Revision of NMR assignment for Morin-3-O-glucoside and microbial production of Morin-2'-O-glucoside.

Morin is a flavonol having 2',4'-dihydroxy group on B-ring identified especially in Moraceae plants. While morin is widely known, its glycosides are relatively rare. To the best of our knowledge, morin-3-O-glucoside (1) was first reported in 2008. However, the reported chemical shift values of 1 were unsatisfactory with those of the aglycone, morin, which is rather similar to quercetin-3-O-glucoside (2). Therefore, we prepared morin-3-O-glucoside (1) by microbial transformation of morin with Cunninghamella sp., and the NMR assignment was reinvestigated. The microbial culture also produced another compound (3). The NMR and MS analyses of 3 revealed it as a novel compound, morin-2'-O-glucoside (3).In this study, the revision of the NMR assignment of morin-3-O-glucoside (1), and the preparation and structural elucidation of a novel compound, morin-2'-O-glucoside (3), were described.

New ψ-Santonin Derivatives from Crossostephium chinense and Their Anti-Proliferative Activities against Leishmania major and Human Cancer Cells A549.

Previously, we reported two cytotoxic ψ-santonin-amino acid conjugates isolated from the EtOAc layer of Crossostephium chinense. However, a further phytochemical investigation seems to be required because of the few reports of similar derivatives. In this study, we targeted the 1-BuOH layer, which resulted in the isolation of seven new ψ-santonin derivatives (1-7) together with ten known compounds (8-17). The structures of 1-7 were elucidated based on spectroscopic methods, including 1D and 2D NMR experiments (1H, 13C, DEPT, COSY, HSQC, and HMBC), IR spectrum, and high-resolution electrospray ionization-mass spectrometry (HR-ESI-MS). The stereochemistry of new compounds was confirmed by NOESY and ECD calculations. All isolated compounds were evaluated by in vitro experiments for their anti-proliferative activities against Leishmania major, human lung cancer cell line A549, and Vero cells. As a result, most of the ψ-santonin derivatives, especially 1-5, showed significant cytotoxicity against L. major with a lower IC50 than the positive control we used (miltefosine).

Two New Cytotoxic Sesquiterpene-Amino Acid Conjugates and a Coumarin-Glucoside from Crossostephium chinense.

The Asteraceae family is a promising source of bioactive compounds, such as the famous Asteraceae plants Tanacetum cinerariifolium (pyrethrin) and Artemisia annua (artemisinin). As a result of our series of phytochemical studies of the subtropical plants, two novel sesquiterpenes, named crossoseamines A and B in this study (1 and 2, respectively), one undescribed coumarin-glucoside (3), and eighteen known compounds (4-21) were isolated from the aerial part of Crossostephium chinense (Asteraceae). The structures of isolated compounds were elucidated by spectroscopic methods, including 1D and 2D NMR experiments (1H, 13C, DEPT, COSY, HSQC, HMBC, and NOESY), IR spectrum, circular dichroism spectrum (CD), and high-resolution electrospray ionization-mass spectrometry (HR-ESI-MS). All isolated compounds were evaluated for their cytotoxic activities against Leishmania major, Plasmodium falciparum, Trypanosoma brucei (gambiense and rhodesiense), and human lung cancer cell line A549 because of the high demand for the discovery of new drug leads to overcome the present side effects and emerging drug-resistant strains. As a result, the new compounds (1 and 2) showed significant activities against A549 (IC50, 1: 3.3 ± 0.3; 2: 12.3 ± 1.0 µg/mL), L. major (IC50, 1: 6.9 ± 0.6; 2: 24.9 ± 2.2 µg/mL), and P. falciparum (IC50, 1: 12.1 ± 1.1; 2: 15.6 ± 1.2 µg/mL).

Crotofolanes, rearranged crotofolanes, and a novel diterpene: isocrotofolane from Croton cascarilloides, collected in Okinawa.

