Sensory-guided isolation and identification of new sweet-tasting dammarane-type saponins from Jiaogulan (Gynostemma pentaphyllum) herbal tea.

The purpose of this study was to elucidate the chemical basis for the sweet property produced by Gynostemma pentaphyllum and find new natural high-potency (HP) sweeteners. Sixteen new compounds (gypenosides YN 1-16) were obtained by sensory-guided isolation and identification, in which fifteen of them were sweet-tasting constituents with sweetness intensities 10-100 times higher than that of sucrose evaluated by human sensory panel test. Their structures were established by 1D and 2D nuclear magnetic resonance spectra, mass spectroscopy, infrared spectroscopy, UV-visible spectroscopy, and chemical method. Gypenoside YN 4 was the sweetest compound with a concentration of 15.504 ± 1.343 mg/kg, while gypenoside YN 12 has the highest concentration (1397.674 ± 12.948 mg/kg), as shown by ultra-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS). Structure-activity relationship analysis implied that the compounds' sweetness intensity was associated with side-chain substitutions at C-20 or the number of glucosyl groups at C-3. These new plant-derived natural products may be potential natural sweeteners.

Repellent, larvicidal and adulticidal activities of essential oil from Dai medicinal plant Zingiber cassumunar against Aedes albopictus.

Zingiber cassumunar is an important plant used in traditional medicine and as a natural mosquito repellent. However, the compounds responsible for the repellent activity of the plant are still unknown. The aim of the study is to identify the components of Z. cassumunar essential oil that show repellent activity against Aedes albopictus. We also evaluated the larvicidal and adulticidal activities of Z. cassumunar essential oil against Ae. albopictus. In-cage mosquito repellent experiments showed that Z. cassumunar essential oil possessed moderate repellent activity with a minimum effective dose (MED) of 0.16 ± 0.01 mg/cm2, compared to reference standard N,N-diethyl-3-methylbenzamide (DEET, 0.03 ± 0.01 mg/cm2). Bioassay-guided fractionation identified the major active compound of Z. cassumunar essential oil as (-)-terpinen-4-ol (1) (MED: 0.19 ± 0 mg/cm2). We also found that Z. cassumunar essential oil showed moderate larvicidal activity against first instar larvae of Ae. albopictus with a LC50 (50% lethal concentration) of 44.9 µg/L after 24 h. Fumigation bioassays showed that Z. cassumunar essential oil exhibits moderate adulticidal activity against Ae. albopictus with a LC50 of 5.44%, while (-)-terpinen-4-ol showed significant adulticidal activity with a LC50 of 2.10% after 24 h. This study verifies that the Z. cassumunar essential oil has mosquito repellent activity, and that (-)-terpinen-4-ol is mainly responsible for this activity. Furthermore, this study provides scientific support for the folk usage of Z. cassumunar essential oil as mosquito repellent and indicates that Z. cassumunar essential oil and (-)-terpinen-4-ol can be used as plant-derived repellents and insecticides for mosquito control.

Bioassay-guided isolation of active compounds from Adenosma buchneroides essential oil as mosquito repellent against Aedes albopictus.

ETHNOPHARMACOLOGICAL RELEVANCE: A folk herb Adenosma buchneroides found in the previous ethnobotanical investigation plays an important role as an insect repellent among the Aini people in southwest of China, but the active compounds responsible for repellent activity of the plant have not yet been investigated. AIM OF THE STUDY: The main purpose of the study is to identify the active components of the essential oil which responsible for its repellent activity against Aedes albopictus to support the usage of the plant as mosquito repellent by Aini people. In addition, to supply a class of potential alternatives characterized carvacrol analogues to develop natural repellent products. MATERIAL AND METHODS: The essential oil from aerial part of Ad. buchneroides was extracted by hydrodistillation. A systematic bioassay-guided isolation of repellent compounds from the essential oil was conducted through chromatographic fractionation combined with in-cage mosquito repellent bioassay. The identification of the essential oil components was accomplished by GC-MS and GC-FID techniques. The structural elucidation of compounds was performed on the basis of IR, HR-ESI-MS and NMR. Larvicidal activity and cytotoxicity of all repellent compounds also tested by larval bioassays and MTS assays, respectively. Structure-activity relationship (SAR) of carvacrol analogues was investigated by in-cage mosquito repellent bioassay. RESULTS: The essential oil of the plant showed strong mosquito repellent activity with minimum effective dosage (MED) of 0.019 ±â€¯0.007 mg/cm2, compared to reference standard N,N-diethyl-3-methylbenzamide (DEET) (0.031 ±â€¯0.014 mg/cm2). 26 compounds representing 97.8% of the essential oil were identified. Carvacrol, carvacrol methyl ether and a new fragrant compound, adenosmin A (1) were found to be repellent compounds by systematic bioassay-guided isolation, with MEDs in the range of 0.011-0.125 mg/cm2. An investigation on SAR of carvacrol analogues led to the discover of three analogues with further lower MEDs (0.002-0.009 mg/cm2) than that of DEET, and other three compounds with similar MEDs (0.029-0.039 mg/cm2) to that of DEET. Carvacrol (LD50 of 24.8 ppm) was the best larvicide among tested repellent compounds. The essential oil and repellent compounds against seven mammalian cell lines revealed low or no cytotoxicity. CONCLUSIONS: Scientific evidences reported here validate the plant's traditional use as insect repellent and imply promising application of the essential oil and carvacrol analogues as natural mosquito repellents.

