Phytochemicals with Chemopreventive Activity Obtained from the Thai Medicinal Plant Mammea siamensis (Miq.) T. Anders.: Isolation and Structure Determination of New Prenylcoumarins with Inhibitory Activity against Aromatase.

With the aim of searching for phytochemicals with aromatase inhibitory activity, five new prenylcoumarins, mammeasins K (1), L (2), M (3), N (4), and O (5), were isolated from the methanolic extract of Mammea siamensis (Miq.) T. Anders. flowers (fam. Calophyllaceae), originating in Thailand. The stereostructures of 1-5 were elucidated based on their spectroscopic properties. Among the new compounds, 1 (IC50 = 7.6 µM) and 5 (9.1 µM) possessed relatively strong inhibitory activity against aromatase, which is a target of drugs already used in clinical practice for the treatment and prevention of estrogen-dependent breast cancer. The analysis through Lineweaver-Burk plots showed that they competitively inhibit aromatase (1, Ki = 3.4 µM and 5, 2.3 µM). Additionally, the most potent coumarin constituent, mammea B/AB cyclo D (31, Ki = 0.84 µM), had a competitive inhibitory activity equivalent to that of aminoglutethimide (0.84 µM), an aromatase inhibitor used in therapeutics.

Total Synthesis of γ-Alkylidenebutenolides, Potent Melanogenesis Inhibitors from Thai Medicinal Plant Melodorum fruticosum.

A hitherto unreported member of γ-alkylidenebutenolides in Melodorum fruticosum (Annonaceae), (4 E)-6-benzoyloxy-7-hydroxy-2,4-heptadiene-4-olide, named as isofruticosinol (4) was isolated from the methanol extract of flowers, along with the known related butenolides, namely, the (4 Z)-isomer (3) of 4, melodrinol (1), and its (4 E)-isomer (2). To unambiguously determine the absolute configuration at the C-6 position in these butenolides, the first total syntheses of both enantiomers of 2-4 were achieved over 6-7 steps from commercially available D- or L-ribose (D- and L-5). Using the same protocol, both enantiomers of 1 were also synthesized. Based on chiral HPLC analysis of all synthetic compounds ( S- and R-1-4), all naturally occurring butenolides were assigned as partial racemic mixtures with respect to the chiral center at C-6 (enantiomeric ratio, 6 S/6 R = ∼83/17). Furthermore, the melanogenesis inhibitory activities of S- and R-1-4 were evaluated, with all shown to be potent inhibitors with IC50 values in the range 0.29-2.9 µM, regardless of differences in the stereochemistry at C-6. In particular, S-4 (IC50 = 0.29 µM) and R-4 (0.39 µM) showed potent inhibitory activities compared with that of reference standard arbutin (174 µM).

Quantitative Determination of Stilbenoids and Dihydroisocoumarins in Shorea roxburghii and Evaluation of Their Hepatoprotective Activity.

A simultaneous quantitative analytical method for 13 stilbenoids including (-)-hopeaphenol (1), (+)-isohopeaphenol (2), hemsleyanol D (3), (-)-ampelopsin H (4), vaticanols A (5), E (6), and G (7), (+)-α-viniferin (8), pauciflorol A (9), hopeafuran (10), (-)-balanocarpol (11), (-)-ampelopsin A (12), and trans-resveratrol 10-C-ß-d-glucopyranoside (13), and two dihydroisocoumarins, phayomphenols A1 (14) and A2 (15) in the extract of Shorea roxburghii (dipterocarpaceae) was developed. According to the established protocol, distributions of these 15 polyphenols (1-15) in the bark and wood parts of S. roxburghii and a related plant Cotylelobium melanoxylon were evaluated. In addition, the principal polyphenols (1, 2, 8, 13-15) exhibited hepatoprotective effects against d-galactosamine (d-galN)/lipopolysaccharide (LPS)-induced liver injury in mice at a dose of 100 or 200 mg/kg, p.o. To characterize the mechanisms of action, the isolates were examined in in vitro studies assessing their effects on (i) d-GalN-induced cytotoxicity in primary cultured mouse hepatocytes; (ii) LPS-induced nitric oxide (NO) production in mouse peritoneal macrophages; and (iii) tumor necrosis factor-α (TNF-α)-induced cytotoxicity in L929 cells. The mechanisms of action of these polyphenols (1, 2, and 8) were suggested to be dependent on the inhibition of LPS-induced macrophage activation and reduction of sensitivity of hepatocytes to TNF-α. However, none of the isolates reduced the cytotoxicity caused by d-GalN.

