Isolation of mitraphylline from Uncaria tomentosa (Willd. ex Schult.) DC. barks and development of spectrophotometric method for total alkaloids determination in Cat's Claw samples

• Published in: Phytochemical analysis 2020-03, Vol.31 (2), p.262-272
• Main Authors: Gouvêa, Marcos Martins, Pusceddu, Breno Henrique, Pereira Netto, Annibal Duarte, Peregrino, Carlos Augusto de Freitas, Macedo, Elizabeth Valverde, Mourão, Samanta Cardozo, Marques, Flávia Ferreira de Carvalho
• Format: Article
• Language: English
• Subjects: Alkaloids; Cat's Claw; Cation exchange; Cation exchanging; Cost analysis; High performance liquid chromatography; Liquid chromatography; Mass spectrometry; Mass spectroscopy; Mathematical analysis; method validation; mitraphylline; NMR; Nuclear magnetic resonance; Oxindoles; Plant Extracts; Quality control; Sample preparation; Solid phases; Spectrophotometry; Statistical methods; Toluene; total alkaloids; Uncaria tomentosa; Uncaria tomentosa (Willd. ex Schult.) DC
• ISSN: 0958-0344; 1099-1565
• DOI: 10.1002/pca.2891

Introduction The usual quality control for Uncaria tomentosa (Willd. ex Schult.) DC. barks requires highly specific analytical standards and methods based on high‐performance liquid chromatography (HPLC), which impacts the costs of the analytical process and the final products. Objective To obtain an analytical reference standard of mitraphylline by isolation from U. tomentosa barks and develop a spectrophotometric method for determination of total alkaloids in samples of U. tomentosa. Methodology An alkaloid‐enriched extract was obtained by acid–base partition and mitraphylline was selectively precipitated using an 80:20 v/v toluene/hexane solution. The compound was characterised by HPLC‐UV/DAD (diode‐array detector), mass spectrometry, UV‐visible, infrared (IR) and 1H‐ and 13C‐nuclear magnetic resonance (NMR) spectroscopy. Sample preparation for the spectrophotometric method consisted of an extraction with boiling methanol (3 × 10 mL, 15 min), followed by a strong cation exchange solid phase extraction (SCX‐SPE) clean‐up. Results Mitraphylline with a purity of 98% was isolated in 0.05% m/m yield. All characterisation results were in agreement with previous published data. The spectrophotometric method showed linear range between 0.40 and 20 μg/mL; limits of detection and quantification of 0.15 and 0.49 μg/mg, respectively; dispersion of results lower than 5% for repeatability and intermediate precision; statistically proven accuracy by comparison with reference values obtained by Soxhlet and an HPLC‐UV/DAD method; and robustness in relation to sample mass extracted and extraction time. Conclusion The methods developed to obtain mitraphylline analytical standard from U. tomentosa barks and to determine total alkaloids by spectrophotometry provided a cheaper and faster quality control alternative for U. tomentosa samples. Uncaria tomentosa is traditionally used against many illnesses. Herbal medicines obtained from this species are already approved to treat certain medical conditions. Their usual quality control requires highly specific and very expensive analytical standards for high‐performance liquid chromatography (HPLC) methods, which considerably impact the cost of the final products. In this work, an efficient and low‐cost method for mitraphylline isolation, and a simple and fast spectrophotometric method suitable for determination of total alkaloids in U. tomentosa samples are presented.