To this day, since about 50% of all medicines are derived from natural sources, natural product chemistry, especially the search for biologically active natural components, remains extremely important (Newman and Cragg in J Nat Prod 83:770-803, 2020). In this review, we deal with our continuing research work for promising constituents from plants collected in the Ryukyu Archipelago. The isolation of islands in the archipelago by the sea or by straits gives rise to endemic plant species that are unique to the islands. The structural diversity of the constituents produced by this unique flora is of great scientific interest in various aspects, including chemical structures, biosynthesis, and biological activities. The components from this structural diversity have great potential as new pharmaceutical seeds. In our continuing studies, we have successfully investigated new but extremely unusual diterpenoids: crotofolanes and their rearranged varieties (nor-crotofolane, trinor-crotofolane, neocrotofolane) and a glycoside with a new skeletal diterpenoid (isocrotofolane glucoside) from Croton cascarilloides. This review summarizes our reports on the investigation of crotofolanes as well as those on crotofolanes by other research groups.

Omphalines A-E: ent-Rosane-Type Diterpenoids from the Madagascar Endemic Plant, Omphalea oppositifolia.

From the less polar fraction of the MeOH extract of the leaves and twigs of Omphalea oppositifolia, five new ent-rosane-type diterpenoids, named omphalines A-E (1-5), were isolated together with one known compound, 7-keto-ent-kaurane-16ß,17-diol (6), by a combination of various kinds of chromatography. The structure of omphaline A (1) was elucidated to be 19-nor-ent-rosane-4,15-diene-2ß,6α-diol-3-one. Omphalines B (2), C (3), D (4), and E (5) possessed two double bonds at 5- and 15-positions, and hydroxy functional groups at 3ß-, 2α,3α-, 2α,3ß-, and 2α,19-positions, respectively. The absolute configuration of 1 was determined by the comparison of the experimental electronic circular dichroism (ECD) spectrum and calculated ECD spectra.

Four new glucosides from the aerial parts of Equisetum sylvaticum.

Two previously undescribed megastigmane glucosides, (3S)-3-hydroxy-4-oxo-7,8-dihydro-ß-ionone-3-O-ß-D-glucopyranoside (1), (3S)-3-hydroxy-4-oxo-ß-ionone-3-O-ß-D-glucopyranoside (2), an apocarotenoid glucoside named equiseoside A (3) and an unusual aromatic compound with a glucose-fused skeleton named equiseoside B (4), together with 35 known compounds (5-39) were isolated from the aerial parts of Equisetum sylvaticum. The structures of these compounds were elucidated by spectroscopic methods, including 1D and 2D NMR, IR, CD, and HR-MS.

Crotofolane-Type Diterpenoids: Crotocascarins R-V, Rearranged Trinorcrotofolane: Crotocascarin δ and a Phorbol Derivative from the Leaves of Croton cascarilloides.

Five new crotofolanes, named crotocascarins R-V (1-5), one rearranged trinorcrotofolane, crotocascarin δ, and one phorbol derivative were isolated from the EtOAc-soluble fraction of the MeOH extract of the leaves of Croton cascarilloides. Crotocascarins R (1), T (3), and U (4) possessed isobutyric acid as an acyl moiety and crotocascarin B (2) an acetyl group, whereas crotocascarin V (5) was elucidated to be a hydroxylated compound of crotocascarin K at the 9-position. Crotocascarin δ (6) was a trinor rearranged crotofolane with a tertiary hemiketal functional group at the 8-position. The absolute configuration of the 8-position was determined by the comparison of the experimental electronic circular dichroism (ECD) spectrum and calculated ECD spectra. Compound 7 was a phorbol ester derivative with a peroxide functional group. The fatty acid attached at the 12-position was found to be a single species-i.e., lauric acid (C-12)-from the evidence of the mass spectral data.

Potency of bisresorcinol from Heliciopsis terminalis on skin aging: in vitro bioactivities and molecular interactions.

