Compositional profile of stingless bee honey from a West African country, Burkina Faso using H1-NMR spectroscopy

We collected 42 honey samples produced by Apis mellifera adansonii (n = 21) and stingless bee species (n = 21) from eight locations in Nahouri and Comoé provinces, Burkina Faso from March to August 2020 and from February to April 2021. Honey samples were collected from managed colonies of honey bees and wild colonies of three stingless bee species: Meliponula bocandei (n=3), Hypotrigona sp. (n=2) and Plebeina armata (n=17). The two first species usually nest in tree or above-ground cavities while P. armata is one of the few species nesting underground (Kajobe & Roubik, 2018).
We harvested honey directly from wild colonies using the “punching holes” method described in Mokaya et al., 2022 which is recommended to avoid alteration of stingless bee honey. After their collection, honey samples were stored in hermetic plastic bottles and kept cool at 4°C during the transport and storage at the Laboratoire de Biologie et Écologie Végétales, Université Joseph KI-ZERBO.
To characterize the compounds and properties of our honey samples, we used H1 Nuclear Magnetic Resonance spectroscopy (hereafter H1-NMR spectroscopy), a state-of the-art analytical technique increasingly used alongside chemometrics statistical approaches for the qualitative and quantitative control of honeys, as well as to assess the botanical origin of honeys and quantify their major constituting compounds
NMR spectroscopy was carried out on all 42 samples described above at the laboratories of Quality Services International GmbH (QSI, Bremen, Germany) using the protocol described in Noiset et al., 2022 (except for quinic acid that has not been detected in our samples, see all the quantified compounds in Table 1). In short, sample preparation method for honey was adapted from Bruker Biospin GmbH (Rheinstetten, Germany). The homogenized honey samples (5 g) were solved in 17.5 ml NMR-buffer (KH2PO4, Merck; NaN3, Fluka; H2O) by shaking the samples for 30 min. Their pH was adjusted to 3.1 using an auto titrator and HCl 1 M (Chemsolute®). To reach 900 μL of each sample, 100 μL of internal standard have been added. The samples have been centrifuged for 15 min at 14,000 rpm and 600 μL of supernatant was ultimately transferred into a 5 mm NMR-tube (Deutero) for direct measurement. The compounds were quantified by using the Honey-Profiling™ 2.0 routine (Bruker Biospin GmbH, Rheinstetten, Germany) by automatic integration of the specific peak areas calculated with an external standard using ERETIC function.