Research Progress on Plant-Derived Cardenolides (2010-2023)

Cardenolides are a class of steroidal glycoside compounds that are mainly distributed in plants, have significant physiological activity in the heart, and have been used clinically for over 200 years. To provide a reference for further research and development of these compounds, the phytochemical and biological properties of natural cardenolides (295 compounds in total) isolated between 2010 and 2023 from 17 families and hundreds of species belonging to 70-80 genera were reviewed. In vitro and in vivo studies have indicated that antitumor, antibacterial, and antiviral activities are the most commonly reported pharmacological properties of cardenolides. Antitumor activities have been thoroughly studied to understand their structure-activity relationships, revealing numerous potential anticancer molecules that lay the theoretical foundation for further development of traditional Chinese medicinal herbs and the creation of new drugs.

Vallaris solanacea induces mitochondrial mediated apoptosis in HL-60 human promyelocytic leukemia cells

In the present study, the apoptosis-inducing potential of a chloroform fraction from an alcoholic extract of Vallaris solanacea aerial parts (VS) was examined using human promyelocytic leukemia HL-60 cells. We discovered a concentration and time-dependent decrease in cell growth using MTT assay. Scanning electron micrographs and fluorescence microscopy were used to observe several well-documented morphological and nuclear alterations, such as reduction in cell size, chromatin condensation, fragmentation, and the creation of cell surface blebs. A considerable rise in the Sub-G0 population was revealed by cell cycle analysis. Additionally, a dose-dependent rise in cells positive for Annexin V was observed. DCFH-DA test on VS-treated HL-60 cells showed an increase in endogenous ROS generation of up to 4.3 fold. Additionally, suppression in Bcl-2 levels and increased mitochondrial membrane depolarization in treated cells were also associated with a rise in cytosolic cytochrome-c levels that was consequently followed by the activation of the caspase cascade. Further, the DNA fragmentation assay exhibited a typical ladder formation at 25 μg/ml, which became prominent in a concentration-dependent manner. Our study revealed that VS has apoptosis-inducing potential towards HL-60 cells in vitro and is an effective candidate for further anti-cancer studies.

Cytotoxic Activities of Different Iranian Solanaceae and Lamiaceae Plants and Bioassay-Guided Study of an Active Extract from Salvia lachnocalyx

Methanol (MeOH), dichloromethane (DCM) and 80% MeOH extractions of fourteen medicinal plants of the families Solanaceae and Lamiaceae collected from different area of Iran were tested for their cytotoxic potential against MOLT-4 human cancer cell lines. Cytotoxicity of the tested plants indicated that 11 plants had one or two active extracts (IC50 ≤50): MeOH extracts of the shoots of Thymus trautvetteri, Solanum luteum and stems of Lycium shawii; DCM extracts of the shoots of Thymus kotschyanus, Salvia persepolitana, Ballota aucheri, Nepeta glomerulosa, Hyoscyamus tenuicaulis, Salvia lachnocalyx, Salvia sharifii as well as the stems of Salvia verticillata and the roots of Salvia multicaulis and S. lachnocalyx; 80% MeOH extracts of the shoots of T. trautvetteri, S. luteum and the stems of L. shawii. The DCM extract of the aerial parts of S. lachnocalyx as one of the most active species was subjected to the cytotoxic bioassay-guided fractionation and purification using combination of chromatography methods. The bioassay-guided fractionation of DCM extract of the shoots of S. lachnocalyx led to the isolation of two cytotoxic compounds: (2 Z,6 Z,10 Z,14 E)-geranylfarnesol (1), a novel natural product, and spathulenol (2). Both of the isolated compounds, especially 1 (IC50 range: 9.6 −20.2 μg/mL), showed good cytotoxic effects against 3 human cancer cell lines, MOLT-4, MCF-7 and HT-29.

Constituents from Entada scandens with TRAIL-resistance Overcoming Activity

Tumor necrosis factor (TNF)-related apoptosis-inducing ligand (TRAIL) has emerged as a promising anticancer agent because of its ability to selectively kill tumor cells. But TRAIL-resistance is a major problem of its therapy. A search for compounds for abrogating TRAIL-resistance has, thus, become an important strategy for anticancer drug discovery. In search of bioactive natural products for overcoming TRAIL-resistance, we previously reported some compounds with TRAIL-resistance overcoming activity. Bioassay guided fractionation of Entada scandens led to the isolation of four compounds (1-4). Of the isolates, compounds 1 and 3 showed moderate TRAIL-resistance overcoming activity in TRAIL-resistant human gastric adenocarcinoma (AGS) cells.

