Bioactive constituents from roots of Bursera tonkinensis

Discovery of Bioactive Compounds by the UIC-ICBG Drug Discovery Program in the 18 Years Since 1998

The International Cooperative Biodiversity Groups (ICBG) Program based at the University of Illinois at Chicago (UIC) is a program aimed to address the interdependent issues of inventory and conservation of biodiversity, drug discovery and sustained economic growth in both developing and developed countries. It is an interdisciplinary program involving the extensive synergies and collaborative efforts of botanists, chemists and biologists in the countries of Vietnam, Laos and the USA. The UIC-ICBG drug discovery efforts over the past 18 years have resulted in the collection of a cumulative total of more than 5500 plant samples (representing more than 2000 species), that were evaluated for their potential biological effects against cancer, HIV, bird flu, tuberculosis and malaria. The bioassay-guided fractionation and separation of the bioactive plant leads resulted in the isolation of approximately 300 compounds of varying degrees of structural complexity and/or biological activity. The present paper summarizes the significant drug discovery achievements made by the UIC-ICBG team of multidisciplinary collaborators in the project over the period of 1998-2012 and the projects carried on in the subsequent years by involving the researchers in Hong Kong.

Discovery of antifungal constituents from the Miao medicinal plant Isodon flavidus

ETHNOPHARMACOLOGICAL RELEVANCE

Leigong Mountain is an area in the Southwest of China where there is a high incidence rate of athlete's foot, but the Miao people, a Chinese minority who reside in this mountainous area have suffered less from this disease due to their use of the herbal medicine Isodon flavidus (Hand.-Mazz.) H. Hara.

AIM OF THE STUDY

The present study is to identify the active chemical constituents responsible for antifungal effects of the folk medicine plant.

MATERIALS AND METHODS

The natural compounds were separated from the methanol extract of the twigs and leaves of I. flavidus by phytochemical study using chromatographic methods, and their chemical structures were determined by analysis of the spectroscopic data including 1D and 2D NMR spectra. The absolute configuration of fladin A (1) was further confirmed by X-ray crystallographic analysis. The compounds were evaluated for their antifungal activity against the athlete's foot fungus Trichophyton rubrum. They were further evaluated for their antimicrobial and anti-biofilm activity against the dental pathogens Streptococcus mutans, Porphyromonas gingivalis and Candida albicans.

RESULTS

Phytochemical and biological studies of I. flavidus led to the discovery of two antifungal compounds, fladin A (1) and lophanic acid (2). Fladin A (1) is a novel diterpene with an unprecedented cyclic ether group formed between C-4 and C-9. Lophanic acid (2) displayed inhibition activity against the athlete's foot fungus Trichophyton rubrum with an MIC value of 7.8μg/mL, and fladin A (1) also showed inhibition activity against the fungus with a MIC value of 62.5μg/mL.

CONCLUSIONS

Our identification of two antifungal compounds provided strong evidence for the Miao people to use I. flavidus as a medicinal plant for treatment of athlete's foot disease. The very different chemical structures of the active compounds from those in the market presents them as potential antifungal lead compounds for follow-up study.

Lignans from the stem bark of Syringa pinnatifolia

Four new lignans, alashinols A-D (1-4), a new hydrolysis product, alashinols E (5), and seven known analogues were isolated from the stem bark of Syringa pinnatifolia Hemsl. These new lignans were characterized using 1D and 2D NMR and MS data, and their absolute configurations were determined by experimental and calculated electronic circular dichroism and X-ray diffraction analyses. Alashinol B (2) exhibited two conformers that adopted an unusual unit cell packing. Anti-inflammatory evaluation revealed that compounds 1, 4, 6, and 8 showed moderate inhibition against NO production in lipopolysaccharide-induced macrophages RAW 264.7 cells with IC₅₀ values range from 43.3-60.9μM, and 1 decreased the TNF-α and IL-6 level in a concentration-dependent manner at 40-160μM and exhibited considerable neuroprotective effect against the glutamate-induced injury in PC12 cell line. Analogues 3 and 9 showed protective effects against oxygen glucose deprivation/reoxygenation in H9c2 cells.