Aromatase Inhibitory Activity of Geranylated Coumarins, Mammeasins C and D, Isolated from the Flowers of Mammea siamensis.

A methanol extract of the flowers of Mammea siamensis (Calophyllaceae) was found to inhibit enzymatic activity against aromatase (IC50=16.5 µg/mL). From the extract, two new geranylated coumarins, mammeasins C (1) and D (2), were isolated together with seven coumarins: 8-hydroxy-5-methyl-7-(3,7-dimethyl-octa-2,6-dienyl)-9-(2-methyl-1-oxobutyl)-4,5-dihydropyrano[4,3,2-de]chromen-2-one (9), 8-hydroxy-5-methyl-7-(3,7-dimethyl-octa-2,6-dienyl)-9-(3-methyl-1-oxobutyl)-4,5-dihydropyrano[4,3,2-de]chromen-2-one (10), mammeas A/AA (14), A/AB (15), A/AA cyclo D (18), E/BA (23), and E/BC cyclo D (25). The structures of 1 and 2 were elucidated on the basis of spectroscopic evidence. Among the isolates including 17 previously reported coumarins, 1 (IC50=2.7 µM), 2 (3.6 µM), and mammea B/AB cyclo D (21, 3.1 µM) showed relatively strong inhibitory activities comparable to the activity of the synthetic nonsteroidal aromatase inhibitor aminoglutethimide (2.0 µM).

Evaluation of Salacia species as anti-diabetic natural resources based on quantitative analysis of eight sulphonium constituents: a new class of α-glucosidase inhibitors.

INTRODUCTION: Stems and roots of Salacia genus plants have been used in Ayurveda as a specific remedy for early stage diabetes. Previous investigations identified four sulphonium sulphates, that is, salacinol (1), kotalanol (3), ponkoranol (5) and salaprinol (7), as the compounds responsible for the anti-diabetic activity. Their desulphonates (2, 4, 6 and 8) were also isolated as active constituents. Two separate quantitative analytical protocols, that is, for 1 and 3 and for 2 and 4, have been developed recently. OBJECTIVE: To: validate the two analytical protocols with respect to all eight sulphoniums; evaluate the quality of a variety of Salacia samples collected in different geographical regions, that is, Thailand, Sri Lanka and India; and determine their distribution in each part of the plant, that is, stems/roots, leaves and fruits. METHODS: Analyses of four sulphonium sulphates in 32 Salacia extracts were carried out on an Asahipak NH2P-50 column, and those of the corresponding desulphonates were conducted on an Inertsil ODS-3 column. RESULTS: Neokotalanol (4) was the major constituent in Salacia samples from Thailand, whereas 1 was the primary constituent in extracts of the stems/roots of plants from Sri Lanka and India. These sulphoniums were only present in trace amounts in leaves and fruits of the plants. CONCLUSION: Two analytical protocols were successfully applied to analyse 32 Salacia samples, and revealed that sulphoniums (1-8) had characteristic distributions due to the plant part and/or due to geographical region.

Structures of Mammeasins P and Q, Coumarin-Related Polysubstituted Benzofurans, from the Thai Medicinal Plant Mammea siamensis (Miq.) T. Anders.: Anti-Proliferative Activity of Coumarin Constituents against Human Prostate Carcinoma Cell Line LNCaP.

