Alpha-glucosidase inhibitors from Nervilia concolor,Tecoma stans,and Bouea macrophylla

Tecoma stans (L.) Juss. Ex Kunth is widely used in folk medicine. In ethnomedicine, it is applied as a cardioprotective, hepatoprotective, antiarthritic, antinociceptive, anti-inflammatory, and antimicrobial. The aqueous extract is considered antidiabetic, and is used as a traditional remedy in Mexico. More than 120 chemical constituents have been identified in its leaves, barks, and roots. However, less is known about the phytochemical properties of T. stans flower extracts. The herbal plant Nervilia concolor (Blume) Schltr. is native to Vietnam, and is used in traditional Chinese medicine to treat diseases such as bronchitis, stomatitis, acute pneumonia, and laryngitis. Only two previous reports have addressed the chemical content of this plant. Bouea macrophylla Griff., commonly known as marian plum or plum mango, is a tropical plant that is used to treat a range of illnesses. Phytochemical analysis of B. macrophylla suggests the presence of volatile components and flavonoids. However, existing data have been obtained from screening without isolation. As part of our ongoing search for alpha-glucosidase inhibitors from Vietnamese medicinal plants, we conducted bioactive-guided isolation of the whole plant N. concolor, the flowers of T. stans, and the leaves of B. macrophylla. We isolated and structurally elucidated five known compounds from T. stans: ursolic acid (TS1), 3-oxours-12-en-28-oic acid (TS2), chrysoeriol (TS3), ferulic acid (TS4), and tecomine (TS5). Three known compounds were isolated from Nervilia concolor: astragalin (NC1), isoquercitrin (NC2), and caffeic acid (NC3). From B. macrophylla, betullinic acid (BM1), methyl gallate (BM2), and 3-O-galloyl gallic acid methyl ester (BM3) were isolated. All compounds showed promising alpha-glucosidase inhibition, with IC₅₀ values ranging from 1.4 to 143.3 µM. The kinetics of enzyme inhibition showed BM3 to be a competitive-type inhibitor. An in silico molecular docking model confirmed that compounds NC1, NC2, and BM3 were potential inhibitors of the α-glucosidase enzyme. Molecular dynamics simulations were carried out with compound BM3 demonstrating the best docking model during simulation up to 100 ns to explore the stability of the complex ligand–protein.     

Phytochemical and chemotaxonomic studies on Pteris wallichiana J. Agardh

A systematic phytochemical investigation of Pteris wallichiana J. Agardh resulted in the isolation of twenty compounds, including five sesquiterpenes (1–5), six flavonoids (6–11), seven phenolic acids (12–18) and two fatty acids (19 and 20). Their structures were deduced from MS, NMR and ORD data. This is the first report of compounds dehydropterosin B (2), (2R,3S)-pterosin C (4), (2R,3R)-pterosin L (5), apigenin (6), luteolin (7), luteolin-7-O-glucoside (10), caffeic acid (13), vanillin (14), 3,4-dihydroxybenzaldehyde (15), chlorogenic acid (17), 3,5-dicaffeoylquinic acid (18), suberic acid (19) and azelaic acid (20) from P. wallichiana and of compounds 15, 19 and 20 from the family Pteridaceae. Furthermore, a chemotaxonomic study of the isolates was performed.     

Phytochemical study on the leaves of Wollemia nobilis

In this work, a phytochemical study performed on the leaves of the rare species, Wollemia nobilis W.G. Jones, K.D. Hill & J.M. Allen, is reported. By means of classical column chromatography and NMR Spectroscopy and Mass Spectrometry, nine compounds were evidenced. These were: pheophorbide a (1), isocupressic acid (2), acetyl-isocupressic acid (3), sandaracopimaric acid (4), agathic acid (5), 7–4′-4‴-tri-O-methyl-agathisflavone (6), 7–4′-7″-4‴-tetra-O-methyl-agathisflavone (7), caffeic acid (8) and shikimic acid (9). Compared to our previous phytochemical analysis on the male cones, some further compounds were identified i.e. compounds 1, 5, 6, 7 and 8. This confirmed the previous chemotaxonomic considerations of the species but also added new ones which were discussed within the text. In addition, a possible different accumulation of secondary metabolites in the tissues and organs of this plant was even noticed.     

