About 0.35 g of frozen fresh G. elata were homogenized and ultrasonically extracted for 30 min in four volumes (g mL−1) water. After centrifugation (13,000 rpm, 10 min), 100 μL aliquots of supernatant were mixed with 10 μl of rutin (101.0 μg mL−1) for quantification of p-HA (λ 270 nm, Rt 6.8 min) and S-(p-HA)-glutathione (m/z 412.12, Rt 8.9 min) using an UPLC-PDA-ESI-Q-TOF-MSE method73. The injection volume was 1 μL. The contents were determined by the peak intensity ratios of the analyte to rutin (m/z 609.14, 15.5 min).