Phosphate buffer interferes dissolution of prazosin hydrochloride in compendial dissolution testing.

The purpose of this study was to elucidate the lack of supersaturation behavior in the dissolution profile of prazosin hydrochloride (PRZ-HCl) in the compendial dissolution test. The equilibrium solubility was measured by a shake-flask method. Dissolution tests were performed by a compendial paddle method with a phosphate buffer solution (pH 6.8, 50 mM phosphate). The solid form of the residual particles was identified by Raman spectroscopy. In the pH range below 6.5, the equilibrium solubility in phosphate buffer was lower than that in the unbuffered solutions (pH adjusted by HCl and NaOH). Raman spectra showed that the residual solid was a phosphate salt of PRZ. In the pH range above 6.5, the pH-solubility profiles in the phosphate buffer solutions and the unbuffered solutions were the same. The residual solid was a PRZ freebase (PRZ-FB). In the dissolution test, PRZ-HCl particles first changed to a phosphate salt within 5 min, then gradually changed to PRZ-FB after several hours. Since the intestinal fluid is buffered by the bicarbonate system in vivo, the dissolution behavior in vivo may not be properly evaluated using a phosphate buffer solution. For drugs with a low phosphate solubility product, it is necessary to consider this aspect.

Chemical structures of constituents from the flowers of Osmanthus fragrans var. aurantiacus.

Three new megastigmane glycosides named floraosmanosides I-III and a new γ-decalactone named floraosmanolactone I together with 16 known constituents were isolated from the flowers of Osmanthus fragrans var. aurantiacus cultivated in Guangxi Zhuang Autonomous Region, China. The chemical structures of the new compounds were elucidated on the basis of chemical and physicochemical evidence. Among them, ligustroside and (+)-pinoresinol significantly inhibited nitric oxide production in lipopolysaccharide-activated RAW264.7 macrophages.

Structure of diarylheptanoids with antiallergic activity from the rhizomes of Curcuma comosa.

The methanolic extract from the dried rhizomes of Curcuma comosa cultivated in Thailand was found to inhibit the release of ß-hexosaminidase as a maker of degranulation from rat basophil leukemia (RBL-2H3) cells. Two new diarylheptanoids, diarylcomosols IV and V, were isolated from the methanolic extract. The chemical structures of the new compounds were elucidated on the basis of chemical and physicochemical evidence. The isolated diarylheptanoids showed inhibitory activity, and the structural requirements of the active constituents for the inhibition were clarified.

A rare glutamine derivative from the flower buds of daylily.

A rare glutamine derivative, hemerocallisamine I (1), was isolated from the methanolic extract of the flower buds of daylily, together with a new pyrrole alkaloid hemerocallisamine II (2) and a new γ-lactam derivative, hemerocallisamine III (3). The chemical structures of the new compounds were elucidated on the basis of chemical and physicochemical evidence. For hemerocallisamine I (1), the absolute configuration was determined by Mo-Kα X-ray crystallographic analysis. This is the first report of a glutamine derivative with a pyrrole ring from natural plants.

Structure of constituents isolated from the flower buds of Cananga odorata and their inhibitory effects on aldose reductase.

Three new terpenoid derivatives, canangaterpenes IV-VI, were isolated from the flower buds of Cananga odorata, cultivated in Thailand, together with eight known flavonoids. The chemical structures of the new compounds were elucidated on the basis of chemical and physicochemical evidence. The inhibitory effects of the isolated compounds on aldose reductase were also investigated. Several terpenoid derivatives and flavonoids were shown to inhibit aldose reductase.

Lignan dicarboxylates and terpenoids from the flower buds of Cananga odorata and their inhibitory effects on melanogenesis.

The methanolic extract from the flower buds of Cananga odorata showed an inhibitory effect on melanogenesis in theophylline-stimulated murine B16 melanoma 4A5 cells. From the methanolic extract, two new lignan dicarboxylates, canangalignans I and II, three new terpenoids, canangaterpenes I, II, and III, and eight known compounds were isolated. The structures of these compounds were elucidated on the basis of chemical/physicochemical evidence. Several mono- and sesquiterpene analogues significantly inhibited melanogenesis. In particular, canangaterpene I and (3R,3aR,8aS)-3-isopropyl-8a-methyl-8-oxo-1,2,3,3a,6,7,8,8a-octahydroazulene-5-carbaldehyde exhibited a potent inhibitory effect on melanogenesis [inhibition (%): 34.7±4.2 (p<0.01), 45.5±5.7 (p<0.01) at 1 µM, respectively] without inducing cytotoxicity. Moreover, the biological effect of these compounds was much stronger than that of the reference compound, arbutin. Thus, these isolated terpenoid derivatives may be promising therapeutic agents for the treatment of several skin disorders.

Structures of acylated sucroses from the flower buds of Prunus mume.

Seven new acylated sucroses, mumeoses P-V, were isolated from the flower buds of Prunus mume, cultivated in Zhejiang province, China. Their chemical structures were elucidated on the basis of chemical and physicochemical evidence. Moreover, mumeoses C, D, and R, were shown to substantially inhibit aldose reductase.