BACKGROUND: A bisresorcinol was isolated as the main constituent of Heliciopsis terminalis's trunk (Proteaceae). Recently, resorcinol is applied as an active whitening agent in various cosmetic products. Because of the structural mimic to resorcinol, benefits of the bisresorcinol as an aging-enzyme antagonist were demonstrated in this study. METHODS: The bisresorcinol was purified from the crude ethanolic extract of H. terminalis's trunk by solvent extraction and preparative chromatography, respectively. Inhibitory activity on collagenase, elastase, and tyrosinase of the compound was investigated by using a different spectroscopic technique. Molecular docking was carried out to predict possible interactions of the substance around the enzyme active sites. RESULTS: The IC50 values on collagenase of the bisresorcinol and caffeic acid were 156.7 ± 0.7 and 308.9 ± 1.6 µmole L-1, respectively. For elastase activity, the IC50 of 33.2 ± 0.5 and 34.3 ± 0.3 µmole L-1 was respectively determined for the bisresorcinol and ursolic acid. The bisresorcinol was inhibitory to tyrosinase by exhibiting the IC50 of 22.8 µmole L-1, and that of 78.4 µmole L-1 was present for ß-arbutin. The bisresorcinol bound to collagenase, elastase, and tyrosinase with the respective binding energies of -5.89, -5.69, and -6.57 kcal mol-1. These binding energies were in the same ranges of tested inhibitors. The aromatic phenol groups in the structure were responsible for principle as well as supporting binding interactions with enzymes. Hydrogen binding due to hydroxyl groups and π-related attractive forces from an aromatic ring(s) provided binding versatility to bisresorcinol. CONCLUSION: The bisresorcinol purified from H. terminalis might be useful for inclusion in cosmetic products as an aging-enzyme antagonist.

Detecting and Differentiating Monosaccharide Enantiomers by 1H NMR Spectroscopy.

Monosaccharides play important roles in living organisms. They are present in essential glycoproteins, nucleic acids, and glycolipids as well as cell walls and bioactive natural product glycosides and polysaccharides. Monosaccharides are optically active, and as a routine, scientists make sure that their absolute configurations are determined when new natural glycosides are isolated. Many determination methods for the absolute configuration of monosaccharides have been reported, and thus far, taking advantage of their optical rotation differences is the most used and efficient method to distinguish enantiomers. This method, however, is not very convenient, because it requires a milligram amount of each pure sample and the availability of a polarimeter. Identification methods dealing with comparison of the retention times of the d- and l-diastereomeric monosaccharide derivatives by GC, TLC Rf values, HPLC, or UPLC have been also reported. Although effective, these methods still require sample preparation and a few milligrams of the test compounds. A new method with simple sample preparation to distinguish enantiomers of monosaccharides by analyzing the 1H NMR spectra of their diastereomeric derivatives has been developed. The monosaccharide components of a commercially available saponin-rich Panax ginseng and monoglycosides have been successfully identified using this procedure.

Pregnane Steroids from the Leaves of Melia Azedarach and Apoptotic Activity against T47D Cells.

OBJECTIVE: Nature has provided us with many pharmaceutical resources so far. Breast cancer shows an increasing trend in the world for the last decade and becomes one of five leading causes of death. Among the plants, Melia azedarach L. has been used widely in traditional medicine for many ailments including breast cancer. Following our previous findings that the ethyl acetate fraction was the most active cytotoxic fraction against T47D cells, we aimed to isolate the cytotoxic compounds and further elucidate their apoptotic mechanisms. METHODS: The compounds were isolated through a series of chromatography with cytotoxicity evaluations. Identification of the isolated compounds was achieved by intensive spectroscopic analysis such as NMR, MS, and IR spectra. Cytotoxicity was evaluated by MTT method using doxorubicin as a reference compound. The expression of apoptosis-related factors was quantified by flow cytometry and immunocytochemistry. RESULTS: Two isomers of pregnane steroids with molecular weight 330.2087 (C21H30O3) were isolated from the EtOAc extract. Spectroscopic analysis revealed the structures as 17-ethylene-3,4-dihydroxy-14-methyl-18-norandrostene-16-one (1) and 17-ethylene-3,4-dihydroxy-5-pregnene-16-one (2), respectively. These compounds showed moderate cytotoxicity (IC50 172.9 and 62.2 µg/mL, respectively) comparable to doxorubicin (IC50 3.08 µg/mL). The execution of apoptosis may be related to the increase of the ratio of BAX/bcl-2 of the cells.  Conclusion: The EtOAc fraction of Melia azedarach L. leaves and the isolated 5-pregnene-16-one steroids are promising reagents for breast cancer treatment by introducing apoptosis to tumor cells. However, further researches are required to highlight its safety and usage in vivo.
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Six New Phenylpropanoid Derivatives from Chemically Converted Extract of Alpinia galanga (L.) and Their Antiparasitic Activities.

