New α-glucosidase inhibitory xanthones from the fruits of Garcinia schomburgkiana.

Two previously unreported xanthones, xanthoschomes A and B (1 and 2), along with six known xanthones, α-mangostin (3), ß-mangostin (4), γ-mangostin (5), garcinone C (6), 2-(γ,γ-dimethylallyl)-1,7-dihydroxy-3-methoxyxanthone (7), and dulxanthone D (8), have been isolated from the fruits of Vietnamese Garcinia schomburgkiana. The structures of all isolated compounds were fully characterised using spectroscopic data and comparison with the previous literature. All isolated compounds were evaluated for their in vitro α-glucosidase inhibitory activity. Compounds 1-8 demonstrated effective α-glucosidase inhibition, with the IC50 ranging from 2.91 to 26.0 µM, outperforming the standard acarbose (IC50 179 µM). Among these isolated compounds, compound 8 exhibited the highest inhibitory activity against α-glucosidase, with an IC50 value of 2.91 µM.

Placoisoflavones A and B, two new cytotoxic isoflavonoids from Placolobium vietnamense N.D.Khôi & Yakovlev.

Two previously unreported isoflavonoids, placoisoflavones A and B (1 and 2), along with five known compounds, calopogonium isoflavone B (3), jamaicin (4), 6-methoxycalopogonium isoflavone A (5), vestitol (6), and caviunin (7) have been isolated from the stems of Placolobium vietnamense N.D.Khôi & Yakovlev. The structures of all isolated compounds were fully characterized using spectroscopic data and comparison with the previous literature. The cytotoxicity of all isolated compounds was evaluated against HepG2 cell line, and compound 1 showed the most potent cytotoxicity with an IC50 value of 8.0 µM.

New prenyl flavanone and diarylbutanol from Uvaria siamensis stem bark and their α-glucosidase inhibitory activity.

One new prenyl flavanone (1), (2S)-8-prenyl-5,6-dihydroxy-7-methoxyflavanone, and one new diarylbutanol (2), (7'S)-3'-hydroxy-linderagatin-A, were isolated from the stem bark of Uvaria siamensis (Annonaceae), along with five known compounds, eriodictyol (3), quercetin (4), paprazine (5), N-trans-caffeoyltyramine (6), and N-trans-feruloyltyramine (7). Their structures were determined through extensive spectroscopic analyses and comparison with the literature. The α-glucosidase inhibitory potential of 1-7 was evaluated. Compound 6 showed the highest inhibitory activity against α-glucosidase and exhibited superior potency compared to the positive control, with an IC50 value of 0.12 µM.

Two new dimethylpyranoflavanones from the roots of Melodorum fruticosum.

Two previously unreported dimethylpyranoflavanones, pyronomelodorones A and B (1 and 2), along with five known compounds, 7-O-methyldihydrowogonin (3), 5,6,7-trimethoxyflavanone (4), 5,6-dihydroxy-7-methoxy-dihydroflavone (5), 5,7,8-trimethoxydihydroflavone (6), and pinostrobin (7), were isolated from the roots of Melodorum fruticosum. The structures of all isolates were fully characterized using spectroscopic data and comparison with the previous literature. All isolates were evaluated for their in vitro α-glucosidase inhibition and their cytotoxicity against KB, HepG2, and MCF7 cell lines. Among the isolates, compound 1 exhibited the most inhibitory activity against α-glucosidase and was superior to the positive control with an IC50 value of 1.32 µM. Compounds 1 and 2 showed weak cytotoxicity against the three human cancer cell lines, with IC50 values in the range of 53.3-79.0 µM.

New Benzil and Isoflavone Derivatives with Cytotoxic and NO Production Inhibitory Activities from Placolobium vietnamense.

The phytochemical investigation of Placolobium vietnamense stems led to the isolation of a new isoflavone derivative (1) and three new benzil derivatives (2-4), together with four known pyranoisoflavones (5-8). The structures of all isolated compounds were determined on the basis of extensive spectroscopic analyses, including NMR and HRMS spectral data, as well as comparison of their spectroscopic data with those reported in the literature. The cytotoxicity of all isolated compounds was assessed against the human liver hepatocellular carcinoma (Hep G2) cell line, and compound 1 displayed the most significant cytotoxicity with an IC50 value of 8.0 µM. Furthermore, all isolated compounds were also tested for their inhibitory activity against NO production in RAW 264.7 macrophages. Of these, compound 1 exhibited the strongest inhibitory efficacy against the LPS-induced NO production with the IC50 value of 13.7 µM.

New Flavonoid Derivatives from Melodorum fruticosum and Their α-Glucosidase Inhibitory and Cytotoxic Activities.

Three new flavonoid derivatives, melodorones A-C (1-3), together with four known compounds, tectochrysin (4), chrysin (5), onysilin (6), and pinocembrin (7), were isolated from the stem bark of Melodorum fruticosum. Their structures were determined on the basis of extensive spectroscopic methods, including NMR and HRESIMS, and by comparison with the literature. Compounds 1-7 were evaluated for their in vitro α-glucosidase inhibition and cytotoxicity against KB, Hep G2, and MCF7 cell lines. Among them, compound 1 exhibited the best activity against α-glucosidase and was superior to the positive control with an IC50 value of 2.59 µM. On the other hand, compound 1 showed moderate cytotoxicity toward KB, Hep G2, and MCF7 cell lines with the IC50 values of 23.5, 19.8, and 23.7 µM, respectively. These findings provided new evidence that the stem bark of M. fruticosum is a source of bioactive flavonoid derivatives that are highly valuable for medicinal development.

A new triterpenoid saponin from Glinus oppositifolius.

