Mushroom tyrosinase inhibitors from Aloe barbadensis Miller

Two new chromones, 5-((S)-2′-oxo-4′-hydroxypentyl)-2-(β-glucopyranosyl-oxy-methyl)chromone (1) and 5-((S)-2′-oxo-4′-hydroxypentyl)-2-methoxychromone (2), together with four known analogues, 8-C-glucosyl-7-O-methyl-(S)-aloesol (3), isoaloeresin D (4), 8-C-glucosyl-(R)-aloesol (5), and aloesin (6) were isolated from the aqueous extract of Aloe barbadensis Miller. Their structures were determined on the basis of spectroscopic evidences (1-D and 2-D NMR, HRMS, UV, and IR data), chemical methods and the literature data. The Mosher's method was applied to establish the absolute configuration of compounds 1 and 2. The inhibitory effects of these chromones on the activity of mushroom tyrosinase were examined, and compound 6 was identified as a noncompetitive tyrosinase inhibitor with an IC₅₀ value of 108.62 μg·mL^− 1.     

Antifungal compounds from turmeric and nutmeg with activity against plant pathogens

The antifungal activity of twenty-two common spices was evaluated against plant pathogens using direct-bioautography coupled Colletotrichum bioassays. Turmeric, nutmeg, ginger, clove, oregano, cinnamon, anise, fennel, basil, black cumin, and black pepper showed antifungal activity against the plant pathogens Colletotrichum acutatum, Colletotrichum fragariae, and Colletotrichum gloeosporioides. Among the active extracts, turmeric and nutmeg were the most active and were chosen for further investigation. The bioassay-guided fractionation led to the isolation of three compounds from turmeric (1–3) and three compounds from nutmeg (4–6). Their chemical structures were elucidated by spectroscopic analysis including HR-MS, 1D, and 2D NMR as curcumin (1), demethoxycurcumin (2) and bisdemethoxy-curcumin (3), erythro-(7R,8R)-Δ^8′-4,7-dihydroxy-3,3′,5′-trimethoxy-8-O-4′-neolignan (4), erythro-(7R,8R)-Δ8′-7-acetoxy-3,4,3′,5′-tetra-methoxy-8-O-4′-neolignan (5), and 5-hydroxy-eugenol (6). The isolated compounds were subsequently evaluated using a 96-well microbioassay against plant pathogens. At 30 μM, compounds 2 and 3 possessed the most antifungal activity against Phomopsis obscurans and Phomopsis viticola, respectively.     

Flavonoids and stilbenoids from Derris eriocarpa

One new resveratrol analogue, 1-(3′,4′,5′-trimethoxyphenyl)-2-methoxy-2-(4″-methoxyphenyl)-ethane-1-ol (1), and two new prenylisoflavones, 4′-hydroxy-5,7-dimethoxy-6-(3-methyl-2-butenyl)-isoflavone (2), and derrubon 5-methyl ether (3), together with 17 known compounds including one new natural product, 5,7-dihydroxy-3-[4′-O-(3-methyl-2-butenyl)-phenyl]-isoflavone (4), were isolated from the stems of ethnomedicinal plant Derris eriocarpa How. (Leguminosae). Their structures were elucidated based on chemical evidence and spectroscopic techniques including two-dimensional NMR methods. All compounds are reported from this species for the first time. Antimicrobial activities of the new compounds were evaluated. Compound 2 exhibited good inhibitory activities against Candida guilliermondii, C. albicans and Microsporium gypseum with the minimal inhibitory concentration (MIC) values of 12.5 μg/ml.     

