Contents lists available at ScienceDirect Talanta journal homepage: www.elsevier.com/locate/talanta Application of benchtop and portable near-infrared spectrometers for predicting the optimum harvest time of Verbena officinalis Cornelia K. Pezzei a , Stefan A. Schönbichler b , Christian G. Kirchler a , Julia Schmelzer a , Shah Hussain a , Verena A. Huck-Pezzei a , Michael Popp c , Justine Krolitzek c , Günther K. Bonn a,d , Christian W. Huck a, ⁎ a Institute of Analytical Chemistry and Radiochemistry, CCB-Center for Chemistry and Biomedicine, Innrain 80/82, 6020 Innsbruck, Austria b Bionorica research, Mitterweg 24, 6020 Innsbruck, Austria c Bionorica SE, Kerschensteinerstrasse 12-15, 92318 Neumarkt/Oberpfalz, Germany d ADSI – Austrian Drug Screening Institute, Innrain 66a, 6020 Innsbruck, Austria ARTICLE INFO Keywords: Near-infrared spectroscopy Hand-held spectrometer Quantitative phytopharmaceutical analysis Verbena officinalis Harvest time ABSTRACT This study examined the applicability of near-infrared (NIR) spectroscopy coupled with multivariate data analysis (MVA) to determine the ideal harvest time of Verbena officinalis. NIR analyses were performed non- invasively on the fresh plant material based on the quantification of the key constituents verbenalin and verbascoside. Vibrational spectroscopic measurements were performed applying a conventional NIR benchtop device as well as a laboratory independent handheld NIR spectrometer. A novel high performance liquid chromatography (HPLC) method was applied as a reference method. For both instruments partial least squares (PLS) regression models were established performing cross validations (CV) and test-set validations (TSV). Quality parameters obtained for the benchtop device revealed that the newly established NIR method enabled reliable quantifications of the main compounds verbenalin and verbascoside related to the dried and fresh plant material. The results of the miniaturised spectrometer revealed that accurate quantitative calibration models could be developed for verbascoside achieving a comparable prediction power to the benchtop device. PLS models for verbenalin were less precise suggesting the application of portable devices including a different spectral range and resolution. The work demonstrated the feasibility of NIR vibrational spectroscopy performing direct measurements on pharmaceutically relevant fresh plant material enabling a quick and simple determination of the ideal harvest time of Verbena officinalis. 1. Introduction Verbena officinalis (Verbenaceae), commonly known as vervain, is a medicinal plant and grows widely in all temperature regions of the globe. The herbal drug Verbenae herba is listed in the European Pharmacopeia and consists of the dried aerial parts of Verbena officinalis collected during flowering [1]. The herb is used in folk medicine as a diuretic, expectorant and anti-rheumatic [2]. Moreover, its extract is one of the components of the frequently used rhinologi- cum Sinupret®. Pharmacological studies indicate anti-inflammatory [3–5], analgesic [4], antibacterial [6], antifungal [7] and antioxidant [7–9] activities of the plant extract. The herbal ingredients of Verbena officinalis can be divided into iridoids, phenylpropanoids, flavonoids, triterpes and monoterpenes [10,11]. Major active components are the iridoid verbenalin and the phenylpropanoid verbascoside. Verbenalin exhibits hepato-protective [12] and sleep-promoting [13] effects. Furthermore, the iridoid shows antitussive, secreting [2] and anti- inflammatory [14] properties. According to the European Pharmacopeia verbenalin is the quality determining parameter with a minimum content of 1.5% [1]. For verbascoside anti-infammatory [15,16], antioxidant [17,18], analgesic [19] and neuro-protective [20,21] activities are reported. The structures of the two plant substances are presented in Fig. 1. Herbal medicinal products contain, in comparison to chemically synthetic medicine, pharmaceutical preparations of plants. As a con- sequence the quality of herbal medicine depends on the quality of the herbal raw material. The raw drug is subjected to natural fluctuations concerning the content of herbal agents. The causes of these variations may have various reasons, for example the climate and soil conditions. For this reason the aim of this study was to determine the optimum http://dx.doi.org/10.1016/j.talanta.2017.03.067 Received 3 March 2017; Received in revised form 18 March 2017; Accepted 21 March 2017 ⁎ Corresponding author. E-mail address: Christian.W.Huck@uibk.ac.at (C.W. Huck). Talanta 169 (2017) 70–76 Available online 22 March 2017 0039-9140/ © 2017 Elsevier B.V. All rights reserved. MARK