Two new antioxidant flavones from the twigs of Eriosema robustum (Fabaceae)

Phytochemical study of the ethanol extract of the twigs of Eriosema robustum, a Cameroonian medicinal plant resulted to the isolation of two new flavones, 2′,3′,5′,5,7-pentahydroxy-3,4′-dimethoxyflavone (1) and 2′,3,5′,5,7-pentahydroxy-4′-methoxyflavone (2), along with five known compounds: 6-prenylpinocembrin (3), 1-O-heptatriacontanoyl glycerol (4), β-sitosterol (5), stigmasterol (6) and 3-O-β-d-glucopyranoside of sitosterol (7). The structure of the isolated compounds were elucidated on the basis of their NMR, UV and MS data, and by comparison with those reported in the literature. The ethanol crude extract, fractions and some isolated compounds (1–4) were evaluated for their radical scavenging capacity using 2,2-diphenyl-1-picryhydrazyl (DPPH). The crude extract, fraction II, the new compounds namely robusflavones A (1) and B (2) exhibited significant antioxidant activity.     

Identification of spirobisnaphthalene derivatives with anti-tumor activities from the endophytic fungus Rhytidhysteron rufulum AS21B

The cultivation of the mangrove-derived fungus Rhytidhysteron rufulum AS21B in acidic condition changed its secondary metabolite profile. Investigation of the culture broth extract led to the isolation and identification of two new spirobisnaphthalenes (1 and 2) together with eleven known compounds (3–13) from the crude extract of the fungus grown under an acidic condition as well as six known compounds (4, 10, 14–17) were isolated from the crude extract of the fungus grown under a neutral condition. Their structures were elucidated on the basis of extensive spectroscopic data. The isolated compounds were evaluated for their cytotoxicity against two human cancer cell lines, Ramos lymphoma and drug resistant NSCLC H1975. Compounds 2 and 10 displayed the most promising anti-tumor activity against both cancer cell lines.     

Chemical investigation of an antimalarial Chinese medicinal herb Picrorhiza scrophulariiflora

An antimalarial medicinal plant Picrorhiza scrophulariiflora was chemically investigated as part of our ongoing research in traditional chinese medicines (TCM). Mass directed fractionation of the active part of the crude extract led to the isolation of ten main components, three new compounds (1–3) and seven known compounds (4–10). Compound 10 inhibited the growth of the Plasmodium falciparum 3D7 malarial parasite line, with an IC₅₀ value of 8.3 μM. This compound accounted for ～95% of P. falciparum growth inhibitory activity in the crude extract confirming, for this TCM, that a single compound was responsible for the antimalarial activity.     

Chemical constituents from Baphia leptobotrys Harms (Fabaceae) and their chemophenetic significance

The chemical investigation of the CH₂Cl₂/MeOH (1:1) extract of the trunk bark and leaves of Baphia leptobotrys Harms (Fabaceae) led to the isolation of nineteen compounds (1–19). Their structures were elucidated based on the analysis of their NMR and MS data. Except for compounds 3–5, 14 and 15, all the isolated compounds are reported from the genus Baphia for the first time. Furthermore, compounds 8, 10, 16, 17 are isolated from the Fabaceae family for the first time. The crude extract and isolated compounds were screened in vitro for their antileishmanial activity against Leishmania donovani 1S (MHOM/SD/62/1S) promastigotes and cytotoxicity towards Raw 264.7 macrophage cells. The crude extract of B. leptobotrys exhibited moderate activity (IC₅₀ = 63.40 μg/mL). Amongst the tested compounds, ergosterol peroxide (9) and germanicol caffeoyl ester (8) exhibited good activity with IC₅₀ values of 9.43 and 10.24 μM, respectively and showed acceptable selectivity towards macrophage cells (SI > 3.85). The chemophenetic significance of these compounds is also discussed.     

Chemical constituents of Mussaenda erythrophylla Schumach. & Thonn. (Rubiaceae) and their chemophenetic significance

The chemical investigation of the CH₂Cl₂/MeOH (1:1) extract from the aerial part of Mussaenda erythrophylla Schumach. & Thonn. (Rubiaceae) resulted in the isolation of sixteen known compounds (1–16) distributed in coumarins, flavonoid glucosides, quinic acid derivatives, triterpenoids, monoglycerid, steroids, tetraterpenoid and polyol. The structures of the compounds were determined by spectrometric and spectroscopic analysis including MS and NMR data followed by their comparison with reported ones in the literature. The chemophenetic significance of the isolated compounds was discussed. The crude extract and some of the isolated compounds were assessed in vitro for their antileishmanial, cytotoxic and antiplasmodial activities. The crude extract of M. erythrophylla showed moderate antileishmanial activity (IC₅₀ = 61.6 μg/mL) while the hexane soluble fraction showed good antileishmanial activity (IC₅₀ = 31.06 μg/mL) compared to the reference drug amphotericin B (IC₅₀ = 0.11 μM). Compounds 11 and 9 also exhibited potent antileishmanial activity (IC₅₀ = 53.7–52.0 μM). The crude extract as well as the ethyl acetate soluble fraction also exhibited good antiplasmodial activity (IC₅₀ = 7.43 ± 0.00 μg/mL and 14.49 ± 2.96 μg/mL respectively), while compounds 11, 15 and 16 showed weak activity with IC₅₀ > 20 μM compared to the reference drug artemisinin (IC₅₀ = 0.014 ± 0.001 μM).     

