Validated spectrophotometric method for quantification of total triterpenes in plant matrices

Triterpenes are ubiquitous secondary metabolites present in plants. They can be found in both forms, as genins or conjugated as glycosides. Although distinct analytical methods to quantify these compounds in vegetal tissues are available in the literature, limitations like high cost, complexity on sample preparation, and selectivity are often challenging issues. This study aimed to develop and to validate a simple and rapid spectrophotometric method to detect and quantify total triterpenes in plant matrices.

The assay was conducted directly into glass tubes using vanillin, acetic acid, and sulphuric acid as reagents, and β-sitosterol as reference standard. The samples were analyzed at 548 nm assessing the quality parameters of selectivity, linearity, precision, accuracy, limit of detection (LOD), limit of quantification (LOQ), and robustness.

The method was selective, with precision and accuracy varying from 0.56% to 4.98% and 96.63% to 113.87%, respectively. The values of the limit of detection and quantification were 0.042 μg.mL^-1 and 0.14 μg.mL^-1, correspondingly. The correlation coefficient (r) at the concentration range of 3.08 μg.mL^-1to 24.61 μg.mL^-1 was 0.9998. The total of triterpenes found in of B. holophylla and M. ilicifolia leaves were 132.36 ± 20.36 mg EβS.g^-1 of dry extract and 53.91 ± 2.6 mg EβS.g^-1 of dry extract, respectively.

The method was reliable to quantify total triterpenes extracted from Maytenus ilicifolia and Bauhinia holophylla. Graphical abstract.