Three new phenolic compounds from the roots of Glycyrrhiza yunnanensis

Three new phenolic compounds (1–3), together with 16 known compounds (4–19), were isolated from the roots of Glycyrrhiza yunnanensis Cheng f. et L. K. Dai. On the basis of 1D and 2D NMR, HR-ESI-MS, and circular dichroism (CD) spectroscopic analysis, structures of the new compounds were elucidated as 2-(2′-methoxy-4′-hydroxy)-aryl-3-methy-6-hydroxy-benzofuran (1), (2S)-6,7-(2,2-dimethyldihydropyrano)-8-prenyl-4′-hydroxyflavanone (2), and 6-prenyl-7,3′,4′-trihydroxyflavone (3). Compounds 1, 3, 5, 12, 14, 15 and 16 showed antioxidant activity by an ABTS-based assay.     

Rigenolide A,a new secoiridoid glucoside with a cyclobutane skeleton,and three new acylated secoiridoid glucosides from Gentiana rigescens Franch

Rigenolide A (1), a new secoiridoid glucoside with a cyclobutane skeleton and three new acylated secoiridoid glucosides, 2′-(2,3-dihydroxybenzoyl)-gentiopicroside (2), 2′-(2,3-dihydroxybenzoyl)-swertiamarin (3), 3′-(2,3-dihydroxybenzoyl)-sweroside (4), along with two noriridoids (7 and 8) and two known secoiridoid glucosides (5 and 6), were isolated from Gentiana rigescens Franch. The structures of new compounds were elucidated by extensive spectroscopic analyses. The isolated compounds were evaluated for DPPH free-radical scavenging activity.     

Natural phosphodiesterase-4 (PDE4) inhibitors from Crotalaria ferruginea

Bioassay-guided fractionation of the ethanol extract of the Chinese folk medicine Crotalaria ferruginea led to the isolation of a new isoflavonoid, 4′-hydroxy-2′-methylalpinum-isoflavone (1), and eight known analogs (2–9). Their structures were elucidated by spectroscopic analysis. Compounds 1, 2, 5, and 8 showed inhibitory activities against phosphodiesterase-4 (PDE4), a therapeutic target of asthma, with IC₅₀ values ranging from 2.57 to 8.94 μM. The possible action mechanism and the structure–activity relationship (SAR) of the active isoflavonoids were explored by using molecular docking and molecular dynamics (MD) simulation methods. Our study herein may explain the anti-inflammatory function of this plant in Chinese folk medicine.     

Flavone glycosides from Mentha longifolia

In addition to isoorientin, vicenin-2, hypolaetin, lucenin-1, luteolin 7-O-glucoside and 7-O-neohesperidoside, the aerial parts of Mentha longifolia yielded three new flavonoids, identified as tricetin 7-O-methylether 3′-O glucoside 5′-O-rhamnoside (1), tricetin 3′-O glucoside 5′-O-rhamnoside (2) and tricetin 3′-O-rhamnosyl-(1→4)-rhamnoside (3).     

Acyl quinic acid derivatives from the stems of Erycibe obtusifolia

Eleven new acyl quinic acid derivatives, 4-O-caffeoyl-3-O-syringoylquinic acid methyl ester (1), 4-O-caffeoyl-3-O-vanilloylquinic acid (2), 4-O-caffeoyl-3-O-vanilloylquinic acid methyl ester (3), 5-O-caffeoyl-3-O-vanilloylquinic acid (4), 5-O-caffeoyl-3-O-vanilloylquinic acid methyl ester (5), 5-O-caffeoyl-3-O-sinapoylquinic acid (6), 5-O-caffeoyl-4-O-vanilloylquinic acid (7), 4-O-(7‴S, 8‴R)-glycosmisoyl-5-O-caffeoylquinic acid methyl ester (8), 4-O-(7‴S, 8‴R)-glycosmisoyl-5-O-caffeoylquinic acid (9), 3-O-(7‴S, 8‴R)-glycosmisoyl-4-O-caffeoylquinic acid (10), and 3-O-(7‴S, 8‴R)-glycosmisoyl-4-O-caffeoylquinic acid methyl ester (11), have been isolated from the stems of Erycibe obtusifolia together with eight known compounds (12–19). Their structures were elucidated on the basis of spectroscopic data analysis (UV, IR, HRESIMS, CD, and 1D and 2D NMR) and chemical evidence. In in vitro assay, compounds 7 and 16–18 exhibited significant neuroprotective effects against rotenone induced PC12 cell damage at 10 μM.     

