Bioactive Glycosides from the Twigs of Litsea cubeba

The genus Litsea: A comprehensive review of traditional uses, phytochemistry, pharmacological activities and other studies

ETHNOPHARMACOLOGICAL RELEVANCE

The genus L. has high medicinal value and has traditional been used to treat a variety of gastrointestinal disorders, as well as diabetes, edema, colds, arthritis, asthma, and traumatic injuries.

AIM OF THE REVIEW

This work addresses the missing information by conducting a comprehensive analysis of the traditional uses, chemical components, and pharmacological applications of the more reported species of the genus L. The origin of the genus, its toxicology, and the use of classical therapies in modern medicine were also discussed. It provides references for historical evidence, resource development, and medical research on the genus.

METHOD

ology: Data about the genus L. were gathered via Web of Science, PubMed, Science Direct, Google Scholar, Connected Papers, China National Knowledge Infrastructure (CNKI), electronic ancient books and local chronicles. The WFO Plant List (wfoplantlist.org) and Flora of China (www.iplant.cn) confirmed L.'s Latin name, and the species information. The program ChemBioDraw Ultra 14.0 was used to create the molecular structures of the compounds that were displayed in the text.

RESULT

Currently, at least 740 constituents have been isolated and identified from L. These include 9 groups of chemicals, such as flavonoids, alkaloids, and terpenoids. They have been shown to have over 20 biological properties in vivo and in vitro, such as antibacterial, anti-inflammatory, and anti-oxidant effects.

CONCLUSION

Based on pharmacological investigations, chemical components, and traditional folk applications, L. is considered a medicinal plant having a variety of pharmacological actions. However, although the pharmacological activity of the L. genus has been preliminary demonstrated, most have only been assessed using simple in vitro cell lines or animal disease models. In order to fully elucidate the pharmacological activity and mechanisms of L., future studies should be conducted in a more comprehensive clinical manner.

Hepatoprotective Lignan Glycosides from the Leaves and Stems of Symplocos cochinchinensis (Lour.) S. Moore

This study investigates Symplocos cochinchinensis (Lour.) S. Moore leaves and stems, commonly known as Symplocos, a plant indigenous to Asia renowned for its traditional use in holistic medicine. A comprehensive phytochemical analysis of S. cochinchinensis led to the isolation of two new lignans, namely symplolignans A and B (1 and 2) along with eleven known lignan glucosides: nortrachelogenin 4-O-β-D-glucopyranoside (3), nortracheloside (4), matairesinol 4-O-β-D-glucopyranoside (5), lariciresinol 4'-O-β-D-glucopyranoside (6), balanophonin 4-O-β-D-glucopyranoside (7), dehydrodiconiferyl alcohol 4-O-β-D-glucopyranoside (8), dehydrodiconiferyl alcohol γ'-O-β-D-glucopyranoside (9), 3-(β-D-glucopyranosyloxymethyl)-2-(4-hydroxy-3-methoxyphenyl)-5-(3-hydroxypropyl)-7-methoxy-(2R,3S)-dihydrobenzofura (10), and pinoresinol 4'-O-β-D-glucopyranoside (11). Their chemical structures were elucidated using 1D- and 2D-NMR, mass spectrometry, and their spectroscopic data were compared with those reported in literatures. Furthermore, all compounds were evaluated for their hepatoprotective effects using the Resazurin reduction assay in HepG2 hepatocellular carcinoma cells. Compounds 1, 5, 7, and 8 exhibited notable hepatoprotective efficacy, with cell viability ranging from 105.0±2.6 to 109.2±3.3 at a concentration of 10 μM. This research highlights the therapeutic potential of these compounds and enhanced to the understanding of lignans and neolignans in liver cell proliferation.

