Stability evaluation of selected polyphenols and triterpene glycosides in black cohosh

Abstract

Black cohosh ( Actaea racemosa L., syn. Cimicifuga racemosa L.) is rich in both triterpene glycosides and polyphenols, which have various biological activities that may be important to its medical use. To evaluate the stability of the polyphenolic constituents and triterpene glycosides of black cohosh, experiments were conducted using three sample types: plant material, extracts of black cohosh, and encapsulated commercial extract. The samples were stored at various temperatures and humidity conditions. Three triterpene glycosides and six major polyphenols in black cohosh were quantitatively measured with an HPLC-PDA method at 0, 3, 6, and 9 weeks. The triterpene glycosides were stable at the tested conditions, whereas the polyphenols were stable only at room temperature and low humidity and not stable at higher temperature and/or humidity due to hydrolysis and/or oxidation. The rate of compound decomposition depended upon the chemical structure of the individual polyphenols. Polyphenols in the extracts decomposed more readily than those in plant material.

Figure 1

Three triterpene glycosides and six major phenolic constituents in black cohosh.

Figure 2

The major polyphenols in the black cohosh extract and in experimental conditions (320 nm). (A): original extract; (B): reflux with water for 1 h; (C): reflux with water for 4 h; (D): heated at 100 °C for 1 h; (E): heated at 100 °C for 4 h.

Figure 3

Decomposition of fukinolic acid (6) and ferulic acid (4) in water (280 nm). Refluxing time: Fukinolic acid: (A): 0 h; (B): 1 h; (C): 4 h. Ferulic acid (D): 0 h; (E): 4 h; (F): 8 h.

Figure 4

Changes in the amounts of the six major polyphenols in black cohosh extract (A) and plant material (B) after storage in a high RH and temperature condition.