New clerodane diterpenoids from Callicarpa pseudorubella and their antitumor proliferative activity.

Six previously undescribed clerodane diterpenes, cardorubellas A-F (1-6), along with seven known ones (7-13), were isolated from the aerial parts of Callicarpa pseudorubella. Their chemical structures were established by analysis of 1D and 2D NMR, HR-ESI-MS, X-ray diffraction, and electronic circular dichroism (ECD) data. Notably, cardorubella B (2) represented the first examples of naturally occurring succinic anhydride-containing clerodane diterpenes derivatives. The anti-proliferative activities of these compounds were assessed. Remarkably, compound 2 exhibited comparable inhibitory activity against HEL cell lines, surpassing the positive control with an IC50 value of 14.01 ± 0.77 µM, compared to 17.02 ± 4.70 µM for 5-fluorouracil.

Lignans from the leaves of Styrax japonicus and their anti-inflammatory activity.

Five novel lignans, namely styraxjaponica A-E (1-5), together with eight known compounds (6-13) were isolated from the leaves of Styrax japonicus Siebold & Zucc. Their chemical structures were characterized by extensive analysis of 1D and 2D NMR, UV, IR, HRESIMS spectroscopic analysis as well as by comparison to the literature. The absolute configurations of the new compounds were further determined by quantum chemical electronic circular dichroism (ECD) calculations powered by time-dependent density functional theory (TDDFT). Moreover, the anti-inflammatory effects of compounds 1-5 in lipopolysaccharide (LPS)-induced RAW 264.7 cells were also evaluated by measuring nitric oxide (NO) concentrations. All compounds displayed significant anti-inflammatory activity without affecting cell viability in vitro.

A New Carvotacetone Derivative from the Aerial Part of Sphaeranthus africanus.

Sphaeranthus africanus L. is native in Vietnam. Little is known about α-glucosidase inhibition of Sphaeranthus africanus and its isolated compounds. A bioactive-guided isolation was applied to the Vietnamese Sphaeranthus africanus to find α-glucosidase inhibitory components. Eight compounds were detected and structurally elucidated. They are 3-angeloyloxy-5-[2'',3''-epoxy-2''-methylbutanoyloxy]-7-hydroxycarvotacetone, 3-angeloyloxy-5-[3''-chloro-2''-hydroxy-2''-methylbutanoyloxy]-7-hydroxycarvotacetone, 3-angeloyloxy-5-[2''R,3''R-dihydroxy-2''-methyl-butanoyloxy]-7-hydroxycarvotacetone, 3-angeloyloxy-5-[2''S,3''R-dihydroxy-2''-methylbutanoyloxy]-7-hydroxycarvotacetone, 3-angeloyloxy-5-[2''S,3''S-dihydroxy-2''-methylbutanoyloxy]-7-hydroxycarvotacetone, 5-angeloyloxy-7-hydroxy-3-tigloyloxycarvotacetone, 3-O-methylquercetin, and chrysosplenol D. Their chemical structures were elucidated by extensive 1D and 2D NMR analysis and high-resolution mass spectroscopy as well as comparisons in literature. 3-Angeloyloxy-5-[2''S,3''S-dihydroxy-2''-methylbutanoyloxy]-7-hydroxycarvotacetone is a new compound. Isolated compounds were evaluated for the α-glucosidase inhibition. Isolated compounds showed moderate activity with IC50 values ranging from 128.9-274.3 µM while others are weak. A molecular docking study was conducted, indicating that isolated compounds are potent α-glucosidase inhibitory compounds.

Structural analysis of previously unknown natural products using computational methods.

Natural products exhibit structural diversity, and biologically active natural products with unprecedented molecular skeletons can potentially be isolated from natural resources in the future. Although it has often been difficult to determine the structures and configurations of new compounds that do not resemble known compounds, the determination of the chemical structures, including the absolute stereo configuration, is very important in drug discovery research. In our efforts to find new bioactive natural products, we have identified novel compounds such as the ubiquitin-proteasome system inhibitors and osteoclast differentiation inhibitors. Various natural products, mixtures of stereoisomers of natural products, and compounds with novel skeletal structures were studied. In cases where it was difficult to determine the structures by NMR spectroscopy, we could successfully determine the chemical structures by computational chemistry. This review presents the results of structural analysis obtained using computational methods for several natural products that we have recently isolated.

