Seikou Nakamura

Salaprinol and ponkoranol with thiosugar sulfonium sulfate structure from Salacia prinoides and α-glucosidase inhibitory activity of ponkoranol and kotalanol desulfate

The methanolic extract from the roots and stems of Indian Salacia prinoides and its water-eluted fraction of Diaion HP-20 column were found to exhibit inhibitory activities against α-glucosidase. From the water-eluted fraction, two new unique constituents with thiosugar sulfonium sulfate, salaprinol (1) and ponkoranol (2), were isolated together with 10 known constituents including salacinol and kotalanol. The structures of 1 and 2 were elucidated on the basis of chemical and physicochemical evidence. Furthermore, ponkoranol (2) and kotalanol desulfate (14) were found to show potent inhibitory activities against α-glucosidase.

Melanogenesis inhibitors from the desert plant Anastatica hierochuntica in B16 melanoma cells.

The methanolic extract from the whole plants of Anastatica hierochuntica, an Egyptian herbal medicine, was found to inhibit melanogenesis in theophylline-stimulated murine B16 melanoma 4A5 cells. Among the constituents isolated, anastatin A, silybin A, isosilybins A and B, eriodictyol, luteolin, kaempferol, quercetin, hierochins A and B, (2R,3S)-2,3-dihydro-2-(3,4-dimethoxyphenyl)-3-hydroxymethyl-5-(2-formylvinyl)-7-hydroxybenzofuran, (+)-dehydrodiconiferyl alcohol, (+)-balanophonin, 1-(4-hydroxy-3-methoxyphenyl)-2-{4-[(E)-3-hydroxy-1-propenyl]-2-methoxyphenoxy}-1,3-propanediol, and 3,4-dihydroxybenzaldehyde substantially inhibited melanogenesis with IC(50) values of 6.1-32 microM. With regard to the mechanism of action of silybins and isosilybins, the inhibition of tyrosinase activity suggested to be important. In addition, isosilybins A and B inhibited the mRNA expression of TRP-2, but silybins A and B oppositely enhanced the mRNA expression of tyrosinase and TRP-1 and -2 at 10 and/or 30 microM, and the inhibition of phosphorylation of extracellular signal-regulated kinases (ERK1/2) is involved in the enhanced expression of mRNA, at least in part, similar to that of PD98059.

Suppressive effects of methoxyflavonoids isolated from Kaempferia parviflora on inducible nitric oxide synthase (iNOS) expression in RAW 264.7 cells

ETHNOPHARMACOLOGICAL RELEVANCE The rhizomes of Kaempferia parviflora Wall. ex Baker have been traditionally used in Thailand to treat abscesses, gout, and peptic ulcers. AIM Previously, we reported that the chloroform fraction of a Kaempferia parviflora extract had an inhibitory effect on rat paw-edema. In the present study, we isolated the constituents of this fraction and investigated the anti-inflammatory mechanism against nitric oxide (NO) production, tumor necrosis factor-α (TNF-α) and the expression of inducible nitric oxide synthase (iNOS) as well as phosphorylated extracellular signal-regulated kinase (p-ERK), and phosphorylated c-Jun N-terminal kinase (p-JNK). In addition, effects of trimethylapigenin (4) on the enzyme activities of protein kinases possibly leading to iNOS expression were examined to clarify the targets. MATERIALS AND METHODS The chloroform fraction was isolated using silica gel column chromatography and HPLC. Isolated compounds were tested against NO and TNF-α using RAW264.7 cells. Cytotoxicity and iNOS, p-ERK and p-JNK expression were also examined. RESULTS Three active components, 5,7-dimethoxyflavone (2), trimethylapigenin (4), and tetramethylluteolin (5), markedly inhibited the production of NO in lipopolysaccharide (LPS)-activated RAW264.7 cells. Compounds 2, 4, and 5 moderately inhibited production of TNF-α. Compounds 2, 4, and 5 strongly inhibited expression of iNOS mRNA and iNOS protein in a dose-dependent manner, but did not inhibit p-ERK or p-JNK protein expression. The most active compound, 4, did not inhibit the enzyme activity of inhibitor of κB kinases or mitogen-activated protein kinases, but inhibited that of spleen tyrosine kinase (SYK). CONCLUSION The mechanism responsible for the anti-inflammatory activity of methoxyflavonoids from the chloroform fraction of the rhizomes of Kaempferia parviflora is mainly the inhibition of iNOS expression, and the inhibition of SYK by 4 may be involved in the suppression of LPS-induced signaling in macrophages.

Alkaloid constituents from flower buds and leaves of sacred lotus (Nelumbo nucifera, Nymphaeaceae) with melanogenesis inhibitory activity in B16 melanoma cells.

Methanolic extracts from the flower buds and leaves of sacred lotus (Nelumbo nucifera, Nymphaeaceae) were found to show inhibitory effects on melanogenesis in theophylline-stimulated murine B16 melanoma 4A5 cells. From the methanolic extracts, a new alkaloid, N-methylasimilobine N-oxide, was isolated together with eleven benzylisoquinoline alkaloids. The absolute stereostructure of the new alkaloid was determined from chemical and physicochemical evidence. Among the constituents isolated, nuciferine, N-methylasimilobine, (-)-lirinidine, and 2-hydroxy-1-methoxy-6a,7-dehydroaporphine showed potent inhibition of melanogenesis. Comparison of the inhibitory activities of synthetic related alkaloids facilitated characterization of the structure-activity relationships of aporphine- and benzylisoquinoline-type alkaloids. In addition, 3-30 μM nuciferine and N-methylasimilobine inhibited the expression of tyrosinase mRNA, 3-30 μM N-methylasimilobine inhibited the expression of TRP-1 mRNA, and 10-30 μM nuciferine inhibited the expression of TRP-2 mRNA.

