Antileishmanial and cytotoxic activity of secondary metabolites from Taberneamontana ventricosa and two aloe species

Absolute configurations of biantraquinones from Eremurus spectabilis BIEB

This report covers extraction, isolation, and characterisation studies on Eremurus spectabilis BIEB (Liliaceae) species. Eremurus spectabilis BIEB was extracted with hexane, chloroform, ethyl acetate, and methanol, respectively. Using chromatographic methods, two known bianthraquinones (ES3, 7,10'-bichrysophanol and ES6, chrysalodin), three known anthraquinones (ES1, chrysophanol; ES2, chrysophanol-8-methyl ether; ES4, aloe emodin) and one known steroidal compound (ES5, daucosterol) were isolated from the chloroform extract. Structures of these isolated compounds were revealed by 1D and 2D NMR and HRMS spectroscopies. Absolute configurations of ES3 and ES6 were determined by single crystal X-Ray diffraction analysis.

Two Novel Iboga-Type and an Oxindole Glucuronide Alkaloid from Tabernaemontana peduncularis Disclose Related Biosynthetic Pathways to Tabernaemontana divaricata

Phytochemical investigation of the two Tabernaemontana species (Apocynaceae) T. peduncularis Wall. and T. divaricata (L.) R.Br. ex Roem. & Schult. indicated closely related biosynthetic pathways leading to lipophilic and hydrophilic alkaloids. In total, 18 specialized metabolites comprising indole-derived alkaloid aglycones, three oxindole-derived alkaloid glycosides, and two iridoid glucosides could be identified in the studied species. Among the alkaloids, the two Iboga-type alkaloids 3,7-coronaridine isoindolenine, coronaridine 3,4-iminium and a javaniside derivative bearing a glucuronic acid, named javanuronic acid, could be described by spectroscopic and spectrometric methods for the first time. A docking experiment using alpha-fold was performed to generate a protein model of the enzyme 7-deoxyloganetic acid glucosyl transferase. Performed bioassays exhibited a growth reduction of neonate Spodoptera littoralis larvae and reduced cell viability of HepG2 cells of the extracts containing Iboga alkaloids, whilst the javaniside derivatives containing hydrophilic fraction did not show any effects. These findings indicate a high flexibility in the formation of bioactive indole alkaloid aglycones by Tabernaemontana species and also evidence similar accumulation trends in both species as well as indicate that biosynthetic routes leading to oxindole alkaloids like javanisides are more widespread than reported. Furthermore, the incorporation of the three novel compounds into potential biosynthetic pathways is discussed.

Models for cytotoxicity screening of antileishmanial drugs: what has been done so far?

A growing number of studies have demonstrated the in vitro potential of an impressive number of antileishmanial candidates in the past years. However, the lack of uniformity regarding the choice of cell types for cytotoxicity assays may lead to uncomparable and inconclusive data. In vitro assays relying solely on non-phagocytic cell models may not represent a realistic result as the effect of an antileishmanial agent should ideally be presented based on its cytotoxicity profile against reticuloendothelial system cells. In the present review, we have assembled studies published in the scientific literature from 2015 to 2021 that explored leishmanicidal candidates, emphasising the main host cell models used for cytotoxicity assays. The pros and cons of different host cell types as well as primary cells and cell lines are discussed in order to draw attention to the need to establish standardised protocols for preclinical testing when assessing new antileishmanial candidates.

In Vitro Investigation of the Antioxidant and Cytotoxic Potential of Tabernaemontana ventricosa Hochst. ex A. DC. Leaf, Stem, and Latex Extracts

Tabernaemontana ventricosa (Apocynaceae) a latex-bearing plant is used in traditional medicine for its therapeutic benefits in reducing fever and hypertension and wound healing. Due to limited information on the plant’s pharmacological activities, this study aimed to investigate the antioxidant potential of the leaf, stem, and latex extracts of T. ventricosa, using the Folin-Ciocalteu (total phenolics), aluminum chloride colorimetric (total flavonoids), 2,2-diphenyl-1-picrylhydrazyl (DPPH), and ferric reducing antioxidant power (FRAP) assays. The cytotoxic activity was evaluated in the human HEK293 (embryonic kidney), HeLa (cervical carcinoma), and MCF-7 (breast adenocarcinoma) cell lines using the MTT assay. The latex extracts possessed the highest total phenolic content (115.36 ± 2.89 mg GAE/g), followed by the stem hexane extracts (21.33 ± 0.42 mg GAE/g), the chloroform leaf (7.89 ± 0.87 mg GAE/g), and the chloroform stem (4.69 ± 0.21 mg GAE/g) extracts. The flavonoid content was substantially high ranging from 946.92 ± 6.29 mg QE/g in the stem hexane, 768.96 ± 5.43 mg QE/g in the latex, 693.24 ± 4.12 mg QE/g in the stem chloroform, and 662.20 ± 1.00 mg QE/g in the leaf hexane extracts. The DPPH assays showed the highest percentage of inhibition at 240 µg/mL, for the stem hexane (70.10%), stem methanol (65.24%), and stem chloroform (60.26%) extracts, with their respective IC50 values of 19.26 µg/mL (stem hexane), 6.19 µg/mL (stem methanol), and 22.56 µg/mL (stem chloroform). The FRAP assays displayed minimal inhibition ranging from 4.73% to 14.40%, except for the latex extracts which displayed moderate inhibition at 15 µg/mL (21.82%) and substantial inhibition at 240 µg/mL (98.48%). The HeLa and MCF-7 cell lines were the most sensitive to the extracts, with the hexane, chloroform, and methanol leaf and stem, and latex extracts significantly affecting the percentage cell survival. Overall, the various parts of T. ventricosa exhibited strong antioxidant activity correlating to its cytotoxicity. Further studies should focus on the isolation of specific antioxidant compounds that could be investigated for their anticancer potential.