Hypoglycemic Constituents Isolated from Trapa natans L. Pericarps

Trapa natans L., called water chestnut or water caltrop, is a floating aquarium plant. Its fruits are widely used as food. Two new tannins, 1 and 2, one new neolignan, 14, one new norlignan, 17, and 20 known compounds, 3-13, 15, 16, and 18-24 were isolated from T. natans pericarps in this study. The 1, 2, 14, and 17 structures were elucidated using a chemical method and extensive spectral evidence. A series of hydrolyzable tannins, 1-8, a lignin, 13, a flavonoid, 16, a norlignan, 17, and phenolic compounds, 18, 20, 21, and 24 resulted in the enhanced glucose uptake activity in C2C12 myotubes. Compounds 4 and 5 significantly increased GLUT4 protein expression in C2C12 myotubes. In addition, 4 and 5 improved the phosphorylation of AMPK, AKT(S473), and AKT(T308). The involvement of AMPK and PI3K in the mechanism of action of compounds 4 and 5 was confirmed by use of AMPK and PI3K inhibitors, which completely suppressed the 4- and 5-mediated activities of glucose uptake in C2C12 myotubes. We also demonstrated that 4 and 5 could increase GLUT4 protein levels in plasma membranes.

Anti-inflammatory and cytotoxic activities of Bursera copallifera

Background:

The plant species Bursera copallifera (DC) bullock is used in traditional medicine to treat inflammation. The leaves of this plant can be prepared as an infusion to treat migraines, bronchitis, and dental pain

Objective:

The purpose of this study was to determine the anti-inflammatory and cytotoxic activities of organic extracts from the stems, stem bark, and leaves of B. copallifera, which was selected based on the knowledge of its traditional use.

Materials and Methods:

We evaluated the ability of extracts to inhibit mouse ear inflammation in response to topical application of 12-O tetradecanoylphorbol-13-acetate. The extracts with anti-inflammatory activity were evaluated for their inhibition of pro-inflammatory enzymes. In addition, the in vitro cytotoxic activities of the organic extracts were evaluated using the sulforhodamine B assay.

Results:

The hydroalcoholic extract of the stems (HAS) exhibited an anti-inflammatory activity of 54.3% (0.5 mg/ear), whereas the anti-inflammatory activity of the dichloromethane-methanol extract from the leaves (DMeL) was 55.4% at a dose of 0.1 mg/ear. Methanol extract from the leaves (MeL) showed the highest anti-inflammatory activity (IC₅₀ = 4.4 μg/mL), hydroalcoholic extract of leaves, and DMeL also reduce the enzyme activity, (IC₅₀ = 6.5 μg/mL, IC₅₀ = 5.7 μg/mL), respectively, from stems HAS exhibit activity at the evaluated concentrations (IC₅₀ =6.4 μg/mL). The hydroalcoholic extract of the stems exhibited the highest cytotoxic activity against a breast adenocarcinoma cell line (MCF7, IC₅₀ = 0.90 μg/mL), whereas DMeL exhibited an IC₅₀ value of 19.9 μg/mL.

Conclusion:

In conclusion, extracts from leaves and stems inhibited cyclooxygenase-1, which is the target enzyme for nonsteroidal anti inflammatory drugs, and some of these extracts demonstrated substantial antiproliferative effects against the MCF7 cell line. These results validate the traditional use of B. copallifera.