New Sweet-Tasting C21 Pregnane Glycosides from the Roots of Myriopteron extensum.

To investigate the sweet-tasting components in the roots of Myriopteron extensum, the phytochemical study of its roots was conducted, which led to the discovery of 12 new C21 pregnane glycosides (extensumside M-X, 1-12) and two known ones (extensumside C and extensumside E, 13-14). Their chemical structure elucidation was accomplished by means of spectroscopic methods: IR, UV, ESI-MS, and NMR (1H NMR, 13C NMR, HSQC, 1H-1H COSY, HMBC, HSQC-TOCSY, and ROESY), as well as the chemical evidence. Sensory analysis of these compounds revealed that nine of them (1, 3, 4, 5, 6, 7, 8, 13, and 14) are highly sweet-tasting compounds. Their sweetness intensities are 25 to 400 times greater than that of sucrose. Analysis of the structure-activity relationship (SAR) indicated that the sweet intensities of the isolated compounds are closely related to the aglycone 3ß,16α-dihydroxy-pregn-5-en-20-one, the number and type of the monosaccharide in the sugar chain linked to C-3 and C-16 and the position of the mBe group.

Antibacterial and antioxidant properties of crude extract, fractions and compounds from the stem bark of Polyscias fulva Hiern (Araliaceae).

BACKGROUND: In our previous work, the dichloromethane-methanol (1:1 v/v) extract, fractions and isolated compounds from Polyscias fulva stem bark showed interesting antifungal activity. As a continuity of that work, this study aimed to bring out complementary informations about the antimicrobial properties of P. fulva stem bark that may be useful in the standardization of phytomedicine from this plant. METHODS: The antibacterial activities of the crude extract, fractions (n-hexane, ethyl acetate, n-butanol and residual) and isolated compounds from Polyscias fulva stem bark were assayed by broth microdilution techniques. Their antioxidant activity were evaluated using 2,2-diphenyl-1-picrylhydrazyl (DPPH), pyrogallol (superoxide anion) and ß-carotene - linoleic acid assays. RESULTS: The crude extract presented antibacterial activities against S. typhi (ATCC 6539), E. aerogenes (ATCC 13045), P. aeruginosa (PA01) and E. coli (ATCC 10536) with MIC values of 2000 to 8000 µg/ml. The fractionation led the ethyle acetate and n-butanol fractions relatively more active (MIC = 500 to 1000 µg/ml) as compared to the crude extract. ß-sitosterol and 3-O-α-L- arabinopyranosyl-hederagenin were the most active compounds on the tested bacteria with MIC values ranging from 6.25 to 100 µg/ml. The most sensitive was P. aeruginosa (PA01) on which all the tested compounds were active with MICs ranging from 6.25 to 400 µg/ml. Among all the tested substances, the crude extract (RSa50 = 84.86 µg/ml) and the methyl atrarate (RSa50 = 14.77 µg/ml), showed the highest scavenging activities against DPPH free radicals and those arising from the oxidation of the linoleic acid respectively. CONCLUSION: From this study, the results obtained reveal that the stem bark of P. fulva possesses antibacterial and antioxidant activities. It may then be useful in the development of an antimicrobial phytomedicine with a large spectrum of actvity endowed with antioxidant properties which can be standardised based on the isolated compounds.

New Sweet-Tasting C21-Pregnane Glycosides from Pericarps of Myriopteron extensum.