Novel flavonolignans from the roots of Indigofera stachyodes.

Two pairs of new enantiomeric flavonolignans, ±stachyols A and B (±1 and ± 2), along with two novel isoflavanelignans, stachyols C and D (3 and 4) were isolated from the roots of Indigofera stachyodes. Their chemical structures and absolute configurations were determined using nuclear magnetic resonance and comparison of experimental and theoretical electronic circular dichroism (ECD) spectra, as well as quantum chemical calculations. Of those compounds, 1 and 2 represented the first examples of flavonolignans with 5-deoxyflavonoids adduct phenylpropanoids. Moreover, 3 and 4 possess an unprecedented skeleton with isoflavanes adduct phenylpropanoids. The antioxidant activity was evaluated for all compounds in terms of ABTS+ and DPPH bioassays. Compounds 3 and 4 exhibited significant radical-scavenging activity in the ABTS+ assay, with IC50 values of 15.15 and 5.83 µM, respectively.

Secondary Metabolites from the Fresh Leaves of Pinus yunnanensis Franch.

Fifteen metabolites, including two flavonols (1-2), three lignans (3-5), and ten diterpenoids (6-15), were isolated from the leaves of Pinus yunnanensis. Among them, flavanonol (1) were identified as undescribed flavonol derivative with natural rarely B-ring fission lactone. Massive spectroscopic methods, the DP4+ probabilities and CD/ECD calculations were applied to establish the structure of component 1. Among these compounds, taxifolin (2) showed potent cytotoxicity, having IC50 values from 21.33 to 45.48 µg/mL, it also showed broad antibacterial activity against human pathogens with MIC values from 32 to 64 µg/mL.

From Vietnamese plants to a biflavonoid that relieves inflammation by triggering the lipid mediator class switch to resolution.

Chronic inflammation results from excessive pro-inflammatory signaling and the failure to resolve the inflammatory reaction. Lipid mediators orchestrate both the initiation and resolution of inflammation. Switching from pro-inflammatory to pro-resolving lipid mediator biosynthesis is considered as efficient strategy to relieve chronic inflammation, though drug candidates exhibiting such features are unknown. Starting from a library of Vietnamese medical plant extracts, we identified isomers of the biflavanoid 8-methylsocotrin-4'-ol from Dracaena cambodiana, which limit inflammation by targeting 5-lipoxygenase and switching the lipid mediator profile from leukotrienes to specialized pro-resolving mediators (SPM). Elucidation of the absolute configurations of 8-methylsocotrin-4'-ol revealed the 2S,γS-isomer being most active, and molecular docking studies suggest that the compound binds to an allosteric site between the 5-lipoxygenase subdomains. We identified additional subordinate targets within lipid mediator biosynthesis, including microsomal prostaglandin E2 synthase-1. Leukotriene production is efficiently suppressed in activated human neutrophils, macrophages, and blood, while the induction of SPM biosynthesis is restricted to M2 macrophages. The shift from leukotrienes to SPM was also evident in mouse peritonitis in vivo and accompanied by a substantial decrease in immune cell infiltration. In summary, we disclose a promising drug candidate that combines potent 5-lipoxygenase inhibition with the favorable reprogramming of lipid mediator profiles.

Phytochemical Analysis of the Fruits of Sea Buckthorn (Hippophae rhamnoides): Identification of Organic Acid Derivatives.