Phenolic Compounds from the Roots of Rhodiola crenulata and Their Antioxidant and Inducing IFN-γ Production Activities

In the present study, two new phenolic compounds 1 and 11, a pair of lignan isomers 12 and 13 with their absolute configurations established for the first time, were isolated from the ethanol extract of the roots of Rhodiola crenulata, together with 13 known phenolic compounds, and their structures were elucidated via NMR, HRESIMS, UV, IR and CD analyses. All the isolated compounds were evaluated for their in vitro antioxidant activities using the 2,2-diphenyl-1-picryhydrazyl (DPPH) and 2,2'-azino-bis (3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) radical scavenging assays. Ten of them exhibited significant antioxidant activities compared to ascorbic acid. Furthermore, the inducibilities of the isolated compounds to IFN-γ production were also assessed. Compounds 1, 8, 9, 12, 13, 14 and 15 could moderately stimulate IFN-γ expression.

Chemical constituents from Sonneratia ovata Backer and their in vitro cytotoxicity and acetylcholinesterase inhibitory activities

Sonneratia ovata Backer, Sonneratiaceae, is a widespread plant in mangrove forests in Vietnam, Cambodia, Thailand, Indonesia. Sonneratia ovata's chemical composition remains mostly unknown. Therefore, we now report on the structural elucidation of three new phenolics, sonnerphenolic A (1), sonnerphenolic B (2), and sonnerphenolic C (23), a new cerebroside, sonnercerebroside (3) together with nineteen known compounds, including nine lignans (5-13), two steroids (14, 15), two triterpenoids (16, 17), three gallic acid derivatives (18-20), two phenolic derivatives (4, 22) and a 1-O-benzyl-β-d-glucopyranose (21) isolated from the leaves of Sonneratia ovata. Their chemical structures were established by spectroscopic data, as well as high resolution mass spectra and comparison with literature data. The in vitro acetylcholinesterase (AChE) inhibition and cytotoxic activities against HeLa (human epithelial carcinoma), NCI-H460 (human lung cancer), MCF-7 (human breast cancer) cancer cell lines and PHF (primary human fibroblast) cell were evaluated on some extracts and purified compounds at a concentration of 100 μg/mL. Compounds (5, 6, 23) exhibited cytotoxicity against the MCF-7 cell line with the IC50 values of 146.9±9.0, 114.5±7.2, and 112.8±9.4 μM, respectively, while they showed nontoxic with the normal cell (PHF) with IC50s >277 μM. Among 15 tested compounds, (S)-rhodolatouchol (22) showed inhibition against AChE with an IC50 value of 96.1±14.5 μM.

New lignans and their biological activities

Lignans, which are widely distributed in higher plants, represent a vast and rather diverse group of phenylpropane derivatives. They have attracted considerable attention due to their pharmacological activities. Some of the lignans have been developed approved therapeutics, and others are considered as lead structures for new drugs. This article is based on our previous review of lignans discovered in the period 2000-2004, and it provides a comprehensive compilation of the 354 new naturally occurring lignans obtained from 61 plant families between 2005 and 2011. We classified five main types according to their structural features, and provided the details of their sources, some typical structures, and diverse biological activities. A tabular compilation of the novel lignans by species is presented at the end. A total of 144 references were considered for this review.

New neolignan glycoside and an unusual benzoyl malic acid derivative from Maytenus senegalensis leaves

Further investigation of the methanol leaf extract of Maytenus senegalensis led to the isolation of six compounds, including mayselignoside (1) and an unusual benzoyl malic acid derivative, benzoyl R-(+)-malic acid (2). Two known lignan derivatives (+)-lyoniresinol (3) and (-)-isolariciresinol (4), a known neolignan derivative dihydrodehydrodiconiferyl alcohol (5) and the triterpenoid, β-amyrin (6) were also isolated. The structures of these compounds were elucidated by a combination of 1D and 2D NMR and mass spectroscopy. All compounds were tested for cytotoxicity against mouse lymphoma cell line (L5178Y) and for antimicrobial activity against strains of bacteria and fungi. None of the compounds showed promising cytotoxic and/or antimicrobial activities.