Coumarinoids from the fruits of Micromelum falcatum

Four new compounds, microminutin B (1), microminutin C (2), micromarinate (3), and secomicromelin (4) as well as 17 known compounds were isolated from the fruits of Micromelum falcatum. All compounds were evaluated for antifungal activity against Pythium insidiosum using disc diffusion assay. P. insidiosum is a fungus-like microorganism for which antifungal agents now available are not effective. The results show that four compounds including secomicromelin (4), 7-methoxy-8-(4′-methyl-3′-furanyl)coumarin (10), micromarin B (17), and isomicromelin (19) could inhibit the mycelia growth of P. insidiosum.     

New terpenoid glycosides obtained from Rosmarinus officinalis L. aerial parts

Five new terpenoid glycosides, named as officinoterpenosides A₁ (1), A₂ (2), B (3), C (4), and D (5), together with 11 known ones, (1S,4S,5S)-5-exo-hydrocamphor 5-O-β-d-glucopyranoside (6), isorosmanol (7), rosmanol (8), 7-methoxyrosmanol (9), epirosmanol (10), ursolic acid (11), micromeric acid (12), oleanolic acid (13), niga-ichigoside F₁ (14), glucosyl tormentate (15), and asteryunnanoside B (16), were obtained from the aerial parts of Rosmarinus officinalis L. Their structures were elucidated by chemical and spectroscopic methods (UV, IR, HRESI-TOF-MS, 1D and 2D NMR). Among the new ones, 1 and 2, 3 and 4 are diterpenoid and triterpenoid glycosides, respectively; and 5 is a normonoterpenoid. For the known ones, 6 was isolated from the Rosmarinus genus first, and 15, 16 were obtained from this species for the first time.     

New icetexane diterpenes with intestinal α-glucosidase inhibitory and free-radical scavenging activity isolated from Premna tomentosa roots

New icetexane diterpenes (1-2); 8, 11, 13-icetexatriene-10-hydroxy, 11, 12, 16-tri acetoxyl (1) and 8, 11, 13-icetexatriene-7, 10, 11-dihydroxy-12, 13-dihydrofuran (2) along with six known compounds namely acetoxy syranzaldehyde (3), syranzaldehyde (4), coniferaldehyde (5), lupeol (6), betulin (7), and 4-(4-methoxy phenyl)-2-butanone (8) were isolated from the roots of Premna tomentosa. The structures of compounds 1 and 2 were established by detailed spectral analysis using UV, IR, ¹H NMR, ¹³C NMR, 1D, 2D and Mass. The newly isolated compounds were screened for rat intestinal α-glucosidase inhibitory and free radical (DPPH) scavenging potentiality. The new icetexane diterpenes (1, 2) and compound 3 were found to have significant α-glucosidase inhibitory and also free radical scavenging (DPPH) activities.     

Isolation of new flavan-3-ol and lignan glucoside from Loropetalum chinense and their antimicrobial activities

Phytochemical and antimicrobial activity study on the ethanol extract of the leaves and stems of Loropetalum chinense led to the isolation of a new flavan-3-ol compounds, 8-[1-(3,4-dihydroxyphenyl)-3-methoxy-3-oxopropyl]-catechin (loropetaliside A) (1) and a new lignan glucoside, 1-(5-hydroxy-3-methoxyphenyl)-2-(2-β-glucopyranosyl-4-hydroxy-5-(1-(E)propen-3-ol)-phenyl)-propane-3-ol (loropetaliside B) (3) and several known compounds manglieside D (2), quercetin (4), kaempferol-3-O-D-glucopyranoside (5), quercetin-3-O-β-L-rhamnoside (6) and tiliroside (7). Their structures were elucidated on the basis of extensive spectroscopic analysis.     

