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

Manasi S Gholkar,Poonam G Daswani,Jia V Li,P Tetali,Tannaz J Birdi

doi:10.1186/s12906-021-03221-5

Manasi S Gholkar, Poonam G Daswani + Show 3 more

Open Access

https://doi.org/10.1186/s12906-021-03221-5

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Abstract

BackgroundHerbal 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.MethodsNinety 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).ResultsOPLS-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.ConclusionsThe 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.

Highlights

A representative 1D 1H-Nuclear Magnetic Resonance (NMR) acquired for 90 guava extracts is depicted in Fig. 1 and representative 1H NMR spectra for seasonal and regional differentiation have been provided as Additional data (Supplementary Fig. S1 and Fig. S2 respectively)
The 1H NMR spectra of quercetin, ferulic acid and gallic acid have been given as Additional data (Supplementary Fig. S3, S4 and S5 respectively)
The fragmentation patterns from LC-Mass Spectroscopy (MS)/MS have been provided as Additional data

Summary

Introduction

Their popularity amongst the population is rising, their acceptability by conventional medical practitioners is yet not satisfactory. An additional factor for the lower acceptance of phytomedicines by the modern practitioners is the restricted acceptance of the holistic concept of herbal medicines which is contrary to the principle of single compound for single therapeutic activity in modern medicine [2]. This holistic approach of herbal medicines is often related to the synergistic action of its constituents. Identification of biomarkers in the absence of knowledge of active principles may not be the most suitable approach towards standardization

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