A New Cycloartane Glucoside from Rhizophora stylosa

Nine secondary metabolites, including a new cycloartane glucoside, rhizostyloside (1), were isolated from a methanol extract of Rhizophora stylosa leaves through several chromatographic experiments. The structures of the compounds were determined on the basis of NMR spectroscopic (1H and 13C NMR, HSQC, HMBC, 1H-1H COSY, NOESY) and HR-ESI-MS data and by comparison with literature values. Compound 1 exhibited significant cytotoxicity against three human cancer cell lines: KB (epidermoid carcinoma), LU-1 (lung adenocarcinoma), and SK-Mel-2 (melanoma). In addition, 1 strongly activated caspase-3/7 in LU-1 cells.

Two novel lignans from Gaultheria yunnanensis

Two new lignans, 9-salicyl-(+)-isolariciresinol (1) and gaultheroside G (2), together with seven known compounds, were isolated from the ethanolic extract of the whole plant of Gaultheria yunnanensis. Their structures were determined by extensive NMR and MS analyses. Gaultheroside G (2) was found to have an unusual ether linkage between the 2 and 9' positions of aryl-tetralin lignan skeleton. All nine compounds were assayed for inhibitory effects against nitric oxide and pro-inflammatory cytokines TNF-α and IL-6 release in LPS-induced RAW 246.7 macrophages, while no significant activities were observed for the evaluated compounds.

Xanthone and lignan glycosides from the aerial parts of Polygonum bellardii all growing in Egypt

A new long chain fatty alcohol acetate identified as 17-hydroxypentacosanyl acetate, (1) together with a new xanthone identified as 1,8-Dihydroxy-3,6-dimethoxy-xanthone-5-O-[α-L-rhamnopyranosyl-(1′′→2′)]-β-D-glucopyranoside (3), as well as two new lignans identified as (+)-Lyoniresinol-3a-O-[α-L-rhamnopyranosyl-(1′′′→6′′)]-β-D-glucopyranoside (4) and (+)-Isolariciresinol-3a-O-[α-L-rhamnopyranosyl-(1′′′→2′′)-α-L-rhamnopyranosyl-(1′′′′→6′′)]-β-D-glucopyranoside (5), in addition to β-sitosterol-3-O-acetate (2) were isolated from the methanolic extract of the aerial parts of Polygonum bellardii growing in Egypt. Their structures were elucidated on the basis of different chemical and spectroscopic evidences. The total extract and its fractions, in addition to compounds (3, 4 and 5) showed significant antioxidant potential by DPPH^· scavenging activity technique.

Phenolic constituents from Parakmeria yunnanensis and their anti-HIV-1 activity

Three new phenolic compounds, yunnanensins A-C (1-3), together with fourteen known ones (4-17), were isolated from the leaves and stems of Parakmeria yunnanensis. The structures of new compounds were established on the basis of extensive spectroscopic analyses. Several compounds showed weak anti-HIV-1 activity.

Cytotoxic podophyllotoxin type-lignans from the steam bark of Bursera fagaroides var. fagaroides

The hydroalcoholic extract of the steam bark of B. fagaroides var. fagaroides displayed potent cytotoxic activity against four cancer cell lines, namely KB (ED₅₀ = 9.6 × 10⁻² μg/mL), PC-3 (ED₅₀ = 2.5 × 10⁻¹ μg/mL), MCF-7 (ED₅₀ = 6.6 μg/mL), and HF-6 (ED₅₀ = 7.1 × 10⁻³ μg/mL). This extract also showed anti-tumour activity when assayed on mice inoculated with L5178Y lymphoma cells. Bioactivity-directed isolation of this extract, afforded seven podophyllotoxin-type lignans identified as podophyllotoxin (1), β-peltatin-A-methylether (2), 5′-desmethoxy-β-peltatin-A-methylether (3), desmethoxy-yatein (4), desoxypodophyllotoxin (5), burseranin (6), and acetyl podophyllotoxin (7) by 1D and 2DNMR and FAB-MS analyses, and comparison with reported values. All the isolated compounds showed potent cytotoxic activity in the cell lines tested, especially compound 3, which exhibited greater activity than camptothecin and podophyllotoxin against PC-3 (ED₅₀ = 1.0 × 10⁻⁵ μg/mL), and KB (ED₅₀ = 1.0 × 10⁻⁵ μg/mL). This is the first report of the isolation of podophyllotoxin and its acetate in a Bursera species.