Anticancer steroids: linking natural and semi-synthetic compounds

Steroids, a widespread class of natural organic compounds occurring in animals, plants and fungi, have shown great therapeutic value for a broad array of pathologies. The present overview is focused on the anticancer activity of steroids, which is very representative of a rich structural molecular diversity and ability to interact with various biological targets and pathways. This review encompasses the most relevant discoveries on steroid anticancer drugs and leads through the last decade and comprises 668 references.

A new triterpenoid and a new glycoside from Pilea cavaleriei

A new triterpenoid, 11α,12α-epoxy-3β-hydroxy-24-nor-olean-4(23)-en-28,13β-olide (1), and a new glycoside, benzyl 2-O-β-d-apiofuranosyl-(1 → 2)-β-d-glucopyranosyl benzoate (2), together with eight known triterpenoids (3-10), were isolated from Pilea cavaleriei subsp. cavaleriei. Their structures were established on the basis of spectroscopic analysis including HR-ESI-MS, 1D NMR, and 2D NMR techniques. All compounds showed no anti-hepatitis C virus activity.

Assessment of antiproliferative and antiplasmodial activities of five selected Apocynaceae species

Background

Studies have shown that the barks and roots of some Apocynaceae species have anticancer and antimalarial properties. In this study, leaf extracts of five selected species of Apocynaceae used in traditional medicine (Alstonia angustiloba, Calotropis gigantea, Dyera costulata, Kopsia fruticosa and Vallaris glabra) were assessed for antiproliferative (APF) and antiplasmodial (APM) activities, and analysed for total alkaloid content (TAC), total phenolic content (TPC) and radical-scavenging activity (RSA). As V. glabra leaf extracts showed wide spectrum APF and APM activities, they were further screened for saponins, tannins, cardenolides and terpenoids.

Methods

APF and APM activities were assessed using the sulphorhodamine B and lactate dehydrogenase assays, respectively. TAC, TPC and RSA were analysed using Dragendorff precipitation, Folin-Ciocalteu and DPPH assays, respectively. Screening for saponins, tannins, cardenolides and terpenoids were conducted using the frothing, ferric chloride, Kedde and vanillin-H₂SO₄ tests, respectively.

Results

Leaf extracts of A. angustiloba, C. gigantea and V. glabra displayed positive APF activity. Dichloromethane (DCM) extract of C. gigantea, and DCM and DCM:MeOH extracts of V. glabra showed strong APF activity against all six human cancer cell lines tested. DCM extract of A. angustiloba was effective against three cancer cell lines. Against MCF-7 and MDA-MB-231 cell lines, DCM extract of C. gigantea was stronger than standard drugs of xanthorrhizol, curcumin and tamoxifen. All five species were effective against K1 strain of Plasmodium falciparum and three species (C. gigantea, D. costulata and K. fruticosa) were effective against 3D7 strain. Against K1 strain, all four extracts of V. glabra displayed effective APM activity. Extracts of D. costulata were effective against 3D7 strain. Selectivity index values of extracts of A. angustiloba, C. gigantea and V. glabra suggested that they are potentially safe for use to treat malaria. Extracts of K. fruticosa had the highest TAC while D. costulata had the highest TPC and RSA. Phytochemical screening of extracts of V. glabra also showed the presence of terpenoids, tannins and saponins.

Conclusions

Leaf extracts of C. gigantea and V. glabra showed great promise as potential candidates for anticancer drugs as they inhibited the growth of all six cancer cell lines. Against K1 strain of P. falciparum, all four extracts of V. glabra displayed effective APM activity. The wide spectrum APF and APM activities of V. glabra are reported for the first time and this warrants further investigation into its bioactive compounds.

Total synthesis and evaluation of Wnt signal inhibition of melleumin A and B, and their derivatives

The total synthesis of melleumin A (1), a novel cyclic depsipeptide isolated from the myxomycete Physarum melleum, and 3-epi-melleumin A (6) was achieved. Melleumin A-like compounds were also designed and synthesized; analysis of these melleumin A-like compounds showed moderate Wnt signal inhibition. Comparison of the inhibition activity of melleumin B and its three epimers, melleumin A, 3-epi-melleumin A and three melleumin A-like compounds led to further investigation of the structural conformation of the active molecules. The scaffold of melleumin is a potential target in the search for "peptide-like" Wnt signaling inhibitors.

Search for bioactive natural products from medicinal plants of Bangladesh

In our continuous search for bioactive natural products from natural resources, we explored medicinal plants of Bangladesh, targeting cancer-related tumor necrosis factor-related apoptosis-inducing ligand-signaling pathway, along with some other biological activities such as prostaglandin inhibitory activity, 1,1-diphenyl-2-picrylhydrazyl free-radical-scavenging activity, and cell growth inhibitory activity. Along with this, we describe a short field study on Sundarbans mangrove forests, Bangladesh, in the review.