Identification of Hypoglycemic Glycolipids from Ipomoea murucoides by Affinity-Directed Fractionation, In Vitro, In Silico and Dynamic Light Scattering Analysis.

In the pursuit of identifying the novel resin glycoside modulators glucose-6-phosphatase and α-glucosidase enzymes, associated with blood sugar regulation, methanol-soluble extracts from the flowers of Ipomoea murucoides (cazahuate, Nahuatl), renowned for its abundance of glycolipids, were employed. The methanol-soluble extracts were fractionated by applying the affinity-directed method with glucose-6-phosphatase enzymes from a rat's liver and α-glucosidase enzymes from its intestines. Mass spectrometry and nuclear magnetic resonance were employed to identify the high-affinity compound as a free ligand following the release from the enzymatic complex. Gel permeation through a spin size-exclusion column allowed the separated high-affinity molecules to bind to glucose-6-phosphatase and α-glucosidase enzymes in solution, which led to the identification of some previously reported resin glycosides in the flowers of cazahuate, where a glycolipid mainly structurally related to murucoidin XIV was observed. In vitro studies demonstrated the modulating properties of resin glycosides on the glucose-6-phosphatase enzyme. Dynamic light scattering revealed conformational variations induced by resin glycosides on α-glucosidase enzyme, causing them to become more compact, akin to observations with the positive control, acarbose. These findings suggest that resin glycosides may serve as a potential source for phytotherapeutic agents with antihyperglycemic properties.

Phytochemical Screening and Isolation of New Ent-Clerodane Diterpenoids from Croton guatemalensis Lotsy.

Phytochemical screening of an ethanol-water extract (EWE) from the bark of Croton guatemalensis led to the isolation and identification of eight compounds, among them: five ent-clerodane diterpenoids [junceic acid (1), 6(s)-acetoxy-15,16-diepoxy-ent-cleroda-3,13(16),14-trien-20-oic acid (crotoguatenoic acid A) (2), 6(s)-hydroxyoxy-15,16-diepoxy-ent-cleroda-3,13(16),14-trien-20-oic acid (crotoguatenoic acid B) (3), formosin F (4), bartsiifolic acid (5)], and three flavonoids [rutin (6), epicatechin (7), and quercetin (8)]. Of these, 2 and 3 are reported here for the first time. Structures were established through conventional spectroscopy methods and their absolute configurations were determined by optical rotation and comparison of experimental electronic circular dichroism (ECD) and theoretical calculated ECD spectra. A suitable high performance liquid chromatography (HPLC) method for quantifying rutin (6) was developed and validated according to standard protocols. Affinity-directed fractionation was used to identify possible in vitro active compounds on α-glucosidases from Saccharomyces cerevisiae. HPLC-ESI-MS was used to identify the inhibitors as free ligands after being released from the enzymatic complex by denaturing acidic conditions. The affinity studies led to the identification of ent-clerodane diterpenoids as active compounds. In silico analysis allowed us to determine the best conformational rearrangement for the α-glucosidase inhibitors.

Glucose-6-Phosphatase and α-Glucosidase Inhibitors from Smilax moranensis Roots Identified by Affinity-Directed Fractionation.

The ethanol/water-soluble extracts of the roots of Smilax moranensis M. Martens & Galeotti, Smilacaceae, which have been appreciated since pre-Hispanic times and traditionally used to treat type 2 diabetes in Mexico, were fractionated by the application of the affinity-directed method to identify glucose-6-phosphatase and α-glucosidase inhibitors. Mass spectrometry was used to identify the inhibitor as free ligands after released from the enzymatic complex by denaturing acidic conditions. The affinity study led to the identification of chlorogenic acid as a glucose-6-phosphatase inhibitor, which is the most abundant metabolite present in the analyzed crude drug. In addition, the affinity studies led to the identification of a flavonolignan glycoside as an α-glucosidase inhibitor. In silico analysis with α-glucosidase MAL12 from the yeast Saccharomyces cerevisiae allowed to determine the best conformational rearrangement for the α-glucosidase inhibitors. Graphical abstract. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1007/s43450-020-00116-3.