Lignan constituents of Tilia amurensis and their biological evaluation on antitumor and anti-inflammatory activities

In the recent decade, numerous lignan derivatives isolated from plants have been proven to have the potential as an anti-cancer substance. On the search for anti-cancer compounds from Korean medicinal plants, the methanolic extract from the trunk of Tilia amurensis Rupr. (Tiliaceae) was found to have significant cytotoxicity against A549 (lung carcinoma), SK-OV-3 (ovary malignant ascites), SK-MEL-2 (skin melanoma), and HCT-15 (colon adenocarcinoma) in our screening test. Hence, a bioassay-guided fractionation and chemical investigation of the methanolic extract resulted in the isolation and identification of 10 lignan derivatives (1-10) including two new lignan glycosides named tiliamurosides A (1) and B (2). The structures of these new compounds were determined by spectroscopic methods, namely 1D and 2D nuclear magnetic resonance (NMR) techniques, high resolution mass spectrometry (HRMS), circular dichroism (CD) data, and chemical methods. Tiliamuroside B (2) and schizandriside (3) showed significant cytotoxicity against A549, SK-OV-3, SK-MEL-2, and HCT-15 cell lines with inhibitory concentration (IC50) values of 3.26-8.89 μM. Moreover, (-)-syringaresinol (8) and (-)-pinoresinol 4-O-β-D-glucopyranoside (10) significantly inhibited nitric oxide (NO) production in murine microglia BV-2 with IC50 values of 15.05 and 34.35 μM, respectively.

Rubesanolides C-E: abietane diterpenoids isolated from Isodon rubescens and evaluation of their anti-biofilm activity

Phytochemical study of the leaves of the medicinal plant Isodon rubescens led to the isolation of three novel abietane diterpenoids, rubesanolides C-E (1-3). These diterpenes contain a unique γ-lactone subgroup formed between C-8 and C-20. Their structures were determined from analysis of spectroscopic data, and were further confirmed by X-ray crystallographic data. The compounds were evaluated for their antibacterial activity, and rubesanolide D (2) demonstrated inhibition activity against biofilm formation of the dental bacterium Streptococcus mutans.

Phenolic compounds from Selaginella moellendorfii

Chemical investigation of the leaves and roots of Selaginella moellendorfii Hieron has resulted in the isolation and characterization of two new flavone glucosides, 7-O-(β-glucopyranosyl(1→2)-[β-glucopyranosyl(1→6)]-β-glucopyranosyl)flavone-3',4',5,7-tetraol (1) and 7-O-(β-glucopyranosyl(1→2)-[β-glucopyranosyl(1→6)]-β-glucopyranosyl)flavone-4',5,7-triol (2), two new biflavonoids, 2,3-dihydroflavone-5,7,4'-triol-(3'→8″)-flavone-5″,6″,7″,4'''-tetraol (3) and 6-methylflavone-5,7,4'-triol-(3'→O→4''')-6″-methylflavone-5″,7″-diol (4), two new lignans, (7'E)-3,5,3',5'-tetramethoxy-8 : 4'-oxyneolign-7'-ene-4,9,9'-triol (5) and 3,3'-dimethoxylign-8'-ene-4,4',9-triol (6), together with two known monolignans, four known lignans, and four known biflavonoids. Their structures were established by spectroscopic means and by comparison with literature values.