Chemical constituents from Eucalyptus citriodora Hook leaves and their glucose transporter 4 translocation activities

Bioassay-guided phytochemical investigation of the EtOAc fraction from the leaves of a Chinese medicinal herb, Eucalyptus citriodora Hook, resulted in the isolation of a new compound rhodomyrtosone E (1), along with 12 known compounds (2–13). The structure of the new compound was established by 1D and 2D NMR, MS data and X-ray crystallographic analysis. Betulinic acid (2) and corosolic acid (5) increased glucose transporter 4 (GLUT-4) translocation by 2.38 and 1.78-fold, respectively.     

Isolation of phenolic constituents and characterization of antioxidant markers from sunflower (Helianthus annuus) seed extract

A new compound, benzyl alcohol β-d-apiofuranosyl-(1→6)-β-d-(4-O-caffeoyl) glucopyranoside (1), was isolated from the seed of sunflower (Helianthus annuus), together with eight known phenolic compounds: caffeic acid (2), methyl caffeoate (3), chlorogenic acid (4), 4-O-caffeoylquinic acid (5), 3-O-caffeoylquinic acid (6), methyl chlorogenate (7), 3,5-di-O-caffeoylquinic acid (8), and eriodictyol 5-O-β-d-glucoside (9). Their structures were elucidated on the basis of spectroscopic methods and chemical evidence. The antioxidative effect of the phenolic constituents from the sunflower seeds was also evaluated based on the oxygen-radical absorbance capacity (ORAC), and the fraction containing caffeic acid derivatives showed a high antioxidant potency.     

Isolation and structural elucidation of two new labdane diterpenoids from the aerial part of Roylea cinerea

Two new labdane diterpenoids, cinereanoid A (1) and cinereanoid B (2), along with five known compounds, calyone (3), pilloin (4), 1-methylindole-3-carboxaldehyde (5), β-sitosterol (6) and stigmasterol (7) were isolated from the aerial parts of Roylea cinerea (Lamiaceae). The new structures were determined by using IR, MS, 1D, 2D NMR spectroscopy. The structure of both new compounds was further confirmed by single crystal X-ray crystallographic analysis. In this study we have also reported single crystal X-ray structure of compound 3 which unambiguously confirmed the relative stereochemistry of tertiary hydroxyl and methyl groups, as it was not established by earlier report. Compounds 4 and 5 were isolated for the first time from this plant. In view of very few reports about this species, this report has increased the phytochemical knowledge about R. cinerea.     

N-Formyllapatin A,a new N-formylspiroquinazoline derivative from the marine-derived fungus Penicillium adametzioides AS-53

N-Formyllapatin A (1), a new spiroquinazoline derivative, and four known quinazoline metabolites, lapatins A (2) and B (3), prelapatin B (4), and glyantrypine (5), along with two known indolediketopiperazine derivatives, fumitremorgin B (6) and verruculogen (7), were characterized from Penicillium adametzioides AS-53, a fungus obtained from the fresh tissue of an unidentified marine sponge. The structure of compound 1 was established by detailed interpretation of NMR and MS data, and its absolute configuration was established by a single-crystal X-ray diffraction analysis. N-Formyllapatin A (1) represents the first N-formylspiroquinazoline secondary metabolite. Compounds 3 and 5–7 showed moderate inhibitory activity against aqua-pathogenic bacterial Vibrio harveyi.     

Secondary metabolites,phytochemical characterization and antioxidant activities of different extracts of Sideritis congesta P.H. Davis et Hub.-Mor.

