Abstract
A feasibility study to predict antimicrobial and antioxidant activity properties of propolis extracts using 700-MHz 1H-NMR spectra and multivariate regression data analysis is presented. The study was conducted with thirty-five propolis samples to develop a rapid and reliable method for the evaluation of their quality. The extracts have been evaluated by measuring phenolic and flavonoid contents; the antioxidant activity; and the antimicrobial activity. The obtained spectral data were submitted to multivariate calibration (partial least squares (PLS) and orthogonal partial least squares (OPLS)) to correlate the relative intensity and position of NMR resonance peaks with the metabolites contents and biological activities. The developed PLS and OPLS model were successfully applied to the determination of the target properties for proof of the concept. The OPLS observed vs. predicted properties plots indicate the absence of systematic errors with determination coefficients between the ranges 0.7207 to 0.9990. Up to 86.1% of explication of variation in the spectral data and 99.9% in the measured properties were attained with 88.6% of prediction capabilities in the best case (S. mutans activity) according to the cross-validation procedure. The figures of merit of the developed PLS and OPLS methods were evaluated and compared as well.
Highlights
Propolis, is a sticky dark-colored hive product collected by bees from living plant sources [1,2]
Streptococcus mutans, Streptococcus oralis and Streptococcus sanguinis as test models
The total phenolic and flavonoid contents and antioxidant activity are in agreement with the literature for poplar propolis [3,6,10]
Summary
Propolis (bee glue), is a sticky dark-colored hive product collected by bees from living plant sources [1,2]. The biological effects of propolis can be associated with its antioxidant activity, and in the last few decades new analytical techniques have been proposed to determine its antioxidant activity [12,13]. They are based, for example, on the determination of total phenolic and flavonoid contents or the antioxidant activity/capacity assays: 1,1-diphenyl-2-picrylhydrazyl (DPPH), ferric reducing/antioxidant power (FRAP), and generation of the (2,20 -azinobis-(3-ethylbenzothiazoline-6-sulfonic acid] (ABTS)) radical cation [14]. The application of 1 H-NMR coupled with multivariate statistical analysis, based on partial least squares, is employed to quantitatively predict the antibacterial and antioxidant activities of propolis extracts. Mexican apiaries and four samples from out of the country (one from Ecuador and three from China) to develop a rapid and reliable method to evaluate the quality of them
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