The in vitro antileishmanial activity of three saponins isolated from ivy, alpha-hederin, beta-hederin and hederacolchiside A1, was investigated on Leishmania infantum. The assessment of possible targets (membrane integrity, membrane potential, DNA synthesis and protein content) was performed in both Leishmania promastigotes and human monocytes (THP1 cells). Results observed in Leishmania showed that the saponins exhibited a strong antiproliferative activity on all stages of development of the parasite by altering membrane integrity and potential: hederacolchiside A1 appeared to be the most active compound against both promastigotes and amastigotes. Results observed in THP1 cells demonstrated that the saponins exerted also a potent antiproliferative activity against human monocytes, by producing a significant DNA synthesis inhibition. The ratio between antileishmanial activity on amastigotes and toxicity to human cells suggested that the saponins could be considered as possible antileishmanial drugs.
On the basis of the biological activities exhibited by the phenolic constituents of Yucca schidigera, the antioxidant activity of the methanol extract of Yucca gloriosa roots was evaluated in the TEAC assay. The strong activity exerted by this extract prompted investigation of its phenolic constituents, yielding three new phenolic derivatives, gloriosaols C, D, and E, along with gloriosaols A and B previously isolated from Y. gloriosa roots and yuccaols C-E isolated from Y. schidigera. ESIMS and NMR data of gloriosaols C-E closely resembled those reported for gloriosaols A and B, two diasteroisomers characterized by unusual spirostructures. Careful inspection of ROESY spectra revealed that gloriosaols C-E are diastereoisomers of gloriosaols A and B. A possible assignment of the relative configuration of gloriosaols C-E, derived according to an integrated NMR-quantum mechanical (QM) approach, which was already applied to the determination of the stereostructures of gloriosaols A and B, is also proposed. Gloriosaols A-E exhibited potent antioxidant activity measured by the TEAC assay, showing the potential use of Y. gloriosa as a source of antioxidant principles.
The roots of Cephalaria gigantea (LEDEB.) BOBROV (Dipsacaceae), an endemic plant of Caucasus growing in Georgia, 1) contain a large amount of triterpene saponins. 2-4) The roots are well-known in traditional medicine as sedative and anti-inflammatory remedies.1) Previous works reported the identification of six triterpene glycosides. 5,6) Antifungal and antiprotozoal activities of giganteosides D and E, major monodesmosides, have been evaluated.7) The present paper describes isolation and structure elucidation of three new triterpene saponins, named giganteosides L (1), M (2) and N (3) from the roots of Cephalaria gigantea. Their structures were established on the basis of 2D-NMR experiments (gs-COSY, gs-HMQC, gs-HMBC and gs-HSQC-TOCSY) and mass spectrometry (MALDI-TOF, ESI-HR-MS). Saponins containing glucuronic acid in the sugar chain are reported for the first time in Cephalaria species. In addition, eight known triterpene glycosides, giganteosides D (4), 5) E (5), 5) G (6), 6) H (7), 6) I (8), 8) K (9), 8) J (10) 9,10) and J 1 (11) 9,10) were isolated from this plant.Dried root of C. gigantea was extracted with boiling 80% MeOH and after filtration the solution was evaporated. The solid residue was dissolved in methanol and precipitated in acetone. A combination of low pressure liquid chromatography and repeated silica gel column chromatography allowed the purification of eleven glycosides (1-11) including three new ones. The structures of the new saponins (1-3) were established on the basis of acid hydrolysis, NMR (Tables 1, 2)
The in vitro antileishmanial activity of three saponins isolated from ivy, alpha-hederin, beta-hederin and hederacolchiside A(1), was investigated on parasites of the species Leishmania mexicana, in their promastigote and amastigote forms compared with their toxicity versus human monocytes. The results showed that saponins exhibited a strong antiproliferative activity on all stages of development of the parasite but demonstrated a strong toxicity versus human cells. Association of subtoxic concentrations of saponins with antileishmanial drugs such as pentamidine and amphotericin B demonstrated that saponins could enhance the efficiency of conventional drugs on both the promastigote and the amastigote stages of development of the parasite. The results demonstrated moreover that the action of saponins on promastigote membrane was cumulative with those of amphotericin B.
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