Chaetoglobosin Y,a new cytochalasan from Chaetomium globosum

Chaetoglobosin Y (1), was isolated from the endolichenic fungal strain Chaetomium globosum (No. 64-5-8-2), along with related six known cytochalasans, chaetoglobosin Fex (2), chaetoglobosin E (3), isochaetoglobosin D (4), chaetoglobosin G (5), cytoglobosin B (6), and cytoglobosin C (7). Their structures were determined by detailed spectroscopic analyses and comparison with those of the closely related compounds previously reported. The cytotoxicity to HCT-116 cell line of 2–7 was evaluated in vitro with doxorubicin as positive control.     

A new acetophenone derivative from flowers of Helichrysum italicum (Roth) Don ssp. italicum

A new acetophenone derivative named gnaphaliol 9-O-propanoate (1) was isolated from the chloroform fraction of EtOH extract of Helichrysum italicum ssp. italicum flowers along with the five known acetophenones 12-acetoxytremetone (2), 13-(2-methylpropanoyloxy)toxol (3), [2,3-dihydro-2-[1-(hydroxymethyl)ethenyl]-5-benzofuranyl]-ethanone (4), 1-[2-[1-[(acetyloxy)methyl]ethenyl]-2,3-dihydro-3-hydroxy-5-benzofuranyl]-ethanone (5) and gnaphaliol (6). The structures of compounds 1–6 were elucidated by extensive spectroscopic methods including 1D- (¹H and ¹³C) and 2D-NMR (DQF-COSY, HSQC, HMBC, TOCSY and ROESY) experiments as well as ESIMS analysis. The isolated compounds were investigated for their cytotoxicity, anti-inflammatory and antioxidant properties. Biological assays on human colonic epithelial cells showed that compound 2 possessed antioxidant effects reducing reactive oxygen species (ROS) production.     

Caffeoylquinic acid derivatives isolated from the aerial parts of Gynura divaricata and their yeast α-glucosidase and PTP1B inhibitory activity

The phytochemical investigation of natural products of Gynura divaricata led to the isolation of eleven caffeoylquinic acid derivatives. They were characterized by spectrometric methods as 5-O-caffeoylquinic acid (1), 5-O-p-coumaroylquinic acid (2), 5-O-feruloylquinic acid (3), methyl 5-O-caffeoylquinate (4), 3,4-dicaffeoylquinic acid (5), 3,5-dicaffeoylquinic acid (6), 4,5-dicaffeoylquinic acid (7), methyl 3,4-dicaffeoylquinate (8), methyl 3,5-dicaffeoylquinate (9), methyl 4,5-dicaffeoylquinate (10) and ethyl 4,5-dicaffeoylquinate (11). The individual compounds were screened for the inhibition of yeast α-glucosidase and Protein Tyrosine Phosphatase 1B (PTP1B) using in vitro assays. Among the isolated compounds, 3,4-dicaffeoylquinic acid (5), 4,5-dicaffeoylquinic acid (7), methyl 3,4-dicaffeoylquinate (8) and methyl 4,5-dicaffeoylquinate (10) exhibited significant inhibitory activities against α-glucosidase. In addition, 5-O-p-coumaroylquinic acid (2), 3,5-dicaffeoylquinic acid (6) and 4,5-dicaffeoylquinic acid (7) had considerable inhibitory effect against PTP1B. Based on these findings, the caffeoylquinic acid derivatives were deduced to be potentially responsible for the anti-diabetic activity of G. divaricata. The preliminary structure–activity relationship study suggests that the number and positioning of caffeoyl groups in the quinic acid derivatives are important for both α-glucosidase and PTP1B inhibitory potency. Moreover, the corresponding methyl esters of some dicaffeoylquinic acids have enhanced inhibitory activity against yeast α-glucosidase.     

