Key Flavanone Glucoside Associated With Sweet Taste of Hawk Tea

Abstract

Hawk tea (Litsea coreana) has been consumed as a unique beverage in southwest China for centuries, but the key components responsible for its sweet taste have not been known clearly. In this study, a taste sensory evaluation-guided isolation of its water extract led to the identification of a key sweet compound (2S)-eriodictyol-3′-O-β-D-glucopyranoside (1). Notably, no ¹³C-NMR, two dimensional NMR data, or absolute configuration determinations have been previously reported. The structure of 1 was elucidated using high-resolution electrospray ionization mass spectrometry (HRESIMS), heteronuclear singular quantum correlation (HSQC) and heteronuclear multiple bond correlation (HMBC), while its absolute configuration was unambiguously confirmed through single-crystal X-ray diffraction analysis. Taste sensory evaluation suggested the relative sweetness of 1 was 2.5 in reference to 5% sucrose solution, and a distinctive fruity taste was revealed. Molecular docking indicated a strong binding energy of −8.5 kcal/mol for ligand 1 with TAS1R2/TAS1R3 receptor. The primary interaction sites were identified as conventional hydrogen bond donors (SER-A-105, ASN-A-106, ASN-A-107, and SER-B-158) and π-alkyl bond interaction sites (VAL-A-56 and PRO-B-181). This compound was revealed as one of the key sweet components due to the high content in the range of 5.155%–6.525% and the knockout and recombination experiments. This is the first report about revealing the key sweet compound of hawk tea and determining the flavour characteristics of this flavanone glucoside.