Accurate quantification of oleanolic acid and ursolic acid in traditional chinese medicine

Importance of the Topic

Traditional Chinese Medicine (TCM) formulations contain complex mixtures of bioactive constituents. Accurate quantification of key marker compounds such as oleanolic acid and ursolic acid is essential for ensuring batch-to-batch consistency, safety and compliance with pharmacopeial standards.

Objectives and Study Overview

This work presents the development of a high-resolution sampling two-dimensional liquid chromatography (2D-LC) method for the simultaneous quantification of oleanolic acid and ursolic acid in Pterocephali Herba extracts, addressing coelution issues observed with conventional one-dimensional HPLC.

Methodology and Instrumentation Used

The method employs orthogonal column chemistries and time-based heart-cutting to isolate target analytes from interferences in a single run:

• First dimension: Agilent InfinityLab Poroshell 120 Phenyl-Hexyl, 2.1 × 100 mm, 1.9 µm with a water/ammonium acetate–methanol gradient.
• High-resolution sampling: eight consecutive 8.63 s cuts over the 1D peak covering 72 % loop fill.
• Second dimension: Agilent InfinityLab Poroshell 120 EC-C18, 3.0 × 50 mm, 2.7 µm with a 0.05 % phosphoric acid–acetonitrile gradient and 2.5 min cycle time.

Applied Instrumentation

• Agilent 1290 Infinity II 2D-LC system
• Two high-speed pumps, multisampler with cooling, multisampler valve drive, two MCTs and two DAD detectors
• Two 2-position/4-port valves and multiple heart-cutting valves with 40 µL loops

Main Results and Discussion

Conventional 1D-LC failed to resolve oleanolic and ursolic acids from matrix interferences. The 2D-LC approach achieved baseline separation in the second dimension for each heart-cut. Calibration curves over 57.5–1 150 µg/mL (oleanolic) and 50–1 000 µg/mL (ursolic) were linear (R² > 0.999). Method repeatability yielded RSDs of 0.8 % and 1.3 %, respectively. Measured sample concentrations were 95.6 µg/mL (oleanolic) and 258.9 µg/mL (ursolic).

Benefits and Practical Applications of the Method

• Reliable quantification of coeluting analytes in complex herbal matrices
• Enhanced selectivity using orthogonal column chemistries
• High throughput enabled by rapid 2D gradients and efficient superficially porous particles
• Compliance with pharmacopeial requirements for TCM quality control

Future Trends and Potential Applications

Advances may include coupling 2D-LC with high-resolution mass spectrometry for structural confirmation, automated loop filling strategies for increased sampling density, and miniaturized systems to reduce solvent consumption and increase throughput in routine quality-assurance labs.

Conclusion

High-resolution sampling 2D-LC on Agilent InfinityLab Poroshell 120 columns provides an efficient, robust solution for the accurate quantification of oleanolic acid and ursolic acid in complex TCM samples, overcoming limitations of conventional HPLC separations.

References

1. Stephan S. High-Resolution Sampling 2D-LC with the Agilent 1290 Infinity II 2D-LC Solution. Agilent Technologies Technical Overview, publication 5991-7637EN, 2016.