Pentacyclic triterpenoids and other constituents isolated from the leaves of Gambeya lacourtiana and their antibacterial activity

The phytochemical study was done on the leaves of Gambeya lacourtiana. This plant has been used in traditional medicine to treat of different ailments such as uterine heamorrhage, metritis and other vaginal infections. Chromatographic fractionation and purification on the leaves crude extract afforded lupeol acetate (1), lupenone (2), lupeol (3), taraxerol (4) stigmasterol (5), erythrodiol (6), chamaedrydiol (7), methyl pheophorbide-a (8), corosolic acid (9), tormentic acid (10), epicatechin (11) and 22-dihydrospinasterol 3-O-β-D-glucopyranoside (12). The structures of compounds 1–12 were elucidated on the basis of 1D and 2D NMR, mass spectrometric and the spectroscopic data as well as comparison with the literature. Compounds 4, 7–10 and 12 were isolated for the first time from Gambeya genus. Crude extract, fractions and compounds 6–12 were evaluated for their antibacterial activity. Methyl pheophorbide-a (8) demonstrated moderate activity against Salmonella typhi CPC with MIC values of 62.5 μg/mL. The chemophenetic significance of these compounds is also discussed.     

A prenylated xanthone and antiproliferative compounds from leaves of Pentadesma butyracea

A new prenylated xanthone, butyraxanthone F (1) together with 20 known compounds were isolated from the leaves of Pentadesma butyracea. Their identification was achieved by spectroscopic means and comparison of the data with literature or by direct comparison on TLC with authentic samples. To the best of our knowledge, this is the first report of 2-hydroxy-2,3-dihydrosqualene (17) from a natural source. Compounds 2–6 and 11–16 were found for the first time in this genus. The antiproliferative activity of the crude extract, fractions and some isolated compounds was evaluated against three human cancer cell lines, BGC-823, Hela and A549. The crude extract, fractions B and C showed weak activities. Globuxanthone (2) and 30-epi-cambogin (7) were found to be the most active compounds on the three cancer cells. The effect of 2 on Hela cells and that of 7 on BGC-823 cells were noteworthy. The antiproliferative potential of allanxanthone A (3), ergosta-4,6,8(14),22-tetraen-3-one (14) and 2-hydroxy-2,3-dihydrosqualene (17) against BGC-823 and Hela cells could be classified as moderate-to-weak.     

ApoE secretion modulating bromotyrosine derivative from the Australian marine sponge Callyspongia sp.

High throughput screening of a pre-fractionated natural product library identified 11 active fractions showing ApoE modulation activity. Mass-directed fractionation of one active crude extract from the Australian marine sponge Callyspongia sp. resulted in the isolation of 13 metabolites, including three new bromotyrosine derivatives, callyspongic acid (1), 3,5-dibromo-4-methoxyphenylpyruvic acid (2), N-acetyl-3-bromo-4-hydroxylphenylethamine (3), and ten known compounds (4–13). The structure elucidation of compounds 1–3 was based on their 1D and 2D NMR and MS spectroscopic data. 3,5-Dibromo-4-methoxyphenylpyruvic acid (2) showed weak activity in increasing the apolipoprotein E secretion from human CCF-STTG1 cells at the concentration of 40 μM.     

New unsaturated fatty acid and other chemical constituents from the roots of Cola rostrata K. Schum. (Malvaceae)

Phytochemical investigation of the roots of Cola rostrata K. Schum. led to the isolation of a new unsaturated fatty acid, named rostratanic acid (1), together with fourteen known compounds, lignoceric acid, friedelan (7), friedelanone (8), bauerenol (3), lupeol (4), herranone (9), acotatarone A (11), betulinic acid (6), betulin (5), nonanedioc acid (2), arjunolic acid (10) stigmasterol, β−sitosterol, and β−sitosterol-3-O-β-D-glucopyranoside. The structure of the new compound as well as those of the known compounds were established by means of spectroscopic methods: NMR analysis (¹H and ¹³C NMR, ¹H–¹H–COSY, HSQC and HMBC) and high-resolution mass spectrometry (HR-ESI-MS), and by comparison with previously reported data. Two of those known compounds were modified chemically to afford three new derivatives. All those compounds were tested for their cytotoxic activity against the human cervix carcinoma KB-3-1 cells and their antibacterial activity against Escherichia coli, Salmonella enterica, Pseudomonas aeruginosa and Staphylococcus aureus. Although the crude extract gave weak antibacterial activity, none of the isolated compounds showed antibacterial activity, and, only the prenylated derivative showed weak cytotoxicity. In addition, the chemotaxonomic significance of the species Cola rostrata is discussed.     

