HPLC Quantification and MS/NMR Confirmation of Javamide-I/-II in Arabica and Robusta Coffee Beans from Different Regions for Finding Better Bean Sources for Javamide-I/-II

Special Article - HPLC

Austin Chromatogr. 2019; 6(1): 1051.

HPLC Quantification and MS/NMR Confirmation of Javamide-I/-II in Arabica and Robusta Coffee Beans from Different Regions for Finding Better Bean Sources for Javamide-I/-II

Park JB¹*, Wang YTT¹, Zhang D², Vega EF² and Meinhardt WL²

¹Diet, Genomics, and Immunology Laboratory, USA

²Department of Agriculture, Sustainable Perennial Crop Laboratory, USA

*Corresponding author:Jae B. Park, Diet, Genomics and Immunology Laboratory, USDA, Beltsville, USA

Received: December 17, 2018; Accepted: January 10, 2017; Published: January 17, 2019

Abstract

Coffee is a popular drink with several positive health effects and javamide- I/-II are bioactive phenolic amides found in coffee. However, there is little information about the quantities of javamide-I/-II in Arabica and Robusta beans from different geographical regions, impossible to categorize better bean sources for javamide-I/-II. Therefore, in this paper, javamide-I/-II were first extracted from twelve coffee beans (eight Arabica beans from Brazil, Colombia, Costa Rica, Ethiopia, Hawaii, Papua New Guinea, Puerto Rico and four Robusta beans from India and Vietnam), and their amounts were quantified using the developed HPLC method with MS/MS and NMR confirmation. In, eight Arabica beans, javamide-I/-II were detected at levels ranging from 0.04-0.05 and 0.08-0.29 mg/g, meanwhile 0.4-0.76 mg/g of javamide-I and 3.5-4.9 mg/g of javamide-II were detected in four Robusta beans. The data showed that the amounts of javamide-I/-II in Robusta beans were much higher than those of javamide-I/ II in Arabica beans with little geographical impact (P<0.05). To validate these data and to explore better coffee beans for javamide-I/-II, eight additional beans (four Arabica and four Robusta beans) were extracted to examine the amounts of javamide-I/-II. The data of the eight additional beans confirmed the data of the twelve coffee beans in the levels of javamide-I/II (P<0.05), suggesting that Robusta beans may be better sources for javamide-I/-II than Arabica beans. In summary, javamide-I/-II may be found at higher levels in Robusta beans than Arabica beans, and Robusta beans are likely to be better bean sources for javamide-I/-II.

Keywords: Javamide-I/-I; MS/MS; NMR; HPLC quantification; Unroasted coffee beans

Introduction

Coffee is a tropical evergreen tree grown around the globe and coffee beans are typically used to produce a popular drink [1-3]. In fact, Coffea arabica (Arabica coffee) and C. canephora (Robusta coffee) are two most commercially important coffee species, primarily cultivated in the equatorial regions of the Americas, Southeast Asia, India, and Africa [3-7]. Arabica and Robusta beans are also known to contain numerous chemicals (e.g., caffeine, chlorogenic acids, javamide-I/-II, others) [7-9]. Recently, javamide-I/-II and their derivatives were reported to contain several biological activities related to human health [10-12]. However, there is little information about the amounts of javamide-I/-II in Arabica and Robusta beans from different geographical regions, although there are increasing inquiries about coffee beans with high amounts of javamide-I/-II and geographical impacts on them [7,8]. Therefore, in this paper, javamide-I/-II in twelve coffee beans (eight Arabica and four Robusta) grown in Brazil, Colombia, Costa Rica, Ethiopia, Hawaii, Papua New Guinea, Puerto Rico, India and Vietnam were first extracted and their identities were confirmed by MS/MS and NMR spectroscopic method. Then, javamide-I/-II were quantified using a HPLC method to gauge the influences of species and geographical influences on javamide-I/-II. Also, to validate the data of the twelve beans and to identify better bean sources for javamide-I/-II, eight additional coffee beans (four Arabica and four Robusta beans) from different regions were purchased and the amounts of javamide-I/-II were further quantified using the developed HPLC method.

Materials and Methods

Javamide-I/-II standards were prepared as reported previously [9]. All other reagents and chemicals were purchased from Sigma Chemical Co. (St. Louis, MO).

