Antioxidant activity, α-glucosidase inhibition, and phytochemical fingerprints ofAnoectochilus roxburghiiformula tea residues with HPLC-QTOF-MS/MS

This study assessed the phytochemical composition, antioxidant activities, and α-glucosidase inhibition of Anoectochilus roxburghii formula tea (ARFT) residue by comparing with that of ARFT infusion and ARFT extract. ARFT residue extract showed the maximum total phenolics, total flavonoids, and total condensed tannins content, with the values of 146.70 GAE mg/g E, 58.50 QE mg/g E, and 312.08 mg CE/g E, respectively, while ARFT infusion exhibited the lowest values. The strongest ABTS+· scavenging ability and α-glucosidase inhibition were also found in ARFT residue extract, but the best DPPH· scavenging ability was observed on the 95% ethanol extract of ARFT. Totally, 29 compounds were tentatively identified from the ARFT residue extract by using HPLC-QTOF-MS/MS, including 2 organic acids, 17 flavonoids, 4 fatty acids, 5 saponins, and 1 sugar. The results indicated that ARFT residue can be a promising source of natural antioxidants and α-glucosidase inhibitors. Practical applications Anoectochilus roxburghii formula tea (ARFT) is a popular health-promoting tea in China, but research on the bio-activities and functional constitution of ARFT and its residues is not available. This study suggested promising antioxidant and α-glucosidase inhibition of ARFT residue and revealed the presence of 29 major phytochemical compounds, which indicated that ARFT residue can be a potential resource of natural antioxidants and α-glucosidase inhibitors in food, cosmetic, and pharmaceutical industry.