1H nuclear magnetic resonance-based metabolite profiling of guava leaf extract: an attempt to develop a prototype for standardization of plant extracts

Abstract

Background Herbal medicines are fast gaining popularity. However, their acceptability by modern practitioners is low which is often due to lack of standardization. Several approaches towards standardization of herbals have been employed. The current study attempted to recognize key peaks from 1H NMR spectra which together would comprise of a spectral fingerprint relating to efficacy of Psidium guajava (guava) leaf extract as an antidiarrhoeal when a number of unidentified active principles are involved. Methods Ninety samples of guava leaves were collected from three locations over three seasons. Hydroalcoholic (water and ethanol, 50:50) extracts of these samples were prepared and their 1H NMR spectra were acquired. Spectra were also obtained for quercetin, ferulic acid and gallic acid as standards. Eight bioassays reflecting different stages of diarrhoeal pathogenesis were undertaken and based on pre-decided cut-offs, the extracts were classified as ‘good’ or ‘poor’ extracts. The bioactivity data was then correlated with the 1H NMR profiles using Regression or Orthogonal Partial Least Square-Discriminant Analysis (OPLS-DA). Results OPLS-DA showed seasonal and regional segregation of extracts. Significant models were established for seven bioassays, namely those for anti-bacterial activity against Shigella flexneri and Vibrio cholerae, adherence of E. coli, invasion of E. coli and S. flexneri and production and binding of toxin produced by V. cholerae. It was observed that none of the extracts were good or bad across all the bioassays. The spectral analysis showed multiple peaks correlating with a particular activity. Based on NMR and LC-MS/MS, it was noted that the extracts contained quercetin, ferulic acid and gallic acid. However, they did not correlate with the peaks that segregated extracts with good and poor activity. Conclusions The current study identified key peaks in 1H NMR spectra contributing to the anti-diarrhoeal activity of guava leaf extracts. The approach of using spectral fingerprinting employed in the present study can thus be used as a prototype towards standardization of plant extracts with respect to efficacy.

Metabolite Fingerprinting Using 1H-NMR Spectroscopy and Chemometrics for Classification of Three Curcuma Species from Different Origins

“…NMR spectroscopy offers some advantages for authentication of medicinal plants such as fast time analysis, simple in sample preparation, high reproducibility, and high robust. Moreover, NMR spectroscopy can be used for simultaneous analysis either primary or secondary metabolites comprehensively in certain samples [19,20]. Combined with chemometrics of multivariate analysis such as principal component analysis (PCA), partial least square-discriminant analysis (PLS-DA), and orthogonal projections to latent structures-discriminant analysis (OPLS-DA) which can manage the huge data generated from NMR measurement, it becomes a powerful analytical tool for metabolite fingerprinting of medicinal plants [21,22].…”

High performance liquid chromatography-based metabolomics of Psidium guajava Linn. leaf extracts

“…The utility of a spectral fingerprint toward standardization of crude extracts was successfully demonstrated in our previous study (Gholkar et al, 2021). The study attempted to develop a prototype for standardization of extracts used 1 H NMR metabolic profiling by correlating peaks to anti-diarrhoeal activity of guava leaf extracts.…”

Profiling of Plant Derived Natural Constituents by Using Magnetic Resonance Techniques

“…Mainly because water is the main building ingredient of many food materials, the MRI technique has a wide range of applications. e study of specific aspects of fruit quality such as at different quality stages has also found uses in magnetic Pineapple waste extracts 1 H NMR Successfully investigated metabolite profile of pineapple peel, crown and core extracted from different ethanolic ratios Also identified toxic compounds and co-relation between plant metabolomics and their bioactivity [48] Short cake biscuits NMR-low field Indicated a reduction in dynamics of water molecules bound to polymer matrix Rheological characteristics such as reduction in hardness of cookies was analysed by NMR imaging [49] Arabidopsis thaliana NMR-MS Identified unknown metabolite accurately such as glucosinolates and glucoraphanin [50] Guava leaf extract 1 H NMR + principle component analyses High degree of variation detected by PCA analyses of 1 H NMR spectra Signals detected aliphatic and aromatic regions suggesting both primary and secondary metabolties such as quercitin, ferullic acid, and gallic acid [51] Coffee arabica roasted beans 1 H NMR and static headspace gas chromatography (SHGH)-MS Detected 20 water-soluble compounds and 43 volatile compounds such as n-methyl pyridiniun, formic acid, caffeine, choline, propionic acid, 2-furyl methanol [52] Corylus avellana leaves (hazelnut) resonance imaging. e use of MRI sequences with an optimised acquisition time, often on a second-to-minute scale is also required for dynamic imaging of cereal products in the processing stage, however, that the water transport in rice kernels observed during cooking may differ depending on the sequence duration.…”