Megastigmane glycoside and phenol glycosides from the bark of Mallotus barbatus

A new megastigmane glycoside, barbatcoside A (1), and two new phenol glycosides, barbatcosides B (2) and C (3), together with eight known compounds (4-11) were isolated from the bark of Mallotus barbatus Müll. Arg. Their structures were elucidated using extensive 1D and 2D NMR as well as HRESIMS spectroscopic data. The stereochemistry of compounds 1 and 2 were established based on the experimental CD curves. The anti-inflammatory activities of compounds 1-11 from M. barbatus were evaluated using LPS-stimulated RAW 264.7 cell models. Compounds 2 and 3 substantially inhibited the release of NO with IC50 values of 34.78 μM and 20.73 μM, respectively.

Pandatonkinosides A and B: two new phenolic glycosides from the roots of Pandanus tonkinensis and their nitric oxide production inhibitory activities

Two new phenolic glycosides, 4-(3-hydroxypropyl)-2,6-dimethoxyphenol β-D-apiofuranosyl-(1→6)-β-D-glucopyranoside (1), trans-cinnamyl alcohol 9-O-(6'-O-β-D-apiofuranosyl)-β-D-glucopyranoside (2), together with nine known phenolic glycosides (3-11) were isolated from the roots of Pandanus tonkinensis. Their structures were determined by extensive analysis of HRESIMS and NMR spectral data, as well as by comparison of their spectral data (including CD spectra) with those reported in the literature. Compounds 1-4 and 6-11 inhibited NO production in LPS-activated RAW264.7 cells with IC50 values in the range from 0.80 ± 0.06 µM to 43.38 ± 3.92 µM, whereas compound 5 was inactive. The NO production inhibitory activities of compounds 1, 4, 8, and 10 with IC50 values of 10.16 ± 1.05, 0.80 ± 0.06, 1.10 ± 0.13, and 2.79 ± 0.21 µM, respectively, are as potent as that of the positive control of NG-monomethyl-L-arginine acetate (L-NMMA) with an IC50 value of 9.80 ± 0.78 µM.

Flavonoids and other phenolics from Camellia nitidissima chi flowers

From Camellia nitidissima Chi flowers four undescribed flavonoids, nitidissimol A, nitidissimol B, sexangularetin 3-O-(6''-trans-p-coumarolyglucopyranoside) and sexangularetin 3-O-(2''-trans-p-coumarolyglucopyranoside) (1-4), and two previously unreported phenolics, nitidissimol C, D (9, 10), were isolated first time along with ten known compounds, kaempferol 3-O-(6''-O-trans-p-coumaroyl)-β-D- glucopyranoside (5), kaempferol-3-O-rhamnoside (6), Quercetin-3'-O-β-D-glucoside (7), kaempferol-7-O-β-D-glucoside (8), erythro-guaiacylglycerol-O-4'-coniferyl ether (11), threo-guaiacylglycerol-O-4'-coniferyl ether (12), protocatechuic acid (13), 1,2-Diethoxybenzene (14), ethyl shikimate (15), 2,4,6-trihydroxybenzoic acid 4-O-allopyranoside (16). The structures of the isolated compounds were elucidated by spectroscopic analysis of 1 D- and 2 D-NMR and MS data. Moreover, all isolated compounds (1-16) were tested for the antibacterial activity against Xanthomonas oryzae pv. oryzae and their quorum sensing inhibitory activity in Pseudomonas aeruginosa PAO1. However, no one showed signifcant inhibition of X. oryzae pv. oryzae (MIC₉₀ > 0.1 mg/mL), nor did they significantly inhibit the pyocyanin synthesis, which is controlled by quorum sensing in PAO1.

