Antiproliferative compounds of Cyphostemma greveana from a Madagascar dry forest

Chemical constituents from the leaves of Sindora siamensis var. maritima and their antimicrobial and α-glucosidase inhibitory activities

Two new glycosides, sindosides A-B (1-2), along with 11 previously identified metabolites (3-13), were isolated from an ethanolic extract of the leaves of Sindora siamensis var. maritima. The structures of the purified phytochemicals were elucidated by interpreting their spectroscopic data (IR, NMR, and HRMS). The absolute configuration of compound 1 was established by experimental and calculated ECD spectra. The antimicrobial results revealed that compound 8 selectively inhibited C. albicans fungal with a MIC value of 64 μg/mL, whereas 11 presented a weak inhibition toward E. faecalis, S. aureus, and B. cereus bacterial strains with the same MIC value of 128 μg/mL. Interestingly, compounds 1, 2, 8, 9, and 11 showed α-glucosidase inhibitory activity with IC50 values ranging from 14.42 ± 0.21 to 30.62 ± 0.18 μM, which were more active than the positive control (acarbose, with an IC50 value of 46.78 ± 1.37 μM). Enzyme kinetic analysis revealed that compounds 1, 2, and 11 behaved as uncompetitive inhibitors with Ki values of 8.60 ± 1.04, 5.16 ± 0.73, and 7.17 ± 0.98 μM, respectively.

Clerodane diterpenoids from the Uygur medicine Salvia deserta with immunosuppressive activity

Six undescribed clerodane diterpenoids along with five known ones were isolated from the aerial parts of Salvia deserta, a traditional Uygur medicine. Their chemical structures including absolute configurations were elucidated by extensive spectroscopic analysis (including 1D and 2D NMR, HRESIMS, and IR), combined with calculated ECD method and single-crystal X-ray diffraction analysis. All the compounds possessed a terminal α,β-unsaturated-γ-lactone moiety, and were assayed for their immunosuppressive activity via inhibiting the secretion of cytokines TNF-α and IL-6 in macrophages RAW264.7. Among them, (5R,8R,9S,10R)-18-nor-cleroda-2,13-dien-16,15-olide-4-one obviously suppressed the secretion of TNF-α and IL-6 with IC50 values of 8.55 and 13.65 μM, respectively.

In vitro antifungal activity of lasiodiplodin, isolated from endophytic fungus Lasiodiplodia pseudotheobromae J-10 associated with Sarcandra glabra and optimization of culture conditions for lasiodiplodin production

A macrolide antibiotic, lasiodiplodin was isolated from the endophytic fungus (EF) Lasiodiplodia pseudotheobromae J-10 associated with the medicinal plant Sarcandra glabra. In vitro antifungal assay demonstrated the inhibitory activity of lasiodiplodin against the growth of six phytopathogenic fungi, with the IC₅₀ values ranging between 15.50 and 52.30 μg/mL. The highest antifungal activities were recorded against Exserohilum turcicum, Colletotrichum capsici, and Pestalotiopsis theae, with IC₅₀ values of 15.50, 15.90, and 17.55 μg/mL, respectively. The underlying mechanism of the antifungal activity of lasiodiplodin against E. turcicum included the alteration of its colony morphology and disturbance of its cell membrane integrity. In addition, the optimization of L. pseudotheobromae J-10 culture conditions increased lasiodiplodin yield to 52.33 mg/L from 0.59 mg/L at pre-optimization. This is the first report on the isolation and identification of antifungal compound from the EF L. pseudotheobromae J-10 associated with S. glabra, as well as on the optimization of L. pseudotheobromae J-10 culture conditions to increase lasiodiplodin yield. The results of this study support that lasiodiplodin is a natural compound with high potential bioactivity against phytopathogens, and provide a basis for further study of the EF associated with S. glabra.

Antibacterial and Antioxidant Activities, in silico Molecular Docking, ADMET and DFT Analysis of Compounds from Roots of Cyphostemma cyphopetalum

Background

Cyphostemma cyphopetalum is a medicinal plant traditionally used to treat various ailments. Limited studies on C. cyphopetalum inspired us to investigate the chemical nature and therapeutic potential of the plant.