Sideritis congesta, an endemic plant to Turkey, is extensively consumed as energizing herbal tea and used as a remedy in folk medicine. This study was designed to comparatively evaluate the phytochemical composition and antioxidant potentials of different extracts (methanol, infusion) and fractions (chloroform, ethyl acetate, and remaining water) of S. congesta. Antioxidant potentials of the samples were evaluated by DPPH radical scavenging, FRAP, CUPRAC, and total antioxidant capacity tests. Total phenolic, phenolic acid, and flavonoid contents were also evaluated spectrophotometrically. Moreover, presence of twenty-two phenolic metabolites were affirmed by using LC-MS/MS in MRM scan mode and then the quantification of verbascoside, martynoside, and leucoseptoside A was performed by using HPTLC densitometry. EtOAc fraction contained the highest phenolic content and the antioxidant activity, as well as the highest verbascoside and martynoside contents followed by R-H₂O fraction. Phytochemical studies on R-H₂O fraction, yielded seven compounds, including a phenylethanoid glycoside, verbascoside (1), two flavonoids, stachyspinoside (2), isoscutellarein 7-O-(6‴-O-acetyl)-β-allopyranosyl-(1 → 2)-β-glucopyranoside (3), a phenolic acid chlorogenic acid (4), an iridoid glycoside ajugoside (5), and a monoterpenoid glucoside mixture betulalbuside A (6) and 1-hydroxylinaloyl 6-O-β-D-glucopyranoside (7). The molecular structures of the isolated compounds were determined by NMR and MS experiments. This is the first phytochemical study on the polar constituent of S. congesta and the first report of the isolation of compounds 2, 6 and 7 from the genus Sideritis L.     

Polyphenols and diterpenoids from Plectranthus forsteri ‘Marginatus’

Polyphenols caffeic acid (1), rosmarinic acid (2), nepetoidins A and B (3) and diterpenoids 7β,6β-dihydroxyroyleanone (4) and 7β-acetoxy-6β-hydroxyroyleanone (5) were identified in the methanolic extract of Plectranthus forsteri ‘Marginatus’ Benth. 6,7-dehydroroyleanone (6) was isolated from essential oil. The structure was identified using spectroscopic analysis and comparing it to standards.     

Diterpenoids from the needles and twigs of the cultivated endangered pine Pinus kwangtungensis and their PTP1B inhibitory effects

Pinus kwangtungensis is an endangered pine species native to China. In the present study, 15 diterpenoids including three new labdane-type analogs were isolated and characterized during a pioneer phytochemical investigation on a mass-limited sample of the needles and twigs of this plant, which is growing in a Cantonese garden. The new structures, (4S,5R,9S,10R)-6-oxo-labd-7,13-dien-16,15- olid-19-oic acid (1), 15(S)-n-butoxypinusolidic acid (2), and β-d-glucopyranosyl- (4S,5R,9S,10R)-labda-8(17),13-dien-15,16-olid-19-oate (3), were established by extensive spectroscopic methods and some chemical transformations. Among the isolates, lambertianic acid (10) and cassipourol (15) showed inhibitory activities against human protein tyrosine phosphatase 1 B (PTP1B), a target for the treatment of type-II diabetes and obesity, with IC₅₀ values of 25.5 and 11.2 μM, respectively.     

Chemical constituents from Silene schimperiana Boiss. belonging to caryophyllaceae and their chemotaxonomic significance

Phytochemical investigation of Silene schimperiana Boiss. ethanolic extract led to the isolation of fifteen compounds (1–15). The isolated compounds were identified by their NMR, MS spectral data analyses and comparing with published data as: vanillic acid (1), ferulic acid (2), caffeic acid (3), ethyl ferulate (4), apigenin (5), hesperetin (6), diosmetin (7), luteolin (8), kaempferol (9), quercetin (10), ecdysterone (11), hesperedin (12), diosmin (13), kaempferol-3-O-rutinoside (14) and rutin (15). The lack of chemical and biological investigations on this plant encouraged us to carry out the above-mentioned work.     

Chemotaxonomic implications of the absence of sesquiterpene lactones in Grazielia multifida (DC.) R.M.King & H.Rob. (Asteraceae)

The phytochemical investigation of Grazielia multifida aerial parts yielded eight compounds, including four ent-kaurenic acid diterpenes derivatives, 15-tiglinoyloxy-ent-kaur-16-en-19-oic acid (1), 15-hydroxy-ent-kaur-16-en-19-oic acid (2), 17-hydroxy-ent-kaur-15-en-19-oic acid (3) and 15-isovaleroyloxy-ent-kaur-16-en-19-oic acid (4), one amino acid, tryptophan (5), and three flavonoids, eupafolin (6), guaijaverin (7) and quercitrin (8). The structures of the isolated compounds were established based on analysis of their spectroscopic data and comparison with literature. All the compounds were isolated from this species for the first time. The chemotaxonomic significance of the absence of sesquiterpene lactones in G. multifida has also been summarized.     

