Talanta 194 (2019) 795–802 Contents lists available at ScienceDirect Talanta journal homepage: www.elsevier.com/locate/talanta Determination of bioactive nonvolatile ginger constituents in dietary T supplements by a rapid and economic HPLC method: Analytical method development and single-laboratory validation ⁎ Hong Youa, , Bailey Irelanda, Michael Moeszingera, Haoshu Zhanga, Laura Snowb, Scott Krepichb, Vivian Takagawac a Eurofins Scientific, Inc., 1365 Redwood Way, Petaluma, CA 94954, United States b Phenomenex, Inc., 411 Madrid Avenue, Torrance, CA 90501, United States c ChromaDex, Inc., 10005 Muirlands Blvd Suite #G, Irvine, CA 92618, United States ARTICLE INFO ABSTRACT Keywords: Most of the validated methods for ginger-containing dietary supplements have long run time and low sensitivity Nonvolatile ginger constituents and only analyze gingerols and shogaols. 6-Paradol and zingerone become popular in modern dietary supple- AOAC validation ment industry as bioactive ginger constituents. Therefore, we developed an efficient HPLC-UV/Vis method to Gingerols analyze all above major constituents. Compared to 282/280 nm used by the current compendial United States Shogaols Pharmacopeia (USP) monograph method and International Organization for Standardization (ISO) 13685-1997 6-paradol method, detection wavelength was optimized to 230 nm which showed a higher sensitivity (signal-to-noise ratio) Zingerone and better peak resolution. For measuring the ginger constituents in AOAC required matrices, the method was demonstrated to be selective, linear (R2 > 0.999), specific, accurate (91.1–103.2% spike recovery rate) and precise (RSDr < 5%, RSDR < 8%). Among 10 commercial ginger-containing samples that we screened using this method, the results were 80–123% of the products’ labeling value. The HPLC running time was successfully shortened from 29 min (USP method) and 40 min (ISO method) to 12 min without the need of using an expensive Mass Spectrometer for analyte separation. The method is the first method that meets all AOAC SMPR 2017.12 requirements and therefore has the potential to be adopted as a consensus industrial reference method for meeting FDA's cGMP Compliance for the manufacture and quality control of dietary supplements and in- gredients. 1. Introduction and oleoresin contain the non-volatile components including gingerols, paradols, shogaols and zingerone. Previous methods and publications Ginger (Zingiber officinale) rhizome is used in several systems of focused on analytical methods that only quantify gingerols and sho- medicine, including traditional Chinese medicine, Ayurveda and gaols [4–7]. However, compared to other ginger non-volatile con- Western herbal medicine. It has been used to treat a great variety of stituents, 6-paradol has shown better anti-hyperglycemic assay activity disorders including colds and flu, dyspepsia, flatulence and colic, mi- in stimulating glucose utilization of 3T3-L1 adipocytes and C2C12 graine, nausea, rheumatic disorders, and vomiting [1]. Gingerols are myotubes [3]. In a separate study, 6-paradol was suggested as a ther- the major bioactive nonvolatile pungent constituents of fresh ginger apeutic agent to effectively protect the brain after cerebral ischemia, rhizome [2]. Gingerols are mainly converted to zingerone and shogaols likely by attenuating neuroinflammation in microglia [8]. As an alka- during drying, prolonged storage, processing, and cooking [3]. The loid with strong antioxidantive activity, zingerone has been proven to shogaols can then be partially transformed to paradols upon cooking or have an ONOO(-) peroxynitrite scavenging ability, which indicates its metabolized to paradols in the animals’ body after being consumed and cellular defensive potential against related-symptoms in several human absorbed by digestive system [3]. Major ingredients of ginger-con- diseases such as stroke, Alzheimer's disease, and atherosclerosis [9]. By taining dietary supplements such as ginger rhizome, powder extract, increasing systemic superoxide dismutase activity, zingerone was also ⁎ Correspondence to: Eurofins Supplement Analysis Center, Eurofins Scientific, Inc., 1365 Redwood Way, Petaluma, CA, 94954, UnitedStates. E-mail addresses: [email protected] (H. You), [email protected] (B. Ireland), [email protected] (M. Moeszinger), [email protected] (H. Zhang), [email protected] (L. Snow), [email protected] (S. Krepich), [email protected] (V. Takagawa). https://doi.org/10.1016/j.talanta.2018.10.075 Received 25 September 2018; Received in revised form 22 October 2018; Accepted 22 October 2018 Available online 25 October 2018 0039-9140/ © 2018 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY license (http://creativecommons.org/licenses/BY/4.0/). H. You et al. Table 1 Test samples used in method validation and optimization studies. ID code Matrices Sample form Major Component(s) Manufacturer Product name Label claim Estimated level (w/w purity) 251 Rhizome powder Raw material Ginger USP Powdered Ginger 100% Ginger rhizome powder 1% Total nonvolatile ginger constituentsa 099 Rhizome dry extract Raw material Ginger Suan Fharm Ginger extract 100% Ginger rhizome dry extract 5% Total nonvolatile powder ginger constituents 063 Tablet Finished Ginger The Ginger People Ginger Rescue, Chewable Ginger 40 mg ginger powder/1.3 g 0.03% Total nonvolatile product Tablets for Kids (665.78 mg/tablet, 3% ginger ginger constituentsa powder) 580 Capsule Finished Ginger Now Foods Ginger Root extract, 250 mg 12.5 mg gingerols/capsule 2.51% Total nonvolatile 796 product (498.02 mg/capsule) ginger constituents 101 Liquid Capsule Finished Bacopa monnieri, Caffeine, p-Synephrine, Nutrex Research Labs Lipo6 Black 10 mg zingerone/3 capsules 0.58% Zingerone product Vinpocetine, Zingerone, Yohimbine (572.61 mg/capsule) 986 Rhizome oleoresin - Raw material Ginger Shaanxi Guanjie Ginger supercritical CO2 extract 100% Ginger rhizome dry extract 50% Total nonvolatile supercritical CO2 extract Technology powder ginger constituents 648 Lean muscle recovery Finished Glycyl-Alanyl-Lysine-L-Leucine, -Isoleucine, -Valine, BPI sports Best BCAA Shredded Lean Muscle 1.25 mg 6-Paradol/11 g 0.01% 6-Paradol supplement powder product and -Citrulline, L-Carnitine, Paradoxine Grains of Recovery Formula, Watermelon Paradise extract (6-Paradol) Ice 889 Softgel capsules Finished Tumeric, ginger Life Extension Advanced Bio-Curcumin, with 60 mg Gingerols/softgel 5.10% total nonvolatile product Ginger & Turmerones (1176.75 mg/softgel) Ginger constituents 740 Rhizome powder Raw material Ginger NIST SRM 3398 (not published) 100% Ginger powder 1% total nonvolatile ginger constituentsa 692 Rhizome dry extract Raw material Ginger NIST SRM 3399 (not published) 100% Ginger extract Unknown a Estimated assuming ginger rhizome powder contains 1% total nonvolatile ginger constituents. Talanta 194(2019)795–802 H. You et al. Talanta 194 (2019) 795–802 suggested to have possible value in the treatment of Parkinson's disease water diluent. The rest of the sample preparation was the same as [10]. The dietary supplement industry has recognized the market of 6- Control. paradol and zingerone and has made them the major bioactive com- • Published enzymatic method [12]: Used 0.5% v/w cellulase solution ponents in commercially available dietary supplements (Table 1; for each gram of ginger powder and the reaction occurs in pH = 5 Sample 101 and 648). The AOAC SMPRs (Standard Method Perfor- water. Incubated sample for 1 h in 50 °C waterbath before adding mance Requirement) are developed by working groups that are com- methanol for further extraction. Final methanol/water ratio was posed of stakeholders from academia, industry, and non-profit organi- 80%/20%. The rest of the sample preparation was the same as zations and designed to serve as guidance for the development of a control. consensus industrial reference method for meeting FDA's cGMP com- • Optimal enzymatic method: Reaction conditions were designed pliances of analyzing dietary supplements and ingredients. Targeting to based on the enzyme manufacturer's recommendations (email meet the AOAC SMPR 2017.12 (Quantitation of Select Nonvolatile communication with Sigma-Aldridge). 0.5% v/w cellulase solution Ginger Constituents) [11] requirements for ginger-containing dietary was used for each gram of ginger powder and the reaction occurs in ingredient and supplements, the method in development is designed to pH = 8 water. Incubated sample for 1 h in 60 °C waterbath before identify and quantitate 6-paradol and zingerone, in addition to the adding methanol for further extraction. Final methanol/water ratio traditional target nonvolatile ginger pungent constituents including 6-, was 80%/20%. Rest of sample preparations was the same as control. 8- and 10-gingerols and 6-, 8- and 10-shogaols. The details of SMPR 2017.12 are discussed later. To further evaluate the impacts of changing 7 factors in the analy- tical procedures, a Youden Ruggedness Trial [13] was conducted. 2. Material and methods Challenging factors were listed in Table 1S (Supplementary data), and 8 aliquots of the ginger rhizome powder sample were extracted and tested 2.1. Reagents and materials using different factor combinations as shown in Table 2S (Supplementary data). Standard 6-gingerol, 8-gingerol, 10-gingerol, 6-shogaol, 8-shogaol and 10-shogaol were provided by ChromaDex (Irvine, CA, USA). 2.4. Sample preparation Zingerone, cellulase (cellulase