Ten novel C21 pregnane glycosides, extensumside C-L (1-10), were isolated as highly sweet-tasting substances from the edible pericarps of Myriopteron extensum (Wight) K. Schum by sensory-guided fractionation and purification. Their structures were determined through 1D and 2D NMR, such as HSQC, HMBC, 1H-1H COSY, HSQC-TOCSY, and ROESY, as well as other spectroscopic analysis combined with chemical evidence. These compounds shared the same aglycone, 3ß,16α-dihydroxy-pregn-5-en-20-one, and contained the deoxysugar chain and the glucose chain which were linked to C-3 and C-16 of the aglycone, respectively. The sweetness potency was evaluated by a human sensory panel test and preliminary structure-taste relationship was discussed. The sweetness intensities of these compounds are between 50 and 400 times greater than that of sucrose. Furthermore, quantitation analyses of compounds 1, 3, 4, and 6 in different parts of M. extensum indicated that the concentrations of these sweet components in the pericarps are obviously higher than those in stems and roots.

Antifungal properties of a new terpernoid saponin and other compounds from the stem bark of Polyscias fulva Hiern (Araliaceae).

BACKGROUND: In our previous studies, it was evident that the dichloromethane-methanol (1:1 v/v) stem barks extract of Polyscias fulva and fractions (ethyl acetate, n-butanol and residue) demonstrated interesting antidermatophytic activities. So, as a continuity of that, this work aimed at identifying active principles with antifungal properties from P. fulva that could be used as markers for possible standardization of this plant as phytomedicine. METHODS: The ethyl acetate, n-butanol and residual fractions of the dichloromethane-methanol (1:1 v/v) stem bark extract of Polyscias fulva were further fractionated by column chromatography and the structures of isolated compounds elucidated based on their spectroscopic data in comparison with existing literature information. Antifungal activity was assayed by broth microdilution techniques on yeasts and dermatophytes spores. RESULTS: The fractionation of the crude dichloromethane-methanol (1:1 v/v) stem bark extract of Polyscias fulva led to the isolation of 10 known compounds (1 to 10) and one new saponin (11: 3-O-[α-L-rhamnopyranosyl (1-2)-α-L-arabinopyranosyl]-28-O-[α-L-4-O-acetyl-rhamnopyranosyl (1-4)-ß-D-glucopyranosyl-(1-6)-ß-D-glucopyranosyl]-hederagenin). Among these compounds, 3-O-α-L- arabinopyranosyl-hederagenin and 3-O-[α-L-rhamnopyranosyl (1-2)-α-L-arabinopyranosyl]-hederagenin were the most active on the tested fungi with MIC values ranging from 0.78 to 100 µg/ml against both yeasts and dermatophytes. CONCLUSION: The results of this work constitute a step forward in the possible development of an antidermatophytic phytomedicine from Polyscias fulva stem bark, the isolated compounds being possible markers for the standardisation.

A new antimicrobial and radical-scavenging glycoside from Paullinia pinnata var. cameroonensis.

A new glycoside, pinnatoside A (1), together with two known compounds (2 and 3), were isolated from the stems of Paullinia pinnata. Their structures were elucidated on the basis of extensive spectroscopic analysis and chemical methods. Compound 1 showed significant antibacterial activity with a minimum inhibitory concentration (MIC) value of 1.56 µg/mL against Escherichia coli, and 2 displayed significant antibacterial activity with a MIC value of 1.56 µg/mL against Enterobacter aerogenes and E. coli. Equally, compound 1 exhibited the best radical-scavenging activity (RSa50 = 25.07 ± 0.49 µg/mL).

Flavonoids and stilbenoids from Derris eriocarpa.

One new resveratrol analogue, 1-(3',4',5'-trimethoxyphenyl)-2-methoxy-2-(4″-methoxyphenyl)-ethane-1-ol (1), and two new prenylisoflavones, 4'-hydroxy-5,7-dimethoxy-6-(3-methyl-2-butenyl)-isoflavone (2), and derrubon 5-methyl ether (3), together with 17 known compounds including one new natural product, 5,7-dihydroxy-3-[4'-O-(3-methyl-2-butenyl)-phenyl]-isoflavone (4), were isolated from the stems of ethnomedicinal plant Derris eriocarpa How. (Leguminosae). Their structures were elucidated based on chemical evidence and spectroscopic techniques including two-dimensional NMR methods. All compounds are reported from this species for the first time. Antimicrobial activities of the new compounds were evaluated. Compound 2 exhibited good inhibitory activities against Candida guilliermondii, C. albicans and Microsporium gypseum with the minimal inhibitory concentration (MIC) values of 12.5 µg/ml.

Chemical constituents of Euphorbia tangutica.