Hippophae rhamnoides L. (Elaeagnaceae), commonly known as "Sea buckthorn" and "Vitamin tree", is a spiny deciduous shrub whose fruit is known for its nutritional composition, such as vitamin C, and is consumed as a dietary supplement worldwide. As part of our ongoing efforts to identify structurally new and bioactive constituents from natural resources, the phytochemical investigation of the extract of H. rhamnoides fruits led to the isolation of one malate derivative (1), five citrate derivatives (2-6), and one quinate derivative (7). The structures of the isolated compounds were elucidated by analysis of 1D and 2D nuclear magnetic resonance (NMR) spectroscopic data and high-resolution electrospray ionization (HR-ESI) liquid chromatography-mass spectrometry (LC/MS) data. Three of the citrate derivatives were identified as new compounds: (S)-1-butyl-5-methyl citrate (3), (S)-1-butyl-1'-methyl citrate (4), and (S)-1-methyl-1'-butyl citrate (6), which turned out to be isolation artifacts. The absolute configurations of the new compounds were established by quantum chemical electronic circular dichroism (ECD) calculation, which is an informative tool for verifying the absolute configuration of organic acid derivatives. The isolated compounds 1-7 were evaluated for their stimulatory effects on osteogenesis. Compounds 1, 3, 4, 6, and 7 stimulated osteogenic differentiation up to 1.4 fold, compared to the negative control. These findings provide experimental evidence that active compounds 1, 3, 4, 6, and 7 induce the osteogenesis of mesenchymal stem cells and activate bone formation.

Absolute configuration of seco-eudesmanolide inuloxin D from experimental and predicted chiroptical studies of its 4-O-acetyl derivative.

Sesquitepenoids inuloxins A-D, belonging to different subgroups, were isolated from Dittrichia viscosa and showed potential biocontrol of some parasitic plants as Pelipanche, Orobanche, and Cuscuta species. The absolute configurations of the first three inuloxins A-C were previously determined by using experimental and computational chiroptical spectroscopic methods. The absolute configuration of inuloxin D remains to be established. The bioactive inuloxin E, closely related to inuloxin D, was recently isolated from the same plant organic extract. The same relative configuration of inuloxin D was assigned to inuloxin E by comparison of their NMR spectroscopic data. The absolute configurations of inuloxin D and inuloxin E are suggested in this work by analysis of the experimental and predicted chiroptical properties of the 4-O-acetyl derivative of inuloxin D.

Aromatin D-J: Seven previously undescribed labdane diterpenoids isolated from Blumea aromatica.

Blumea aromatica is a traditional Chinese medicine used for treating various diseases such as rheumatoid arthritis, eczema, and pruritus. Previous studies on B. aromatica used a mass defect-filtering strategy via the ultra-high-performance liquid chromatography-quadrupole time-of-flight mass spectrometry and reported the presence of several labdane diterpenoids (LADs). To determine the actual structures of these LADs and investigate their biological activities, seven previously undescribed LADs (aromatin D-J) were isolated from the whole B. aromatica herb. The structures of these isolated compounds were characterized using high-resolution mass spectrometry and extensive 1D and 2D NMR analyses. In addition, the absolute configurations of these compounds were determined by comparing the experimental and calculated electronic circular dichroism (ECD) spectra as well as using X-ray crystallographic analysis. All isolated compounds were evaluated for their ability to activate adenylate cyclase by measuring the levels of cyclic adenosine 3',5'-monophosphate (cAMP) in rat ventricular tissue. Aromatin E, F, and J showed moderate activities with an increase in cAMP levels by 67%, 69%, and 64%, respectively, compared with the control group.

Three new sesquiterpenoids with cytotoxic activity from Artemisia argyi.

A new eudesmane sesquiterpenoid, artemisargin A (1), two new guaianolide sesquiterpenoids, artemisargins B (2) and C (3), along with three known sesquiterpenoids (4-6), were isolated from the leaves of Artemisia argyi. Their structures were determined by extensive spectroscopic methods and electronic circular dichroism calculations. Biological evaluation showed that 1 could inhibit the growth of cancer cells, especially in BGC-823 cells with an IC50 value of 49.87 µM.

Discovery of Dihydrophaseic Acid Glucosides from the Florets of Carthamus tinctorius.

Carthamus tinctorius L. (Compositae; safflower or Hong Hua) has been used in Korean traditional medicine for maintaining the homeostasis of body circulation. Phytochemical investigation was performed on the florets of C. tinctorius by liquid chromatography-mass spectrometry (LC/MS), which afforded two dihydrophaseic acid glucosides (1 and 2). Isolated compounds were structurally confirmed using a combination of spectroscopic methods including 1D and 2D nuclear magnetic resonance and high-resolution electrospray ionization mass spectroscopy. Their absolute configurations were established by quantum chemical electronic circular dichroism calculations and enzymatic hydrolysis. The anti-adipogenesis activity of the isolated compounds was evaluated using 3T3-L1 preadipocytes. Treatment with the dihydrophaseic acid glucoside (1) during adipocyte differentiation prevented the accumulation of lipid droplets and reduced the expression of adipogenic genes, Fabp4 and Adipsin. However, compound 2 did not affect adipogenesis. Our study yielded a dihydrophaseic acid glucoside derived from C. tinctorius, which has potential advantages for treating obesity.