Chemical conversion of the extract of natural resources is a very attractive way to expand the chemical space to discover bioactive compounds. In order to search for new medicines to treat parasitic diseases that cause high morbidity and mortality in affected countries in the world, the ethyl acetate extract from the rhizome of Alpinia galanga (L.) has been chemically converted by epoxidation using dioxirane generated in situ. The biological activity of chemically converted extract (CCE) of A. galanga (L.) significantly increased the activity against Leishmania major up to 82.6 ± 6.2 % at 25 µg/mL (whereas 2.7 ± 0.8% for the original extract). By bioassay-guided fractionation, new phenylpropanoids (1-6) and four known compounds, hydroquinone (7), 4-hydroxy(4-hydroxyphenyl)methoxy)benzaldehyde (8), isocoumarin cis 4-hydroxymelein (9), and (2S,3S,6R,7R,9S,10S)-humulene triepoxide (10) were isolated from CCE. The structures of isolated compounds were determined by spectroscopic analyses of 1D and 2D NMR, IR, and MS spectra. The most active compound was hydroquinone (7) with IC50 = 0.37 ± 1.37 µg/mL as a substantial active principle of CCE. In addition, the new phenylpropanoid 2 (IC50 = 27.8 ± 0.34 µg/mL) also showed significant activity against L. major compared to the positive control miltefosine (IC50 = 7.47 ± 0.3 µg/mL). The activities of the isolated compounds were also evaluated against Plasmodium falciparum, Trypanosoma brucei gambisense and Trypanosoma brucei rhodeisense. Interestingly, compound 2 was selectively active against trypanosomes with potent activity. To the best of our knowledge, this is the first report on the bioactive "unnatural" natural products from the crude extract of A. galanga (L.) by chemical conversion and on its activities against causal pathogens of leishmaniasis, trypanosomiasis, and malaria.

Ardisiatetrons A and B: tetronic acid derivatives and triterpenes from the leaves of Ardisia quinquegona and their biological activity.

From the leaves of Ardisia quinquegona, two alkylated tetronic acid derivatives, named ardisiatetrons A and B (1, 2), and four triterpenoids (3-6) were isolated together with one known compound (7) by a combination of various kinds of chromatography. The structure of new methyl migrated triterpene (3) was confirmed by X-ray crystallographic analysis. Compounds 2, 3, and 7 showed moderate anti-Leishmania activity and cytotoxicity towards A549 cells.

Isolation of Three New Diterpenes from Dodonaea viscosa.

An investigation into the methanol extracts obtained from the stems of Dodonaea viscosa led to the isolation of one nor-clerodane diterpene (1) and two labdane diterpenes (2, 3), as well as 17 known compounds (4-20). The structures of these compounds were elucidated based on chemical and spectral evidence. The stereochemical structure of the nor-clerodane diterpene was confirmed via its circular dichroism spectrum and calculated electronic circular dichroism spectrum. Isolated compounds were evaluated for their inhibitory effects on collagenase and tyrosinase. Since 5,7,4'-trihydroxy-3'-(4-hydroxy-3-methylbutyl)-5'-(3-methylbut-2-enyl)-3,6-dimethoxyflavone (9) showed collagenase inhibitory activity and scopoletin (12) had significant tyrosinase inhibitory activity, they were considered to be good candidates for cosmetic agents.

Symplocosins C-P: Fourteen Triterpene Saponins from the Leaves of Symplocos cochinchinensis var. philippinensis.

Extensive phytochemical work on the 1-BuOH-soluble fraction of a MeOH extract of the leaves of Symplocos cochinchinensis var. philippinensis resulted in the isolation of 14 new triterpenene saponins, along with four known ones. Their structures were elucidated by comparison of NMR spectroscopic data with related compounds reported in the literature. Three oleanane-type saponins, symplocosins K, M, and P, possessed glucuronic acid as a sugar component, and their carboxyl groups appeared as methyl esters. These are probably formed during extraction and isolation procedures. Symplocosin K (9) showed moderate cytotoxicity toward A549 cells. In addition, all isolated compounds did not show α-glucosidase inhibitory activity.

Zanthosides A-D: Four Aromatic Glucosides from the Leaves of Zanthoxylum ailanthoides.