A methanol extract of the flowers of Mammea siamensis (Miq.) T. Anders. (Calophyllaceae) showed anti-proliferative activity against human prostate carcinoma LNCaP cells (IC50 = 2.0 µg/mL). Two new coumarin-related polysubstituted benzofurans, mammeasins P (1) and Q (2), and a known polysubstituted coumarin mammea B/AC cyclo F (39) were isolated from the extract along with 44 previously reported polysubstituted coumarin constituents (3-38 and 40-47). The structures of two new compounds (1 and 2) were determined based on their spectroscopic properties derived from the physicochemical evidence including NMR and MS analyses and taking the plausible generative pathway into account. Among the coumarin constituents, mammeasins A (3, IC50 = 1.2 µM) and B (4, 0.63 µM), sugangin B (18, 1.5 µM), kayeassamins E (24, 3.0 µM) and G (26, 3.5 µM), and mammeas E/BA (40, 0.88 µM), E/BB (41, 0.52 µM), and E/BC (42, 0.12 µM) showed relatively potent anti-proliferative activity.

Antidiabetogenic oligostilbenoids and 3-ethyl-4-phenyl-3,4-dihydroisocoumarins from the bark of Shorea roxburghii.

A methanol extract of the bark of Shorea roxburghii (Dipterocarpaceae) was found to inhibit plasma glucose elevation in sucrose-loaded mice. From the extract, three new 3-ethyl-4-phenyl-3,4-dihydroisocoumarins, 1'S-dihydrophayomphenol A(2) (1) and phayomphenols B(1) (2) and B(2) (3), were isolated together with 24 known compounds including 20 stilbenoids and oligostilbenoids. The structures of 1-3 were determined on the basis of their spectroscopic properties as well as of chemical evidences. Among the isolates, (-)-hopeaphenol (6), hemsleyanol D (8), (+)-α-viniferin (15), and (-)-balanocarpol (18) showed inhibitory activity against plasma glucose elevation in sucrose-loaded rats at doses of 100-200mg/kg, p.o. To clarify the mode of action of the antihyperglycemic property, effects of these oligostilbenoids on gastric emptying in mice, those on glucose uptake in isolated intestinal tissues as well as inhibitory activities against rat intestinal α-glucosidase and rat lens aldose reductase were examined.

Suppressive effects of coumarins from Mammea siamensis on inducible nitric oxide synthase expression in RAW264.7 cells.

A methanol extract of the flowers of Mammea siamensis (Calophyllaceae) was found to inhibit nitric oxide (NO) production in lipopolysaccharide-activated RAW264.7 cells. From the extract, two new geranylated coumarins, mammeasins A (1) and B (2), were isolated together with 17 known compounds including 15 coumarins. The structures of 1 and 2 were determined on the basis of their spectroscopic properties as well as of their chemical evidence. Among the isolates, 1 (IC(50) = 1.8 µM), 2 (6.4 µM), surangins B (3, 5.0 µM), C (4, 6.8 µM), and D (5, 6.2 µM), kayeassamins E (7, 6.1 µM), F (8, 6.0 µM), and G (9, 0.8 µM), mammea A/AD (11, 1.3 µM), and mammea E/BB (16, 7.9 µM) showed NO production inhibitory activity. Compounds 1, 9, and 11 were found to inhibit induction of inducible nitric oxide synthase (iNOS). With regard to mechanism of action of these active constituents (1, 9, and 11), suppression of STAT1 activation is suggested to be mainly involved in their suppression of iNOS induction.

Structures of two new phenolic glycosides, kaempferiaosides A and B, and hepatoprotective constituents from the rhizomes of Kaempferia parviflora.

Two new phenolic glycosides, kaempferiaosides A and B were isolated from the rhizomes of Kaempferia parviflora (Zingiberaceae) together with 24 known compounds. Their structures including absolute stereochemistry were elucidated on the basis of chemical and spectroscopic evidence. Among the isolates, 5,3'-dihydroxy-3,7,4'-trimethoxyflavone showed higher activity than silybin, a commercial hepatoprotective agent.

Invasion inhibitors of human fibrosarcoma HT 1080 cells from the rhizomes of Zingiber cassumunar: structures of phenylbutanoids, cassumunols.