Methods

Silica gel column chromatographic separation was used for isolation. 1D and 2D NMR spectroscopic analysis and literature data were used for structural elucidation. Agar well diffusion assay was used for evaluation of antibacterial activity against E. coli, P. aeruginosa, and S. aureus. DPPH assay was used to evaluate radical scavenging activities. Molecular docking was done by AutoDock Vina 4.2 open-source program. DFT calculations were performed using the Gaussian 16 program package.

Results

Dichloromethane/methanol (1:1) roots extract afforded a new hydroxyl-spongiane diterpenoid lactone derivative, 3-hydroxyisoagatholactone (1), along with β-sitosterol (2) and ε-viniferin (3) whereas methanol extract afforded trans-resveratrol (4), gnetin H (5), tricuspidatol A (6), ε-viniferin-diol (7) and parthenostilbenin B (8). At 50 μg/mL, compound 3 recorded the highest inhibition against E. coli (8.55 ± 0.45 mm) and S. aureus (9.30 ±1.39 mm). Against P. aeruginosa, compound 5 consistently outperformed chloramphenicol (11.76 ± 0.77 mm, at 30 g/mL). Maximum binding affinity were observed by compound 3 against DNA gyrase B (-7.6 kcal/mol) where as compound 5 displayed maximum binding against PqsA (-8.8 kcal/mol) and S. aureus PK (-5.8 kcal/mol). Compounds 1, 3 and 4 satisfy Lipinski’s rule of five. Trans-resveratrol (4) demonstrated strong DPPH scavenging activity at 12.5 g/mL, with IC₅₀ values of 0.052 µg/mL, compared to ascorbic acid (IC₅₀ value of 0.0012 µg/mL).

Conclusion

In this work, eight compounds were identified from the roots extracts of C. cyphopetalum including a new hydroxyl-spongiane diterpenoid lactone, 3-hydroxyisoagatholactone (1). Compounds 3 and 5 exhibited good antibacterial activity and binding affinities. The docking result is in agreement with the invitro antibacterial study. Overall, the study result suggests that the isolated compounds have the potential to be used as therapeutic agents, which supports the traditional uses of C. cyphpetalum roots.

New enantiomeric lignans and new meroterpenoids with nitric oxide release inhibitory activity from Piper puberulum

Six new lignans with various type of linkage between two C6-C3 fragments (1a, 1b, 2a, 2b, 3, 4), two new meroterpenoids (5, 6) and 24 known compounds (7-30) were isolated from an EtOH extract of the stems and leaves of Piper puberulum. The absolute configurations of enantiomers 1a and 1b were determined by single-crystal X-ray diffraction analysis, 2a and 2b were determined by comparing their calculated and experimental ECD spectra. Biogenetically, all the new lignans may come from the polymerization of two molecules of hydroxychavicol (30). In the anti-neuroinflammation activity assay, the IC₅₀ values of fifteen compounds were lower than those of the positive control minocycline, and compound 1a showed good activity, but its enantiomer 1b showed no activity. Compound 1a have notable anti-neuroinflammatory activity, and can significantly decrease mRNA levels of proinflammatory cytokines (IL-1β, IL-6, TNF-α) in a dose-dependent manner.

Natural resorcylic acid lactones: A chemical biology approach for anticancer activity

Resorcylic acid lactones (RALs) are fungal polyketides that consist of a β-resorcylic acid residue (2,4-dihydroxybenzoic acid) embedded in a macrolactone ring. RALs exhibit a broad range of biological activities, including anticancer activities. Following discovery of the selective Hsp90 inhibition activity of radicicol, the kinase inhibition activity of hypothemycin, monocillin II, 5Z-7-oxo-zeaenol, and L-783,277 RALs, and the nuclear factor kappa B (NF-κB) inhibition activity of the RAL zearalenone, have attracted great attention as potential therapeutics for cancer treatment. In this minireview, we focus on natural RALs that possess cytotoxic activities [IC₅₀ values < 10 μM (or 4-5 μg/ml)], discussing their structures, isolation, occurrence, biological activities, and anticancer molecular mechanisms.

