Glycosidic Acid Content from the Roots of Operculina hamiltonii (Brazilian Jalap) and Some of Their Phytopharmaceuticals with Purgative Activity

Inhibition of multidrug-resistant MCF-7 breast cancer cells with combinations of clinical drugs and resin glycosides from Operculina hamiltonii

The jalap roots, Operculina hamiltonii D.F. Austin & Staples (Convolvulaceae), are extensively commercialized as a depurative and laxative remedy in traditional medicine of the north and northeast regions of Brazil. The purification by recycling HPLC and structure elucidation of three new acyl sugars or resin glycosides are described here from a commercial product made of powdered roots. Three macrocyclic structures of a tetrasaccharide of (11S)-hydroxyhexadecanoic acid, operculinic acid C (1), the undescribed hamiltonins II and III (3 and 4), in addition to the known batatinoside III (5), presented a diastereoisomeric relationship as one residue of n-dodecanoic acid esterified the oligosaccharide core on a different position in each compound. Furthermore, hamiltonin IV (6) was characterized as an ester-type homodimer of acylated operculinic acid C with the same substitution pattern identified in hamiltonins II (3) and III (4) for each of the dimer subunits. All the isolated resin glycosides did not display any intrinsic cytotoxicity (IC50 > 25 μM). However, a combination of the individual isolated compounds 3-6 (1-50 μM) demonstrated an enhancement of cytotoxic effects with sublethal doses of vinblastine and podophyllotoxin (0.003 μM) in multidrug-resistant breast carcinoma epithelial cells (MCF-7/Vin).

Hederifolic acids A-D, hepta and hexasaccharides from the resin glycosides of Ipomoea hederifolia

Scarlet morning glory, Ipomoea hederifolia L. (Convolvulaceae), is an ornamental vine native to the Americas with oxytocic, cytotoxic, antipsychotic, anti-inflammatory, antioxidant, and antimicrobial properties. A chemical study of the glycosidic acids from the resin glycosides contained in the aerial parts was carried out, through their isolation as peracetylated derivatives, by recycling preparative liquid chromatography. Structure elucidation was performed by HR-MS in accordance with NMR. Four peracetylated derivatives of glycosidic acids, named hederifolic acids A-D, were identified as heptaglycosides and hexaglycosides linked to 3S,12S-dihydroxyheptadecanoic acid or 12 S-hydroxyheptadecanoic acid. Consequently, hederifolic acids B and D were found to be dehydroxylated homologs at C-3 of the fatty acid aglycones of hederifolic acids A and C, respectively.

Resin Glycosides from Operculina hamiltonii and Their Synergism with Vinblastine in Cancer Cells

Operculina hamiltonii is a vine native to the north and northeast region of Brazil, where its roots are traded as a depurative and laxative remedy with the name of Brazilian jalap in traditional medicine. Procedures for the isolation, purification by recycling HPLC, and structure elucidation of three undescribed resin glycosides are presented herein. Hamiltonin I (1) represents a macrocyclic structure of a tetrasaccharide of (11S)-hydroxyhexadecanoic acid. Additionally, two acyclic pentasaccharides, named hamiltoniosides I (2) and II (3), were also isolated, which are related structurally to the known compounds 4 and 5, macrocyclic lactone-type batatinosides. The tetrasaccharide core of 1 was diacylated by n-decanoic acid and the unusual n-hexadecanoic acid moiety, while the pentasaccharides 2-5 were esterified by one unit of n-decanoic or n-dodecanoic acid. All the isolated compounds were found to be inactive as cytotoxic agents. However, when they were evaluated (1-25 μM) in combination with a sublethal concentration of the anticancer agent vinblastine (0.003 μM), a significant enhancement of the resultant cytotoxicity was produced, especially for multidrug-resistant breast carcinoma epithelial cells. Such combined synergistic potency may be beneficial for chemotherapy, making resin glycosides potential candidates for drug repurposing of conventional chemotherapeutic drugs to reduce their side effects.

Calysepins I-VII, Hexasaccharide Resin Glycosides from Calystegia sepium and Their Cytotoxic Evaluation

Seven new hexasaccharide resin glycosides, named calysepins I-VII (1-7), with 27-membered rings, were obtained from the aerial parts of Calystegia sepium. Their structures with absolute configuration were established on the basis of spectroscopic data interpretation analysis and the use of chemical methods. They were defined as hexasaccharides composed of one d-quinovose, four d-glucose, and one l-rhamnose unit, and their sugar moieties were partially acylated by (2S)-methylbutanoic acid in 1-7 and (2R,3R)-nilic acid in 1-5 and 7, which mainly differed at the positions of acylation. Additionally, calysepin IV (4) exhibited cytotoxicity against A549 cells with an IC₅₀ value of 5.2 μM.