Hydrangeic acid from the processed leaves of Hydrangea macrophylla var. thunbergii as a new type of anti-diabetic compound.

Hydrangeic acid (3-100 microM), a stilbene constituent of the processed leaves of Hydrangea macrophylla var. thunbergii (Hydrangeae Dulcis Folium), promoted adipogenesis of 3T3-L1 cells. Hydrangeic acid significantly increased the amount of adiponectin released into the medium, the uptake of 2-deoxyglucose into the cells, and the translocation of glucose transporter 4 (GLUT4). Hydrangeic acid also increased mRNA levels of adiponectin, peroxisome proliferator-activated receptor gamma2 (PPARgamma2), GLUT4, and fatty acid-binding protein (aP2) while it decreased the expression of tumor necrosis factor alpha (TNF-alpha) mRNA. However, it did not activate PPARgamma directly different from troglitazone in a nuclear receptor cofactor assay system. Furthermore, hydrangeic acid significantly lowered blood glucose, triglyceride, and free fatty acid levels after its administration for 2 weeks at a dose of 200 mg/kg/day (p.o.) in KK-A(y) mice.

Cucurbitacin E as a new inhibitor of cofilin phosphorylation in human leukemia U937 cells

Cucurbitane-type triterpenes, cucurbitacins B and E, were reported to exhibit cytotoxic effects in several cell lines mediated by JAK/STAT3 signaling. However, neither compound inhibited phosphorylation of STAT3 in human leukemia (U937) cells at low concentrations. We therefore synthesized a biotin-linked cucurbitacin E to isolate target proteins based on affinity for the molecule. As a result, cofilin, which regulates the depolymerization of actin, was isolated and suggested to be a target. Cucurbitacins E and I inhibited the phosphorylation of cofilin in a concentration-dependent manner, and their effective concentrations having the same range as the concentrations at which they had cytotoxic effects in U937 cells. In addition, the fibrous-/globular-actin ratio was decreased after treatment with cucurbitacin E in HT1080 cells. These findings suggested that the inhibition of cofilins phosphorylation increased the severing activity of cofilin, and then the depolymerization of actin was enhanced after treatment with cucurbitacin E at lower concentrations.

Structures of New Cucurbitane-Type Triterpenes and Glycosides, Karavilagenins D and E, and Karavilosides VI, VII, VIII, IX, X, and XI, from the Fruit of Momordica charantia

Two new cucurbitane-type triterpenes, karavilagenins D and E, and six new cucurbitane-type triterpene glycosides, karavilosides VI, VII, VIII, IX, X, and XI, were isolated from the fruit of Momordica charantia L. (Cucurbitaceae) cultivated in Sri Lanka. Their structures were elucidated on the basis of chemical and physicochemical evidence.

Acylated oleanane-type triterpene saponins with acceleration of gastrointestinal transit and inhibitory effect on pancreatic lipase from flower buds of chinese tea plant (Camellia sinensis).

The MeOH extract and its BuOH-soluble fraction (crude saponin fraction) from the flower buds of Chinese tea plant (Camellia sinensis (L.) O. KUNTZE; Fujian Province) were found to exhibit accelerating effects on gastrointestinal transit in mice and inhibitory effects against pancreatic lipase. From the BuOH-soluble fraction, three new acylated oleanane-type triterpene oligoglycosides, chakasaponins I, II, and III (1-3, resp.), were isolated together with 13 known compounds. The chemical structures 1-3 were elucidated on the basis of chemical and physicochemical evidence. Compounds 1-3 showed accelerating effects on gastrointestinal transit in mice and inhibitory effects against porcine pancreatic lipase (IC(50)=150-530 microM).

Perennisosides I-VII, Acylated Triterpene Saponins with Antihyperlipidemic Activities from the Flowers of Bellis perennis

The methanolic extract and its saponin fraction (methanol-eluted fraction) of the flowers of Bellis perennis were found to suppress serum triglyceride elevation in olive oil-treated mice. From the saponin fraction, seven new triterpene saponins, perennisosides I (1), II (2), III (3), IV (4), V (5), VI (6), and VII (7), were isolated together with four known saponins, bellidioside A (8), asterbatanoside D (9), bernardioside B 2 (10), and bellissaponin BS6 (11). The stereostructures of 1- 7 were elucidated on the basis of chemical and spectroscopic evidence. Among these saponins, perennisosides I (1) and II (2) showed inhibitory effects on serum triglyceride elevation at doses of 25-50 mg/kg, po.

Alkaloids from Sri Lankan curry-leaf (Murraya koenigii) display melanogenesis inhibitory activity: Structures of karapinchamines A and B

A methanolic extract and its ethyl acetate-soluble fraction from Sri Lankan curry-leaf, the leaves of Murraya koenigii, inhibited melanogenesis in theophylline-stimulated murine B16 melanoma 4A5 cells. Two new carbazole alkaloids, karapinchamines A and B, were isolated from the ethyl acetate-soluble fraction together with 12 known carbazole alkaloids. The structures of karapinchamines A and B were determined by physicochemical analyses. The principal alkaloid constituents were found to display potent melanogenesis inhibitory activity. The structural requirements of the carbazole alkaloids for melanogenesis inhibitory activity were discussed.