Constituents from Dendrobium aphyllum: Bibenzyls, furfurals, phenanthrenes, and phenylpropanoids and their antioxidant and anti-inflammatory potentials

Chemical investigation on the aqueous extract of Dendrobium aphyllum led to the isolation of thirty-one constituents with structures identified by analysis of the extensive spectroscopic data (1D/2D NMR, MS, UV, and ECD), including previously undescribed two bibenzyls, one furfural, and one phenolic acid, namely trigonopol D (1), trigonopol C (2), dendrofunan A (10), and 6-(4-hydroxy-3-methoxyphenyl)-3,6-dioxohexyl acetate (30), respectively, as well as twenty-seven known ones. Among them, there were one new natural product (11), seven compounds (6-7, 9, 12, 20, 28, 31) described from the genus Dendrobium for the first time, and fifteen compounds (8, 13-17, 19, 21-27, 29) isolated from D. aphyllum for the first time. Further, the antioxidant and anti-inflammatory potentials of fifteen compounds (4-5, 8, 11-12, 14-19, 22, 24, 26, and 29) with significant scavenging capacities against DPPH and hydroxyl radicals, and virtual docking activities inhibiting COX-2 and 5-LOX, respectively. Our study may draw the attention of medicinal plant taxonomists and supply potential quality markers for discrimination of D. aphyllum from other species in Dendrobium genus.

Chemical composition and anticholinesterase activity of Lepisanthes rubiginosa (Roxb.) Leenh. essential oil

Essential oils obtained from medicinal plants show high therapeutic potential against several types of pathologies, including Alzheimer’s disease. The purpose of this work was to study the chemical composition and anticholinesterase inhibitory activity of the essential oil obtained from Lepisanthes rubiginosa leaves collected from Malaysia. Twenty-four components were identified using gas chromatography-flame ionization detection (GC-FID) and gas chromatography/mass spectrometry (GC-MS), which represent 99.5% of the essential oil. The identified major components include α-cadinol (40.0%), safrole (12.6%), α-amorphene (9.5%), (E)-isosafrole (5.0%), δ-cadinene (4.2%), and t-muurolol (4.1%). Anticholinesterase activity was assessed using Ellman method, and the essential oil demonstrated a moderate inhibitory activity against acetylcholinesterase (I%: 75.2%) and butyrylcholinesterase (I%: 70.2%) at conconcetration of 1000 μg/mL. The current study is the first to report chemical composition and anticholinesterase activity of the essential oil obtained from L. rubiginosa, which may have implications on the characterization, pharmaceutical, and therapeutic applications of Lepisanthes genus essential oils.

Chemical composition and bioactivities of Magnolia candollii H.Keng essential oil

Several Magnolia species have exhibited potent biological activities such as anti-inflammatory, anti-angiogenesis, anticonvulsant, anti-obesity, and antiviral activities. However, the Magnolia candollii from Malaysia has not been investigated yet. Hence, this study aims to investigate the chemical composition and bioactivities of the essential oil of Magnolia candollii H.Keng from Malaysia. The hydrodistillation process was used to produce the essential oil, and gas chromatography (GC) and gas chromatography-mass spectrometry (GC-MS) were used to analyse it. In total, 44 chemical components were identified in the bark oil, accounting for 98.4%. The major components of the essential oil were α-pinene (29.7%), elemol (10.2%), β-pinene (8.5%), β-caryophyllene (7.2%), α-terpineol (7.0%), guaiol (5.4%), and bulnesol (4.9%). Acetylcholinesterase and anti-inflammatory activities were also evaluated using the Ellman method and lipoxygenase enzyme, respectively, in which the essential oil showed moderate inhibitory activity against acetylcholinesterase (I%: 70.2%) and lipoxygenase (I%: 72.5%). Thus, the findings may be helpful for identifying the medicinal and therapeutic uses of the essential oil from the Magnolia genus.

Seven compounds from Portulaca oleracea L. and their anticholinesterase activities

A novel lignan, identified as 4-(3,4-dihydroxyphenyl)-6,7-dimethoxy-3a,4-dihydronaphtho[2,3-c]furan-1(3H)-one, named oleralignan A (1), together with six known compounds, loliolide (2), isololiolide (3), dehydrololiolide (4), daphnetin (5), esculetin (6), and trans-coumaric acid methyl ester (7) was obtained from Portulaca oleracea L., while compounds 3, 4, 6, and 7 were isolated from the plant for the first time. Their structures were elucidated using spectroscopic methods, including one- and two-dimensional NMR and high-resolution electrospray ionization time-of-flight mass spectrometry. In addition, the results of activity assay demonstrated that compounds 1-7 have anticholinesterase activities.

