Pseudo-univariate calibration as an analytical tool to determine antioxidant activity: An alternative to DPPH method applied to the evaluation from extracts of turmeric powder

Abstract

A pseudo-univariate calibration model was proposed as an alternative method to determine the antioxidants activity (%RSA) in extract from turmeric powder by using the relative intensity from multivariate curve resolution with alternating least squares (MCR-ALS) from near-infrared (NIR) spectra. An extraction was performed by using an ultrasound with probe, ethanol 70% and time 15 minutes. For pseudo-univariate calibration, eight independent samples were prepared from the curcuminoid extracts. NIR spectra were collect from 900 to 1700 nm, and to these samples the percentage of inhibition of DPPH was determined with reference method. The signal for antioxidants was isolated from the signal to the other analytes in the sample by applying MCR-ALS to the NIR spectra. The relative intensity profile related to the antioxidants was employed in a pseudo-univariate calibration against the %RSA obtained by the reference conventional method based on DPPH. The results of the %RSA determination in four independent samples with mean %RSA (obtained by the reference method) of 90.26% show a mean %RSA of 87.5%, showing the possibility of %RSA determination directly from NIR spectra of turmeric powder extracts by using the multivariate resolution method MCR-ALS.