Diarylheptanoids with inhibitory effects on melanogenesis from the rhizomes of Curcuma comosa in B16 melanoma cells.

The methanolic extract from the dried rhizomes of Curcuma comosa cultivated in Thailand was found to inhibit melanogenesis in theophylline-stimulated murine B16 melanoma 4A5 cells. From the methanolic extract, three new diarylheptanoids, diarylcomosols I-III, were isolated together with 12 known diarylheptanoids. Their chemical structures were elucidated on the basis of chemical and physicochemical evidence. The diarylheptanoids inhibited melanogenesis, and several structural requirements of the active constituents for the inhibition were clarified. In particular, (3R)-1,7-bis(4-hydroxyphenyl)-(6E)-6-hepten-3-ol exhibited stronger inhibitory effect [IC50=0.36 µM] without inducing cytotoxicity. The biological effect was much stronger than that of a reference compound, arbutin [IC50=174 µM]. We conclude that diarylheptanoid analogs are promising therapeutic agents for the treatment of skin disorders.

Acylated sucroses and acylated quinic acids analogs from the flower buds of Prunus mume and their inhibitory effect on melanogenesis.

The methanolic extract from the flower buds of Prunus mume, cultivated in Zhejiang Province, China, showed an inhibitory effect on melanogenesis in theophylline-stimulated B16 melanoma 4A5 cells. From the methanolic extract, five acylated sucroses, mumeoses A-E, and three acylated quinic acid analogs, 5-O-(E)-p-coumaroylquinic acid ethyl ester, and mumeic acid-A and its methyl ester, were isolated together with 13 known compounds. The chemical structures of the compounds were elucidated on the basis of chemical and physicochemical evidence. Inhibitory effects of the isolated compounds on melanogenesis in theophylline-stimulated B16 melanoma 4A5 cells were also investigated. Acylated quinic acid analogs substantially inhibited melanogenesis. In particular, 5-O-(E)-feruloylquinic acid methyl ester exhibited a potent inhibitory effect [inhibition (%): 21.5±1.0 (P<0.01) at 0.1 µM]. Moreover, its biological effect was much stronger than that of the reference compound, arbutin [inhibition (%): 10.6±0.6 (P<0.01) at 10 µM]. Interestingly, the obtained acylated quinic acid analogs displaying melanogenesis inhibitory activity showed no cytotoxicity [cell viability >97% at 10 µM]. It is concluded that acylated quinic acid analogs are promising therapeutic agents for the treatment of skin disorders.

Medicinal flowers. XXXVIII. structures of acylated sucroses and inhibitory effects of constituents on aldose reducatase from the flower buds of Prunus mume.

The methanolic extract from the flower buds of Prunus mume, cultivated in Zhejiang province, China, showed an inhibitory effect on aldose reductase. From the methanolic extract, five new acylated sucroses, mumeoses F-J, were isolated together with 29 known compounds. The chemical structures of the new compounds were elucidated on the basis of chemical and physicochemical evidence. The inhibitory effects of the isolated compounds on aldose reductase were also investigated. Acylated quinic acid analogs, which are one of the major compounds of the flower buds of P. mume, were shown to substantially inhibit aldose reductase. In particular, mumeic acid-A was found to exhibit a potent inhibitory effect [IC50=0.4 µm].

Structures of acylated sucroses and an acylated flavonol glycoside and inhibitory effects of constituents on aldose reductase from the flower buds of Prunus mume.

Five new acylated sucroses, mumeoses K-O, and a new acylated flavonol glycoside, mumeflavonoside A, were isolated from the flower buds of Prunus mume, cultivated in Zhejiang province, China. The chemical structures of the new compounds were elucidated on the basis of chemical and physicochemical evidence. The inhibitory effects of the isolated acylated sucroses and flavonol glycosides on aldose reductase were also investigated. Several flavonol glycosides including mumeflavonoside A were shown to inhibit aldose reductase.

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.

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.

Medicinal flowers. XXXV. Nor-oleanane-type and acylated oleanane-type triterpene saponins from the flower buds of Chinese Camellia japonica and their inhibitory effects on melanogenesis.

The methanolic extract and its 1-butanol-soluble fraction from the flower buds of Camellia japonica, cultivated in Yunnan Province, China, showed inhibitory effects on melanogenesis in theophylline-stimulated B16 melanoma 4A5 cells. From the 1-butanol-soluble fraction, a new 28-nor-oleanane-type and three new oleanane-type triterpene saponins, sanchakasaponins A-D, were isolated together with four known triterpene saponins. Their chemical structures were elucidated on the basis of chemical and physicochemical evidence. The inhibitory effects on melanogenesis in theophylline-stimulated B16 melanoma 4A5 cells and structure-activity relationships of the saponins were investigated.

Melanogenesis inhibitory and fibroblast proliferation accelerating effects of noroleanane- and oleanane-type triterpene oligoglycosides from the flower buds of Camellia japonica.