Callnudoids A-H: Highly modified labdane diterpenoids with anti-inflammation from the leaves of Callicarpa nudiflora

Eight undescribed 3,4-seco-norlabdane diterpenoids, callnudoids A-H, as well as two known analogues were isolated from the leaves of Callicarpa nudiflora. The structures were elucidated using spectroscopic methods and were compared with published NMR spectroscopic data. The absolute configurations of callnudoids D and E were defined based on ECD data or single-crystal X-ray diffraction. Callnudoids A-C are the highly modified labdane diterpenoids featuring rearranged 3,4-seco-ring and the formation of an undescribed cyclohexene moiety via C2-C18 cyclization. They only contain 15 carbon atoms on the carbon skeleton. Callnudoid D represents the unusual 3,4-seco-15,16-norlabdane diterpenoid with C13-C17 cyclization, and a putative biosynthesis pathway for callnudoids A, B, D, and E was proposed. All compounds were evaluated for their anti-inflammatory activities by inhibiting the lipopolysaccharide (LPS)-induced nitric oxide (NO) released in RAW264.7 cells; callnudoids A-E and H, and methylcallicarpate obviously inhibited pro-inflammatory cytokines TNF-α and IL-1β in a dose-dependent manner.

Phenolic glycosides from the leaves of Iodes cirrhosa Turcz. with cytotoxic and antimicrobial effects

In the present study, 14 phenolic glycosides, including one new neolignan glycoside, iodescirrhoside A ( 1 ), three new flavonol glycosides, iodescirrhosides B-D ( 2-4 ), and 10 known metabolites were obtained from the methanol extract of Iodes cirrhosa leaves. Structural elucidation was performed by interpretating the 1D- and 2D- NMR, HRESIMS, and CD spectra in comparison with literature data. All compounds were noncytotoxic to LU-1, HepG2, MCF-7, SK-Mel-2, and LNCaP cancer cell lines. Compound 11 significantly inhibited the growth of E. faecalis . In contrast, weak inhibition was observed for 1-9 and 14 against E. faecalis , for 1 , 6-8 , and 11 against S. aureus , for 6 and 13 against B. cereus , and 2 , 4 , and 6-9 against C. albicans .

Bioactive sesquineolignans from the twigs of Litsea cubeba

In a continuing search for biological natural products with structure diversity from traditional Chinese herbs, five new sesquineolignans (1-5) were isolated from an ethyl acetate extract of the twigs of Litsea cubeba. Their structures were elucidated based on MS, 1D and 2D NMR spectroscopic data, as well as experimental electronic circular dichroism (ECD) spectra. Compounds 1-5 showed moderate inhibitory effects against LPS-induced NO production in RAW264.7 macrophages, with IC₅₀ values of 16.2, 20.2, 22.1, 15.1, and 16.6 μmol·L^-1, respectively.

Illiciumlignans G-O from the leaves of Illicium dunnianum and their anti-inflammatory activities

Phytochemical investigations on the dry leaves of Illicium dunnianum have led to the isolation of 24 lignans. Illiciumlignans G–K (1–5) were five undescribed benzofuran lignans, illiciumlignan L (6) was one undescribed ditetrahydrofuran lignan, illiciumlignans M–O (7–9) were three new sesquilignans, and compounds 10, 12, 13, 15, and 18–21 were firstly isolated from the genus Illicium. Their structures were elucidated by detailed spectroscopic analyses (UV, IR, HR-ESI-MS, and NMR) and CD experiments. All isolates were evaluated by measuring their inhibitory effects on PGE₂, and NO production in LPS-stimulated RAW 264.7 macrophages.

Phytochemical investigations on the dry leaves of Illicium dunnianum have led to the isolation of 24 lignans.

Novel Isoquinoline Alkaloid Litcubanine A - A Potential Anti-Inflammatory Candidate