Essential oil of Cyphostemma juttae (Vitaceae): Chemical composition and antitumor mechanism in triple negative breast cancer cells

The genus Cyphostemma (Planch.) Alston (Vitaceae) includes about 150 species distributed in eastern and southern Africa and Madagascar. Some species are used in traditional medicine and their biological activities, including antiproliferative effects against cancer cell lines, have been demonstrated. To date no investigations on Cyphostemma essential oils have been carried out. Essential oils, which play important roles in plant defenses have been demonstrated to be active in the treatment of several human diseases and to enhance bioavability of other drugs. The aim of this paper was to identify the chemical composition of the essential oil of the leaves of Cyphostemma juttae (Dinter & Gilg) Desc. and to verify some biological activities on two triple negative breast cancer cell lines (MDA-MB-231, SUM 149), characterized by the over-expression of the transcription factor NF-κB. In the essential oil, obtained by hydrodistillation and analysed by gas chromatography-mass spectrometry, 39 compounds were detected and with phytol (30%) dominating the chemical composition. C. juttae essential oil reduced cell growth and showed a pro-oxidant activity in both cell lines. Moreover, C. juttae essential oil caused a substantial decrease of NF-κB activation and consequently a significant reduction of some NF-κB target genes. The present study shows for the first time the cytotoxic properties of C. juttae essential oil and highlight its availability to interfere with NF-κB pathway, suggesting a potential therapeutic use in triple negative breast cancers (TNBCs) of this essential oil.

Novel Bioactive Natural Products Isolated from Madagascar Plants and Marine Organisms (2009-2017)

Madagascar's rain forests and tropical dry forests are home to numerous endemic plant species and the island is considered a biodiversity hotspot. About 80% of the Madagascan (Malagasy) population relies on traditional medicines that have been proven to contain a variety of biologically active compounds. In the search for bioactive compounds from Madagascan biodiversity, we accessed and collected most of the literature dealing with the isolation, structure elucidation, and biological activities of organic small molecules originating from Madagascan plants and marine organisms. Since we published the first review of this work in 2009 (Curr. Med. Chem., 17, 2010, Hou and Harinantenaina), the present paper covers the isolation, structures, and bioactivity of 182 new secondary metabolites isolated from Malagasy higher plants and marine organisms in the last seven years (2009-2017).

Ceanothane-type triterpenoids from Cyphostemma adenocaule

Phytochemical investigation of the methanol extract of Cyphostemma adenocaule liana (bark and wood) led to the isolation of two new ceanothane-type triterpenoids, cyphostemmic acid A 1 and cyphostemmic acid B 2, together with the known triterpenoids 3-7, β-sitosterol and its glucoside. The structures of the isolated compounds were established by 1D- and 2D-NMR spectroscopy. Ozonolysis of cyphostemmic acid A 1, epigouanic acid A 3 and betulin 6 yielded semisynthetic derivatives, cyphostemmic acid C 8, cyphostemmic acid D 9, and 3β,28-dihydroxy-30-norlupan-20-one 10 respectively. Compounds 1-4, 6, 8-10 were tested in vitro, for their antiplasmodial activity against Plasmodium falciparum 3D7 strain and showed weak activity.

Labdane and Clerodane Diterpenoids from Colophospermum mopane

Five labdane (1-5), an isolabdane (6), and five clerodane diterpenoids (7-11), were isolated from seeds, husks, and leaves of Colophospermum mopane. Compounds 1-3 and 6-9 are new, and their structures were elucidated by means of physical data analysis (1D and 2D NMR, HRESIMS). The absolute configurations of 1, 7, and 10 were determined by single-crystal X-ray diffraction with Cu Kα radiation. For compounds 2 and 6, the absolute configurations were established by the modified Mosher's method and corroborated by comparison of experimental and calculated electronic circular dichroism spectra of their 3-p-bromobenzoate derivatives. The crude extracts and compounds were evaluated for antimicrobial activity. The leaf extract was the most active against Staphylococcus aureus (125 μg/mL). Compound 11 showed the best inhibitory activity, with minimum inhibitory values of 15.6 μg/mL against Escherichia coli and Staphylococcus aureus and 31.3 μg/mL against Enterococcus faecalis.