[A new nor-sesquiterpene glycoside from Corydalis edulis].

This study is to investigate the chemical constituents from the whole plant Corydalis edulis. The chemical constituents were separated and purified by macroporous resin D101, silica gel, Sephadex LH-20, ODS, and semi-preparative HPLC. Their structures were determined by physicochemical properties and spectroscopic data. Four compounds were isolated from the dichloromethane and water extracts of the whole plant C. edulis, and identified as 6'-ß-D-xylosylicariside B2(1),(3S,5R,6S,7E)-5,6-epoxy-3-hydroxy-7-megastigmen-9-one(2), loliolide(3), and 5,5'-dimethoxybiphenyl-2,2'-diol(4), respectively. Compound 1 is a new compound, of which the absolute configuration was established by electronic circular dichroism(ECD) calculations. Compound 4 is obtained from the plants of Papaveraceae family for the first time. Compounds 2 and 3 are firstly isolated from the Corydalis genus.

Lanostane triterpene glycosides from the flowers of Lyonia ovalifolia var. hebecarpa and their antiproliferative activities.

Sixteen lanostane-type triterpene glycosides including eight new ones, named lyonicarposides A-H (1-8), were isolated from the flowers of Lyonia ovalifolia var. hebecarpa (Franch. ex F.B. Forbes & Hemsl.) Chun (Ericaceae). The chemical structures of the new compounds were elucidated by the comprehensive spectroscopic techniques and chemical methods. The Mo2(OAc)4-induced electronic circular dichroism method was used to determine the absolute configurations of C-24 in lyonicarposides A (1), C (3), and E (5). This is the first phytochemical study on the flowers of L. ovalifolia var. hebecarpa. All the isolates were evaluated for their antiproliferative activities against SMMC-7721, HL-60, SW480, MCF-7, and A-549 cell lines. Lyonicarposides A (1) and B (2) showed moderate antiproliferative activities against five cancer cell lines with IC50 values ranging from 12.39 to 28.71 µM. Lyonicarposides C (3) and G (7) and lyonifoloside M (12) selectively inhibited the proliferation of HL-60 and MCF-7 cell lines with IC50 values ranging from 13.03 to 17.71 µM. Interestingly, lyonifoloside L (13) selectively inhibited the proliferation of MCF-7 cell line with an IC50 value of 16.27 µM. Their structure-activity-relationships were discussed.

Cytotoxic arylalkenyl α,ß-unsaturated δ-lactones from Cryptocarya brachythyrsa.

Three new arylalkenyl α,ß-unsaturated δ-lactones, cryptobrachytones A-C (1-3), together with one known analogue kurzilactone (4), were isolated from the leaves and twigs of Cryptocarya brachythyrsa. Their structures were elucidated based on extensive spectroscopic data and electronic circular dichroism (ECD) analysis. All the isolates were evaluated in vitro for anti-proliferative activity against a panel of five human cancer cell lines and one human normal cell, respectively, and the results showed 1, 2 and 4 possessing significant selective cytotoxicity toward the human cancer cell lines with IC50 values from 5.41 to 15.43 µM. This is the first study for C. brachythyrsa.

Novel phthalide dimers from the aerial parts of Ligusticum sinense Oliv cv. Chaxiong.

Five new phthalide dimers, chaxiongnolides C-G (1-5), the two enantiomers of riligustilide (6a and 6b) and tokinolide B (7) were isolated from the aerial parts of Ligusticum sinense Oliv cv. Chaxiong. The structures of 1-5 were elucidated through extensive spectroscopic analysis, and the relative configurations of compounds 2 and 3 were further confirmed by an X-ray diffraction experiment. The absolute configurations of 1-3 were assigned by comparing calculated and experimental ECD spectra. The ECD exciton chirality method was used to confirm the absolute configurations of compounds 4, 5, 6a and 6b. Compounds 1-3 are the first dimeric phthalides to be reported that are comprising a sedanolide unit. The compounds were evaluated in vitro for their cytotoxic activity against select human cell lines.

