Structure elucidation and NMR spectral assignment of five new xanthones from the bark of Garcinia xanthochymus

Prenylated xanthones with α-glucosidase and α-amylase inhibitory effects from the pericarp of Garcinia mangostana

Two new prenylated xanthones, mangoxanthones A-B (1-2), together with four known compounds 3-6, were isolated from the ethanol extract of the pericarp of Garcinia mangostana. The structures of these compounds have been elucidated based on spectroscopic analysis. The analysis results of chiral HPLC revealed compounds 1 and 2 were scalemic mixtures respectively. All isolated compounds were biologically evaluated for their α-glucosidase and α-amylase inhibitory effects using in-vitro assays. Compound 1 showed moderate inhibitory activities against α-glucosidase and α-amylase with IC₅₀ of 29.06 ± 1.86 and 22.74 ± 2.07 μM, respectively. Molecular docking predicted the binding sites of compound 1 to α-glucosidase and α-amylase. A preliminary structure-activity relationship was discussed.

Simultaneous identification and quantification of three biologically active xanthones in Garcinia species using a rapid UHPLC-PDA method

Xanthones are well recognized as chemotaxonomic markers for the plants belonging to the genus Garcinia. Xanthones have many interesting pharmacological properties. Efficient extraction and rapid liquid chromatography methods are essentially required for qualitative and quantitative determination of xanthones in their natural sources. In the present investigation, fruit rinds extracts of 8 Garcinia species from India, were prepared with solvents of varying polarity. Identification and quantification of 3 xanthones, namely, α-mangostin, β-mangostin, and γ-mangostin in these extracts were carried out using a rapid and validated ultra-high-performance liquid chromatography–photodiode array detection (UHPLC–PDA) method at 254 nm. γ-Mangostin (3.97 ± 0.05 min) was first eluted, and it was followed by α-mangostin (4.68 ± 0.03 min) and β-mangostin (5.60 ± 0.04 min). The calibration curve for α-mangostin, β-mangostin, and γ- mangostin was linear in the concentration range 0.781–100 μg/mL. α-Mangostin was quantified in all 4 extracts of Garcinia mangostana. Its content (%) in hexane, chloroform, ethyl acetate, and methanol extracts of G. mangostana was 10.36 ± 0.10, 4.88 ± 0.01, 3.98 ± 0.004, and 0.044 ± 0.002, respectively. However, the content of α-mangostin was below the limit of detection or limit of quantification in the extracts of other Garcinia species. Similarly, β-mangostin was quantified only in hexane (1.17 ± 0.01%), chloroform (0.39 ± 0.07%), and ethyl acetate (0.28 ± 0.03%) extracts of G. mangostana. γ-Mangostin was quantified in all 4 extracts of G. mangostana. Its content (%) in hexane, chloroform, ethyl acetate, and methanol extracts of G. mangostana was 0.84 ± 0.01, 1.04 ± 0.01, 0.63 ± 0.04, and 0.15 ± 0.01, respectively. γ-Mangostin was also quantified in hexane (0.09 ± 0.01), chloroform (0.05 ± 0.01), and ethyl acetate (0.03 ± 0.01) extracts of G. cowa, ethyl acetate extract of G. cambogia (0.02 ± 0.01), G. indica (0.03 ± 0.01), and G. loniceroides (0.07 ± 0.01). Similarly, γ-mangostin was quantified in 3 extracts of G. morella, namely, hexane (0.03 ± 0.01), chloroform (0.04 ± 0.01), and methanol (0.03 ± 0.01). In the case of G. xanthochymus, γ-mangostin was quantified in chloroform (0.03 ± 0.001) extract only. α-Mangostin and β-mangostin were not detected in any of 4 extracts of G. pedunculata.