Ceramide,cerebroside and triterpenoid saponin from the bark of aerial roots of Ficus elastica (Moraceae)

Three compounds, ficusamide (1), ficusoside (2) and elasticoside (3), were isolated from the bark of aerial roots of Ficus elastica (Moraceae), together with nine known compounds, including four triterpenes, three steroids and two aliphatic linear alcohols. The chemical structures of the three compounds were established by extensive 1D and 2D NMR spectroscopy, mass spectrometry and by comparison with published data. The growth inhibitory effect of the crude extract and isolated compounds was evaluated against several microorganisms and fungi. The cytotoxicity against human cancer cell lines was also assessed. Ficusamide (1) displayed a moderate in vitro growth inhibitory activity against the human A549 lung cancer cell line and a strong activity against Staphylococcus saprophyticus, while elasticoside (3) showed a potent activity on Enterococcus faecalis.     

Separation and purification of bioactive botrallin and TMC-264 by a combination of HSCCC and semi-preparative HPLC from endophytic fungus Hyalodendriella sp. Ponipodef12

Two dibenzo-α-pyrones, botrallin (1) and TMC-264 (2) were preparatively separated from crude ethyl acetate extract of the endophytic fungus Hyalodendriella sp. Ponipodef12, which was isolated from the hybrid ‘Neva’ of Populus deltoides Marsh × P. nigra L. using a combination of high-speed counter-current chromatography (HSCCC) and semi-preparative HPLC. Botrallin (1) with 74.73 % of purity and TMC-264 (2) with 82.29 % of purity were obtained through HSCCC by employing a solvent system containing n-hexane–ethyl acetate–methanol–water at a volume ratio of 1.2:1.0:0.9:1.0. It was the first time for TMC-264 (2) to be isolated from this fungus. TMC-264 (2) showed strong antimicrobial and antinematodal activity, and botrallin (1) exhibited moderate inhibitory activity on acetylcholinesterase.     

Depsidones from Talaromyces stipitatus SK-4, an endophytic fungus of the mangrove plant Acanthus ilicifolius

An endophytic fungus (Talaromyces stipitatus SK-4) was isolated from the leaves of a mangrove plant Acanthus ilicifolius. Its crude extract exhibited significant antibacterial activity and was purified to afford two new depsidones, talaromyones A and B (1 and 2), along with five known depsidone analogs (3–7). Their structures, including absolute configuration, were elucidated through extensive spectroscopic data analysis and modified Mosher's method. Compound 2 showed antibacterial activity against Bacillus subtilis with an MIC value of 12.5 μg/mL. In the inhibitory assay against α-glucosidase, compounds 2, 4 and 5 displayed moderate activities with IC₅₀ values ranging from 48.4 to 99.8 μM.     

New wedelolides, (9R)-eudesman-9,12-olide δ-lactones,from Wedelia trilobata

From the crude ethanol extract of Wedelia trilobata leaves, hexane and dichloromethane fractions exhibited in vitro antimalarial activity against the Plasmodium falciparum parasite (strain PFB), with IC₅₀ values of 27.0 and 13.0 μg/mL, respectively. Specifically, two new (9R)-eudesman-9,12-olide δ-lactones, wedelolide G (1) and wedelolide H (2), were isolated from the dichloromethane extract and showed IC₅₀ values of 3.42 and 5.96 μM, respectively. Six known compounds are also present in the extract. The structures of 1⿿8 were elucidated through spectroscopic studies.     

Bisabololoxide derivatives from Artemisia persica,and determination of their absolute configurations by ECD

Five antiplasmodial bisabololoxide sesquiterpene diesters were isolated from an EtOAc extract of the aerial parts of Artemisia persica following an HPLC-time-based activity profiling of the extract. Structure elucidation was achieved by 1D and 2D NMR experiments. Relative configurations of cyclohexenone/cyclohexene and tetrahydropyran moieties of 1–5 were established on the basis of ³J_H–H coupling constants and NOE difference spectra. Stereochemical correlation of the two rings, and assignment of absolute configuration of 1–5 were achieved by comparison of experimental ECD spectra with simulated ECD data for possible stereoisomers, by using time dependent density function theory (TDDFT). Bisaboloids 1–4 exhibited in vitro antimalarial activity against Plasmodium falciparum, with IC₅₀ values ranging from 2.8 to 20.1 μM, and selectivity indices (SI) in L-6 cells of 3.7–11.9.     

