–9 were determined from data obtained by optical rotation and electronic circular dichroism (ECD) exciton chirality methods. Butanolides and lignan glucosides have not been isolated previously from this genus. Several isolated compounds were evaluated for antiproliferative activity against human tumor cell lines. Lignans 15 and 16 were slightly active against chemosensitive tumor cell lines A549 and MCF-7, respectively. Furthermore, both compounds displayed significant activity (IC₅₀ = 5 µM) against a P-glycoprotein overexpressing multidrug-resistant tumor cell line (KB-VIN) but were less active against its parent chemosensitive cell line (KB).

Bioactive constituents study of Pugionium cornutum L. Gaertn on intestinal motility

Thirty-one compounds were obtained and identified from the dried roots of Mongolian medicinal and edible plant, Pugionium cornutum L. Gaertn. Eight of them were new ones, and named as pugcornols A (1), B (2), C (3), and D (4), pugcornosides A (5), B (6), C (7), and D (8), respectively. Among them, 1-4 were rare naturally occurring thiohydantoin derivatives. Meanwhile, all the isolates were determined for their activities on isolated mice jejunum contraction, and ten of them increased height of the spontaneous contractions. Moreover, we partly clarified the mechanism of 5-(methylsulfinyl)-pentanenitrile (9), a characteristic compound in P. cornutum by using different kinds of inhibitor.

The identification of phenylpropanoids isolated from the root bark of Ailanthus altissima (Mill.) Swingle

Chemical investigation of 75% EtOH exact of the root bark of Ailanthus altissima (Mill.) Swingle led to the isolation and identification of two new phenylpropanoids (1-2), along with six known compounds (3-8). Their chemical structures were elucidated by extensive spectroscopic data analyses including NMR experiments and HRESIMS analyses, as well as computer-assisted structure elucidation software (ACD/Spectrus Processor). All compounds were evaluated for cytotoxic activities against Hep 3B and Hep G2 cells. Compound 1 and 7 displayed weak cytotoxic activities against the Hep 3B cell line.

Pinoresinol-lariciresinol reductases, key to the lignan synthesis in plants

This paper provides an overview on activity, stereospecificity, expression and regulation of pinoresinol-lariciresinol reductases in plants. These enzymes are shared by the pathways to all 8-8' lignans derived from pinoresinol. Pinoresinol-lariciresinol reductases (PLR) are enzymes involved in the lignan biosynthesis after the initial dimerization of two monolignols. They catalyze two successive reduction steps leading to the production of lariciresinol or secoisolariciresinol from pinoresinol. Two secoisolariciresinol enantiomers can be synthetized with different fates. Depending on the plant species, these enantiomers are either final products (e.g., in the flaxseed where it is stored after glycosylation) or are the starting point for the synthesis of a wide range of lignans, among which the aryltetralin type lignans are used to semisynthesize anticancer drugs such as Etoposide^®. Thus, the regulation of the gene expression of PLRs as well as the possible specificities of these reductases for one reduction step or one enantiomer are key factors to fine-tune the lignan synthesis. Results published in the last decade have shed light on the presence of more than one PLR in each plant and revealed various modes of action. Nevertheless, there are not many results published on the PLRs and most of them were obtained in a limited range of species. Indeed, a number of them deal with wild and cultivated flax belonging to the genus Linum. Despite the occurrence of lignans in bryophytes, pteridophytes and monocots, data on PLRs in these taxa are still missing and indeed the whole diversity of PLRs is still unknown. This review summarizes the data, published mainly in the last decade, on the PLR gene expression, enzymatic activity and biological function.

A concise approach for determining the relative configuration of H-7 and H-8 in 8,4′-oxyneolignans by 1H NMR spectroscopy

The chemical shift difference between H-9a and H-9b can be used to accurately and rapidly determine the relative configuration of H-7 and H-8 in three types of 8,4′-oxyneolignan glucosides.

Phenylpropanoids and lignans from Prunus tomentosa seeds as efficient β-amyloid (Aβ) aggregation inhibitors

Alzheimer's disease (AD) is characterized by the progressive accumulation of extracellular β-amyloid (Aβ) aggregates. Recently, lignans and phenylpropanoids are attracting increasing attention to discovery useful agents of inhibition on Aβ aggregation. In the present study, to develop potential agents for slowing the progression of AD, Prunus tomentosa seeds were selected as a raw material for bioactive compounds, which led to the separation of two pairs of new enantiomeric lignans and phenylpropanoids using chiral HPLC. The planar structures of these compounds were elucidated by spectroscopic data analyses. And their absolute configurations were determined by comparing of experimental and calculated electronic circular dichroism (ECD). The biosynthesis pathway was also discussed. Additionally, the inhibitory activity on Aβ aggregation of all optical pure compounds was tested by thioflavin T (ThT) assay. The isolates (1a, 1b, 2a and 2b) showed more potent inhibitory activity than positive control curcumin with inhibitory rate of 73.89 ± 3.41% 78.69 ± 1.50%, 63.25 ± 2.68%, and 67.13 ± 0.90% at 20 μM, respectively. More importantly, the inhibition profiles were explained by molecular dynamics and docking simulation studies.