Macrophages play a critical role in innate and adaptive immunity, and the regulation of macrophage function in inflammatory disease treatment has been widely studied. Litsea cubeba is an important Chinese medicinal plant used for the treatment of inflammatory diseases. However, the inflammatory bioactive ingredients in L. cubeba and underlying molecular mechanisms are poorly understood. Herein, we first obtained and elucidated a novel isoquinoline alkaloid, Litcubanine A (LA), from L. cubeba. An in vitro study indicated that LA could significantly inhibit LPS-induced activation of inflammatory macrophages via the NF-κB pathway, leading to the decrease of inflammatory factors including iNOS, TNF-α, and IL-1β. Moreover, LA showed an inhibiting effect on the expression of NO in macrophages by directly binding to iNOS protein. Molecular simulation docking also demonstrated that active LA created an interaction with GLU 371 residue of iNOS via attractive charge derived from the N→O group, revealing its highly selective inhibition toward iNOS. By using the IκK inhibitor and iNOS inhibitor, these two regulatory targets of LA on inflammatory macrophages were verified in vitro. Finally, by using a caudal fin resection model in zebrafish larvae, and the skin wound healing model in mice, we proved in vivo that LA down-regulated the secretion of local inflammatory factors by inhibiting macrophage recruitment and activation at the early stage of the injury. Collectively, our study demonstrated that the novel isoquinoline alkaloid LA suppresses LPS-induced activation of inflammatory macrophages by modulating the NF-κB pathway, suggesting that inflammatory macrophage activation pathway is an effective target for inflammation treatment, and LA is a new pharmacophore for the development of novel and effective anti-inflammatory agents to regulate local macrophages.

Lignans and phenylpropanoids from the roots of Ficus hirta and their cytotoxic activities

One undescribed lignan, one new natural product, along with fourteen known compounds, were isolated from the roots of Ficus hirta. The structures of the isolates were elucidated by comprehensive spectroscopic technologies, including UV, IR, HRESIMS, and NMR. The absolute configuration of 1 was determined by comparison of experimental and calculated ECD data. The cytotoxicity of all the compounds against HeLa and HepG2 cell lines was evaluated and compound 7 showed considerable cytotoxic effect towards HepG2 cells. Also, the apoptotic effect of 7 on HepG2 cells and the effect of 7 on the key proteins (p-JNK and p-p38) in MAPK (Mitogen-activated protein kinases) pathways were studied by flow cytometry and western blotting experiment. As a result, compound 7 induced the apoptosis of HepG2 cells, and dose-dependently increased the phosphorylation of JNK and p38. Thus, 7 might trigger HepG2 cells apoptosis via JNK/p38 MAPK signaling pathway.

Unraveling Plant Natural Chemical Diversity for Drug Discovery Purposes

The screening and testing of extracts against a variety of pharmacological targets in order to benefit from the immense natural chemical diversity is a concern in many laboratories worldwide. And several successes have been recorded in finding new actives in natural products, some of which have become new drugs or new sources of inspiration for drugs. But in view of the vast amount of research on the subject, it is surprising that not more drug candidates were found. In our view, it is fundamental to reflect upon the approaches of such drug discovery programs and the technical processes that are used, along with their inherent difficulties and biases. Based on an extensive survey of recent publications, we discuss the origin and the variety of natural chemical diversity as well as the strategies to having the potential to embrace this diversity. It seemed to us that some of the difficulties of the area could be related with the technical approaches that are used, so the present review begins with synthetizing some of the more used discovery strategies, exemplifying some key points, in order to address some of their limitations. It appears that one of the challenges of natural product-based drug discovery programs should be an easier access to renewable sources of plant-derived products. Maximizing the use of the data together with the exploration of chemical diversity while working on reasonable supply of natural product-based entities could be a way to answer this challenge. We suggested alternative ways to access and explore part of this chemical diversity with in vitro cultures. We also reinforced how important it was organizing and making available this worldwide knowledge in an "inventory" of natural products and their sources. And finally, we focused on strategies based on synthetic biology and syntheses that allow reaching industrial scale supply. Approaches based on the opportunities lying in untapped natural plant chemical diversity are also considered.

