Simultaneous quantification of anthrones and chromones in Aloe ferox ("Cape aloes") using UHPLC-MS

Aloe ferox is an important medicinal plant indigenous to South Africa where it has primarily been used as a purgative and also to treat skin disorders. Modern day uses include; health (tonic) drinks, flavourant in alcoholic beverages, treatment of digestive disorders and inclusion in cosmetic formulations. Due to increased commercialization of aloe products, a rapid, sensitive and reliable quality control method for the raw material has become a necessity. Ultra-high performance liquid chromatography coupled to mass spectrometry (UHPLC-MS) was investigated as an ultrafast, accurate, and sensitive method in the quantification of chromones (aloeresin A, aloesin) and anthrones (aloin A and B) in 101 A. ferox exudates. The method was validated for accuracy, precision and limits of detection and quantification. The calibration curves showed good linearity (R² > 0.99) within the concentration range and the recoveries of the four analytes ranged from 100-114% with the relative standard deviation lower than 2%. The limits of detection and quantification for all compounds were within a range of 0.2-1.1 μg/ml. Quantitative determination of the four biomarkers showed high levels of aloeresin A (129.0-371.6 μg/mg) and aloesin (111.8-561.8 μg/mg) while aloin A (21.3-133.4 μg/mg) and aloin B (18.4-149.7 μg/mg) were present in lower amounts. Hierarchical cluster analysis revealed two major groups within the dataset. However, geographical locality was not a major factor in the clustering observed. This validated, ultra-fast method for simultaneous quantification of chromones and anthrones present in A. ferox is recommended for routine quality control analysis.