Antiproliferative Diterpenes from a Malleastrum sp. from the Madagascar dry forest

An ethanol extract of leaves of the plant species Malleastrum sp. collected in northern Madagascar afforded the new clerodane diterpene 18-oxo-cleroda-3,13-dien-16,15-olide (1), together with the three known clerodane diterpenes 16,18-dihydroxykolavenic acid lactone (2), solidagolactone (3) and (-)-kolavenol (4), and the known labdane diterpene 3-oxo-ent-Iabda-8(17),13-dien-15,16-olide (5). Compounds 1, 3, and 4 showed moderate antiproliferative activities against the A2780 ovarian cancer cell line, with the IC50 values of 3.01 ± 0.8, 7.84 ± 0.2, and 17.9 ± 3 µM, respectively. The structure elucidations of all compounds were carried out based on analysis of NMR and mass spectroscopic data. The relative stereochemistry of compound 1 was determined by NOESY NMR spectrum.

Antiproliferative Diterpenes from a Malleastrum sp. from the Madagascar dry forest [1]

An ethanol extract of leaves of the plant species Malleastrum sp. collected in northern Madagascar afforded the new clerodane diterpene 18-oxo-cleroda-3,13-dien-16,15-olide (1), together with the three known clerodane diterpenes 16,18-dihydroxykolavenic acid lactone (2), solidagolactone (3) and (-)-kolavenol (4), and the known labdane diterpene 3-oxo-ent-Iabda-8(17),13-dien-15,16-olide (5). Compounds 1, 3, and 4 showed moderate antiproliferative activities against the A2780 ovarian cancer cell line, with the IC50 values of 3.01 ± 0.8, 7.84 ± 0.2, and 17.9 ± 3 μM, respectively. The structure elucidations of all compounds were carried out based on analysis of NMR and mass spectroscopic data. The relative stereochemistry of compound 1 was determined by NOESY NMR spectrum.

Bioactive cadinane-type compounds from the soft coral Sinularia scabra

Two new cadinane-type sesquiterpenoids, scabralins A (1) and B (2) were obtained from the soft coral Sinularia scabra. Metabolite 1 was shown to exhibit moderate to weak cytotoxicity against MCF-7, WiDr, Daoy, and HEp 2 cancer cell lines. Also, incubation with 10 µM compound 1 significantly inhibited the accumulation of the pro-inflammatory inducible nitric oxide synthase protein in lipopolysaccharide-stimulated RAW264.7 macrophage cells.

Four diphenylpropanes and a cycloheptadibenzofuran from Bussea sakalava from the Madagascar dry forest

Investigation of the endemic Malagasy plant Bussea sakalava for antiproliferative activity against the A2780 ovarian cancer cell line led to the isolation of the four new diphenylpropanes 1-4 and the new cycloheptadibenzofuran 5; compound 5 has a previously unreported natural product skeleton. The structure elucidation of these compounds was based on the analysis of their 1D and 2D NMR and mass spectroscopic data. Compounds 1-5 were tested for antiproliferative activity against the A2780 human ovarian cancer cell line.

Antiproliferative compounds from Pongamiopsis pervilleana from the Madagascar Dry Forest

Bioassay-guided fractionation of an ethanol extract of the roots of the endemic Malagasy plant Pongamiopsis pervilleana led to the isolation of the three new compounds (2'R)-4'-hydroxyemoroidocarpan (1), pongavilleanine (3), and epipervilline (4) together with two known compounds, identified as emoroidocarpan (2) and rotenolone (5). The structures of all compounds were determined by physical, chemical, and spectroscopic evidence. The stereochemistry at C-2' of the previously reported compound emoroidocarpan was determined to be R by the observation of a negative Cotton effect at 474 nm in the CD spectrum of its osmate ester derivative. Compounds 2-5 displayed moderate antiproliferative activity against the A2780 human ovarian cancer cell line, and rotenolone also showed micromolar antiproliferative activity toward the breast cancer BT-549, prostate cancer DU 145, NSCLC NCI-H460, and colon cancer HCC-2998 cell lines.