A new cycloartane-type triterpene and a new eicosanoic acid ester from fruits of Paullinia pinnata L.

A phytochemical study of the MeOH-soluble portion from the CH₂Cl₂/MeOH extract of the fruits of Paullinia pinnata resulted in the isolation of a new triterpenoid, cyclopinnatol (1), and a new eicosanoic acid ester, paulliniester (2), together with five known compounds including cycloart-22(E)-ene-3β,25-diol (3), cycloartenol (4), β-sitosterol (5), betulonic acid (6) and oleanonic acid (7). The structures of the new compounds were elucidated by spectroscopic analyses (NMR and MS) and comparisons with published data. Cyclopinnatol (1) and the MeOH-soluble portion exhibited significant and weak antibacterial activities against Staphylococcus aureus, with MICs of 32 and 50 μg/mL, respectively.     

Isopimarane diterpenes and flavan derivatives from the twigs of Caesalpinia furfuracea

The first phytochemical investigation of Caesalpinia furfuracea twigs led to the isolation and identification of four new compounds including two isopimarane diterpenes, caesalfurfuric acids A (1) and B (2), and two flavans, (2R)-caesalflavans A (5) and B (6), together with four known compounds, 4-epi-isopimaric acid (3), methyl (E)-3-(3,4-dihydroxyphenyl)acrylate (4), (E)-resveratrol (7) and oxyresveratrol (8). Their structures were elucidated by intensive spectroscopic analysis. Compound 1 was found to exhibit antibacterial activity against MRSA SK1 with an MIC value of 16 μg/mL.     

Chemical constituents from the buds of Lonicera macranthoides in Sichuan,China

The phytochemical investigation of the dried buds of L. macranthoides Hand. -Mazz. Symb. Sin. collected in Sichuan, China resulted in the isolation of three aliphatic glycosides (1–3), a caffeoyl glucoside (4), a secoiridoid glycoside (5), and two caffeoylquinic acid analogs (6 and 7). Among them, compound 1 was novel and identified as n-butyl-β-d-apiofuranosyl-(1→6)-β-d-glucopyranoside based on the detailed spectroscopic analyses and chemical studies. Compounds 1–4 were isolated for the first time from Caprifoliaceae family; compounds 5–7 were isolated for the first time from L. macranthoides. The chemotaxonomic significance of these compounds was summarized.     

Chemical constituents from Stauntonia brachyanthera Hand–Mazz

The present phytochemical investigations of Stauntonia brachyanthera Hand–Mazz resulted in the isolation of a triterpenoid glucoside (3-O-α-l-arabinopyranosyl-Akebonic acid, 1), four phenylpropanoids (staunoside C, cyclo-olivil-9-O-β-d-glucopyranoside, ficuscarpanoside B, ficuscarpanoside A, 2–5), three phenylethanoid glycosides (2-(3,4-dihydroxyphenyl)ethyl-β-d-glucopyranoside, 1′-O-phenethyl-α-l-rhamnopyranosyl-(1 → 6)-β-d-glucopyranoside, calceolarioside B, 6–8), a phenolic glycoside (seguinoside K, 9) and a chlorogenic acid analogue (methyl chlorogenate, 10). Among them, compounds 1, 2 are isolated for the first time from this plant, compound 8 is firstly reported from genus Stauntonia and compounds 4–7, 9 and 10 are new for the family of Lardizabalacea. The chemotaxonomic importance of these compounds was also summarized.     

Chemical constituents from Striga asiatica and its chemotaxonomic study

Six flavonoids, diosmetin (1), apigenin (2), luteolin (3), chrysoeriol (4), apigenin-7-O-glucuronide (5) and acacetin (6), two caffeic acid sugar esters, verbascoside (7) and isoverbascoside (8), as well as one norsesquiterpene, blumenol A (9) were isolated or detected from the EtOAc and n-BuOH extract of the whole plants of Striga asiatica. Their structures were identified by ¹H & ¹³C NMR, HR-LC-TOF-MS and co-injection with the reference standards. Among them, blumenol A (9) was firstly found from the Scrophulariaceae. Diosmetin (1) and isoverbascoside (8) were firstly reported from the genus Striga, while verbascoside (7) was reported from this plant for the first time. Based on our chemotaxonomic studies and the previous phytochemical studies on Scrophulariaceae, Striga could be tentatively treated as a member of the family Scrophulariaceae instead of Orobanchaceae.     