Antiproliferative Activity and Antioxidant Potential of Extracts of Garcinia gardneriana

The aim of this study was to evaluate the antiproliferative activity, the antioxidant potential, and the chemical profile obtained from the whole fruit and from leaves of Garcinia gardneriana, a fruit tree from Brazilian Cerrado. To determine in vitro antiproliferative activity, the following neoplastic cell lines were considered, along with an immortalized nontumor cell line. The antioxidant potential was determined, and the evaluation of antiradical air activity was performed. The levels of vitamin C and carotenoids were determined. The chemical profile was analyzed by high-performance liquid chromatography coupled to a diode array detector and a mass spectrometer using electrospray ionization interface. The chloroform fraction of the leaf showed antioxidant activity. The vitamin C content had lower values in fruits and higher in leaves. The content of carotenoids for fruits and leaves was expressive. The ethanolic extract and the hexane and chloroform fractions of fruits were active in all neoplastic lines tested. The leaves showed cytotoxic activity in the hexane fraction in the breast carcinoma line. The analysis of data obtained verified the presence of dimers, monomers, and tetramers of hexoses, polycarboxylic acids, xanthones, flavonoids, biflavonoids, and benzophenones.

Garcinia xanthochymus extract protects PC12 cells from H2O2-induced apoptosis through modulation of PI3K/AKT and NRF2/HO-1 pathways

The aim of the present study was to investigate the protective effects and underlying mechanisms of Garcinia xanthochymus, a perennial medicinal plant native to Yunnan, China, against H₂O₂-induced oxidative damage in rat pheochromacytoma PC12 cells. Preincubation of PC12 cells with fruit EtOAc fraction (fruit-EFr., 12.5-50 µmol·L^-1) of G. xanthochymus for 24 h prior to H₂O₂ exposure markedly improved cell viability and increased the activities of antioxidant enzymes (superoxide dismutase, catalase, and heme oxygenase-1 [HO-1]), prevented lactate dehydrogenase release and lipid peroxidation malondialdehyde production, attenuated the decrease of matrix metalloproteinases (MMP), and scavenged reactive oxygen species (ROS). Fruit-EFr. also reduced BAX and cytochrome C expression and improved BCL-2 expression, thereby decreasing the ratio of BAX to BCL-2. Fruit-EFr. activated the nuclear translocation of NRF2 to increase HO-1 and induced the phosphorylation of AKT. Its cytoprotective effect was abolished by LY294002, a specific inhibitor of PI3K. Taken together, the above findings suggested that fruit-EFr.of G. xanthochymus could enhance cellular antioxidant defense capacity, at least in part, through upregulating HO-1 expression and activating the PI3K/AKT pathway and that it could suppress H₂O₂-induced oxidative damage via PI3K/AKT and NRF2/HO-1 signaling pathways.

Biomimetic Total Synthesis of (±)-Griffipavixanthone via a Cationic Cycloaddition-Cyclization Cascade

We report the concise, biomimetic total synthesis of the dimeric, Diels-Alder natural product griffipavixanthone from a readily accessible prenylated xanthone monomer. The key step utilizes a novel intermolecular [4+2] cycloaddition-cyclization cascade between a vinyl p-quinone methide and an in situ generated isomeric diene promoted by either Lewis or Brønsted acids. Experimental and computational studies of the reaction pathway suggest that a stepwise, cationic Diels-Alder cycloaddition is operative.

Polyprenylated Tetraoxygenated Xanthones from the Roots of Hypericum monogynum and Their Neuroprotective Activities

Ten new polyprenylated tetraoxygenated xanthones, monogxanthones A-J (1-10), together with eight known analogues (4b, 11-17) were identified from the roots of Hypericum monogynum. The structures of these new polyprenylated xanthones (1-10), a class of compounds rarely found in plants of the genus Hypericum, were elucidated by the interpretation of their HRESIMS, 1D and 2D NMR, and electronic circular dichroism data. Compounds 1 and 2 exhibited neuroprotective effects against corticosterone (Cort)-induced lesions of PC12 cells at concentrations of 6.25, 12.50, and 25.00 μM, with cell viability greater than 75%, as well as inhibitory effects on nitric oxide production in lipopolysaccharide-induced BV2 microglia cells, with IC50 values of 7.47 ± 0.65 and 9.60 ± 0.12 μM, respectively. Collectively, these results shed new light on the potential of polyprenylated xanthones from the genus Hypericum in the development of antidepression therapies.