Sixteen known compounds isolated from the whole plants of Euphorbia tangutica, including phorbol-13-actate (1) previously synthesised and obtained from a natural source for the first time, were evaluated in vitro against a panel of human cancer cell lines using the MTT method. Among them, ergosterol (6) exhibited significant cytotoxic activity against HL-60 cell line with an IC(50) value of 3.3 µM, and 3ß,5α-dihydroxy-15ß-cinnamoyloxy-14-oxolathyra-6 Z,12 E-diene (7) also displayed moderate activity.

Monoterpenoid indole alkaloids from the bark of Alstonia scholaris.

Six new monoterpenoid indole alkaloids, scholarisines B-G (1- 6), together with 15 known analogues (7- 21), were isolated from the bark of Alstonia scholaris. Their structures were determined by 1D and 2D NMR spectra and MS analyses. The structure of 1 was further supported by the single-crystal X-ray.

Antimicrobially active isoquinoline alkaloids from Litsea cubeba.

Bioassay-guided fractionation of the alkaloidal extract of the aerial part of Litsea cubeba led to the isolation of two new isoquinoline alkaloids, (+)- N-(methoxycarbonyl)-N-norboldine (1) and (+)-isoboldine beta-N-oxide (2), together with 11 known analogues (3-13). Their structures were established by extensive spectroscopic techniques and by comparing spectroscopic data with those in the literature. Compounds 1 and 4 showed antimicrobial activities. This is the first report on the presence of compounds 1, 2, 6, 8, 9, 11, and 12 in this plant and on the antimicrobial activities of 1 and 4. The bioactivities of isoquinoline alkaloids are also at least partly responsible for the pharmacological function of the folk medicinal plant Litsea cubeba.

Volatile organic nitrogen-containing constituents in ambrette seed Abelmoschus moschatus Medik (Malvaceae).

A detailed investigation of the basic fraction of a CO2 extract of ambrette seeds (Abelmoschus moschatus) revealed a total of 58 nitrogen-containing compounds. The identification of these compounds was carried out by GC-MS and NMR. All the identified nitrogen-containing compounds are reported here for the first time in ambrette seeds. Among these are 27 pyrazine derivatives and 12 pyridines, including the tentative identification of four new natural compounds, 1-(6-ethyl-3-hydroxypyridin-2-yl)ethanone (1), 1-(3-hydroxy-5,6-dimethylpyridin-2-yl)ethanone (2), 1-(3-hydroxy-6-methylpyridin-2-yl)ethanone (3), and 1-(3-hydroxy-5-methylpyridin-2-yl)ethanone (4). The odor of the basic fraction was assumed to be due to these pyrazines and pyridines and also the presence of seven thiazoles. The odors described suggest that these N-compounds contribute to what is described in perfumery terms as the "natural and rounded" character of the ambrette extract.

Volatiles from leaves and rhizomes of Fragrant Acorus spp. (Acoraceae).

Three horticultural selections of Acorus gramineus Soland were investigated to determine the chemical composition of their leaves and rhizomes. The variety 'liquorice' was found to contain methylchavicol (49%) which accounts for the unusual anisic odor of this variety, while beta-asarone was the main component of A. christophii (43%) and 'yodo-no-yuki' (20%). The results are compared with calamus oils, and the possible biosynthetic precursors of the main components methylchavicol and beta-asarone are considered.

A cage-monoterpene indole alkaloid from Alstonia scholaris.

An unprecedented cage-like alkaloid, scholarisine A was isolated from the leaves of Alstonia scholaris and its structure determined on the basis of 1D and 2D NMR, FTIR, UV, and high-resolution mass spectroscopic data. This alkaloid might be derived from picrinine via oxygenation, rearrangement, and lactonization.

Two new antifungal saponins from the Tibetan herbal medicine Clematis tangutica.

Bioassay-guided fractionation of the ethanol extract of the aerial parts of Clematis tangutica led to the isolation of two new antifungal triterpene saponins. Their structures were determined to be 3- O-alpha- L-arabinopyranosyl hederagenin 28- O-alpha- L-rhamnopyranosyl ester ( 1) and 3- O-beta- D-glucopyranosyl-(1--> 4)-alpha- L-arabinopyranosyl hederagenin 28- O-alpha- L-rhamnopyranosyl ester ( 2) on the basis of spectral data and chemical evidence. Inhibitory activities of the two saponins against seven fungal strains were evaluated. Compounds 1 and 2 showed evident antifungal activity (MIA approximately 2.5 micrograms/disc) against Saccharomyces cerevisiae, similar to the positive control amphotericin B and ordinary activities (MIA approximately 10 micrograms/disc) against Penicillium avellaneum UC-4376, Candida glabrata, Trichosporon beigelii and Pyricularia oryzae. Compound 2 is a better antifungal agent than compound 1 against most of the fungal strains that were tested.