The Peptide AmPep1 Derived from Amaranth Recognizes the Replication Hairpin of TYLCV Disturbing Its Replication Process in Host Plants.

Antiviral compounds targeting viral replicative processes have been studied as an alternative for the control of begomoviruses. Previously, we have reported that the peptide AmPep1 has strong affinity binding to the replication origin sequence of tomato yellow leaf curl virus (TYLCV). In this study, we describe the mechanism of action of this peptide as a novel alternative for control of plant-infecting DNA viruses. When AmPep1 was applied exogenously to tomato and Nicotiana benthamiana plants infected with TYLCV, a decrease in the synthesis of the two viral DNA strands (CS and VS) was observed, with a consequent delay in the development of disease progress in treated plants. The chemical mechanism of action of AmPep1 was deduced using Raman spectroscopy and molecular modeling showing the formation of chemical interactions such as H bonds and electrostatic interactions and the formation of π-π interactions between both biomolecules contributing to tampering with the viral replication.

Structure Elucidation, Conformation, and Configuration of Cytotoxic 6-Heptyl-5,6-dihydro-2 H-pyran-2-ones from Hyptis Species and Their Molecular Docking to α-Tubulin.

Cytotoxic 6-heptyl-5,6-dihydro-2 H-pyran-2-ones are chemical markers of Hyptis (Lamiaceae) and are responsible for some of the therapeutic properties of species with relevance to traditional medicine. The present investigation describes the isolation of known pectinolides A-C (1-3), in addition to the new pectinolides I-M (4-8), from two Mexican collections of H. pectinata by HPLC. The novel biosynthetically related monticolides A (9) and B (10) were also isolated by high-speed countercurrent chromatography from H. monticola, an endemic species of the Brazilian southeastern high-altitude regions. A combination of chemical correlations, chiroptical measurements, and Mosher ester NMR analysis was used to confirm their absolute configuration. The utility of DFT-NMR chemical shifts and JH-H calculations was assessed for epimer differentiation. Molecular docking studies indicated that 6-heptyl-5,6-dihydro-2 H-pyran-2-ones have a high affinity for the pironetin-binding site of α-tubulin, which may be a possible mechanism contributing to the cytotoxic potential of these small and flexible molecules.

Morning glory resin glycosides as α-glucosidase inhibitors: In vitro and in silico analysis.

Twenty-seven individual resin glycosides from the morning glory family (Convolvulaceae) were evaluated for their α-glucosidase inhibitory potential. Four of these compounds displayed an inhibitory activity comparable to acarbose, which was used as a positive control. Molecular modeling studies performed by docking analysis were accomplished to predict that the active compounds and acarbose bind to the α-1,4-glucosidase enzyme catalytic site of MAL12 from the yeast Saccharomyces cerevisiae through stable hydrogen bonds primarily with the amino acid residues HIS279 and GLN322. Docking studies with the human maltase-glucoamylase (MGAM) also identified binding modes for resin glycosides inside the catalytic site in the proximity of TYR1251. These results postulate that resin glycosides may be a source of phytotherapeutic agents with antihyperglycemic properties for the prophylaxis and treatment of non-insulin-dependent type 2 diabetes mellitus.

HPLC-MS profiling of the multidrug-resistance modifying resin glycoside content of Ipomoea alba seeds

ABSTRACT High performance liquid chromatography profiling with mass spectrometry detection was applicable to identify known and novel multidrug-resistance glycolipid inhibitors from the complex resin glycosides mixture of Ipomoea alba L., Convolvulaceae, seeds. Albinosides X and XI were purified by recycling liquid chromatography and their structural elucidation was accomplished by nuclear magnetic resonance. Albinoside XI exerted a strong potentiation of vinblastine susceptibility in multidrug-resistant human breast carcinoma cells.