Yanhusanines A-F, Isoquinoline-Derived Alkaloid Enantiomers from Corydalis yanhusuo and Their Biological Activity

Six new pairs of isoquinoline alkaloid enantiomers, designated as yanhusanines A-F (1-6), were isolated from an aqueous extract of Corydalis yanhusuo tubers. The structures of these enantiomers were elucidated via physicochemical analysis and a variety of spectroscopic methods. All compounds were resolved into their enantiomers via chiral-phase HPLC, and their configurations were determined by DP4+ NMR calculation methods, specific rotations, and comparison of experimental and calculated ECD spectra. Compounds 1-6 bear a rare 9-methyl moiety, and compound 1 possesses a rare 1-oxa-6-azaspiro[4.5]decane core containing an N-CHO group. Compounds (+)-2, (-)-2, (+)-4, (-)-4, (+)-5, (-)-5, (+)-6, and (-)-6 exhibited selective inhibitory activities against human carboxylesterase (hCE2), in the IC₅₀ value range of 2.0-13.2 μM.

Chemical constituents from the stems of Securidaca inappendiculata Hassk

Three new neolignan glycosides, (7R,8S)-4-hydroxy-3,3'-dimethoxy-8,4'-oxyneoligna-7,9,9'-triol-4-O-β-d-glucopyranosyl-(1 → 4)-β-D-glucopyranoside (1), (7R,8S)-4-hydroxy-3,5'-dimethoxy-4',7-epoxy-8,3'-neoligna-9,9'-diol-9'-O-β-d-glucopyranosyl-4-O-[β-d-glucopyranosyl-(1 → 4)]-β-D-glucopyranoside (2), and (7R,8S)-4-hydroxy-3,5,5'-trimethoxy-4',7-epoxy-8,3'-neoligna-9,9'-diol-9'-O-β-d-glucopyranosyl-4-O-[β-d-glucopyranosyl-(1 → 4)]-β-D-glucopyranoside (3), one new phenolic glycoside, securiphenoside B (4) and two new hemiterpene glycosides, securiterpenoside E-F (5-6) were isolated from the stems of Securidaca inappendiculata Hassk. Their structures were elucidated on the basis of 1D and 2D NMR, HRESIMS, CD and chemical evidence. Furthermore, compound 2 showed moderate hepatoprotective activity compared with bicyclol in vitro.

Lignans and Neolignans: Plant secondary metabolites as a reservoir of biologically active substances

Lignans and neolignans are plant secondary metabolites derived from the oxidative coupling of phenylpropanoids. Biological activity of these phenolic compounds ranges from antioxidant, antitumor (terminaloside P, IC₅₀ = 10 nM), anti-inflammatory, anti-neurodegenerative (schibitubin B, IC₅₀ = 3.2 nM) and antiviral (patentiflorin A, IC₅₀ = 14-23 nM) to antimicrobial. In addition, it was observed that several members of this group, namely enterolactone and its biochemical precursors also known as phytoestrogens, possess important protective properties. Most of these lignans and neolignans are presented in reasonable amounts in one's diet and thus the protection they provide against the colon and breast cancer, to name a few, is even more important to note. Similarly, neuroprotective properties were observed (schisanwilsonin G, IC₅₀ = 3.2 nM) These structural motives also serve as an important starting point in the development of anticancer drugs. Presumably the most famous members of this family, etoposide and teniposide, synthetic derivatives of podophyllotoxin, are used in the clinical treatment of lymphocytic leukemia, certain brain tumors, and lung tumors already for nearly 20 years. This review describes 413 lignans and neolignans which have been isolated between 2016 and mid-2018 being reported in more than 300 peer-reviewed articles. It covers their source, structure elucidation, and bioactivity. Within the review, the structure-based overview of compounds as well as the bioactivity-based overview of compounds are described.