Syringaresinol Inhibits UVA-Induced MMP-1 Expression by Suppression of MAPK/AP-1 Signaling in HaCaT Keratinocytes and Human Dermal Fibroblasts

Ultraviolet (UV) irradiation induces detrimental changes in human skin which result in photoaging. UV-induced intracellular changes cause degradation of extracellular matrix (ECM). UV-stimulated cleavage of collagen in ECM occurs via matrix metalloproteinases (MMPs). (±)-syringaresinol (SYR), a phytochemical which belongs to the lignan group of polyphenols, was investigated for its ability to reverse the UVA-induced changes in human HaCaT keratinocytes and dermal fibroblasts (HDFs) in vitro. Effect of SYR on UVA-induced changes was investigated by production and activation of MMPs and its transcriptional upstream effectors; mitogen-activated protein kinases (MAPKs) and pro-inflammatory mediators. Levels of expression were determined using ELISA, RT-PCR and immunoblotting. UVA irradiation stimulated the production of MMP-1 and inhibited collagen production. SYR treatment suppressed MMP-1 and enhanced collagen production in UVA-irradiated HaCaT keratinocytes and HDFs. SYR repressed the UV-induced phosphorylation of p38, ERK and JNK MAPKs in HaCaT keratinocytes while only suppressing JNK phosphorylation in HDFs. In addition, SYR was able to inhibit UVA-induced production of inflammatory cytokines; TNF-α, COX-2, IL-1β and IL-6. Moreover, SYR suppressed the activator protein-1 (AP-1), a heterodimer of phosphorylated transcription factors c-Jun and c-Fos. SYR-treatment decreased nuclear levels of activated c-Fos and c-Jun as a mechanism to inhibit UVA-induced transcriptional activities leading to MMP-1 production. In conclusion, current results demonstrated that SYR could inhibit UVA-induced upregulation of MMP-1 by suppressing MAPK/AP-1 signaling in HaCaT keratinocytes and HDFs. Therefore, SYR was suggested as a potential compound with antiphotoaging properties against UVA-induced skin aging.

Chemical composition and biological activities of Dipterocarpus cornutus Dyer essential oil

The design of this study was developed to examine the chemical composition, anticholinesterase and anti-inflammatory inhibitory activities of the essential oil of Dipterocarpus cornutus Dyer from Malaysia. Gas chromatography (GC) and gas chromatography/mass spectrometry (GC-MS) analysis of the essential oil revealed 20 components, representing 94.6% of the oil. The major components identified were α-gurjunene (50.6%), α-selinene (8.3%), spathulenol (5.7%), and bicyclogermacrene (5.4%). Anticholinesterase and anti-inflammatory activity were also evaluated using the Ellman method and lipoxygenase (LOX) enzyme, respectively, in which the essential oil revealed weak inhibitory activity against the acetylcholinesterase (AChE) (I%: 30.2%) and butyrylcholinesterase (BChE) (I%: 32.5%), while moderate inhibitory activity was reported in the LOX (I%: 70.2%). The approach adopted in this study and results are reported for the first time which could be useful for the characterization, pharmaceutical and therapeutic applications of the essential oil from Dipterocarpus genus.

Insights into the inhibitory mechanism and molecular interaction of novel alkaloids from Beilschmiedia glabra with lipoxygenase and acetylcholinesterase

In this study, the mechanism underlying acetylcholinesterase (AChE) and 5-lipoxygenase (LOX) inhibition by two novel alkaloids, beilschglabrine A and beilschglabrine B, as well as their interaction footprints on the binding pockets were investigated. The results showed that beilschglabrine A and beilschglabrine B inhibit both AChE and LOX in a competitive manner by binding to their active sites thereby interfering with substrate access. The interaction of the alkaloids with the enzymes was favorable and stable with low binding energy values which correlate well with their IC[Formula: see text]. The depicted molecular interaction, structure-energetic pattern and binding conformations confirmed that beilschglabrine A is more potent than beilschglabrine B. The differences in the binding pose and potency of the alkaloids is occasioned by an extra methyl moiety on beilschglabrine B. The chemical scaffold of the alkaloids respected Lipinski’s rule of five and may be relevant in the development of new anti-inflammatory and anti-neurodegenerative disease drugs acting via AChE and LOX inhibition.

