Crotalaria spectabilis as a source of pyrrolizidine alkaloids and phenolic compounds: HPLC‐MS/MS dereplication and monocrotaline quantification of seed and leaf extracts

Abstract

Introduction: Crotalaria spectabilis is an important species used as a pre-plant cover for soybean crops to control the proliferation of endoparasitic nematodes. Species from the Crotalaria genus are known for presenting pyrrolizidine alkaloids (PAs) in their composition, however, C. spectabilis is still considered chemically underexplored. Objective: The goal of this manuscript is the development and validation of a method for PAs and flavonoids identification and quantification of C. spectabilis seeds and leaves, a toxic plant used for nematode proliferation control in soil, especially in soybean crops. Materials and methods: Seeds and leaves extracts were analysed by highperformance liquid chromatography coupled to tandem mass spectrometry (HPLC-MS/MS) for the identification of the compounds. Results: PAs and phenolic compounds could be identified in both samples based on the MS/MS fragmentation pattern. Molecular formulas of the annotated compounds were confirmed by ultra-high-performace liquid chromatography-quadrupole time-of-flight (UHPLC-QToF), and monocrotaline could also be confirmed by standard comparison. The quantification of monocrotaline was performed by HPLC-MS/MS, resulting in 123 times higher monocrotaline content in seeds than in the leaves, which could explain its efficiency in combating nematode proliferation in soil. Conclusion: This was the first report of phenolic compounds in C. spectabilis. The current study highlights the importance of C. spectabilis for nematode control due to the presence of toxic PAs, and the employment of analytical techniques for identification and quantification of compounds present in the extracts.

Monocrotaline presence in the Crotalaria (Fabaceae) plant genus and its influence on arthropods in agroecosystems

“…In Brazil, the genus Crotalaria includes 31 native and 11 exotic species, popularly known as "xique-xique" or "guizo de cascavel" because of the rattling sound when the pod is shaken, similar to the rattle of Crotalus sp. (Reptilia: Viperidae) (Tokarnia et al, 2000;Flores et al, 2009;Scupinari et al, 2020).…”

“…The quantification of monocrotaline levels present in Crotalaria species has been under-documented. However, a recent study successfully quantified the amount of monocrotaline present in leaves and seeds of C. spectabilis using the HPLC/MS/MS method (Scupinari et al, 2020). The amounts of monocrotaline quantified by the authors in C. spectabilis leaves were 0.141 mg.g -1 (5.88%), and in the seeds, it was 17.393 mg.g -1 (3.037%) Thus, it is known that C. spectabilis plants have a symbiosis with nitrifying bacteria (characterized by the presence of rhizobial nodules) and produce monocrotaline which is not considered functionally involved in symbiosis (Irmer et al, 2015;Schramm et al, 2019).…”

“…Regarding the influence of Crotalaria on the fauna associated with agricultural crops, four characteristics that are possibly related to its activity can be listed: (i) floral characteristics (Meagher Junior et al, 2019); (ii) the presence of monocrotaline above ground (Hartmann, 1999;Scupinari et al, 2020); (iii) the peculiarities of its root system (Wang et al, 2002;Irmer et al, 2015;Leal et al, 2018) and; (iv) and dry mass decomposition products (straw) (Oliveira et al, 2007;Gill et al, 2010;Nowak et al, 2016) (Figure 1). A summary of the main effects of the Crotalaria species on the associated fauna is shown in Table 2.…”

UPLC-Q-TOF-MS/MS Analysis of Seco-Sativene Sesquiterpenoids to Detect New and Bioactive Analogues From Plant Pathogen Bipolaris sorokiniana

“…Mass spectrometry, especially tandem mass spectrometry, has been one of the most important physicochemical approaches for the characterization of secondary metabolites due to its rapidity and sensitivity ( Jin et al, 2018 ; Liang et al, 2018 ; Conceição et al, 2020 ; Scupinari et al, 2020 ). Molecular weight and formula are often inconclusive for metabolite identification; however, fragmentation patterns represent a specific feature for a certain structural class.…”

Pyrrolizidine-Derived Alkaloids: Highly Toxic Components in the Seeds of Crotalaria cleomifolia Used in Popular Beverages in Madagascar

“…The genus Crotalaria is used in traditional medicine as deworming, in malaria treatment, and in management of fever [ 2 , 3 ]. In agriculture, the crotalaria species are used as a pre-plant cover for soybean crops to avoid the spread of parasites [ 4 ]. However, Crotalaria genus is known for its toxicity.…”