Ethnobotanical approach versus random approach in the search for new bioactive compounds: support of a hypothesis

CONTEXT

Whether natural product drug discovery programs should rely on wild plants collected "randomly" from the natural environment, or whether they should also include plants collected on the basis of use in traditional medicine remains an open question.

OBJECTIVE

This study analyzes whether plants with ethnomedical uses from Vietnam and Laos have a higher hit rate in bioassay testing than plants collected from a national park in Vietnam with the goal of maximizing taxonomic diversity ("random" collection).

MATERIALS AND METHODS

All plants were extracted and subjected to bioassay in the same laboratories. Results of assays of plant collections and plant parts (samples) were scored as active or inactive based on whether any extracts had a positive result in a bioassay. Contingency tables were analyzed using χ(2) statistics.

RESULTS

Random collections had a higher hit rate than ethnomedical collections, but for samples, ethnomedical plants were more likely to be active. Ethnomedical collections and samples had higher hit rates for tuberculosis, while samples, but not collections, had a higher hit rate for malaria. Little evidence was found to support an advantage for ethnomedical plants in HIV, chemoprevention and cancer bioassays. Plants whose ethnomedical uses directly correlated to a bioassay did not have a significantly higher hit rate than random plants.

DISCUSSION

Plants with ethnomedical uses generally had a higher rate of activity in some drug discovery bioassays, but the assays did not directly confirm specific uses.

CONCLUSIONS

Ethnomedical uses may contribute to a higher rate of activity in drug discovery screening.

Absolute configuration of podophyllotoxin related lignans from Bursera fagaroides using vibrational circular dichroism

The ethanol extract from the dried exudate of Bursera fagaroides (Burseraceae) showed significant cytotoxic activity in the HT-29 (human colon adenocarcinoma) test system. The extract provided four podophyllotoxin related lignans, identified as (7'R,8R,8'R)-(-)-deoxypodophyllotoxin (3), (7'R,8R,8'R)-(-)-morelensin (4), (8R,8'R)-(-)-yatein (5), and (8R,8'R)-(-)-5'-desmethoxyyatein (6), whose spectroscopic and chiroptical properties were compared with those of (7R,7'R,8R,8'R)-(-)-podophyllotoxin (1) and its acetyl derivative (2). Their absolute configurations were assigned by comparison of the vibrational circular dichroism spectra of 1 and 3 with those obtained by density functional theory calculations.

Further investigation into maple syrup yields 3 new lignans, a new phenylpropanoid, and 26 other phytochemicals