Phytochemicals and Tyrosinase Inhibitory Activity from Piper caninum and Piper magnibaccum

Background: Piper species are aromatic plants used as spices in the kitchen, but their secondary metabolites have also shown biological effects on human health. In traditional medicine, Piper species have been used worldwide to treat several diseases such as urological problems, skin, liver and stomach ailments, for wound healing, and as antipyretic and anti-inflammatory agents. In the present study, we attempted to isolate the phytochemicals from Piper caninum and Piper magnibaccum and evaluate their tyrosinase inhibitory activity. Methods: Phytochemical constituents of the extracts were investigated using various chromatographic and spectroscopic methods. The structures of the isolated phytochemicals were established by analysis of their spectroscopic data, as compared to that of reported data. Tyrosinase inhibitory activity was also tested on the extracts and selected compounds using mushroom tyrosinase as the enzyme. Results: Fractionation and purification of the extracts of Piper caninum and Piper magni­baccum afforded nine known compounds which were cepharanone A (1), cepharadione A (2), aristolactam AII (3), 5,7-dimethoxyflavone (4), 24-methylenecycloartan-3-one (5), β-sitosterol (6), piperumbellactam A (7), 24S-ethylcholesta-5,22,25-trien-3β-ol (8) and stigmast-3,6-dione (9). Ethyl acetate extracts from leaves of P. magnibaccum gave the highest inhibition value at 48.35%, while the tested compounds displayed weak tyrosinase activity compared to the positive control, kojic acid. Conclusion: These phytochemical results suggested that the extracts could assist as a potential source of bioactive compounds. Further research is needed in which the extract could possibly be exploited for pharmaceutical use.

Combined In Vitro Studies and in Silico Target Fishing for the Evaluation of the Biological Activities of Diphylleia cymosa and Podophyllum hexandrum

This paper reports the in silico prediction of biological activities of lignans from Diphylleia cymosa and Podophyllum hexandrum combined with an in vitro bioassays. The extracts from the leaves, roots and rhizomes of both species were evaluated for their antibacterial, anticholinesterasic, antioxidant and cytotoxic activities. A group of 27 lignans was selected for biological activities prediction using the Active-IT system with 1987 ligand-based bioactivity models. The in silico approach was properly validated and several ethnopharmacological uses and known biological activities were confirmed, whilst others should be investigated for new drugs with potential clinical use. The extracts from roots of D. cymosa and from rhizomes and roots of P. hexandrum were very effective against Bacillus cereus and Staphylococcus aureus, while podophyllotoxin inhibited the growth of Staphylococcus aureus and Escherichia coli. D. cymosa leaves and roots showed anticholinesterasic and antioxidant activities, respectively. The evaluated extracts showed to be moderately toxic to THP-1 cells. The chromatographic characterization indicated that podophyllotoxin was the major constituent of P. hexandrum extract while kaempferol and its hexoside were the main constituents of D. cymosa leaves and roots, respectively. These results suggest that the podophyllotoxin could be the major antibacterial lignan, while flavonoids could be responsible for the antioxidant activity.

Cholinesterase inhibitory alkaloids from the rhizomes of Coptis chinensis

Coptis chinensis has been used as a medicinal herb in traditional oriental medicine. In this study, chemical investigation of a water extract of C. chinensis identified two new quaternary protoberberines (1, 2), a new tricyclic amide (3), together with five known compounds. Their chemical structures were elucidated by analysis with 1D and 2D NMR and high-resolution mass spectroscopy, as well as by comparison with those reported in the literature. Compounds 4, 5, and 7 showed potent inhibition against acetylcholinesterase (AChE) with IC₅₀ values of 1.1, 5.6, and 12.9 μM, respectively. Compounds 2 and 4 showed inhibition of butyrylcholinesterase (BChE) with IC₅₀ values of 11.5 and 27.8 μM, respectively. The kinetic activities were investigated to find out the type of enzyme inhibition involved. The types of AChE inhibition shown by compounds 5 and 7 were noncompetitive; BChE inhibition by compound 2 was also noncompetitive.

Inhibitory effects of serratene-type triterpenoids from Lycopodium complanatum on cholinesterases and β-secretase 1

Phytochemical investigation of Lycopodium complanatum whole plants led to the isolation of two new serratene-type triterpenoids (1 and 2) along with eight known triterpenoids (3-10). Their structures were established using 1D and 2D NMR spectroscopic techniques and mass spectrometry. These compounds did not inhibit acetylcholinesterases (AChE) and butyrylcholinesterase (BChE), but did inhibit β-secretase 1 (BACE1). Compounds 1 and 6 showed potent BACE1 inhibition with IC₅₀ values of 2.79 ± 0.28 and 2.49 ± 0.12 μM, respectively. The kinetic study of BACE1 inhibition revealed that compound 1 showed competitive inhibition, whereas 6 showed mixed-type inhibition. Furthermore, molecular docking results showed that the tested inhibitors 1 and 6 exhibited good binding affinities toward BACE1, with binding energies of -8.8 and -10.3 kcal/mol, respectively.