Skip to main page content
Access keys NCBI Homepage MyNCBI Homepage Main Content Main Navigation
, 15 (3), 27

Identification of Antiplasmodial Triterpenes From Keetia Species Using NMR-based Metabolic Profiling

Affiliations

Identification of Antiplasmodial Triterpenes From Keetia Species Using NMR-based Metabolic Profiling

Rafael Teixeira Freire et al. Metabolomics.

Abstract

Introduction: The increase in multidrug resistance and lack of efficacy in malaria therapy has propelled the urgent discovery of new antiplasmodial drugs, reviving the screening of secondary metabolites from traditional medicine. In plant metabolomics, NMR-based strategies are considered a golden method providing both a holistic view of the chemical profiles and a correlation between the metabolome and bioactivity, becoming a corner stone of drug development from natural products.

Objective: Create a multivariate model to identify antiplasmodial metabolites from 1H NMR data of two African medicinal plants, Keetia leucantha and K. venosa.

Methods: The extracts of twigs and leaves of Keetia species were measured by 1H NMR and the spectra were submitted to orthogonal partial least squares (OPLS) for antiplasmodial correlation.

Results: Unsupervised 1H NMR analysis showed that the effect of tissues was higher than species and that triterpenoids signals were more associated to Keetia twigs than leaves. OPLS-DA based on Keetia species correlated triterpene signals to K. leucantha, exhibiting a higher concentration of triterpenoids and phenylpropanoid-conjugated triterpenes than K. venosa. In vitro antiplasmodial correlation by OPLS, validated for all Keetia samples, revealed that phenylpropanoid-conjugated triterpenes were highly correlated to the bioactivity, while the acyclic squalene was found as the major metabolite in low bioactivity samples.

Conclusion: NMR-based metabolomics combined with supervised multivariate data analysis is a powerful strategy for the identification of bioactive metabolites in plant extracts. Moreover, combination of statistical total correlation spectroscopy with 2D NMR allowed a detailed analysis of different triterpenes, overcoming the challenge posed by their structure similarity and coalescence in the aliphatic region.

Keywords: In vitro antiplasmodial activity; Keetia leucantha; Keetia venosa; NMR-based metabolomics; STOCSY; Triterpenes.

Conflict of interest statement

The authors declare that they have no conflict of interest.

Figures

Fig. 1
Fig. 1
Chemical structures of dihydroxy cinnamic acid and triterpenoidal (oleanolic- and ursolic acids) moieties identified in Keetia species, and typical 1H NMR spectra (600 MHz, CH3OH-d4) of CH2Cl2 extracts of K. venosa twigs (a) and leaves (b), and K. leucantha twigs (c) and leaves (d) in phenolic (δ 6.0–7.7) and aliphatic region (δ 0.7–1.2). H-2, H-5, H-6, H-7 and H-8 are H of dihydroxy cinnamic acid moiety
Fig. 2
Fig. 2
Score plot (PC1 × PC2) (a) and PC1 loading plot (b) of principal component analysis of K. leucantha and K. venosa samples (leaves and twigs), and OPLDS–DA score plot (c) (t1/to1) and S-plot (d) using two species classes. 1: K. leucantha, 2: K. venosa, o: Leaves, •: twigs. *: methyl signals of triterpenoids. Red (•) and blue dots (•) in (d) are methyl signals of triterpenoids and squalene, respectively
Fig. 3
Fig. 3
Score (a) and loading plot (b) of OPLS modelling with log IC50 of in vitro antiplasmodial assay against 3D7 and W2 P. falcifarum strains t1 of 1H NMR data versus u1 of log IC50 of in vitro antiplasmodial activity. r2 for the correlation = 0.487. Red bars in (b) are IC50 values against 3D7 and W2 P. falcifarum strains and blue bars in (b) are 1H resonances of triterpenoids and phenylpropanoids associated with the activity
Fig. 4
Fig. 4
STOCSY plot using drivers peak at δ 7.55 (a), δ 1.56 (b) and δ 1.59 (c). Signal assignments; (a) *driver peak at δ 7.55 (H-7 of ferulic acid moiety), 1: H-2 of ferulic acid moiety, 2: H-6 of ferulic acid moiety, 3: H-5 of ferulic acid moiety, 4: H-8 of ferulic acid moiety, 5: H-12 of ursolic- and oleanolic acid, 6: OCH3 of ferulic acid moiety, 7: H-3 of ursolic- and oleanolic acid, 8: H-11 of ursolic- and oleanolic acid, 9: H-6 of ursolic- and oleanolic acid, 10: H-27 of ursolic- and oleanolic acid, 11: H-25 of ursolic- and oleanolic acid, 12: H-26 of ursolic- and oleanolic acid, 13: H-24 of ursolic- and oleanolic acid. (b) *Driver peak at δ 1.56 (H-6 of ursolic- and oleanolic acid), 1: H-12 of ursolic- and oleanolic acid, 2: H-3 of ursolic- and oleanolic acid, 3: H-11 of ursolic- and oleanolic acid, 4: H-27 of ursolic- and oleanolic acid, 5: H-25 of ursolic- and oleanolic acid, 6: H-26 of ursolic- and oleanolic acid, 7: H-24 of ursolic- and oleanolic acid. (c) *Driver peak at δ 1.59 (CH3 attached to C-6 of squalene), 1: H-3, H-7 and H-11 of squalene, 2: H-4 and H-8 of squalene, 3: H-1 and H-9 of squalene, 4: H-1 and H-2 of squalene. For the 1H assignments see the chemical structures in Figs. 1 and 5
Fig. 5
Fig. 5
Chemical structures of squalene and two phenylpropanoid conjugated triterpenes, 3β-hydroxy-27-(E)-feruloyloxyolean-12-en-28-oic acid (1) and 3β-hydroxy-27-(E)-feruloyloxyurs-12-en-28-oic acid (2)

Similar articles

See all similar articles

Cited by 1 article

References

    1. Abreu AC, Coqueiro A, Sultan AR, Lemmens N, Kim HK, Verpoorte R, et al. Looking to nature for a new concept in antimicrobial treatments: Isoflavonoids from Cytisus striatus as antibiotic adjuvants against MRSA. Scientific Reports. 2017;7(1):3777. doi: 10.1038/s41598-017-03716-7. - DOI - PMC - PubMed
    1. Achan J, Mwesigwa J, Edwin CP, D’alessandro U. Malaria medicines to address drug resistance and support malaria elimination efforts. Expert Review of Clinical Pharmacology. 2018 doi: 10.1080/17512433.2018.1387773. - DOI - PubMed
    1. Beaufay C, Bero J, Quetin-Leclercq J. Natural antimicrobial agents; sustainable development and biodiversity. Cham: Springer; 2018. Antimalarial terpenic compounds isolated from plants used in traditional medicine (2010–July 2016) pp. 247–268.
    1. Beaufay C, Henry G, Streel C, Bony E, Hérent MF, Bero J, Quetin-Leclercq J. Optimization and validation of antimalarial triterpenic esters in Keetia leucantha plant and plasma. Journal of Chromatography B. 2019 doi: 10.1016/j.jchromb.2018.11.003. - DOI - PubMed
    1. Beaufay C, Hérent MF, Quetin-Leclercq J, Bero J. In vivo anti-malarial activity and toxicity studies of triterpenic esters isolated form Keetia leucantha and crude extracts. Malaria Journal. 2017;16(406):1–8. doi: 10.1186/s12936-017-2054-y. - DOI - PMC - PubMed

Publication types

LinkOut - more resources

Feedback