A 28-noroleanane-type triterpene oligoglycoside, camellioside E (4), an oleanane-type triterpene oligoglycoside, camellioside F (5), and the known compounds camelliosides A (1) and D (3) were isolated from a 50% EtOH extract of Camellia japonica flower buds from Korea. The principal constituents (1 and 5) significantly inhibited melanogenesis in theophylline-stimulated B16 melanoma 4A5 cells. Camellioside B (2), a major constituent of C. japonica grown in Japan, showed potent inhibition of melanogenesis [95.0 ± 1.0% (p < 0.01) at 20 µM]. The inhibitory effects of 1, 2, and 5 were stronger than that of the reference compound, arbutin. We believe the melanogenesis inhibitory effects of 2 and 5 are partly related to the proliferation inhibitory effects in B16 melanoma 4A5 cells. Conversely, camelliosides tended to enhance proliferation in normal human neonatal skin fibroblasts. Interestingly, camellioside B (2) significantly accelerated fibroblast proliferation. This biological selectivity could make camellioside B useful for treating skin disorders. Herein, we report the first scientific investigation of a triterpene that displays an inhibitory effect on melanogenesis, but that also has an enhancing effect on fibroblast proliferation.

Medicinal flowers. XXXVI.1) Acylated oleanane-type triterpene saponins with inhibitory effects on melanogenesis from the flower buds of Chinese Camellia japonica.

Four acylated oleanane-type triterpene oligoglycosides, sanchakasaponins E-H, were isolated from the flower buds of Camellia japonica cultivated in Yunnan province, China, together with four known triterpene oligoglycosides. The chemical structures of the new triterpene oligoglycosides were elucidated on the basis of chemical and physicochemical evidence. The inhibitory effects of the triterpene oligoglycoside constituents on melanogenesis in theophylline-stimulated B16 melanoma 4A5 cells were investigated.

Medicinal Flowers. XXXI. Acylated oleanane-type triterpene saponins, Sasanquasaponins I-V, with antiallergic activity from the flower buds of Camellia sasanqua.

The methanolic extract and its 1-butanol-soluble fraction from the flower buds of Camellia sasanqua THUNB. were found to show inhibitory activities on the release of ß-hexosaminidase from rat basophile leukemia (RBL-2H3) cells. From the 1-butanol-soluble fraction, five new acylated oleanane-type triterpene saponins, sasanquasaponins I-V, were isolated together with a known saponin and their chemical structures were elucidated on the basis of chemical and physicochemical evidence. The principal saponin constituents, sasanquasaponins I-III, with an acyl group at the 22-position of the aglycon part showed the inhibitory effects on the release of ß-hexosaminidase and some structure-activity relationships were reported.

Hemoglobin-mediated selenium export from red blood cells.

On the basis of the fact that selenium from selenite binds to hemoglobin (Hb), we investigated the missing process in the selenium export from red blood cells (RBCs), i.e., the transfer of selenium bound to Hb to RBC membrane proteins. To elucidate the molecular events of the Hb-associated selenium export from RBC, a Hb-Se complex was synthesized from thiol-exchange of Cys-beta93 in Hb with penicillamine-substituted glutathione selenotrisulfide, as a model of major metabolic intermediates, and then interactions between the Hb-Se complex and RBC inside-out vesicles (IOVs) were examined. Selenium bound to Hb was transferred to the IOV membrane on the basis of the intrinsic interactions between Hb and the cytoplasmic domains of band 3 protein (CDB3). The observed selenium transfer was inhibited by the pretreatments of IOVs with iodoacetamide and the alpha-chymotrypsin digestion, indicating that the Hb mediates the selenium transfer to the thiol groups of CDB3. In addition, it was found that deoxygenated Hb, with a high binding affinity for CDB3, more favorably transferred selenium to the IOV membranes than oxygenated Hb, with a low affinity. When selenium export from RBC to the plasma was examined by continuously introducing nitrogen gas, the selenium export rate was promoted with an increase in the rate of deoxygenated Hb. Overall, these data suggested that Hb could possibly play a role in the selenium export from RBC treated with selenite in an oxygen-linked fashion.

Selenium binding to human hemoglobin via selenotrisulfide.

Selenotrisulfide (e.g., glutathione selenotrisulfide (GSSeSG)) is an important intermediate in the metabolism of selenite. However, its reactivity with biological substances such as peptides and proteins in the subsequent metabolism is still far from clearly understood, because of its chemical instability under physiological conditions. Penicillamine (Pen) is capable of generating a chemically stable and isolatable selenotrisulfide, PenSSeSPen. To explore the metabolic fate of selenite in red blood cells (RBC), we investigated the reaction of selenotrisulfide with human hemoglobin (Hb) using PenSSeSPen as a model. PenSSeSPen rapidly reacted with Hb under physiological conditions. From the analysis of selenium binding using the Langmuir type binding equation, the apparent binding number of selenium per Hb tetramer almost corresponded to the number of reactive thiol groups of Hb. The thiol group blockade of Hb by iodoacetamide treatment completely inhibited the reaction of PenSSeSPen with Hb. In addition, MALDI-TOF mass spectrometric analysis of the selenium-bound Hb revealed that PenSSe moiety binds to the beta subunits of Hb. Overall, the reaction of PenSSeSPen with Hb appears to involve the thiol exchange between Pen and the cysteine residues on the beta subunit of Hb.