Antioxidant capacity of Camellia japonica cultivars assessed by near- and mid-infrared spectroscopy
Camellia japonica antioxidant capacity highly differs among its cultivars and could be successfully predicted by near- and mid-infrared spectroscopy.
Camellia japonica is a Theaceae family species which are mainly used as an ornamental plant due to its colourful flowers presenting over than 32,000 recognized cultivars. However, this species have been somehow neglected due to the popular tea source, Camellia sinensis. In this study, the antioxidant profile (total phenolic and flavonoid content and total antioxidant capacity—TPC, TFC and TAC) of 31 C. japonica cultivars leaves was determined and further assessed by near- and mid-infrared spectroscopy. The leaves’ antioxidant profile was revealed to be highly dependent on the cultivars analysed being in some cases distinct even for different trees of the same cultivar. Near- and mid-infrared spectroscopy proved to be suitable techniques to predict the total phenolic and flavonoid content as well as the total antioxidant capacity. The best results were obtained with near-infrared spectroscopy whose root mean square error of the prediction set samples was of 5.7 mg of gallic acid/g dry leaf; 3.5 mg catechin/g dry leaf and 3.3 mM Trolox/g dry leaf for TPC, TFC and TAC (with coefficients of the determinations equal to or higher than 0.93). Moreover, the range error ratios were higher than 15 meaning that the developed partial least-squares models are very good for calibration and quantification determinations according to the guidelines for near-infrared models development and maintenance. In this work, the antioxidant profile of several C. japonica cultivars leaves was determined for the first time, being that a rapid and low cost spectroscopic-based method was also proposed for its determination.
KeywordsInfrared spectroscopy Camellia japonica cultivars Antioxidants Phenolic compounds Flavonoids Chemometrics
This work received financial support from the European Union (FEDER funds through POCI/01/0145/FEDER/007265 and COMPETE POCI-01-0145-FEDER-016735) and National Funds (FCT/MEC, Fundação para a Ciência e Tecnologia and Ministério da Educação e Ciência) under the Partnership Agreement PT2020 UID/QUI/50006/2013 and the project PTDC/AGR-PRO/6817/2014. Clara Sousa was funded through the NORTE-01-0145-FEDER-000024—“New Technologies for three Health Challenges of Modern Societies: Diabetes, Drug Abuse and Kidney Diseases”. Thanks are due to Viveiro da Câmara Municipal do Porto (http://www.cm-porto.pt/jardins-e-parques-urbanos/viveiro-municipal) and to Jardim Botânico do Porto (https://jardimbotanico.up.pt/index.php) for providing Camellia japonica leaves.
Compliance with ethical standards
Conflict of interest
The authors have no competing interests.
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