Six new compounds from the flowers of Chrysanthemum morifolium and their biological activities

Flower of Chrysanthemum morifolium is widely used in China and Japan as a folk medicine in treatment of many diseases. However, its active compounds remain largely unknown. In the present work, we have isolated, purified and characterized six new compounds (1-6), including two new arylnaphthalene lignans and four new phenolic glycosides, together with eight known compounds (7-14), from the flower of C. morifolium. Their structures and absolute configurations were elucidated in detail using 1D and 2D NMR, UV, IR, ORD, HRESIMS and ECD spectrometric data. In addition, compounds 1-3 possessed the significant neuroprotective activity against hydrogen peroxide-induced neurotoxicity in human neuroblastoma SH-SY5Y cells.

Bioactive Constituents from the Aerial Parts of Pluchea indica Less

Four new thiophenes, (3''R)-pluthiophenol (1), (3''R)-pluthiophenol-4''-acetate (2), 3''-ethoxy-(3''S)-pluthiophenol (3), 3''-ethoxy-(3''S)-pluthiophenol-4''-acetate (4), together with twenty-five known compounds were obtained from the 70% ethanol-water extract of the aerial parts of Pluchea indica Less. Their structures were elucidated by spectroscopic methods. Among the known isolates, compounds 7, 8, 11, 14, 15, 18, 20, 23, 25⁻27 were isolated from Asteraceae family firstly, while compounds 6, 9, 10, 12, 13, 16, 19, 21, 28 were isolated from Pluchea genus for the first time. Meanwhile, compounds 1, 2, 10, 13, 18, 23 displayed significant inhibitory activities on LPS-induced NO production at 40 µM from RAW 264.7 macrophages, while compounds 3, 4, 26⁻29 possessed moderate inhibitory effects.

Phenolic Glycosides from Capsella bursa-pastoris (L.) Medik and Their Anti-Inflammatory Activity

A new sesquilignan glycoside 1, together with seven known phenolic glycosides 2–8 were isolated from the aerial parts of Capsella bursa-pastoris. The chemical structure of the new compound 1 was elucidated by extensive nuclear magnetic resonance (NMR) data (¹H- and ¹³C-NMR, ¹H-¹H correlation spectroscopy (¹H-¹H COSY), heteronuclear single-quantum correlation (HSQC), heteronuclear multiple bond correlation (HMBC), and nuclear overhauser effect spectroscopy (NOESY)) and HR-FABMS analysis. The anti-inflammatory effects of 1–8 were evaluated in lipopolysaccharide (LPS)-stimulated murine microglia BV-2 cells. Compounds 4 and 7 exhibited moderate inhibitory effects on nitric oxide production in LPS-activated BV-2 cells, with IC₅₀ values of 17.80 and 27.91 µM, respectively.

Recent advances in research on lignans and neolignans

Covering: 2009 to 2015Lignans and neolignans are a large group of natural products derived from the oxidative coupling of two C6-C3 units. Owing to their biological activities ranging from antioxidant, antitumor, anti-inflammatory to antiviral properties, they have been used for a long time both in ethnic as well as in conventional medicine. This review describes 564 of the latest examples of naturally occurring lignans and neolignans, and their glycosides in some cases, which have been isolated between 2009 and 2015. It comprises the data reported in more than 200 peer-reviewed articles and covers their source, isolation, structure elucidation and bioactivities (where available), and highlights the biosynthesis and total synthesis of some important ones.

Wasabisides A-E, Lignan Glycosides from the Roots of Wasabia japonica

Five new lignan glycosides, wasabisides A-E (1-5), and four known phenolic compounds (6-9), were isolated from the roots of Wasabia japonica. The chemical structures of the new compounds (1-5) were determined through spectroscopic analysis and chemical methods. All isolated compounds (1-9) were evaluated for their potential neuroprotective effects through induction of nerve growth factor in C6 glioma cells, for their effects on nitric oxide levels in lipopolysaccharide-stimulated murine microglia BV2 cells, and for their cytotoxicity against four human tumor cell lines (A549, SK-OV-3, SK-MEL-2, and BT549).

Two new compounds from the fruits of Arctium lappa

Phytochemical investigation of the extract of Arctii Fructus led to the isolation and characterization of two new compounds, named arctiisesquineolignan B (1) and arctiiphenolglycoside A (2). Their structures were elucidated by means of spectroscopic methods (UV, IR, HR-ESI-MS, 1D and 2D NMR) and chemical evidence, as well as by comparison with known analogs in the literature. Compound 2 exhibited stronger antioxidant activity than the positive control ascorbic acid at a concentration of 10 μM.