The methanolic extract and its EtOAc-soluble fraction from the rhizomes of Zingiber cassumunar inhibited invasion of human fibrosarcoma HT 1080 cells. From the EtOAc-soluble fraction, eight new phenylbutanoids, cassumunols A-H, were isolated together with 30 known constituents. The structures of new phenylbutanoids were elucidated on the basis of chemical and physicochemical evidence. Principal constituents were examined the inhibitory effects on the invasion of HT 1080 cells. Among them, phlain I and III, (E)-1-(3,4-dimethoxyphenyl)buta-1,3-diene, (E)-1-(2,4,5-trimethoxyphenyl)buta-1,3-diene, and (-)-ß-sesquiphellandrene showed anti-invasion effects. Interestingly, (E)-1-(2,4,5-trimethoxyphenyl)buta-1,3-diene [inhibition (%) 46.8 ± 7.2 (p<0.05) at 30 µM] significantly inhibited the invasion, and only a weak cytotoxic effect was observed.

Anti-proliferative activities of coumarins from the Thai medicinal plant Mammea siamensis (Miq.) T. Anders. against human digestive tract carcinoma cell lines.

Geranylated coumarins named mammeasins G-J (1-4) were isolated from the methanol extract of the flowers of Mammea siamensis (Miq.) T. Anders. (Calophyllaceae) originating in Thailand. Their structures were established based on detailed spectroscopic analyses. The isolates, including previously reported coumarin constituents (5-28), exhibited anti-proliferative activities against human carcinoma cell lines HSC-2, HSC-4, MKN-45, and MCF-7. Mammeasin A (7, IC50 = 13.6 µM) and surangin B (15, 15.2 µM), both consisting of the geranyl group, were found to show relatively strong activities against HSC-4 cells and their mechanisms of action were found to involve apoptotic cell death.

Geranylated Coumarins From Thai Medicinal Plant Mammea siamensis With Testosterone 5α-Reductase Inhibitory Activity.

Geranylated coumarin constituents, kayeassamin I (1) and mammeasins E (2) and F (3) were newly isolated from the methanol extract of the flowers of Mammea siamensis (Calophyllaceae) originating in Thailand, along with five known isolates, such as mammea E/BC (23), deacetylmammea E/AA cyclo D (31), deacetylmammea E/BB cyclo D (32), mammea A/AA cyclo F (34), and mammea A/AC cyclo F (35). These compounds (1-3) were obtained as an inseparable mixture (ca. 1:1 ratio) of the 3″R and 3″S forms, respectively. Among the isolated coumarins from the extract, mammeasins E (2, 22.6 µM), A (4, 19.0 µM), and B (5, 24.0 µM), kayeassamins E (9, 33.8 µM), F (10, 15.9 µM), and G (11, 17.7 µM), surangin C (13, 5.9 µM), and mammeas A/AA (17, 19.5 µM), E/BB (22, 16.8 µM), and A/AA cyclo F (34, 23.6 µM), were found to inhibit testosterone 5α-reductase.

Structures of new phenylbutanoids and nitric oxide production inhibitors from the rhizomes of Zingiber cassumunar.

The methanolic (MeOH) extract from the rhizomes of Zingiber cassumunar showed nitric oxide (NO) production inhibitory effects induced by lipopolysaccharide (LPS) in mouse peritoneal macrophages. From the MeOH extract, six new phenylbutanoids, phlains I-VI, were isolated together with 16 known constituents. The structures of new phenylbutanoids were determined on the basis of physicochemical and chemical evidence. In addition, the inhibitory effects of the principal constituents on the NO production were examined. Among them, phlain III (IC50=24 microM), (E)-1-(3,4-dimethoxyphenyl)buta-1,3-diene (69 microM), (E)-1-(2,4,5-trimethoxyphenyl)buta-1,3-diene (83 microM), and cassumunaquinone 1 (47 microM) were found to show the inhibitory effects.

Salacia chinensis stem extract and its thiosugar sulfonium constituent, neokotalanol, improves HbA1c levels in ob/ob mice.