Preparation and extraction of coffee beans samples

Eight Arabica beans grown in Brazil, Colombia, Costa Rica, Ethiopia, Hawaii, Papua New Guinea and Puerto Rico and four Robusta beans grown in India and Vietnam were obtained from the Sustainable Perennial Crops Laboratory coffee collection (USDA, ARS). The species identity of all twelve coffee beans were verified using SNP markers as described previously [13]. Additionally, four Arabica and four Robusta beans were separately purchased from online stores to validate the data for javamide-I/-II. All unroasted coffee beans were grinded with a coffee grinder, and then pulverized using a mortar and pestle. The resulting fine powder was extracted with 80% methanol (50ml per 1g coffee bean) with a gentle shaking at room temperatures for 24 hr. Then, the samples were extracted three times, providing 1st, 2nd and 3rd extraction samples. The extraction samples were utilized to isolate javamide-I/-II for HPLC, MS/MS and NMR analysis and determining the extraction recovery.

High-Performance Liquid Chromatography (HPLC) analysis

HPLC analysis was performed with a C18 column and a mixed step and linear gradient condition. Briefly, a 150 mm × 4.6 mm i.d., 5 μm, Eclipse Plus C18 (Agilent, Santa Clara, CA) was used as the stationary phase to analyze the standards and coffee samples. The samples were separated using a mobile-phase condition; buffer A (5 mM phosphate, pH 5) for 0-2 min, 5% buffer B (60% acetonitrile) for 2-5 min, a linear gradient from 5%-100% buffer B (60% acetonitrile) for 5-35 min, and buffer B for 5 min (1 mL/min). The samples were injected by an autosampler into an Alliance 2690 HPLC system (Waters, Milford, MA), and were monitored by a CoulArray electrochemical detector with four electrode channels (ESA, Chelmsford, MA).

Liquid Chromatography-Mass Spectrometry (LC-MS/MS)

The LC MS/MS mass spectra were measured with Electrospray Ionization (ESI) on a Water MicroMass TQD Tandom Mass Spectrometer running under Waters Empower 3 Chromatography Data Software.

Nuclear Magnetic Resonance (NMR) analysis

The peaks of javamide-I/-II were isolated from the coffee samples using the method described previously [8,9]. The chemical structures of javamide-I/-II were verified using NMR spectroscopic methods. NMR samples were prepared by dissolving javamide-I/-II (20 mg) in d6-DMSO (0.75 mL). 1H and 13C spectra were acquired at ambient temperature on the JEOL BCX-400 NMR spectrometer operating 400 MHz for 1H and 100 MHz for 13C.

Quantification of javamide-I/-II in coffee beans

Twelve coffee beans obtained from the Sustainable Perennial Crops Laboratory coffee collection (USDA, ARS) were individually analyzed using the HPLC method as described in “Materials and Method”. Since the extraction was performed three times (1st, 2nd and 3rd), the 1st, 2nd and 3rd extraction samples were individually analyzed to determine the amounts of javamide-I/-II in each extraction. In addition, additional eight coffee beans were separately purchased from online stores and the extraction was prepared as described in “Materials and Methods”. The amounts of javamide-I/-II were quantified using Coul Array electrochemical detector with four electrode channels (ESA, Chelmsford, MA).

Statistical analysis

All statistic analyses were performed with the SigmaPlot 11.0 (Chicago, IL). Data points in all figures were represented as the mean ± SD of five measurements for each sample. P value was calculated using one-way ANOVA with Holm-Sidak method and P<0.05 was considered as statistically significant.

Results

Development and validation of HPLC method

The HPLC, mobile-phase and detector conditions were developed for optimizing the detection, separation, resolution and reproducibility of the peaks of javamide-I/-II in the chromatography as described in “Materials and Methods”. Using the developed HPLC method, javamide-I/-II standards were reliably separated and detected with fine separation and resolution; total HPLC running time for the assay was 40 min, and javamide-I/-II were detected at a retention time of 27.7 and 26.5 min, respectively (Figure 1A). To validate the HPLC method, standard samples of javamide-I/-II (0-400 pmol) were prepared and HPLC assay was conducted. The detection limit was approximately <5 pmol with SD lower than 15%. In this standard curve, satisfactory linear responses (n=4) for the amides were obtained at the concentrations between 5 to 400 pmol (correlation coefficient (R) = 0.998). Also, intra-assay and inter-assay precision of the method was evaluated as described previously [8] (Data not shown here).