Xanthones from the Leaves of Garcinia cowa Induce Cell Cycle Arrest, Apoptosis, and Autophagy in Cancer Cells

Two new xanthones, cowaxanthones G (1) and H (2), and 23 known analogues were isolated from an acetone extract of the leaves of Garcinia cowa. The isolated compounds were evaluated for cytotoxicity against three cancer cell lines and immortalized HL7702 normal liver cells, whereby compounds 1, 5, 8, and 15-17 exhibited significant cytotoxicity. Cell cycle analysis using flow cytometry showed that 5 induced cell cycle arrest at the S phase in a dose-dependent manner, 1 and 16 at the G2/M phase, and 17 at the G1 phase, while 16 and 17 induced apoptosis. Moreover, autophagy analysis by GFP-LC3 puncta formation and western blotting suggested that 17 induced autophagy. Taken together, our results suggest that these xanthones possess anticancer activities targeting cell cycle, apoptosis, and autophagy signaling pathways.

Rapid screening and identification of α-amylase inhibitors from Garcinia xanthochymus using enzyme-immobilized magnetic nanoparticles coupled with HPLC and MS

α-Amylase inhibitors play an important role in management of diabetes and obesity. In order to rapidly discover potent α-amylase inhibitors from medicinal plants, a ligands-screening method based on enzyme-immobilized magnetic nanoparticles integrated with HPLC was developed. Amine-terminated magnetic nanoparticles were prepared for the immobilization of α-amylase. Based on the affinity theory, the α-amylase-coated magnetic nanoparticles were employed to fish out the ligands from the extracts of Garcinia xanthochymus, and the elutes were examined by HPLC. As a result, three ligands were screened out. Isolation and identification were carried out subsequently. By analyzing the UV, MS and NMR spectra, they were identified as three biflavonoids including GB2a glucoside (2), GB2a (3) and fukugetin (4). The IC50 values of the three compounds were also determined. The results suggest the proposed approach is efficient and accurate, and has great potential in rapid discovery of drug candidates from medical plants.

Biphenyl Derivatives from Garcinia Schomburgkiana and the Cytotoxicity of the Isolated Compounds

Study of the chemical constituents of the stems of Garcinia schomburgkiana Pierre (Guttiferae), collected in Thailand, led to the isolation and identification of five known compounds and two new biphenyl derivatives, schomburgbiphenyl A (1) and B (2). Six phenolic compounds isolated from this plant were screened for their cell growth inhibition activity using several human leukemia cell lines. One compound, oblongifolin C (7), showed significant cytotoxic activity towards Jurkat, NALM6, K562 and HPB-ALL cells.

Xanthones from the stem bark of Garcinia bracteata with growth inhibitory effects against HL-60 cells

Five xanthones, 1,4,5,6-tetrahydroxyxanthone (1) and bracteaxanthones III-VI (2-5) together with twenty-six known compounds (6-31), were isolated from the ethanol extract of the stem bark of Garcinia bracteata. Their structures were elucidated via spectroscopic analyses. Growth inhibitory activities of these compounds against the human leukaemic HL-60 cell line were measured in vitro. Compounds 7, 11, and 29 exhibited moderate activities with GI(50) values of 2.8, 3.4, and 3.1 μM, respectively, and a preliminary structure-activity relationship is discussed.

Triterpenes and xanthones from the stem bark of Garcinia tetralata

A new compound, 3β,18,19β-trihydroxylupane, was isolated from Garcinia tetralata, along with five known compounds, garcinexanthone B, morolic acid acetate, toxyloxanthone A, 6,11-dihydroxy-2,2-dimethylpyrano[3,2-c]xanthen-7(2H)-one, and 1,4-dihydroxy-5,6-dimethoxy-xanthone. The structure of the new compound was established by extensive spectroscopic techniques.