Resistance-modifying Activity in Vinblastine-resistant Human Breast Cancer Cells by Oligosaccharides Obtained from Mucilage of Chia Seeds (Salvia hispanica).

The multidrug resistance (MDR) phenotype is considered as a major cause of the failure in cancer chemotherapy. The acquisition of MDR is usually mediated by the overexpression of drug efflux pumps of a P-glycoprotein. The development of compounds that mitigate the MDR phenotype by modulating the activity of these transport proteins is an important yet elusive target. Here, we screened the saponification and enzymatic degradation products from Salvia hispanica seed's mucilage to discover modulating compounds of the acquired resistance to chemotherapeutic in breast cancer cells. Preparative-scale recycling HPLC was used to purify the hydrolysis degradation products. All compounds were tested in eight different cancer cell lines and Vero cells. All compounds were noncytotoxic at the concentration tested against the drug-sensitive and multidrug-resistant cells (IC50  > 29.2 µM). For the all products, a moderate vinblastine-enhancing activity from 4.55-fold to 6.82-fold was observed. That could be significant from a therapeutic perspective. Copyright © 2017 John Wiley & Sons, Ltd.

Resin Glycosides from Ipomoea alba Seeds as Potential Chemosensitizers in Breast Carcinoma Cells.

Multidrug resistance is the expression of one or more efflux pumps, such as P-glycoprotein, and is a major obstacle in cancer therapy. The use of new potent and noncytotoxic efflux pump modulators, coadministered with antineoplastic agents, is an alternative approach for increasing the success rate of therapy regimes with different drug combinations. This report describes the isolation and structure elucidation of six new resin glycosides from moon vine seeds (Ipomoea alba) as potential mammalian multidrug-resistance-modifying agents. Albinosides IV-IX (1-6), along with the known albinosides I-III (7-9), were purified from the CHCl3-soluble extract. Degradative chemical reactions in combination with NMR spectroscopy and mass spectrometry were used for their structural elucidation. Four new glycosidic acids, albinosinic acids D-G (10-13), were released by saponification of natural products 3-6. They were characterized as tetrasaccharides of either convolvulinolic (11S-hydroxytetradecanoic) or jalapinolic (11S-hydroxyhexadecanoic) acids. The potentiation of vinblastine susceptibility in multidrug-resistant human breast carcinoma cells of albinosides 1-6 was evaluated by modulation assays. The noncytotoxic albinosides VII (4) and VIII (5), at a concentration of 25 µg/mL, exerted the strongest potentiation of vinblastine susceptibility, with a reversal factor (RFMCF-7/Vin+) of 201- and >2517-fold, respectively.

Resin glycosides from Ipomoea wolcottiana as modulators of the multidrug resistance phenotype in vitro.

Recycling liquid chromatography was used for the isolation and purification of resin glycosides from the CHCl3-soluble extracts prepared using flowers of Ipomoea wolcottiana Rose var. wolcottiana. Bioassay-guided fractionation, using modulation of both antibiotic activity against multidrug-resistant strains of Gram-negative bacteria and vinblastine susceptibility in breast carcinoma cells, was used to isolate the active glycolipids as modulators of the multidrug resistance phenotype. An ester-type dimer, wolcottine I, one tetra- and three pentasaccharides, wolcottinosides I-IV, in addition to the known intrapilosin VII, were characterized by NMR spectroscopy and mass spectrometry. In vitro assays established that none of these metabolites displayed antibacterial activity (MIC>512 µg/mL) against multidrug-resistant strains of Escherichia coli, and two nosocomial pathogens: Salmonella enterica serovar Typhi and Shigella flexneri; however, when tested (25 µg/mL) in combination with tetracycline, kanamycin or chloramphenicol, they exerted a potentiation effect of the antibiotic susceptibility up to eightfold (64 µg/mL from 512 µg/mL). It was also determined that these non-cytotoxic (CI50>8.68 µM) agents modulated vinblastine susceptibility at 25 µg/mL in MFC-7/Vin(+) cells with a reversal factor (RFMCF-7/Vin(+)) of 2-130 fold.