Maple syrup is made by boiling the sap collected from certain maple ( Acer ) species. During this process, phytochemicals naturally present in tree sap are concentrated in maple syrup. Twenty-three phytochemicals from a butanol extract of Canadian maple syrup (MS-BuOH) had previously been reported; this paper reports the isolation and identification of 30 additional compounds (1-30) from its ethyl acetate extract (MS-EtOAc) not previously reported from MS-BuOH. Of these, 4 compounds are new (1-3, 18) and 20 compounds (4-7, 10-12, 14-17, 19, 20, 22-24, 26, and 28-30) are being reported from maple syrup for the first time. The new compounds include 3 lignans and 1 phenylpropanoid: 5-(3″,4″-dimethoxyphenyl)-3-hydroxy-3-(4'-hydroxy-3'-methoxybenzyl)-4-(hydroxymethyl)dihydrofuran-2-one (1), (erythro,erythro)-1-[4-[2-hydroxy-2-(4-hydroxy-3-methoxyphenyl)-1-(hydroxymethyl)ethoxy]-3,5-dimethoxyphenyl]-1,2,3-propanetriol (2), (erythro,threo)-1-[4-[2-hydroxy-2-(4-hydroxy-3-methoxyphenyl)-1-(hydroxymethyl)ethoxy]-3,5-dimethoxyphenyl]-1,2,3-propanetriol (3), and 2,3-dihydroxy-1-(3,4- dihydroxyphenyl)-1-propanone (18), respectively. In addition, 25 other phenolic compounds were isolated including (threo,erythro)-1-[4-[(2-hydroxy-2-(4-hydroxy-3-methoxyphenyl)-1-(hydroxymethyl)ethoxy]-3-methoxyphenyl]-1,2,3-propanetriol (4), (threo,threo)-1-[4-[(2-hydroxy-2-(4-hydroxy-3-methoxyphenyl)-1-(hydroxymethyl)ethoxy]-3-methoxyphenyl]-1,2,3-propanetriol (5), threo-guaiacylglycerol-β-O-4'-dihydroconiferyl alcohol (6), erythro-1-(4-hydroxy-3-methoxyphenyl)-2-[4-(3-hydroxypropyl)-2,6-dimethoxyphenoxy]-1,3-propanediol (7), 2-[4-[2,3-dihydro-3-(hydroxymethyl)-5-(3-hydroxypropyl)-7-methoxy-2-benzofuranyl]-2,6-dimethoxyphenoxy]-1-(4-hydroxy-3-methoxyphenyl)-1,3-propanediol (8), acernikol (9), leptolepisol D (10), buddlenol E (11), (1S,2R)-2-[2,6-dimethoxy-4-[(1S,3aR,4S,6aR)-tetrahydro-4-(4-hydroxy-3,5-dimethoxyphenyl)-1H,3H-furo[3,4-c]furan-1-yl]phenoxy]-1-(4-hydroxy-3-methoxyphenyl)-1,3-propanediol (12), syringaresinol (13), isolariciresinol (14), icariside E4 (15), sakuraresinol (16), 1,2-diguaiacyl-1,3-propanediol (17), 2,3-dihydroxy-1-(4-hydroxy-3,5-dimethoxyphenyl)-1-propanone (19), 3-hydroxy-1-(4-hydroxy-3,5-dimethoxyphenyl)propan-1-one (20), dihydroconiferyl alcohol (21), 4-acetylcatechol (22), 3',4',5'-trihydroxyacetophenone (23), 3,4-dihydroxy-2-methylbenzaldehyde (24), protocatechuic acid (25), 4-(dimethoxymethyl)pyrocatechol (26), tyrosol (27), isofraxidin (28), and 4-hydroxycatechol (29). One sesquiterpene, phaseic acid (30), which is a known metabolite of the phytohormone abscisic acid, was also isolated from MS-EtOAc. The antioxidant activities of MS-EtOAc (IC(50) = 75.5 μg/mL) and the pure isolates (IC(50) ca. 68-3000 μM) were comparable to that of vitamin C (IC(50) = 40 μM) and the synthetic commercial antioxidant butylated hydroxytoluene (IC(50) = 3000 μM), in the diphenylpicrylhydrazyl radical scavenging assay. The current study advances scientific knowledge of maple syrup constituents and suggests that these diverse phytochemicals may impart potential health benefits to this natural sweetener.

Rubesanolides A and B: diterpenoids from Isodon rubescens

From the medicinal plant Isodon rubescens, we isolated two novel diterpenes, rubesanolides A (1) and B (2). The compounds contain a unique β-lactone subgroup. This is the first discovery for a natural diterpene having rings A, B, and C in chair, boat, and twist-chair conformations, respectively. The structures were elucidated by analysis of spectroscopic data, and the absolute configuration of 1 was determined by X-ray diffraction.

Two new glycosides from Breynia vitis-idaea

A new sulfur-containing spiroketal glycoside, breynin I (1), and a new terpenic glycoside, breyniaionoside E (2), together with 10 known compounds, were isolated from the aerial parts of Breynia vitis-idaea (Euphorbiaceae), a traditional Chinese medicine used for the treatment of chronic bronchitis and wounds. Their structures were elucidated on the basis of spectroscopic analysis and modified Mosher's method.