From the leaves of Zanthoxylum ailanthoides, four new phenolic glucosides, termed zanthosides A-D (1-4), were isolated. Their structures were elucidated by means of spectroscopic evidence. Zanthoside A was enzymatically hydrolyzed and thus the aglycone obtained was found to be (1'S,2'R)-(-)-trans-decursidinol, isolated from Angelica decursiva.

Firmosides A and B: two new sucrose ferulates from the aerial parts of Silene firma and evaluation of radical scavenging activities.

Two new tri-ferulates of sucrose, firmosides A and B (1 and 2, respectively), together with 18 known compounds (3-20), were isolated from the aerial parts of Silene firma. The structures of the isolated compounds were elucidated by various spectroscopic methods, including 1D, 2D NMR, and high-resolution electro-spray ionization-mass spectrometry (HR-ESI-MS). All the isolated compounds were evaluated for their free radical scavenging activity using 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical. As a result, two new compounds (1, 2) and 11 demonstrated significant radical scavenging activity, implying the usefulness as antioxidant agents.

New Methyl Threonolactones and Pyroglutamates of Spilanthes acmella (L.) L. and Their Bone Formation Activities.

In our continuing research for bioactive constituents from natural resources, a new methyl threonolactone glucopyranoside (1), a new methyl threonolactone fructofuranoside (2), 2 new pyroglutamates (3 and 4), and 10 known compounds (5-14) were isolated from the whole plant of Spilanthes acmella (L.) L. The structures of these compounds were determined based on various spectroscopic and chemical analyses. All of the isolated compounds were evaluated on bone formation parameters, such as ALP (alkaline phosphatase) and mineralization stimulatory activities of MC3T3-E1 cell lines. The results showed that the new compound, 1,3-butanediol 3-pyroglutamate (4), 2-deoxy-D-ribono-1,4-lactone (6), methyl pyroglutamate (7), ampelopsisionoside (10), icariside B1 (11), and benzyl α-L-arabinopyranosyl-(1→6)-ß-D-glucopyranoside (12) stimulated both ALP and mineralization activities.

Lasianosides F-I: A New Iridoid and Three New Bis-Iridoid Glycosides from the Leaves of Lasianthus verticillatus (Lour.) Merr.

A series of iridoid glycosides were isolated from the leaves of Lasianthus verticillatus (Lour.) Merr., belonging to family Rubiaceae. A new iridoid glycoside, lasianoside F (1), and three new bis-iridoid glycosides, lasianosides G-I (2-4), together with four known compounds (5-8) were isolated. The structures were established by spectroscopic methods, including 1D and 2D NMR experiments (1H, 13C, DEPT, COSY, HSQC, HMBC, and NOESY) in combination with HR-ESI-MS and CD spectra.

Eudesmane-type sesquiterpene glycosides: sonneratiosides A-E and eudesmol ß-D-glucopyranoside from the leaves of Sonneratia alba.

Five eudesmane-type sesquiterpene glycosides, named sonneratiosides A-E (1-5), were isolated from the leaves of Sonneratia alba (Lythraceae). The aglycone of sonneratioside A was identified as cryptomeridiol also known as proximadiol. X-ray crystallographic analysis of sonneratioside A confirmed its structure and its absolute stereochemistry. Eudesmol ß-D-glucopyranoside (6) was also isolated from nature for the first time. The tyrosinase inhibitory activity was assayed for the new compounds together with seven known compounds. Among them, arbutin (12) showed the expected activity and luteolin 7-O-rutinoside (10) showed comparable activity to arbutin.

Ebenamariosides A-D: Triterpene Glucosides and Megastigmanes from the Leaves of Diospyros maritima.

The 1-BuOH-soluble fraction of the methanol (MeOH) extract of Diospyros maritima was separated by chromatographic techniques to give three new oleanane-type and one new ursane-type triterpene glucoside, named ebenamariosides A-D (1-4); two megastigmanes were also isolated. The structures of triterpene glucosides was elucidated with extensive investigation by one and two dimensional NMR spectroscopy and the structures were confirmed by partial enzymatic hydrolyses to give the corresponding mono-glucosides and aglycones. The structures of the megastigmanes, including their absolute stereochemistries, were elucidated by spectroscopic evidence and by the modified Mosher's method. Two megastigmanes were chemically correlated and their absolute structures were unambiguously determined. The cytotoxicity of the triterpene glucosides and their degradation products were assayed. They did not show any significant activity.