2.10 Determination of MT contents
A 0.3 g sample was ground with liquid nitrogen and placed in 2 mL of
pre-cooled extraction solution (isopropanol:water:concentrated
hydrochloric acid, v:v:v=2:1:0.002), vortexed for 1 min, and left it in
the dark at -20°C for 24 h. Then, the sample was centrifuged at 4°C and
4000 rpm for 10 min, and the supernatant transferred to a new 10 mL
centrifuge tube. After adding 1 mL of dichloromethane, samples were left
in the dark at -20°C for 30 minutes, and centrifuged at 4°C and 4000 rpm
for 10 minutes. The supernatant was transferred to a new 10 mL
centrifuge tube and dried with nitrogen gas. After drying, 200 μL of
chromatographic grade methanol was added, mixed well, and filtered
through a 0.22 μm organic membrane before injection. Detection was
performed using LC-MS (SCIEX, QTRAP5500) with an injection volume of 2
μL.