Multi-target mode of action of a Clerodane-type diterpenoid from Polyalthia longifolia targeting African trypanosomes

Abstract

Natural products have made remarkable contributions to drug discovery and therapy. In this work we exploited various biochemical approaches to investigate the mode of action of 16-α-hydroxy-cleroda-3,13 (14)-Z-dien-15,16-olide (HDK-20), which we recently isolated from Polyalthia longifolia, on Trypanosoma brucei bloodstream trypomastigotes. HDK20 at concentrations ≥ EC50 (0.4 μg/ml) was trypanocidal, with its effect irreversible after only a brief exposure time (<1 h). Fluorescence microscopic assessment of DNA configuration revealed severe cell cycle defects after 8 h of incubation with the compound, the equivalent of a single generation time. This was accompanied by DNA fragmentation as shown by Terminal deoxynucleotidyl transferase dUTP Nick-End Labelling (TUNEL) assays. HDK-20 also induced a fast and profound depolarisation of the parasites’ mitochondrial membrane potential and depleted intracellular ATP levels of T. brucei. Overall, HDK20 showed a multi-target mechanism of action, which provides a biochemical explanation for the promising anti-trypanosomatid activity in our previous report.

Process optimization for biosynthesis of mono and bimetallic alloy nanoparticle catalysts for degradation of dyes in individual and ternary mixture

“…Polyalthia longifolia is a lofty, straight columnar and evergreen plant with horizontal short branches. It is a multipurpose tree whose extracts and isolated compounds have been studied for various biological activities [20][21][22] . To explore further the aqueous leaf extract of P. longifolia was utilized for biosynthesis of NPs of novel monometallic (Au, Ag) and bimetallic (Au-Ag) alloy.…”

Potent Antitrypanosomal Activities of 3-Aminosteroids against African Trypanosomes: Investigation of Cellular Effects and of Cross-Resistance with Existing Drugs

“…PI is a red fluorophore that is not taken up by live, intact trypanosomes but does enter, and bind to trypanosome nucleic acids, when the plasma membrane is compromised as a result of loss of cellular integrity [42,43]. The effects of 3-aminosteroids differ significantly from digitonin, a known cell membrane lysis agent, which causes rapid trypanosome cell permeabilization reaching maximum fluorescence in the first few minutes [44]. The much slower, concentration-dependent membrane permeabilization effect of the 3-aminosteroids suggests that these compounds do not directly cause membrane leakage by a physicochemical effect as their main mode of action, but rather that over time an increasing number of cells becomes sufficiently permeable to PI to elicit a fluorescence response.…”

Diterpene Synthase‐Catalyzed Biosynthesis of Distinct Clerodane Stereoisomers

“…Plant clerodane diterpenoids form a diverse group of natural products that have attracted increasing attention for their potential therapeutic applications . Examples include columbin which has anti‐inflammatory and anticancer efficacy, HDK20 (6‐α‐hydroxy‐cleroda‐3,13‐dien‐15,16‐olide) for treating infectious sleeping sickness, and salvinorin A, which has entered phase 1 clinical trials for its possible application in the treatment of drug addictions and neuropsychiatric disorders (https://clinicaltrials.gov/ IDs: NCT03418714, NCT00996411) . Although elaborate multistep chemical synthesis routes have been devised for clerodane products such as salvinorin A, reliable and scalable platforms for producing these compounds remain limited in many, if not most, cases.…”