The antidiabetic effects of a hot water extract of the stems of Salacia chinensis (SCE) were evaluated in vivo in ob/ob mice (genetically obese hyperglycemic mice). Administration of dietary feed containing 0.20 and 0.50% of SCE for 23 days to ob/ob mice significantly suppressed the elevation of both blood glucose and HbA1c levels, without significantly changing body weight and food intake. To characterize the antidiabetic effects of the thiosugar sulfonium constituent neokotalanol (1), which has potent α-glucosidase inhibitory activity, we performed a similar in vivo study. HbA1c levels were significantly suppressed in ob/ob mice after the administration of dietary feed containing 0.0003% of neokotalanol (1) for 20 days. These results indicate that SCE and neokotalanol (1) are potential leads for the development of novel antidiabetic agents.

Two new aromatic glycosides, elengiosides A and B, from the flowers of Mimusops elengi.

Two new aromatic glycosides, elengiosides A (1) and B (2), were isolated from the methanolic extract of the flowers of Mimusops elengi (Sapotaceae) together with 26 known compounds. Their stereostructures were elucidated based on their spectroscopic properties and chemical evidence. Among the isolates, a phenylethanoid glycoside, undatuside C (14), was found to exhibit hyaluronidase inhibitory activity.

Simultaneous quantitative analysis of 12 methoxyflavones with melanogenesis inhibitory activity from the rhizomes of Kaempferia parviflora.

A methanol extract from the rhizomes of Kaempferia parviflora Wall. ex Baker (Zingiberaceae) has shown inhibitory effects against melanogenesis in theophylline-stimulated murine B16 melanoma 4A5 cells (IC50 = 9.6 µg/mL). Among 25 flavonoids and three acetophenones isolated previously (1-28), several constituents including 5-hydroxy-7,3',4'-trimethoxyflavone (6, IC50 = 8.8 µM), 5,7,3',4'-tetramethoxyflavone (7, 8.6 µM), 5,3'-dihydroxy-3,7,4'-trimethoxyflavone (12, 2.9 µM), and 5-hydroxy-3,7,3',4'-tetramethoxyflavone (13, 3.5 µM) showed inhibitory effects without notable cytotoxicity at the effective concentrations. Compounds 6, 7, 12, and 13 inhibited the expression of tyrosinase, tyrosine-related protein (TRP)-1, and TRP-2 mRNA, which could be the mechanism of their melanogenesis inhibitory activity. In addition, a quantitative analytical method for 12 methoxyflavones (1, 2, 4-11, 13, and 14) in the extract was developed using HPLC. The optimal condition for separation and detection of these constituents were achieved on an ODS column (3 µm particle size, 2.1 mm i.d. × 100 mm) with MeOH-0.1 % aqueous acetic acid solvent systems as the mobile phase, and the detection and quantitation limits of the method were estimated to be 0.08-0.66 ng and 0.22-2.00ng, respectively. The relative standard deviation values of intra- and interday precision were lower than 0.95 and 1.08 %, respectively, overall mean recoveries of all flavonoids were 97.9-102.9 %, and the correlation coefficients of all the calibration curves showed good linearity within the test ranges. For validation of the protocol, extracts of three kinds of the plant's rhizomes collected from different regions in Thailand (Leoi, Phetchabun, and Chiang Mai provinces) were evaluated. The results indicated that the assay was reproducible, precise, and could be readily utilized for the quality evaluation of the plant materials.

Salacinol and related analogs: new leads for type 2 diabetes therapeutic candidates from the Thai traditional natural medicine Salacia chinensis.

