Antiparasitic triterpenic ester and ursolic acid lipid nanocapsule design, cytotoxicity, and permeability evaluation for oral delivery

Introduction
Ursolic acid (UA), the antimalarial triterpenic mixture 8TTE (containing C-27 feruloyl and coumaroyl esters of ursane and oleane skeletons), and the semi-synthetic antitrypanosomal derivative ursolic acid O-phenyl propionate (UAOPP) exhibit high lipophilicity, which may limit their oral bioavailability. This study aimed to develop lipid nanocapsules (LNCs) to improve the solubility, intestinal permeability, and antiparasitic activity of these triterpenic compounds for potential oral delivery.

Methods

LNCs formulations containing UA, 8TTE, and UAOPP were prepared and evaluated. A sensitive UPLC\x{2013}MS method was developed and validated for selected triterpenes quantification during transport studies across Caco-2 cell monolayers [limit of detection (LOD): 2 nM; limit of quantification (LOQ): 25 nM]. Cytotoxicity and permeability studies were conducted on Caco-2 cells to assess formulation safety and intestinal transport.
In vitro
antiparasitic activity of free and formulated compounds was evaluated against
Plasmodium falciparum
and
Trypanosoma brucei brucei
(Tbb).

Results and discussion

The formulations were non-toxic to Caco-2 cells at concentrations up to 2 mg/mL. Permeability studies demonstrated enhanced transport for the formulated triterpenic esters, with permeability increases of up to 2.68-fold, shifting their classification from poorly absorbed to moderately absorbed compounds in humans [apparent permeability coefficient (Papp) > 1 × 10
–6
cm/s]. Free UA showed the highest Papp value (4.95 × 10
–6
cm/s ± 1.29 × 10
–7
), but caused epithelial integrity disruption after 2 h of incubation and during the following 48 h, whereas formulated UA induced minimal integrity loss at the same concentration. In antiparasitic assays, blank LNCs exhibited maximum non-toxic concentrations of 165 μg/mL against
P. falciparum
and 65 μg/mL against Tbb. At these maximum concentrations, formulated UA and 8TTE showed enhanced antiplasmodial activity; however, blank LNCs produced comparable effects. In contrast, UAOPP-loaded LNCs showed significantly improved antitrypanosomal activity by approximately 20% at 2.15 μM (cell viability: 38.20% ± 5.41) compared with free UAOPP (20.38% ± 8.80). These findings suggest that LNCs represent promising oral delivery systems for lipophilic triterpenes. Further in vivo pharmacokinetic and efficacy studies are needed to confirm their therapeutic potential.