Bio-guided isolation of potential antimicrobial and antioxidant agents from the stem bark of Trilepisium madagascariense

Aim

This study describes the activity-guided isolation of antimicrobial and antioxidant agents from Trilepisium madagascariense stem bark.

Methods

The methanol crude extract of T. madagascariense was partitioned sequentially into n-hexane, ethyl acetate, n-butanol and the residual aqueous fractions. The ethyl acetate fraction was subjected to column chromatography and the structures of isolated compounds were elucidated using GC-MS and/or NMR data by comparing with those reported in the literature. Antimicrobial activity was assayed by agar well diffusion and broth microdilution techniques on 8 bacteria and 10 yeasts. The antioxidant activity was determined by DPPH radical scavenging method.

Results

The bioassay-guided fractionation of the crude methanol extract of T. madagascariense afforded two known compounds [vanillic acid () and isoliquiritigenin ()] and two mixtures of fatty acids (n-hexane fraction and first column fraction of ethyl acetate fraction, F1). The fractionation of the crude methanol extract enhanced the antimicrobial activity. Compound 2 was generally more active than compound 1. For all the tested samples, the most sensitive microbes were Enterococcus faecalis ATCC 10541 (MIC range of 60-780 μg/ml) for bacteria and Candida guillermondi (MIC range of 0.01-190 μg/ml) for yeasts. The DPPH radical scavenging activity (RSa) of compound 2 (RSa₅₀ = 28.73 μg/ml) was comparable to that of the crude methanol extract (RSa₅₀ = 29.92 μg/ml).

Conclusion

The antimicrobial activities and the antioxidant properties of the methanol crude extract, fractions and compounds 1 and 2 from the stem bark of T. madagascariense are being reported for the first time. These results may justify the traditional use of this plant for the treatment of gastrointestinal disorders.     

Glycopentanolones A-D,four new geranylated quinolone alkaloids from Glycosmis pentaphylla

The ethanolic extract obtained from the stems of Glycosmis pentaphylla was found to suppress antigen-mediated degranulation of rat basophilic leukemia (RBL-2H3) cells. Four new geranylated 2-quinolone alkaloids, named glycopentanolones A–D (1–4), and 12 known metabolites (5–16) were isolated from the ethanolic extract from the stems of G. pentaphylla using bioassay-guided fractionation. Their structures were elucidated by a combination of 1D and 2D NMR, and HRESI-MS. The inhibitory effects of the isolated constituents on β-hexosaminidase release from RBL-2H3 cells were examined, and compounds 1, 5, 8 and 11 exhibited potent inhibitory activity with IC₅₀ values between 0.05 and 4.28 μM.     

Chemical constituents from the fungus Stereum sp. YMF1.04183

The chemical constituents of the basidiomycete Stereum sp. YMF1.04183 were studied. Three new sesquiterpenes, stereumenes A–C (1–3), were isolated and identified from the EtOAc extract of Stereum sp. YMF1.04183 culture broth. Stereumene B showed weak nematicidal activity against Caenorhabditis elegans.     

New acylphloroglucinol derivatives from the leaves of Baeckea frutescens

Three new acylphloroglucinols, baeckenones A–C (1–3), were isolated from the chloroform extract of the leaves of Baeckea frutescens together with three known compounds 4–6. The structures of the isolated compounds were determined using extensive spectroscopic analyses including IR, NMR, and HRMS. Baeckenone B (2) exhibited a moderate antibacterial activity against Bacillus subtilis with an MIC value of 40 μM.     

Antimicrobial selaginellin derivatives from Selaginella pulvinata

Six selaginellin derivatives, including three new analogues selaginellins D–F (1–3), were isolated from the EtOAc extract of the whole plant of Selaginella pulvinata (Hook. et Grev.) Maxim. Their structures were determined on the basis of extensive physical and chemical evidence. Compounds 1 and 4 demonstrated antifungal activities against Candida albicans; compounds 4–6 exhibited significant antibacterial activity against Staphylococcus aureus.     

Steroidal glycosides from Marsdenia tenacissima

Three new compounds 1–3 as C₂₁ steroidal glycosides of diester derivatives of tenacigenin B were isolated from the ethanolic extract of stems of Marsdenia tenacissima. All compounds were prepared and evaluated inhibitory activity of nitric oxide in RAW276.4 macrophages. Compounds 1–3 exhibited inhibitory effects against nitric oxide (NO).