Injecting the juice would imo not have been part of a folk...

Injecting the juice would imo not have been part of a folk remedy. It would have been some idiot claiming they had a cure for everything by injecting juice.
The folk remedy probably involved drinking the juice as a lot of folk remedies in China do.
Thete are a lot of good folk remedies in China such as Green tea, tea made from ginger garlic and lemo etc.