Combined shake-flask, chromatographic and in silico approaches for evaluating the physicochemical and ADME properties of aloin A and aloe-emodin.

Abstract

Aloe vera has a long history of medicinal use due to its diverse biological activities, including antioxidant, anti-inflammatory and antimicrobial. This study investigates the physicochemical and ADME (absorption, distribution, metabolism, excretion) properties of two primary anthraquinones from Aloe vera, aloin A and aloe-emodin. The focus of this research was to evaluate the lipophilicity, solubility, and pharmacokinetic profiles of aloin A and aloe-emodin through a combination of computational predictions, the shake-flask method, and chromatographic techniques. The optimised shake-flask method was successfully employed to determine the log P values of phyto-chemicals. Aloin A was found to be more hydrophilic than aloe-emodin, likely due to the presence of an attached β-d-glucopyranosyl unit. All RP-TLC and RP-HPLC lipophilicity indices were higher for aloe-emodin compared to aloin A, aligning with their log P values (obtained through in silico and shake-flask methods). IAM (immobili sed artificial membrane)-HPLC results suggest that unlikely partitioning in the n-octanol/water system or C18 chains, partition into phospholipids involves not only hydrophobic intermolecular recognition forces but also electrostatic interactions. The presence of a sugar moiety (β-d-glucopyranosyl unit) at the C-10 position of aloin A considerably enhanced its affinity to phospholipids compared to its affinity to alkyl chains. HSA (human serum albumin)-HPLC and AGP (α1-acid glycoprotein)-HPLC data confirmed aloe-emodin's stronger affinity to plasma proteins. The integration of computational and experimental approaches provided a detailed understanding of aloin A and aloe-emodin physicochemical and ADME properties.