Context: This is the first study on the phytochemistry, antioxidant, anticholinesterase, and antibacterial activities of Sedum caeruleum L. (Crassulaceae).

Objective: The objective of this study is to isolate the secondary metabolites and determine the antioxidant, anticholinesterase, and antibacterial activities of S. caeruleum.

Materials and methods: Six compounds (1–6) were isolated from the extracts of S. caeruleum and elucidated using UV, 1D-, 2D-NMR, and MS techniques. Antioxidant activity was investigated using DPPH^•, CUPRAC, and ferrous-ions chelating assays. Anticholinesterase activity was determined against acetylcholinesterase (AChE) and butyrylcholinesterase (BChE) enzymes using the Ellman method. Antibacterial activity was performed according to disc diffusion and minimum inhibitory concentration (MIC) methods.

Results: Isolated compounds were elucidated as ursolic acid (1), daucosterol (2), β-sitosterol-3-O-β-d-galactopyranoside (3), apigenin (4), apigetrin (5), and apiin (6). The butanol extract exhibited highest antioxidant activity in all tests (IC₅₀ value: 28.35 ± 1.22 µg/mL in DPPH assay, IC₅₀ value: 40.83 ± 2.24 µg/L in metal chelating activity, and IC₅₀value: 23.52 ± 0.44 µg/L in CUPRAC), and the highest BChE inhibitory activity (IC₅₀ value: 36.89 ± 0.15 µg/L). Moreover, the chloroform extract mildly inhibited (MIC value: 80 µg/mL) the growth of all the tested bacterial strains.

Discussion and conclusion: Ursolic acid (1), daucosterol (2), β-sitosterol-3-O-β-d-galactopyranoside (3), apigenin (4), apigetrin (5), and apiin (6) were isolated from Sedum caeruleum for the first time. In addition, a correlation was observed between antioxidant and anticholinesterase activities of bioactive ingredients of this plant.

Four previously undescribed and one known oleanolic acid glycosides were isolated from the roots of Weigela stelzneri, and one previously undescribed and three known hederagenin glycosides were isolated from the leaves. Their structures were elucidated mainly by 2D NMR spectroscopic analysis and mass spectrometry as 3-O-β-D-glucopyranosyl-(1 → 2)-[β-D-xylopyranosyl-(1 → 4)]-β-D-xylopyranosyl-(1 → 4)-β-D-xylopyranosyl-(1 → 3)-α-L-rhamnopyranosyl-(1 → 2)-α-L-arabinopyranosyloleanolic acid, 3-O-β-D-glucopyranosyl-(1 → 2)-[β-D-xylopyranosyl-(1 → 4)]-β-D-xylopyranosyl-(1 → 4)-β-D-xylopyranosyl-(1 → 3)-α-L-rhamnopyranosyl-(1 → 2)-β-D-xylopyranosyloleanolic acid, 3-O-β-D-glucopyranosyl-(1 → 2)-[β-D-glucopyranosyl-(1 → 4)]-β-D-xylopyranosyl-(1 → 4)-β-D-xylopyranosyl-(1 → 3)-α-L-rhamnopyranosyl-(1 → 2)-β-D-xylopyranosyloleanolic acid, 3-O-β-D-glucopyranosyl-(1 → 2)-[β-D-xylopyranosyl-(1 → 4)]-β-D-xylopyranosyl-(1 → 4)-β-D-xylopyranosyl-(1 → 3)-α-L-rhamnopyranosyl-(1 → 2)-α-L-arabinopyranosyloleanolic acid 28-O-β-D-glucopyranosyl-(1 → 6)-β-D-glucopyranosyl ester, and 3-O-β-D-glucopyranosyl-(1 → 2)-α-L-arabinopyranosylhederagenin 28-O-β-D-xylopyranosyl-(1 → 6)-[α-L-rhamnopyranosyl-(1 → 2)]-β-D-glucopyranosyl ester. The majority of the isolated compounds were evaluated for their cytotoxicity against two tumor cell lines (SW480 and EMT-6), and for their anti-inflammatory activity. The compounds 3-O-β-D-glucopyranosyl-(1 → 2)-[β-D-xylopyranosyl-(1 → 4)]-β-D-xylopyranosyl-(1 → 4)-β-D-xylopyranosyl-(1 → 3)-α-L-rhamnopyranosyl-(1 → 2)-α-L-arabinopyranosyloleanolic acid and 3-O-β-D-glucopyranosyl-(1 → 2)-[β-D-xylopyranosyl-(1 → 4)]-β-D-xylopyranosyl-(1 → 4)-β-D-xylopyranosyl-(1 → 3)-α-L-rhamnopyranosyl-(1 → 2)-β-D-xylopyranosyloleanolic acid exhibited the strongest cytotoxicity on both cancer cell lines. They revealed a 50% significant inhibitory effect of the IL-1β production by PBMCs stimulated with LPS at a concentration inducing a very low toxicity of 23% and 28%, respectively.

Saponins are bioactive compounds occurring in many plant species having a wide range of biological activities such as immunoadjuvant, cytotoxic, analgesic, antimicrobial and anti-inflammatory activities, just to mention a few. The aim of our researches concerns the isolation, structural elucidation and biological investigation of saponins from various plant species [1]. In this context, the study of the roots and leaves of Weigela stelzneri(Caprifoliaceae) led to isolation of four new and two known oleanane-type saponins mainly by medium pressure- and vacuum-liquid chromatography on silica gel (normal and reversed-phase RP-18) [1]. The new compounds were elucidated by a combination of spectroscopic techniques including 1D-, 2D-NMR, and mass spectrometry as glycosides of oleanolic acid, three of them being monodesmosides at C-3 with a branched oligosaccharidic chain made of six sugar units, whereas the known ones were hederagenin derivatives. The six compounds were evaluated for their cytotoxicity against a human cancer cell line (colorectal SW480) and a mouse cancer cell line (mammary EMT6), and for their anti-inflammatory activity. The results show that two new compounds differing only by the first sugar unit of the hexasaccharidic chain at C-3 (arabinopyranosyl instead of xylopyranosyl) exhibited the strongest cytotoxicity on both cell lines (IC₅₀ 5.41 µM and 1.54 µM, respectively), which was better than those of the positive controls etoposide and methotrexate. Furthermore, they revealed a significant modulatory effect of the IL-1β production on human lymphocytes stimulated with endotoxins, showing therefore a strong anti-inflammatory potential.

Three steroidal glycosides were isolated from the bark of Dracaena fragrans (L.) Ker Gawl. "Yellow Coast", and a fourth from the roots and the leaves. Their structures were characterized on the basis of extensive 1D and 2D NMR experiments and mass spectrometry, and by comparison with NMR data of the literature. These saponins have the spirostane-type skeleton and are reported in this species for the first time.