From the ethanol extract of Glinus oppositifolius, collected at Phu Yen province, Viet Nam, one new triterpenoid saponin (1) and four known compounds (2-5) were isolated. By means of NMR and HR-ESI-MS analyses, their structure was elucidated as 3-O-(ß-D-xylopyranosyl-(1→3)-ß-D-xylopyranosyl)spergulagenin A or glinusopposide V (1), glinusopposide L (2), spergulin B (3), vitexin (4) and astralagin (5). Two compounds (1-2) showed weak inhibitory activity against α-glucosidase.

Bougainvinones NP, three new flavonoids from Bougainvillea spectabilis.

In an effort to identify natural bioactive compounds, three new flavonoids (1-3) and six known compounds (4-9) were isolated from the stem bark of Bougainvillea spectabilis. The structures of these compounds were accomplished using comprehensive spectroscopic methods, including 1D and 2D NMR spectra with references to the literatures, as well as high-resolution mass spectrometric analysis. Their cytotoxicity against KB and HeLa S-3 cell lines was also evaluated.

Tetrahydroxanthone-chromanone heterodimers from lichen Usnea aciculifera and their cytotoxic activity against human cancer cell lines.

Four new tetrahydroxanthone-chromanone heterodimers, usneaxanthones E-H (1-4) together with eleven known compounds (5-15) were isolated from lichen Usnea aciculifera Vain (Parmeliaceae). Their structures and absolute configurations, particularly the central and axial chiralities, were unambiguously demonstrated by a combination of spectroscopic data (1D, 2D NMR, HRESIMS), electronic circular dichroism (ECD) experiments, and single-crystal X-ray crystallographic analyses. The cytotoxicity of new compounds was evaluated on four human cancer cell lines including HCT116 colorectal cancer, MCF-7 breast cancer, A549 lung cancer, and OVCAR-3 ovarian cancer. Compounds 1-4 exhibited good cytotoxicity against all tested cancer cell lines, except ovarian cancer, with the best IC50 value of 3.37 µM. All compounds showed potent cytotoxicity against HCT116 colon cancer with IC50 value from 3.37 to 4.53 µM.

Dimeric tetrahydroxanthones from the lichen Usnea aciculifera.

Four unusual heterodimeric tetrahydroxanthones, usneaxanthones A-D (1-4) were isolated from lichen Usnea aciculifera Vain (Parmeliaceae). Their structures and absolute configurations, particularly the central and axial chiralities, were unambiguously demonstrated by a combination of spectroscopic data (1D, 2D NMR, HRESIMS), electronic circular dichroism (ECD) experiments, and single-crystal X-ray crystallographic analyses. Cytotoxic effects of isolated compounds (1, 2 and 4) were evaluated on HT-29 human colorectal cancer cells. Compound 4 showed potent cytotoxicity against HT-29 with IC50 values of 2.41 µM.

A sesquiterpenoid tropolone and 1,2,3,4-tetrahydronaphthalene derivatives from Olax imbricata roots.

The methanol extract of Olax imbricata roots afforded one new sesquiterpenoid tropolone and three new 1,2,3,4-tetrahydronaphthalene derivatives, olaximbrisides A-D (1-4). Their structures were determined by 1D and 2D NMR experiments in combination of HRESIMS. The relative configurations were assigned by the NOESY experiments. The absolute configurations were established by a combination of X-ray diffraction analysis and electronic circular dichroism (ECD) experiments. All isolated compounds were evaluated for their cytotoxic effects against some cancer cell lines. Among them, compound 1 exhibited the cytotoxicities against MCF-7, HepG2 and LU cell lines with IC50 values of 16.3, 34.3 and 8.0 µM, respectively.

Cytotoxic Flavones from the Stem Bark of Bougainvillea spectabilis Willd.

Five new flavones possessing a fully substituted A-ring with C-6 and C-8 methyl groups, bougainvinones I - M (1: -5: ), along with three known congeners, 2'-hydroxydemethoxymatteucinol (6: ), 5,7,3',4'-tetrahydroxy-3-methoxy-6,8-dimethylflavone (7: ) and 5,7,4'-trihydroxy-3-methoxy-6,8-dimethylflavone (8: ), were isolated from the EtOAc extract of the stem bark of Bougainvillea spectabilis. Their structures were established by means of spectroscopic data (ultraviolet, infrared, high-resolution electrospray ionization mass spectrometry, and one-dimensional and two-dimensional nuclear magnetic resonance) and single-crystal X-ray crystallographic analysis. The in vitro cytotoxicity of all isolated compounds against five cancer cell lines (KB, HeLa S-3, MCF-7, HT-29, and HepG2) was evaluated. Compound 5: showed promising cytotoxic activity against the KB and HeLa S-3 cell lines, with IC50 values of 7.44 and 6.68 µM. The other compounds exhibited moderate cytotoxicity against the KB cell line.

Bougainvinones A-H, Peltogynoids from the Stem Bark of Purple Bougainvillea spectabilis and Their Cytotoxic Activity.

Eight new peltogynoids, named bougainvinones A-H (1-8), were obtained from the stem bark of Bougainvillea spectabilis. Their structures were elucidated by means of physical data (1D and 2D NMR, HRESIMS) and single-crystal X-ray crystallographic analyses. The peltogynoids, a rare type of modified flavonoids, are reported for the first time from this species of the genus Bougainvillea. All isolated compounds were evaluated for their cytotoxic effects against five cancer cell lines including KB, Hela S-3, HT-29, MCF-7, and HepG2. Among them, compound 7 showed cytotoxicity against five cancer cell lines with IC50 values in the 7.4-9.7 µM range, and compounds 2 and 3 exhibited cytotoxicity against the KB cell line with IC50 values of 6.6 and 9.0 µM.