Lignans from the Twigs of Litsea cubeba and Their Bioactivities

Litsea cubeba, an important medicinal plant, is widely used as a traditional Chinese medicine and spice. Using cytotoxicity-guided fractionation, nine new lignans 1–9 and ten known analogues 10–19 were obtained from the EtOH extract of the twigs of L. cubeba. Their structures were assigned by extensive 1D- and 2D-NMR experiments, and the absolute configurations were resolved by specific rotation and a combination of experimental and theoretically calculated electronic circular dichroism (ECD) spectra. In the cytotoxicity assay, 7′,9-epoxylignans with feruloyl or cinnamoyl groups (compounds 7–9, 13 and 14) were selectively cytotoxic against NCI-H1650 cell line, while the dibenzylbutyrolactone lignans 17–19 exerted cytotoxicities against HCT-116 and A2780 cell lines. The results highlighted the structure-activity relationship importance of a feruloyl or a cinnamoyl moiety at C-9′ or/and C-7 ketone in 7′,9-epoxylignans. Furthermore, compound 11 was moderate active toward protein tyrosine phosphatase 1B (PTP1B) with an IC₅₀ value of 13.5 μM, and compounds 4–6, 11 and 12 displayed inhibitory activity against LPS-induced NO production in RAW264.7 macrophages, with IC₅₀ values of 46.8, 50.1, 58.6, 47.5, and 66.5 μM, respectively.

Two new terpenoid ester glycosides from the twigs of Litsea cubeba

A new sesquiterpenoid ester glycoside (1) and a new monoterpenoid ester glycoside (2) have been isolated from an ethanol extract of the twigs of Litsea cubeba. Their structures were elucidated by extensive 1D- and 2D-NMR experiments, and the absolute configurations were determined by chemical methods, specific rotation, and a combination of experimental and theoretically calculated electronic circular dichroism spectra. Compound 1 exhibited selective cytotoxicity against A549 and HCT-8 cell lines with the IC₅₀ values of 8.9 and 9.6 μM, respectively.

Structures and Biological Evaluation of Monoterpenoid Glycosides from the Roots of Paeonia lactiflora

Fractionation of an aqueous extract of the air-dried roots of a traditional Chinese medicinal plant, Paeonia lactiflora, yielded the new monoterpenoid glycosides 1-10. Their structures were assigned via spectroscopic techniques, and the absolute configurations of 1, 4-6, and 8 were verified via chemical methods, specific rotation, and electronic circular dichroism data. Compounds 1-4 are rare compared to the reported cage-like paeoniflorin derivatives; that is, they comprised two monoterpenoidal moieties. In the in vitro assay, compounds 5, 8, and 9 showed weak inhibitions against lipopolysaccharide-induced nitric oxide production in RAW264.7 macrophages, with IC₅₀ values of 64.8, 60.1, and 97.5 μM, respectively.

Bysspectin A, an unusual octaketide dimer and the precursor derivatives from the endophytic fungus Byssochlamys spectabilis IMM0002 and their biological activities

Bysspectin A (1), a polyketide-derived octaketide dimer with a novel carbon skeleton, and two new precursor derivatives, bysspectins B and C (2 and 3), were obtained from an organic extract of the endophytic fungus Byssochlamys spectabilis that had been isolated from a leaf tissue of the traditional Chinese medicinal plant Edgeworthia chrysantha, together with a known octaketide, paecilocin A (4). Their structures were determined by HRMS, 1D and 2D NMR spectroscopic analysis. A plausible route for their biosynthetic pathway is proposed. Compounds 1-3 were tested for their antimicrobial activities. Only compound 3 was weakly active against Escherichia coli and Staphyloccocus aureus with MIC values of 32 and 64 μg/mL, respectively. Further, the inhibitory effects on human carboxylesterases (hCE1, hCE2) of compounds 1 and 4 were evaluated. The results demonstrated that bysspectin A (1) was a novel and highly selective inhibitor against hCE2 with the IC₅₀ value of 2.01 μM. Docking simulation also demonstrated that active compound 1 created interaction with the Ser-288 (the catalytic amino-acid in the catalytic cavity) of hCE2 via hydrogen bonding, revealing its highly selective inhibition toward hCE2.