Screening for Triterpenoid Saponins in Plants Using Hyphenated Analytical Platforms

Abstract

Abstract:Recently the number of studies investigating triterpenoid saponins has drastically increased due to their diverse and potentially attractive biological activities. Currently the literature contains chemical structures of few hundreds of triterpenoid saponins of plant and animal origin. Triterpenoid saponins consist of a triterpene aglycone with one or more sugar moieties attached to it. However, due to similar physico-chemical properties, isolation and identification of a large diversity of triterpenoid saponins remain challenging. This study demonstrates a methodology to screen saponins using hyphenated analytical platforms, GC-MS, LC-MS/MS, and LC-SPE-NMR/MS, in the example of two different phenotypes of the model plant Barbarea vulgaris (winter cress), glabrous (G) and pubescent (P) type that are known to differ by their insect resistance. The proposed methodology allows for detailed comparison of saponin profiles from intact plant extracts as well as saponin aglycone profiles from hydrolysed samples. Continuously measured 1D proton NMR data during LC separation along with mass spectrometry data revealed significant differences, including contents of saponins, types of aglycones and numbers of sugar moieties attached to the aglycone. A total of 49 peaks were tentatively identified as saponins from both plants; they are derived from eight types of aglycones and with 2-5 sugar moieties. Identification of two previously known insect-deterrent saponins, hederagenin cellobioside and oleanolic acid cellobioside, demonstrated the applicability of the methodology for relatively rapid screening of bioactive compounds.

The cytochrome P450 CYP72A552 is key to production of hederagenin‐based saponins that mediate plant defense against herbivores

“…S7), and this may reflect that it is colocalised with other genes related with resistance to flea beetles. We have previously shown that CYP716s and OSCs are promiscuous enzymes (Khakimov et al, 2015), both with respect to substrate and product specificity, and this may explain how B. vulgaris with a limited number of genes in the pathway may accumulate up to 49 different saponins (Khakimov et al, 2016).…”

“…Hederagenin-based saponins are a major deterrent to both diamondback moth and tobacco hornworm Barbarea vulgaris plants accumulate both mono-and bidesmocidic saponins, with between two to five sugars attached to the C-3 or C-28 positions; the corresponding monoglycosides are usually not present (Khakimov et al, 2016). The sapogenins (saponin aglycons) are not active against crucifer herbivores, but only become deterrent when they are 3-O-glucosylated (Nielsen et al, 2010;Augustin et al, 2012).…”

A new liquid chromatography-high resolution Orbitrap mass spectrometry-based strategy to characterize Glucuronide Oleanane-type Triterpenoid Carboxylic Acid 3, 28-O-Bidesmosides (GOTCAB) saponins.A case study of Gypsophila glomerata Pall ex M. B. (Caryophyllaceae)

“…ESI mode, most oleanane type triterpenoid saponins afforded abundant [M-H] -; the adduct process is not reproducible [25]. It has been reported that the [M−H]are the major ions generated in the negative ion mode of UHPLC-ESI-QTOF-MS analyses [23,26].…”

Evolution of Structural Diversity of Triterpenoids

“…β-amyrin is a precursor of glycyrrhizin, a triterpenoid saponin found in the roots and stolons of liquorice (Glycyrrhiza glabra) well known for its pharmaceutical properties and as a natural sweetener (Hayashi et al, 2002). β-amyrin is also precursor for the antifungal saponin avenacin A-1 in oat and for the potent insect-feeding deterrent hederagenin glycosides in the Brassicaceae Barbarea vulgaris (Kuzina et al, 2009;Nielsen et al, 2010;Khakimov et al, 2016;Liu et al, 2019);. Additionally, β-amyrin seems to play a role in root development in oat (Kemen et al, 2014) and in Lotus japonicus (Krokida et al, 2013), suggesting that triterpenoids like lupeol and β-amyrin are not exclusively involved in plant defense.…”

“…Triterpenoid saponin biosynthesis has evolved recurrently in evolution and thus the organization of the genes may not be conserved. In recent years, the Barbarea genus has appeared as a unique plant model as it is the only genus in the agronomically important cabbage family (Brassicaceae) known to accumulate saponins (Khakimov et al, 2016). Some of these saponins (e.g., hederagenin cellobioside) are highly deterrent to Brassica specialist herbivores such as flea beetles (Phyllotreta nemorum) and the diamondback moth (Plutella xylostella) (Kuzina et al, 2009;Kuzina et al, 2011;Liu et al, 2019).…”