Seven new cassane furanoditerpenes from the seeds of Caesalpinia minax

A bioassay-guided study led to the isolation of seven new cassane furanoditerpenes, designated as spirocaesalmin B (1), caesalpinin M₁ (2), caesalpinin M₂ (3), caesalmin E₁ (4), caesalmin E₂ (5), caesalmin E₃ (6), caesalpinin F₁ (7) and three known compounds neocaesalpin A(8), neocaesalpin L(9), neocaesalpin L₁(10) from the seeds of Caesalpinia minax Hance. Compound structures were determined on the basis of extensive spectroscopic analyses, including X-ray crystallographic analysis, HRESI-MS, UV, IR, 1D and 2D NMR (HSQC, HMBC, NOESY) methods. Some absolute configurations were confirmed via the circular dichroism (CD) spectra. Compound 1 is the first example of an A-seco-rearranged cassane furanoditerpene with an unusual skeleton isolated from the genus Caesalpinia. All compound inhibitory effects on influenza virus neuraminidase (NA) in vitro were valued for the first time. Compared with the positive control (Zanamivir), new compounds were found to show moderate inhibitory activity.     

Triglyceride accumulation inhibitory effects of phenylpropanoid glycosides from Boschniakia rossica Fedtsch et Flerov

Bioassay-guided fractionation led to isolation of five new phenylpropanol glycosides, rossicasides G (1), H (2), I (3), J (4), and K (5), together with seven known compounds (6–12) from Boschniakia rossica. Their structures were elucidated by chemical and spectroscopic methods (UV, IR, HRESI-TOF-MS, 1D and 2D NMR). Activity screening results showed that some isolates had TG accumulation inhibitory effects in HepG2 cells. Furthermore, the structure–activity relationship was partly clarified.     

Four new diterpenoids from the roots of Euphorbia fischeriana

Four new diterpenoids (1,4,5,9), together with 7 known diterpenoids (2,3,6–8,10,11), were isolated from the roots to Euphorbia fischeriana. On the basis of 1D and 2D NMR, HR-ESI-MS spectroscopic analysis, structures of the new compounds were elucidated as 11β-hydroxy-8,14-epoxy-ent-abieta-13(15)-en-16,12-olide (1), 3,20-dihydroxy-ent-1(10), 15-rosadiene (4), 3,7-dihydroxy-ent-1(10), 15-rosadiene (5), ingenol 6,7-epoxy-3- tetradecanoate (9). The compounds isolated were evaluated for their cytotoxicity against four cancer cell lines (A549, BEL7402, HCT116, and MDA-MB-231). Three ingenol diterpenoids (9–11) showed significant cytotoxicity against A549 with IC₅₀ value of 3.35, 2.85, 2.88 μg/mL, respectively.     

New secoiridoids from the fruits of Ligustrum lucidum Ait with triglyceride accumulation inhibitory effects

Five new secoiridoids, nuzhenal C (1), 6'-O-trans-cinnamoyl iso-8-epikingisidic acid (2), ligulucidumosides A (3), B (4), and C (5), were obtained from the fruits of Ligustrum lucidum Ait. Their structures were elucidated by chemical and spectroscopic methods (UV, IR, HRESI-TOF-MS, 1D and 2D NMR). Among them, compound 3 is the first 1-OCH₃ substituent secoiridoid obtained from plant kingdom. Furthermore, activity screening results showed that all of the isolates had triglyceride accumulation inhibitory effects in HepG2 cells.     

Triterpenoids and α-glucosidase inhibitory constituents from Salacia hainanensis

Thirteen triterpenoids (1–13), including two new lupane triterpenoids, salacinins A and B (1 and 2), as well as one new friedelane triterpenoid, salacinin C (3), were isolated from the roots and stems of Salacia hainanensis. The structures of new compounds were elucidated by extensive spectroscopic analysis including 1D and 2D NMR, and MS experiments. Compound 1 possesses rare 2,3-seco-lupane skeleton. Compounds 4, 6 and 7 showed inhibitory effects on α-glucosidase in vitro.