Selection methodology with scoring system: application to Mexican plants producing podophyllotoxin related lignans

As most anticancer drugs are derived from natural sources, the screening of local medicinal flora should be considered a primary step in the search for new sources for antineoplastic agents. In Mexico, more than 6000 medicinal plant species are used for the treatment of various diseases, including cancer. A multifactorial plant selection method, employing various criteria was designed and applied in order to select alternative sources of podophyllotoxin lignan analogues. For each criterion (chemotaxonomy, traditional medical uses and published scientific data), an arbitrary score system was ascribed to the species and the sum of these enabled us to compare potential candidates. The resulting selected plants were tested for cytotoxic activity and the compounds responsible for this activity were evaluated by liquid chromatography-mass spectroscopy (LC-MS). Around 50 species from the Mexican flora were initially considered. From these, six species were selected by referring to the results from the scoring system and these were then collected. Three extracts were evaluated as being highly cytotoxic against three different cancer cell lines. Finally, podophyllotoxin-like lignans could be identified by observing the fragmentation pattern on mass spectra, obtained from the LC-MS in two species: Linum scabrellum and Hyptis suaveolens.

Lignans and other constituents of the fruits of Euterpe oleracea (Acai) with antioxidant and cytoprotective activities

Using a hydroxyl radical scavenging assay, bioactivity-guided fractionation of a methanol-soluble extract of the fruits of Euterpe oleracea (acai) led to the isolation of 22 compounds of previously known structure. Altogether, 14 of these isolates were found to be active in an in vitro hydroxyl radical scavenging assay and seven of these isolates in a 1,1-diphenyl-2-picrylhydrazyl radical scavenging assay. Dihydroconiferyl alcohol, (+)-lariciresinol, (+)-pinoresinol, (+)-syringaresinol, and protocatechuic acid methyl ester exhibited cytoprotective activity in cultured MCF-7 cells stressed by H2O2. Lignans have not been previously reported as constituents of this species and were found to be representative of the aryltetrahydronaphthalene, dihydrobenzofuran, furofuran, 8-O-4'-neolignan, and tetrahydrofuran structural types.

Preparation of botanical samples for biomedical research

Plants are chemical storehouses, a fact which has driven countless multidisciplinary quests for bioactive compounds. As the very first step of botanical research, the whole desire is to find "hit" plants with specific bioactivities. It is logical to use some strategies that can maximize the chances of finding these "hits" with limited time and resources. In addition to selecting the right plants for screening, how the plant extracts are prepared can also influence the bioactivity screening outcomes. An extract from the same plant material can be quite different in chemical composition having different preparations. Because of the complex mixture nature of plant extracts, it is possible artifact activities may be observed. Thus confirmatory activity tests are often necessary to warrant the next laborious isolation step. A bioassay directed isolation approach may be the most efficient in identifying the bioactive compounds because of the narrowed focus at each isolation step, but a phytochemistry isolation approach is appropriate to characterize a purified bioactive extract. In fact, these two approaches can be taken intermittently whenever efficiency can be improved. Finally, use of the identified active compounds is now broader. In addition to determining a lead compound to continue a drug development path, there is an increasing interest in support for the use of botanical extracts as botanical drugs. Instead of dropping the extract after extracting the lead compound, the natural analogues representing the purified extract now have a chance to become leading compounds in the pursuit of novel therapies for metabolic syndrome and other diseases.

"Studies on biodiversity of Vietnam and Laos" 1998-2005: examining the impact

The impact of the University of Illinois at Chicago-based Vietnam-Laos International Cooperative Biodiversity Group (ICBG) Program "Studies on Biodiversity of Vietnam and Laos", which has been in operation for the period of 1998-2005, touches on five major areas of endeavor: (a) biodiversity inventory and conservation; (b) studies on medicinal plants; (c) drug discovery and development; (d) economic development; and (e) issues on intellectual property rights and benefit sharing in natural products drug discovery and development. Highlights are presented and the significance is discussed.