Chemical constituents from Sophora tonkinensis and their glucose transporter 4 translocation activities

Bioassay-guided phytochemical investigation of the EtOAc fraction (ST-EtOAc) from the roots of Sophora tonkinensis resulted in the isolation of a new compound 6aR,11aR-1-hydroxy-4-isoprenyl-maackiain (1), along with 12 known compounds (2–13). The structure of the new compound was established by 1D and 2D NMR, MS data and circular dichroism analysis. Polyprenylated flavonoids 6–9 and 11–13 increased GLUT-4 translocation by the range of 1.35–2.75 folds. Sophoranone (8) exerted the strongest activity with 2.75 folds GLUT-4 translocation enhancement at the concentration of 10 μM. This is the first report of the GLUT-4 translocation activity of the plant Sophora tonkinensis.     

Chemical constituents from the leaves and branches of Annona coriacea Mart. (Annonaceae)

The phytochemical investigation of the leaves and branches of Annona coriacea Mart. (Annonaceae) led to the isolation and characterization of eight compounds: five isoquinoline-derived alkaloids, including pukateine (1), liriodenine (4), anonaine (5), obovanine (6), and norisocorydine (7); one terpene lactone known as loliolide (3); one benzoic acid derivative, 2-methoxybenzoic acid (2), and 3,4,5-trimethoxyphenol (8). All compounds, except liriodenine, are being described for the first time in the species A. coriacea, and their chemophenetics relationships were discussed. The structures were elucidated by extensive analyses of 1D and 2D NMR (COSY, HSQC, and HMBC) spectroscopy in combination with MS, and the data were compared with literature values. The NMR dataset of pukateine and obovanine was reviewed. Our results showed that A. coriacea is a typical species of the Annonaceae family and an important source of aporphine alkaloids with chemophenetic relationships with Xylopia, Duguetia, Guatteria, Artabotrys, and Goniothalamus genera.     

Bioactivity-guided isolation of anti-inflammatory triterpenoids from the sclerotia of Poria cocos using LPS-stimulated Raw264.7 cells

Poria cocos Wolf (Polyporaceae) has been used as a medicinal fungus to treat various diseases since ancient times. This study aimed to investigate the anti-inflammatory chemical constituents of the sclerotia of P. cocos. Based on bioassay-guided fractionation using lipopolysaccharide (LPS)-stimulated Raw264.7 cells, chemical investigation of the EtOH extract of the sclerotia of P. cocos resulted in the isolation and identification of eight compounds including six triterpenoids, namely poricoic acid A (1), 3-O-acetyl-16α-hydroxydehydrotrametenolic acid (2), polyporenic acid C (3), 3β-hydroxylanosta-7,9(11),24-trien-21-oic acid (4), trametenolic acid (5), and dehydroeburicoic acid (6), as well as (−)-pinoresinol (7) and protocatechualdehyde (8). The structures of the isolated compounds were determined by spectroscopic analysis, including ¹H and ¹³C NMR spectra, and LC/MS analysis. The anti-inflammatory activities of the isolates were evaluated by estimating their effect on the production of nitric oxide (NO) and prostaglandin E₂ (PGE₂) in LPS-stimulated Raw264.7 as well as on the expression of inducible nitric oxide synthase (iNOS) and cyclooxygenase-2 (COX-2). Compounds 1–5 inhibited NO production and iNOS expression in LPS-stimulated Raw264.7 cells. Among them, compound 1 exerted the highest anti-inhibitory activity and reduced PGE₂ levels via downregulation of COX-2 protein expression. The findings of this study provide experimental evidence that the sclerotia of P. cocos are a potential source of natural anti-inflammatory agents for use in pharmaceuticals and functional foods. Furthermore, the most active compound 1, seco-lanostane triterpenoid, could be a promising lead compound for the development of novel anti-inflammatory agents.