Batatins VIII-XI, glycolipid ester-type dimers from Ipomoea batatas.

Sweet potato (Ipomoea batatas) is native to the tropics of Central and South America, where many varieties have been consumed for more that 5000 years. In developing countries, this crop is a recognized effective food for fighting malnutrition. Purification of the minor lipophilic glicolipids found in the n-hexane-soluble resin glycosides from the white-skinned variety was performed by preparative-scale recycling HPLC. Application of column overload, peak shaving, heart cutting, and recycling techniques permitted the purification of four new oligosaccharide ester-type dimer derivatives of jalapinolic acid, batatins VIII-XI (1-4). The structural characterization of these complex lipo-oligosaccharides was performed through NMR spectroscopy and MS, indicating that batatins VIII-XI (1-4) possess an oligomeric structure consisting of two pentasaccharide units of the known simonic acid B.

Resin glycosides from the yellow-skinned variety of sweet potato (Ipomoea batatas).

Native to tropical America, Ipomoea batatas has been cultivated for over 5000 years in Mexico. The yellow-skinned tuber crop variety, with an orange flesh, has a higher nutritional value than potato. Raw sweet potato can cause a purge due to its resin glycoside content. Purification of the chloroform-soluble resin glycosides from the roots of this variety was accomplished by preparative-scale HPLC, which allowed for the collection of six oligosaccharides, batatin VII (1) and batatinosides VII-IX (2-4), all of novel structure, together with the known resin glycosides pescaprein I and batatinoside IV. High-field NMR spectroscopy and FAB mass spectrometry were used to characterize each structure, identifying operculinic acid A for compounds 2 and 4, and simonic acid B for 3, as their pentasaccharide glycosidic cores. Batatin VII (1) represents a dimer of the know batatinoside IV, consisting of two units of simonic acid B.

Batatins III-VI, glycolipid ester-type dimers from Ipomoea batatas.

Batatins III-VI (1-4), glycolipid ester-type dimers, were isolated from the tuberous roots of sweet potato (Ipomoea batatas) using recycle high performance liquid chromatography. Their structures were characterized by means of several high-resolution NMR and mass spectrometry techniques. These compounds are the first examples of ester-type dimers which consist of two units of the heterotetrasaccharide operculinic acid C. Each unit was esterified by a different amount and type of acid residues: (2S)-methylbutanoic, cinnamic, decanoic (capric) and dodecanoic (lauric) acids. Batatins III-VI (1-4) are an example of the presence of a large number of resin glycoside congeners in each morning glory species caused by partial acylation of their constitutive saccharide cores.

Batatinosides II-VI, acylated lipooligosaccharides from the resin glycosides of sweet potato.

Sweet potato ( Ipomoea batatas) belongs to the Convolvulaceae (morning glory family) and is native to Mexico and Central America. Its edible tuberous roots have been much appreciated since pre-Hispanic times in Mesoamerica and now play an important role as a basic diet staple and a medicinal plant worldwide. The hexane-soluble extract from roots, through preparative-scale recycling HPLC, yielded five new lipophilic oligosaccharides of jalapinolic acid, batatinosides II-VI ( 1- 5), as well as the known pescapreins I ( 6) and VII ( 7) and murucoidin I ( 8), which are part of the purgative resin glycoside mixture. NMR spectroscopy and FAB mass spectrometry were used to characterize their structures. Compounds 1 and 2 are tetraglycosidic lactones of operculinic acid C. The pentasaccharide structures for compounds 3 and 4 were confirmed to be macrolactones of simonic acid B, and that characterized for 5 was derived from operculinic acid A. The lactonization site of the aglycone was placed at C-3 of the second saccharide unit in all compounds except 4, where it was placed at C-2. All compounds contain an esterifying residue that is composed of a long-chain fatty acid, n-decanoic acid (capric) or n-dodecanoic acid (lauric). In compound 3, an additional short-chain fatty acid, (2 S)-methylbutyric acid, was also identified.