Novel sesquiterpenoids isolated from Chimonanthus praecox and their antibacterial activities.

In the present study, four new sesquiterpenoids, chimonols A-D (compounds 1-4), together with four known compounds (5-8) were isolated from the EtOAc extract of Chimonanthus praecox Link. The structures of these new compounds were elucidated on the basis of spectroscopic techniques (UV, IR, MS, and 1D and 2D NMR), and their absolute configurations were established by comparing experimental and calculated electronic circular dichroism (ECD) spectra. Compounds 1-8 were evaluated for antimicrobial activities and the minimum inhibitory concentrations (MICs) were determined by the broth microdilution method in 96-well culture plates. Compounds 1, 2, and 7 exhibited weak antibacterial effects for S. aureus (ATCC 6538), E. coli (ATCC 11775), and P. aeruginosa (ATCC 10145) with MIC values being 158-249 µg·mL-1. Compounds 3-7 showed activities against C. glabrata (ATCC 2001) and S. aureus (ATCC 43300) with MIC values being 128-197 µg·mL-1. Compounds 1-4 showed activity against S. aureus (ATCC 25923) with MIC values being 162-254 µg·mL-1. The present study provided a basis for future evaluation of these compounds as antibacterial agents.

Absolute configuration assignment to anticancer Amaryllidaceae alkaloid jonquailine.

Jonquailine, a new alkaloid recently isolated from Narcissus jonquilla quail, an Amaryllidaceae species cultivated for its flowers fragrance in Europe and USA, shows very significant anti-proliferative activity against several malignant cancer cell types. Although it was reported that this activity is related to the functionalities and to its stereochemistry at C-8 of B ring, the absolute configuration at this stereocenter was not known. Density functional theory (DFT) calculations of chiroptical properties, namely electronic circular dichroism (ECD), vibrational circular dichroism (VCD), and optical rotatory dispersion (ORD) are employed here to complete assignment of absolute configuration of jonquailine, and then, by extension, to its analogues pretazettine and 8-O-methylpretazettine. While ECD is not discriminating and ORD is of limited use, VCD reveals decisive in the task of absolute configuration assignment.

Resolution and identification of scalemic caged xanthones from the leaf extract of Garcinia propinqua having potent cytotoxicities against colon cancer cells.

A new scalemic 8,8a-dihydro caged xanthone (1) was isolated from the leaf extract of Garcinia propinqua. Five other known natural products, the three caged xanthones (2, 5 and 6) and the two neocaged xanthones, (3 and 4) were also isolated as scalemic mixtures. Their structures were characterized by spectroscopic methods. The enantiomeric ratios (er) of compounds 1-6 ranged from 1:0.7 to 1:0.9. These compounds were also resolved by semipreparative chiral HPLC. The absolute configurations of (+)-2 and (+)-3 were determined by single-crystal X-ray diffraction analysis using Cu Kα radiation while the absolute configurations of the other compounds were determined by comparisons of their ECD spectra. Compounds (-)-4, (+)-4, (-)-5, (+)-5, and (-)-6 showed potent cytotoxicities against a colon cancer cell line HCT116 with IC50 values of 2.60, 7.02, 1.47, 3.37, and 4.14µM, respectively, which were better than the standard control doxorubicin (IC50 9.74µM).

Isobenzofuranones from the aerial parts of Leontopodium leontopodioides (Wild.) Beauv.

A phytochemical investigation to obtain new triglyceride (TG) accumulation inhibitors resulted in the isolation of six new isobenzofuranones, leontopodiols A (1), B (2), leontopodiosides C (3), D (4), E (5), F (6), together with three known ones (7-9) from the aerial parts of Leontopodium leontopodioides (Willd.) Beauv. The structures of these isolates were identified by routine NMR experiments, optical rotation determination, electronic circular dichroism (ECD) calculation, along with chemical reaction. Moreover, compounds 1, 2, 5, and 7-9 displayed TG accumulation inhibitory effects on HepG2 cells.