Identification and characterization of human UDP-glucuronosyltransferases responsible for the in-vitro glucuronidation of arctigenin

Objectives

This study aimed to characterize the glucuronidation pathway of arctigenin (AR) in human liver microsomes (HLM) and human intestine microsomes (HIM).

Methods

HLM and HIM incubation systems were employed to catalyse the formation of AR glucuronide. The glucuronidation activity of commercially recombinant UGT isoforms towards AR was screened. A combination of chemical inhibition assay and kinetic analysis was used to determine the UGT isoforms involved in the glucuronidation of AR in HLM and HIM.

Key findings

AR could be extensively metabolized to one mono-glucuronide in HLM and HIM. The mono-glucuronide was biosynthesized and characterized as 4′-O-glucuronide. UGT1A1, 1A3, 1A7, 1A8, 1A9, 1A10, 2B4, 2B7 and 2B17 participated in the formation of 4′-O-G, while UGT2B17 demonstrated the highest catalytic activity in this biotransformation. Both kinetic analysis and chemical inhibition assays demonstrated that UGT1A9, UGT2B7 and UGT2B17 played important roles in AR-4′-O-glucuronidation in HLM. Furthermore, HIM demonstrated moderate efficiency for AR-4′-O-glucuronidation, implying that AR may undergo a first-pass metabolism during the absorption process.

Conclusion

UGT1A9, UGT2B7 and UGT2B17 were the major isoforms responsible for the 4′-O-glucuronidation of AR in HLM, while UGT2B7 and UGT2B17 were the major contributors to this biotransformation in HIM.

New Butyrolactone Type Lignans from Arctii Fructus and Their Anti-inflammatory Activities

Arctiidilactone (1), a novel rare butyrolactone lignan with a 6-carboxyl-2-pyrone moiety, and 11 new butyrolactone lignans (2-12) were isolated from the fruits of Arctium lappa L., together with 5 known compounds (13-17). Their structures were elucidated by interpretation of their spectroscopic data (1D and 2D NMR, UV, IR, ORD, and HRESIMS) and comparison to literature data. The absolute configurations of compounds 1-12 were determined by a combination of rotating-frame nuclear Overhauser effect spectroscopy (ROESY), circular dichroism (CD) spectroscopy, and Rh2(OCOCF3)4-induced CD spectroscopy. All of the compounds were tested for their anti-inflammatory properties in terms of suppressing the production of NO in lipopolysaccharide-induced BV2 cells. Compounds 1, 6, 8, and 10 exhibited stronger anti-inflammatory effects than the positive control curcumin, particularly 1, which exhibited 75.51, 70.72, and 61.17% inhibition at 10, 1, and 0.1 μM, respectively.

Four new neolignan glucosides from the fruits of Arctium lappa

Four new neolignan glucosides named (7S, 8R)-4,7,9,9'-tetrahydroxy-3,3'-dimethoxy-8-O-4'-neolignan-9'-O-β-d-apiofuranosyl-(1 → 6)-O-β-d-glucopyranoside (1), (8R)-4,9,9'-trihydroxy-3,3'-dimethoxy-7-oxo-8-O-4'-neolignan-4-O-β-d-glucopyranoside (2), (7R, 8S)-dihydrodehydrodiconiferyl alcohol-7'-oxo-4-O-β-d-glucopyranoside (3), and (7'S, 8'R, 8S)-4,4',9'-trihydroxy-3,3'-dimethoxy-7',9-epoxylignan-7-oxo-4-O-β-d-glucopyranoside (4) were isolated from the fruits of Arctium lappa L. Their structures and absolute configurations were elucidated on the basis of comprehensive spectroscopic analyses (UV, IR, HR-ESI-MS, 1D and 2D NMR, CD), as well as by comparison with known analogues in the literature.

NMR spectroscopic method for the assignment of 3,5-dioxygenated aromatic rings in natural products

In recent years, certain "new" naturally occurring compounds (1-28) with 3,5-dioxygenated aromatic rings have been reported. A comparison of the NMR data of these compounds with the data of four model compounds (A-D) indicated that the structures of these "new" compounds were erroneous. The reason for the incorrect elucidation of the structures of 1-28 was attributed to "deceptively simple" (1)H NMR spectra, which displayed two broad singlets with integrations of 1:2 for H-2 and H-5, H-6, respectively. To expose the misleading results from the spectra, serial (1)H NMR experiments on compounds A-D were performed using various deuterated solvents and temperatures. The results revealed separated proton signals for the ABX system in certain deuterated solvents. Additionally, the characteristic differences between 3,4- and 3,5-dioxygenated aromatic rings in their (13)C NMR spectra are summarized based on our experiment and data reported. This approach is useful for analyzing the patterns of dioxygenated aromatic rings in natural products, especially when "deceptively simple" (1)H NMR spectra are displayed.