Structural characterisation of new immunoadjuvant saponins from leaves and the first study of saponins from the bark of Quillaja brasiliensis by liquid chromatography electrospray ionisation ion trap mass spectrometry

Abstract

Introduction Quillaja brasiliensis (St. A. ‐Hil. & Tul) Mart (Quillajaceae) is a species native to South America, which is rich in saponins. Saponins are used in different industries, so there is a constant demand for this type of compound. Based on the wide range of applications for the saponins found in this species, notably as immunoadjuvants, we conducted a comprehensive study of this tree and its saponins. Objective The purpose of this work is to complete the characterisation of the immunoadjuvant saponin fraction from Q. brasiliensis leaves and further study the saponin fraction obtained from Q. brasiliensis bark. Methodology Saponin fractions were studied using mass spectrometry in combination with classical methods of monosaccharide and methylation analysis. We performed direct infusion and liquid chromatography/electrospray ionisation ion trap multiple‐stage mass spectrometry (DI‐ESI‐IT‐MSn and LC‐ESI‐IT‐MS2). Results Seventy‐five saponins, 21 from leaves and 54 from bark, were tentatively identified according to their molecular mass, fragmentation pattern and chromatographic behaviour. This work represents the first investigation of saponins from the bark of Q. brasiliensis and some of them presented new structural motifs not previously reported in the genus Quillaja. Conclusion The efficiency and selectivity of the data dependent LC‐MS2 method allowed the rapid profiling of saponins from Q. brasiliensis. The results of the monosaccharide and methylation analysis performed in saponins from Q. brasiliensis fractions and Q. saponaria Molina (Quillajaceae) fraction gives further support to the structures proposed according to the mass spectral data, validating the strategy used in the present work.

Saponin production from Quillaja genus species. An insight into its applications and biology

“…They have two sugar moieties attached to a central triterpene aglycone structure and are classified as bidesmosidic molecules (Van setten and van de Werken, 1996). Detailed descriptions of molecular structures of QS and/or QB saponins have already been presented (Van Setten and van de Werken, 1996;Kite et al, 2004;Fleck et al, 2019;Wallace et al, 2017Wallace et al, , 2019. The most common triterpene aglycon skeleton is quillaic acid (Figure 2), which is generally glycosylated at C-3 and C-28 (Bankefors et al, 2010;Fleck et al, 2019).…”

“…According to recent studies, 58 saponins in QS bark have been reported (Fleck et al, 2019). For QB, it has been recently described 48 saponin in leaves and 54 saponins in bark (Wallace et al, 2017(Wallace et al, , 2019. Additionally, aqueous extracts of QS contain a set of other components including calcium, oxalate, proteins, sugars, and tannins (Maier et al, 2015).…”

“…According to most references, genes and enzymes of Quillaja species are similar to other β-amyrin derived triterpene accumulating species. Nevertheless, characterization of new genes, for Fleck et al, 2019 andWallace et al, 2019). Ac: acetyl group; Ara: arabinose; DeHex: dehydrohexose; Fa: 3,5 dihidroxy-octanoic acid; Glc: glucose; GlcA: glucuronic acid; Hex: hexose; MeBu: 2-methylbutanoyl; OHMeHex: 3-hydroxy-4-Methylhexanoyl; Pen: pentose; Rha: rhamnose.…”

“…Since the identification of saponins as the main metabolites in Quillaja species, many studies have investigated their composition and applications, mainly on QS and, to a lesser extent, on QB. In the latter, characterization of saponins and the analyses of their potential uses are relatively recent (Costa et al, 2014;Cibulski et al, 2018;Wallace et al, 2017Wallace et al, , 2019. In this review, we analyze historical aspects of the utilization of Quillaja species, and the progress in the characterization and applications of their saponins, incorporating general advances in the identification of saponin biosynthetic pathways, and related genes.…”

“…Unlike QS, QB leaves contain more saponins than bark (0.085 % vs 0.022 % of dry weight) (Magedans et al, 2019). The renewable use of bioactive saponins from QB leaves has gained more importance in recent years (Yendo et al, 2014;Costa et al, 2013Costa et al, , 2014Velazco et al, 2018;Cibulski et al, 2017Cibulski et al, -2018Fleck et al, 2009Fleck et al, , 2019Wallace et al, 2017Wallace et al, , 2019. According to the Brazilian National Center for Flora Conservation (CNCF, 2012), QB is an endangered species due to overgrazing and inadequate management, despite its economic importance.…”