The antidiabetic effect of a hot water extract of stems of Salacia chinensis (SCE) was evaluated in vivo in KK-Ay mice, a typical type 2 diabetes mellitus mice model. Administration of CE-2 dietary feed containing 0.25 and/or 0.50% of SCE for three weeks to KK-Ay mice significantly suppressed the elevation of both blood glucose and HbA1c levels without significant changes in body weight or food intake. Glucose tolerance was improved by administration to KK-Ay mice for 27 days of AIN93M purified dietary feed containing 0.12% of SCE. No suppressive effect with respect to HbA1c level was observed when AIN93M/Glc dietary feed in which all digestible glucides were replaced with glucose was administered with SCE. Thus, α-glucosidase inhibitory activity approved as the mechanism of action of the antidiabetic effect of SCE by in vitro investigation was reconfirmed also in in vivo studies. Evaluation of the α-glucosidase inhibitory activity of the active constituents, salacinol (1), kotalanol (3), and neokotalanol (4), by employing human α-glucosidases revealed that these compounds inhibited them as potently (IC50 = 3.9-4.9 µM for maltase) as they inhibited rat small intestinal α-glucosidase. The principal sulfonium constituents (1-4) were highly stable in an artificial gastric juice. In addition, 1-4 were hardly absorbed from the intestine in an experiment using the in situ rat ligated intestinal loop model. The results indicate that these sulfoniums are promising leads for a new type of anti-diabetic agents.

Gastroprotective effects of phenylpropanoids from the rhizomes of Alpinia galanga in rats: structural requirements and mode of action.

The effects of 1'S-1'-acetoxychavicol acetate and related phenylpropanoids isolated from the rhizomes of Alpinia galanga on ethanol-induced gastric lesions in rats were examined. Among them, 1'S-1'-acetoxychavicol acetate and 1'S-1'-acetoxyeugenol acetate markedly inhibited the ethanol-induced gastric mucosal lesions (ED(50)=0.61 and ca. 0.90 mg/kg). In addition, 1'S-1'-acetoxychavicol acetate inhibited the lesions induced by 0.6 M HCl (ED(50)=0.73 mg/kg) and aspirin (ED(50)=0.69 mg/kg) but it did not show a significant effect on indomethacin-induced gastric lesions and acid output in pylorus-ligated rats at doses of 0.5-5.0 mg/kg. From the gastroprotective effects of various related compounds, the 1'-acetoxyl group of 1'S-1'-acetoxychavicol acetate and 1'S-1'-acetoxyeugenol acetate was found to be essential for their strong activity. With regard to the mode of action, the gastroprotective effects of 1'S-1'-acetoxychavicol acetate were attenuated by pretreatment with indomethacin and N-ethylmaleimide, and 1'S-1'-acetoxychavicol acetate significantly increased the glutathione levels of gastric mucosa in rats. These findings suggest that endogenous prostaglandins and sulfhydryl compounds are involved in the protective effect of 1'S-1'-acetoxychavicol acetate.

[Biological activities of Salacia chinensis originating in Thailand: the quality evaluation guided by alpha-glucosidase inhibitory activity].

In the course of our characterization studies on anti-obese and antidiabetogenic principles in medicinal foodstuffs, we found that the methanolic extract from the stems of Salacia chinensis (Hippocerateaceae) showed potent anti-hyperglycemic effects in oral sucrose or maltose-loaded rats, inhibitory effects on intestinal alpha-glucosidase, rat lens aldose reductase, formation of Amadori compounds and advanced glycation end-products, nitric oxide production from lipopolysaccharide-activated mouse peritoneal macrophage, and radical scavenging activities. Those in vivo and in vitro biological activities were compared with those of S. oblonga and S. reticulata. In addition, we isolated the principal alpha-glucosidase inhibitor, salacinol, from the stems of S. chinensis and examined alpha-glucosidase inhibitory activities of eleven samples of S. chinensis collected in Thailand.

New flav-3-en-3-ol glycosides, kaempferiaosides C and D, and acetophenone glycosides, kaempferiaosides E and F, from the rhizomes of Kaempferia parviflora.

Two new flav-3-en-3-ol glycosides, kaempferiaosides C (3) and D(4), and two new acetophenone glycosides, kaempferiaosides E (5) and F (6), were isolated from the Thai natural medicine Krachai Dum, the rhizomes of Kaempferia parviflora Wall. ex Baker. Their structures were established mainly on the basis of 1D and 2D NMR spectral data.