Qualitative and quantitative analysis of triterpene saponins from tea seed pomace (Camellia oleifera Abel) and their activities against bacteria and fungi

Abstract

A method using LC-ESI-IT-TOF/MS and LC/UV-ELSD was established to qualitatively analyze triterpene saponins obtained from the tea seed pomace (Camellia oleifera Abel). In addition, the quantitative analysis of oleiferasaponin A1 using LC/UV was developed. The purified total saponins did not exhibit any inhibitory effects at concentrations ranging from 0.1 to 10 mg/mL against the tested bacteria, except for Staphyloccocus aureus and Escherichia coli. By contrast, higher inhibitory activity was seen against the tested fungi, especially against Bipolaris maydis. Following treatment with an MIC value of 250 μg/mL for 24 h, the mycelial morphology was markedly shriveled in appearance or showed flattened and empty hyphae, with fractured cell walls, ruptured plasmalemma and cytoplasmic coagulation or leakage. These structural changes hindered the growth of mycelia.

Figure 1

TLC and HPLC/UV analysis of saponins ((A) Crude saponins and (B) Purified saponins).

Figure 2

Typical chromatograms of saponins in tea seed pomace (C. oleifera). (A) Chromatogram at UV 280 nm (LC/UV); (B) Chromatogram at ELSD (LC/ELSD); (C) Total ion chromatogram (LC/TOF-MS).

Figure 3

The genin structures of triterpene saponins.

Figure 4

The standard curve for HPLC/UV analysis of oleiferasaponin A₁ (280 nm).

Figure 5

The morphological alteration of B. maydis mycelium treated by total saponin at a concentration of 250 μg/mL for 24 h observed with optical microscope. (A) Healthy mycelium; (B) treated mycelium.

Figure 6

Transmission electron microscopy of mycelial ultrastructure of B. maydis treated by total saponin at a concentration of 250 μg/mL for 24 h. (A) Healthy mycelium; (B) treated mycelium; A ×7,000 and B ×10,000 magnification.